An 18-year-old woman is brought to the emergency department by her parents for altered mental status that began today.  Two months ago, the patient began restricting her dietary intake due to fear of being overweight.  Since then, she has experienced notable weight loss and has felt weaker overall.  The patient's parents have been encouraging her to eat, and today, she agreed to eat watermelon and pineapple for breakfast.  Afterward, she fell while walking and appeared very somnolent.  The patient is otherwise healthy with no chronic medical conditions and takes no medications.  BMI is 16 kg/m2, decreased from 18.5 kg/m2 a few months ago.  The patient is oriented to name only and has a poor attention span.  Pupils are equal and reactive, but she has nystagmus and lateral gaze palsy.  Strength and sensations are equal in the bilateral extremities.  The patient walks in short steps and has difficulty maintaining her balance.  Abdominal and skin examinations are unremarkable.  Head imaging reveals no hemorrhage.  This patient's clinical findings are most likely due to which of the following? Wernicke encephalopathy Risk factors Chronic alcohol use (most common) Malnutrition (eg, anorexia, gastric bypass surgery) Pathophysiology Thiamine deficiency → impaired glucose metabolism & ATP production → neuronal injury/death (eg, mammillary bodies) May be precipitated by high metabolic demand or high glucose load Clinical findings Encephalopathy Oculomotor dysfunction Ataxia Management & prognosis Thiamine infusion reverses most symptoms. Memory impairment may be chronic/irreversible (Korsakoff syndrome). This patient has anorexia (eg, restricted diet, BMI of 16 kg/m2) and acutely developed encephalopathy, ataxia, and oculomotor dysfunction after ingesting glucose, findings suspicious for Wernicke encephalopathy (WE).  WE is a complication of thiamine (vitamin B1) deficiency and most commonly occurs in patients with chronic malnutrition (eg, chronic alcohol use, anorexia). Thiamine is a cofactor for several enzymes involved in glucose metabolism, and deficiency results in decreased glucose use and impaired ATP production.  In patients with low glucose intake, thiamine deficiency may be asymptomatic.  However, this patient ingested a large quantity of glucose, which likely rapidly depleted her limited thiamine stores. Without thiamine, cerebral energy production is impaired, increasing neuronal susceptibility to oxidative stress and causing disruption of the tight junctions that form the blood-brain barrier.  The resulting neuronal injury primarily affects areas of the brain with the highest metabolic demand and leads to the classic triad of WE: Encephalopathy (mammillary bodies):  somnolence, confusion, inattention Ataxia (cerebellum):  gait and balance disturbances Oculomotor dysfunction:  nystagmus, lateral gaze palsy (Choice A)  Anorexia increases the risk for deficiency of fat-soluble vitamins, such as vitamin E, an antioxidant that protects the cerebellum from reactive oxygen species.  Deficiency may result in ataxia, but encephalopathy and oculomotor dysfunction would not be expected. (Choice B)  Encephalopathy is common in patients with impaired hepatic clearance of ammonia; ataxia and nystagmus can also occur.  However, symptoms are usually insidious, not acute, in onset, and jaundice and asterixis would be expected. (Choice D)  Vitamin K is synthesized by gut microflora and is a cofactor for carboxylase enzymes involved in coagulation factor synthesis.  Patients with vitamin K deficiency are at increased risk for bleeding, such as a hemorrhagic stroke causing focal neurologic findings and/or altered mental status.  However, this patient's lack of hemorrhage on imaging is inconsistent with this diagnosis. (Choice E)  Clostridium botulinum is a spore-forming bacterium that produces a neurotoxin upon germinating which can cause cranial nerve motor dysfunction (eg, lateral gaze palsy) and descending muscle weakness.  However, this patient has normal extremity strength, and spore ingestion is mostly associated with infant botulism. Educational objective: Thiamine is a cofactor for several enzymes involved in glucose metabolism.  A complication of thiamine deficiency is Wernicke encephalopathy (encephalopathy, ataxia, oculomotor dysfunction), which can be precipitated by a high glucose load causing rapid depletion of limited thiamine stores.Convert this UWorld question into ultra high-yield USMLE notes: 1. Diagnosis: 2. Key clue from question stem (1 line): 3. Why correct answer (max 2 lines): 4. Why others wrong (1 line each): 5. Buzzword trigger: 6. Trap / trick tested: 7. One-liner memory hook: Make it extremely concise. No paragraphs. now as per new rules usmle is testing more on nutrition so make notes hpw test maker gonna ask acc.to my question

So I have understood that thiamine is necessary for many, many steps in this gluconeogenesis or glycolysis. I don't know, I'm not sure. I think glycolysis. So if we give more, if you get, if you have, if you give directly more sugar and in a thiamine depleted condition, what happens? Like this high glucose levels can damage the neurons.

So in alcoholic patients, they usually check transketolase to check if the thiamine is deficient or not, right? Why can't they check thiamine directly and what's the role of transketolase activity checking in the serum?

I found the chance to just now that transketolase gives you have more half-life and that's why if you check that, you'll have you can see the serum time index or something like that.

A 66-year-old man comes to the office after his employer urged him to undergo medical evaluation for repeated mistakes at work.  The patient was a highly successful accountant until 6 months ago when he started making uncharacteristic errors and turning in projects late.  He says, "I don't know why, but it's suddenly really hard for me to organize and plan for these projects."  His wife has had to take over managing their finances at home.  The patient is also having difficulty shopping for groceries and preparing meals.  He has not seen a physician in many years and takes no medications.  Blood pressure is 159/96 mm Hg and pulse is 72/min.  Physical examination shows impaired executive neurocognitive function.  Reflexes are 2+ in the right lower extremity and 3+ in the left.  Strength is 5/5 on the right side and 4/5 in the left lower extremity.  He has an unsteady gait.  Which of the following is the most likely pathophysiologic process underlying this patient's condition? Vascular dementia Pathophysiology Ischemia and/or infarcts due to: Large-vessel atherosclerosis Small-vessel disease (eg, arteriolosclerosis) Cerebral amyloid angiopathy Clinical manifestations Early, prominent executive dysfunction Subtypes: Multi-infarct: often with stepwise decline Strategic infarct: associated with localizing cortical deficits Subcortical vascular encephalopathy: associated with subcortical signs (eg, urinary incontinence, gait disturbances) Imaging findings Cortical infarcts Subcortical lacunar infarcts White matter hyperintensities This patient's relatively abrupt cognitive decline with prominent executive dysfunction (eg, difficulty planning and organizing) and localizing neurologic findings (eg, asymmetric reflexes, asymmetric muscle weakness, gait disturbances) is strongly suggestive of vascular dementia (VaD) due to unrecognized stroke(s) 6 months ago.  VaD is often caused by 2 (potentially overlapping) mechanisms: Large artery infarction (often causing an overt stroke) produces a cortical-type VaD, in which accompanying neurologic signs/symptoms reflect the specific cortical region involved (eg, middle cerebral artery infarction causing contralateral weakness and sensory impairment). Small artery (ie, arteriole) infarcts can combine to cause enough cumulative damage to the brain, resulting in noticeable cognitive deficits.  Although the clinical picture is varied, a subcortical-type VaD is common because there is less arteriole collateralization in the subcortical regions compared to the cerebral cortex.  As in this patient, subcortical-type VaD is often accompanied by focal motor deficits (eg, reflex asymmetry, strength differences), abnormal gait, urinary symptoms, and psychiatric symptoms (eg, depressive syndromes). Subcortical VaD is due to either cerebral amyloid angiopathy or, more commonly, small vessel arteriolosclerosis.  Arteriolosclerosis is common in older patients, especially those with a history of hypertension. (Choice B)  Degeneration of the cholinergic neurons of the basal forebrain is seen in Alzheimer disease, which presents with progressive memory loss and functional impairments.  However, Alzheimer disease typically progresses gradually with early, prominent short-term memory loss, and it would not cause focal neurologic findings (eg, strength deficits, reflex asymmetry). (Choice C)  Degeneration of dopaminergic neurons in the substantia nigra is characteristic of Parkinson disease, which can cause executive and visuospatial dysfunction with relatively mild memory impairment.  However, Parkinsonian features (eg, rigidity, resting tremor, bradykinesia) occur at least a year before the onset of dementia. (Choice D)  Sudden acceleration-deceleration or rotational forces during blunt head injury can cause diffuse shearing of the long white matter tracts (diffuse axonal injury).  Patients have a history of acute trauma and neurologic impairment out of proportion to neuroimaging findings. (Choice E)  Neuronal loss and atrophy of hypothalamic mamillary bodies characteristically occurs in Wernicke encephalopathy, a complication of thiamine deficiency.  Although it can cause ataxia and confusion, it also typically presents with oculomotor dysfunction (nystagmus, ophthalmoplegia), and patients typically have a history of either chronic alcohol use or malnutrition. Educational objective: Small artery cerebral arteriolosclerosis can lead to ischemia that predominantly affects the subcortical areas.  This can lead to vascular dementia associated with focal motor deficits, abnormal gait, urinary symptoms, and psychiatric symptoms.Convert this UWorld question into ultra high-yield USMLE notes: 1. Diagnosis: 2. Key clue from question stem (1 line): 3. Why correct answer (max 2 lines): 4. Why others wrong (1 line each): 5. Buzzword trigger: 6. Trap / trick tested: 7. One-liner memory hook: Make it extremely concise. No paragraphs.

​​​​​​​A 54-year-old woman is brought to the emergency department due to acute-onset mental status changes and double vision.  Examination shows that the patient is awake but disorientated to time and place and has a decreased attention span.  Further questioning reveals memory impairment that appears to have been most severe during the last few months.  Examination of the eyes shows horizontal nystagmus evoked on lateral gaze with bilateral weakness of the lateral rectus muscles.  Strength is equal bilaterally, but the patient is unable to walk without support.  She receives appropriate treatment based on the most likely diagnosis, and most of the clinical findings resolve.  However, she continues to have residual memory deficits.  This patient was most likely treated for which of the following conditions? Wernicke encephalopathy Risk factors Chronic alcohol use (most common) Malnutrition (eg, anorexia, gastric bypass surgery) Pathophysiology Thiamine deficiency → impaired glucose metabolism & ATP production → neuronal injury/death (eg, mammillary bodies) May be precipitated by high metabolic demand or high glucose load Clinical findings Encephalopathy Oculomotor dysfunction Ataxia Management & prognosis Thiamine infusion reverses most symptoms. Memory impairment may be chronic/irreversible (Korsakoff syndrome). This patient has characteristic manifestations of Wernicke encephalopathy, a condition caused by chronic thiamine (vitamin B1) deficiency. The clinical features and course of Wernicke encephalopathy are as follows: Oculomotor dysfunction (eg, nystagmus, lateral rectus palsy) occurs due to impairment of the oculomotor nuclei.  It is rapidly reversible with thiamine administration. Ataxia is caused by damage to the cerebellar cortex and vestibular nuclei.  Unlike oculomotor function, ataxia takes longer to resolve, and some patients may have permanent symptoms. Encephalopathy, ranging from decreased attention span to disorientation and stupor, can occur, and impaired memory/learning may be apparent.  Acute mental status changes respond well to treatment, but memory and learning abnormalities usually persist, as a condition known as Korsakoff syndrome. Korsakoff syndrome is associated with damage to the anterior and dorsomedial thalamic nuclei.  This results in chronic, irreversible memory loss, both short-term retrograde (recent events) and anterograde (unable to form new memories) amnesia.  Patients with Korsakoff syndrome also often have a psychologic phenomenon called "confabulation"; when such patients are unsure of a fact, they subconsciously fill in the memory gap with a fabricated story that they believe to be true. Thiamine should be administered immediately for suspected Wernicke encephalopathy because it decreases the risk for irreversible neurologic damage. (Choice A)  Abrupt discontinuation of antidepressants may cause transient, nonspecific neurologic symptoms, including dizziness, fatigue, and headache; a gradual taper often leads to symptom resolution.  However, oculomotor dysfunction and memory deficits would not be seen. (Choice B)  Localized muscle weakness is a common adverse effect of botulinum toxin injection and usually resolves with time.  Although extraocular muscle involvement causing diplopia may occur, this patient's acute mental status changes and ataxia are inconsistent with this diagnosis. (Choice C)  Fluctuating extraocular muscle weakness occurs in myasthenia gravis and may rapidly improve with pyridostigmine.  However, ataxia and mental status changes would not occur. (Choice D)  Pituitary apoplexy (acute hemorrhage into the pituitary gland) may compress the optic chiasm, leading to acute vision loss or diplopia that resolves with surgical decompression.  However, ataxia, disorientation, and memory deficits would not be seen. Educational objective: Oculomotor dysfunction, ataxia, and confusion form the triad of Wernicke syndrome.  Most of these symptoms usually resolve after thiamine administration.  Korsakoff syndrome is a chronic and irreversible complication of Wernicke encephalopathy, the hallmarks of which are permanent memory loss and confabulation.

​​​​​​​A 10-year-old boy is brought to the office due to ataxia, myoclonus, and vision defects.  His parents say that he began acting strangely and having difficulty with schoolwork several months ago.  The family recently immigrated to the United States.  After the appropriate work-up is performed, a brain biopsy is obtained; an RNA virus containing hemagglutinin is cultured from the tissue sample.  Which of the following is the most likely diagnosis? Explanation Measles virus (rubeola) Clinical presentation Prodrome (eg, cough, coryza, conjunctivitis, fever, Koplik spots) Maculopapular exanthem Cephalocaudal & centrifugal spread Spares palms & soles Complications Primary measles pneumonia Secondary bacterial infections (pneumonia & otitis media) Neurologic Encephalitis (within days) Acute disseminated encephalomyelitis (within weeks) Subacute sclerosing panencephalitis (within years) Prevention Live attenuated measles vaccine Measles virus is an enveloped, single-stranded RNA virus in the Paramyxoviridae family.  Its genome codes for several viral structural proteins, including membrane-bound hemagglutinin (mediates cell surface adhesion) and matrix protein (important for viral assembly). Subacute sclerosing panencephalitis (SSPE) is a rare complication of measles that occurs in children and young adults 7-10 years after initial infection.  It is likely caused by a measles virus variant with a mutated or absent matrix protein that prevents mature (enveloped) virion particles from forming.  However, the virus continues to replicate intracellularly, leading to a persistent, nonproductive infection that evades the immune system. Accumulation of viral nucleocapsids within neurons and oligodendrocytes results in the formation of intranuclear inclusions in many areas of the brain.  It eventually leads to inflammation, demyelination, and gliosis, findings that may be seen on brain biopsy.  Patients with SSPE also have high measles antibodies titers in the serum and cerebrospinal fluid (detectable as oligoclonal bands).  The disease causes progressive neurologic deficits (eg, personality changes, myoclonus, ataxia, vision defects) and dementia and is fatal. (Choice A)  Creutzfeldt-Jakob disease is a rare form of rapidly progressive dementia caused by prions (abnormally folded proteins).  It usually develops in older patients, although younger patients can be affected after consuming prion-infected meat products.  Brain biopsy shows spongiform transformation of the cerebral cortex. (Choice B)  Guillain-Barré syndrome is a postinfectious autoimmune demyelinating disorder of the peripheral nervous system.  Unlike this case, it typically presents acutely as a symmetrical ascending weakness. (Choice C)  Multiple sclerosis usually manifests in young adults with visual (eg, optic neuritis, internuclear ophthalmoplegia) and other sensory deficits in a relapsing-remitting pattern.  Brain biopsy shows focal demyelinated plaques with relative axonal sparing. (Choice D)  Progressive multifocal leukoencephalopathy is an infectious demyelinating disorder caused by JC virus, a double-stranded DNA virus.  Manifestations include progressive neurologic deficits in individuals with immunocompromising conditions (eg, lymphoma, leukemia, HIV infection). (Choice E)  Progressive supranuclear palsy is a form of parkinsonism resulting from neurodegeneration of the midbrain and frontal subcortical white matter.  It presents with rapidly progressive gait dysfunction, executive function loss, and vertical gaze palsy.  Brain biopsy shows deposits of abnormally phosphorylated tau proteins. Educational objective: Subacute sclerosing panencephalitis is a rare complication of measles that occurs years after infection and causes progressive neurologic deficits (eg, personality changes, myoclonus).  Oligoclonal bands of measles virus antibodies are found in cerebrospinal fluid, and brain biopsy reveals the RNA virus containing hemagglutinin.

are you making tables only of ultra ahy right becoz i want super consice test makerlevel concepts not extra fuzz

the above notes what you made is hy then i will copy that only the goal is i have to pass step[ 1

no iam asking yo for hrlp for my prep to crack usmle step 1

A 40-year-old man comes to the office due to a 6-month history of sleep abnormalities, constipation, and generalized slowing of activity.  In addition, he has difficulty rising from a seated position.  Medical history is significant for a traumatic head injury 3 years ago, which required a prolonged hospital stay.  The patient has no other medical conditions and takes no medication.  He does not use tobacco, alcohol, or recreational drugs.  Vital signs are normal.  Examination shows resistance to passive movement in the upper extremities, which is slightly greater on the left than on the right.  Left hand tremor and decreased arm swing occur during walking.  Which of the following is the most likely explanation for this patient's current condition?  A. Astrocyte swelling  (9%)  B. Degeneration of neurons  (58%)  C. Degeneration of oligodendrocytes  (19%)  D. Disruption of vascular endothelial cells  (4%)  E. Vascular amyloid deposition  (8%) his patient has bradykinesia (eg, slowing of activity, decreased arm swing) with an asymmetric hand tremor and rigidity (increased resistance to passive movement around a joint).  In addition, he also has sleep abnormalities and constipation.  This constellation of symptoms is concerning for Parkinson disease. Parkinson disease originates from a loss of dopaminergic neurons in the substantia nigra.  This usually occurs gradually, leading to clinical onset typically in the sixth or seventh decade. Traumatic brain injury, especially with prolonged loss of consciousness, is associated with both an increased incidence and an earlier onset of Parkinson disease.  This is due to the accelerated degeneration of neurons both at the time of injury and through ongoing neurotoxic cascades that lead to the accumulation of alpha-synuclein filaments and accelerated neurodegeneration. (Choice A)  Astrocyte swelling occurs in the early phase of traumatic brain injury and can lead to cerebral edema and life-threatening increased intracranial pressure.  It does not seem to directly contribute to dopaminergic neurodegeneration. (Choice C)  Degeneration of oligodendrocytes (myelin-forming cells) leads to demyelinating diseases such as multiple sclerosis, which typically presents with neurologic deficits disseminated in space and time. (Choice D)  Disruption of vascular endothelial cells can occur due to shearing forces during traumatic brain injury.  This can disrupt the blood-brain barrier, leading to cerebral edema and petechial hemorrhaging.  However, it is not the primary cause of Parkinson disease. (Choice E)  Vascular amyloid deposition is responsible for cerebral amyloid angiopathy, which is the most common cause of lobar intracranial hemorrhage.  The amyloidogenic proteins are usually the same as those seen in Alzheimer dementia, but they are not associated with Parkinson disease, which is associated with alpha-synuclein deposition. Educational objective: Bradykinesia, resting tremor, and rigidity are features of Parkinson disease, which is caused by dopaminergic neurodegeneration.  Traumatic brain injuries can accelerate neurodegeneration, leading to a higher incidence and earlier onset of Parkinson disease.

i have attached a pile of 4 questions of ALS how test makers asked twisted make Hy notes as you said

​​​​​​​A 55-year-old woman is brought to the office by her husband for evaluation of strange behavior.  She has been spending large amounts of money to buy expensive clothes and jewelry.  The patient has also offered sex to unknown men in the neighborhood and has become increasingly indifferent toward her family, about whom she used to care deeply.  She usually drinks 1 or 2 glasses of wine on weekends but lately has been drinking 2 or 3 glasses almost every day.  When asked about these changes during the interview, the patient states that she has not noticed any change in her behavior.  Vital signs are normal.  The general physical and neurologic examinations are normal.  This patient's condition is most likely due to abnormal accumulation of which of the following? his patient with disinhibition (eg, soliciting sex from strangers), loss of empathy toward her family, complex compulsive behaviors (eg, excessive shopping), and hyperorality (eg, increase in drinking wine) likely has frontotemporal dementia (FTD).  FTD is characterized by degeneration of the prefrontal cortex, which progresses to include the anterior temporal lobes.  The disease process results in accumulation of different neurotoxic proteins, including: Tau, a protein associated with neuronal microtubules that normally takes part in microtubule stabilization.  In patients with FTD, tau becomes hyperphosphorylated and disassociates from the microtubules, which may lead to instability and disrupted axonal transport.  It also forms paired helical filaments, which create intracellular tangled clumps of tau proteins predominantly in the frontal and temporal lobes, as well as the hippocampi.  Tau-related neurofibrillary tangles are also found in patients with Alzheimer dementia. TDP-43 (transactive response DNA-binding protein 43), a protein that normally functions as a transcription inhibitor or a DNA repair protein.  Abnormal ubiquitination leads to immunoreactive inclusions of TDP-43.  Pathologic TDP-43 is also found in patients with amyotrophic lateral sclerosis. (Choices A and C)  CAG trinucleotide (polyglutamine) repeats can lead to neurotoxic protein formation.  When this occurs in the ataxin genes, it can lead to spinocerebellar ataxia.  When it occurs in the huntingtin protein, it leads to Huntington disease, which can present with prominent changes in mood or cognition.  However, both spinocerebellar ataxia and Huntington disease also typically present with significant gait abnormalities (ie, ataxia). (Choice B)  Extracellular accumulation of beta-amyloid occurs in Alzheimer disease.  Alzheimer disease commonly presents with early and prominent memory impairment with language deficits and spatial disorientation.  Although personality changes can occur, they typically occur later in the disease process.  This patient's early personality changes are more characteristic of FTD. (Choice D)  Excessive prion accumulation causes Creutzfeldt-Jakob disease.  Although behavioral changes are common, dementia is rapidly progressive and associated with myoclonus and/or seizures. Educational objective: Frontotemporal dementia presents with early personality change, executive dysfunction, compulsivity, and hyperorality.  It is associated with neurofibrillary tangles due to abnormal tau proteins (also seen in Alzheimer dementia) and pathologically ubiquitinated TDP-43 (also seen in amyotrophic lateral sclerosis).

A 66-year-old man comes to the emergency department due to dizziness, dysarthria, and bilateral limb ataxia.  His symptoms have been steadily worsening over the last 2 weeks.  He has no other medical problems and takes no medications.  He has a 50-pack-year smoking history and does not use alcohol or illicit drugs.  Chest x-ray shows a mass in his right lung.  He is admitted to the hospital for evaluation, but his neurologic symptoms continue to progress.  He dies several months later despite receiving appropriate treatment.  Autopsy shows extensive cerebellar Purkinje cell degeneration.  Which of the following best describes the etiology of this patient's neurologic condition? Features of common paraneoplastic syndromes Clinical presentation Frequently associated neoplasms Etiology Cushing syndrome Small cell lung cancer Pancreatic cancer Ectopic production of adrenocorticotropic hormone/corticotropin-releasing hormone Syndrome of inappropriate antidiuretic hormone secretion Small cell lung cancer Ectopic vasopressin production Subacute cerebellar degeneration Small cell lung cancer Breast, ovarian & uterine cancer Anti-Yo, anti-P/Q & anti-Hu antibodies Lambert–Eaton myasthenic syndrome Small cell lung cancer Voltage-gated calcium channel antibodies Myasthenia gravis Thymoma Acetylcholine receptor antibodies Hypercalcemia Squamous cell lung cancer Ectopic production of parathyroid hormone–related protein Dermatomyositis/polymyositis Variable Autoimmune Erythrocytosis Renal cell cancer Ectopic erythropoietin production This patient's lung mass, cerebellar symptoms, and autopsy findings are consistent with paraneoplastic cerebellar degeneration.  This paraneoplastic syndrome is most commonly associated with small cell lung cancer as well as breast, ovarian, and uterine malignancies.  Patients exhibit progressively worsening dizziness, limb and truncal ataxia, dysarthria, and visual disturbances (eg, diplopia, oscillopsia).  Paraneoplastic cerebellar degeneration is due to an immune response against tumor cells that cross-reacts with Purkinje neuron antigens, leading to acute-onset rapid degeneration of the cerebellum.  Anti-Yo, anti-P/Q, and anti-Hu are the most common antibodies detected in the serum.  Antibodies are not always detectable; thus, paraneoplastic cerebellar degeneration is diagnosed clinically after excluding other conditions. (Choice B)  Some paraneoplastic syndromes occur due to the production of hormone-like substances from tumor cells, but these would not cause the neurological findings described in this case. (Choice C)  Acute cerebellitis (post-viral cerebellar ataxia) occurs most often in children 2-3 weeks following varicella, measles, or Epstein-Barr virus infection.  It presents with cerebellar symptoms (eg, ataxia, nystagmus, dysarthria) that usually resolve completely within 3 weeks. (Choice D)  Cerebellar metastasis can cause progressively worsening subacute cerebellar symptoms.  Additional findings such as headaches or decreased consciousness are often present due to significant mass effect from the tumor.  However, autopsy would show metastatic cancer cells with surrounding inflammation as opposed to Purkinje cell degeneration. (Choice E)  Adverse effects from systemic chemotherapy can include a wide range of neurologic complications.  However, this patient's symptoms began before the lung mass was identified and his autopsy findings are more specific for subacute cerebellar degeneration. (Choice F)  Cerebellar infarction presents with vertigo, nystagmus, ipsilateral limb ataxia, and truncal lateropulsion (falling toward the lesion).  Although repeated vascular events could result in a stepwise progressive loss in neurologic function, this process would most likely occur over several years and affect multiple vascular territories throughout the brain (causing a wide range of neurologic deficits).  Autopsy would show areas of liquefactive necrosis (acute infarcts) and glial scarring (chronic infarcts). Educational objective: Paraneoplastic syndromes can occur due to the production of hormone-like substances from tumor cells.  They can also result from immune reactions against tumor cells that cross-react with normal cells, causing dysfunction and/or damage to healthy organs and tissues.  Neurologic paraneoplastic syndromes (eg, paraneoplastic cerebellar degeneration) are an autoimmune phenomenon.

A 65-year-old man comes to the office due to bothersome tremors.  The patient was diagnosed with idiopathic Parkinson disease 10 years ago and has since been successfully treated with levodopa-carbidopa.  However, over the last several months, he has developed frequent freezing episodes characterized by a sudden loss of mobility.  More recently, the patient's tremors worsened after he reduced his levodopa dose following the development of involuntary body movements.  On examination, he has a bilateral resting tremor that is worse on the right, bradykinesia, and cogwheel rigidity.  His symptoms have significantly degraded his quality of life, and he is now interested in discussing surgical options.  This patient would benefit most from a treatment targeted at suppressing neuronal activity in which of the following brain structures? oss of dopaminergic neurons in Parkinson disease (PD) leads to a reduced amount of dopamine available to inhibit the striatum (nigrostriatal pathway).  This results in overactivation of the subthalamic nucleus (STN), leading to increased stimulation of the globus pallidus interna (GPi).  In turn, the GPi increases its inhibitory output to the thalamus.  Decreased stimulation of the motor cortex by the thalamus then leads to the classic symptoms of bradykinesia and rigidity. Restoration of dopamine levels in the brain by treatment with levodopa (precursor to dopamine able to cross the blood-brain barrier) and carbidopa (inhibits peripheral metabolism of levodopa to increase availability to the brain) improves the motor symptoms of PD.  However, levodopa has a narrow therapeutic window that worsens with disease progression; over time, periodic dosing inevitably results in motor fluctuations (eg, freezing when dopamine levels drop) as well as dyskinesia (eg, involuntary movements, tremor when dopamine levels spike). When levodopa becomes ineffective, the neuronal pathways from the basal ganglia to the thalamus can be surgically interrupted (eg, deep brain stimulation, lesioning procedures).  The most effective surgical targets are the STN (reduces excess GPi excitation) and the GPi (reduces excess thalamic inhibition); inhibition of either nucleus has been shown to improve motor fluctuations and dyskinesia seen with advanced PD. (Choice A)  The globus pallidus externa normally inhibits the STN.  If inhibitory impulses from this region are down-regulated, output would increase from the STN, worsening Parkinson symptoms. (Choice B)  Global inhibition of the motor cortex is responsible for the symptoms of PD; increased inhibition would further worsen this patient's bradykinesia. (Choice C)  The rubrospinal tract originates from the red nucleus and contributes to upper extremity flexor tone.  Inhibition of this nucleus would result in decerebrate (extensor) posturing, as seen with brain herniation. (Choice E)  The ventral intermediate nucleus of the thalamus is involved in generating pathologic oscillatory tremors (eg, Parkinson disease, essential tremor).  Although suppression of output from the ventral intermediate nucleus is effective for treating refractory tremor, it does not improve bradykinesia nor rigidity. Educational objective: Nigrostriatal degeneration in Parkinson disease impairs thalamic stimulation of the motor cortex, resulting in bradykinesia, rigidity, and resting tremor.  Patients with medically intractable symptoms may benefit from surgery to decrease output of the globus pallidus interna or subthalamic nucleus, promoting thalamocortical disinhibition with improvement in Parkinson symptoms.

​​​​​​​A 72-year-old woman comes to the office for a routine follow-up visit accompanied by her son.  The patient has experienced progressive memory loss over the last 2 years.  She now needs help with her daily activities, such as shopping and housekeeping.  The patient's son says, "She used to be such an independent person, but now she needs help with most things.  She even forgot my name the other day!"  Medical history includes hypertension, hyperlipidemia, and type 2 diabetes mellitus.  Family history includes major depressive disorder in her father.  MRI reveals diffuse cortical and hippocampal atrophy.  Which of the following biochemical changes is most likely contributing to this patient's condition? Clinical features of Alzheimer disease Early findings Anterograde memory loss (ie, immediate recall affected, distant memories preserved) Visuospatial deficits (eg, lost in own neighborhood) Language difficulties (eg, difficulty finding words) Cognitive impairment with progressive decline Late findings Neuropsychiatric (eg, hallucinations, wandering) Dyspraxia (eg, difficulty performing learned motor tasks) Lack of insight regarding deficits Noncognitive neurologic deficits (eg, pyramidal & extrapyramidal motor, myoclonus, seizures) Urinary incontinence Alzheimer disease (AD) is the most common cause of dementia.  It has the following characteristic features: Prevailing clinical symptom: slow, progressive memory loss Macroscopic brain appearance: mild-to-moderate generalized brain atrophy Microscopic brain changes: neurofibrillary tangles, senile plaques, and amyloid angiopathy Biochemical abnormalities: decreased acetylcholine levels in the hippocampus and nucleus basalis of Meynert The most important biochemical abnormality noted in AD is a decrease in the acetylcholine level.  This occurs due to a deficiency of choline acetyltransferase.  The decline in acetylcholine is most notable in the nucleus basalis of Meynert, which participates in memory and cognition.  This nucleus is located at the base of the forebrain and widely projects to the neocortex.  Another involved structure is the hippocampus:  The major function of the hippocampus is the formation of new memories. Symptomatic management of AD includes cholinesterase inhibitors, which target the acetylcholine deficit by inhibiting the degradation of acetylcholine at the synaptic cleft. (Choice B)  Loss of dopaminergic neurons in the substantia nigra is seen in Parkinson disease and dementia with Lewy bodies. (Choice C)  The raphe nuclei form the medial part of the brain stem's reticular formation (medulla, pons, and midbrain).  Many neurons in the nuclei are serotonergic.  Serotonin is implicated in the pathogenesis of anorexia, depression, and sleep disorders. (Choice D)  Atrophy of the caudate nucleus is seen in Huntington disease. (Choice E)  The locus ceruleus is thought to play a role in the pathogenesis of panic attacks and panic disorder.  It is located in the pons and contains cell bodies of noradrenergic neurons that synthesize norepinephrine. Educational objective: Alzheimer disease is characterized by decreased levels of acetylcholine in the nucleus basalis of Meynert and the hippocampus, caused by diminished activity of choline acetyltransferase. A 71-year-old woman is brought to the physician by her daughter.  She says that her mother went shopping yesterday and could not find her way back home.  Two years ago, her mother "started forgetting things like where she put her keys" and "began to have problems remembering the right words."  Now she has trouble keeping up with her activities of daily living and refuses to pay her bills because "it's a waste of money."  The patient's past medical history is unremarkable.  Brain magnetic resonance imaging (MRI) is most likely to show atrophy of which of the following structures? Alzheimer's disease is a neurodegenerative disorder that presents with insidiously progressive memory loss.  It is the most common cause of dementia and usually affects people > 60 years of age.  Language deficits (word-finding difficulty) and impaired visuospatial ability (misplacement of items) can occur early in the course of the disease.  Later, as impairment in executive function and associated behavioral abnormalities become more pronounced, patients can have trouble performing everyday functions (eg, shopping, cooking, and managing money). Advanced Alzheimer's disease is associated with diffuse brain atrophy.  Atrophy is most pronounced in the temporoparietal lobes and hippocampus.  Hippocampal atrophy is evident even in the early stages of the disease and can be detected by brain MRI. The cerebellum (Choice B), corpus callosum (Choice C), pons (Choice D), and thalamus (Choice E) are not obviously atrophied in Alzheimer's disease. Educational objective: The hippocampus is the area of the brain demonstrating the greatest degree of atrophy in Alzheimer's disease.  Hippocampal atrophy on MRI is highly suggestive of the diagnosis. An 82-year-old woman comes to the clinic due to memory loss.  She lives with her daughter, who reports that her mother has had difficulty remembering recent conversations.  The patient has also forgotten recent events, such as her grandson's birthday party last month.  Two years ago, she was forced to give up driving after repeatedly getting lost in her own neighborhood and being involved in a minor motor vehicle accident.  The patient still enjoys reminiscing about old times with friends and playing bingo at church.  The daughter now manages her mother's finances and acts as her health care proxy.  Which of the following is the most likely pathological finding in this patient? Clinical features of Alzheimer disease Early findings Anterograde memory loss (ie, immediate recall affected, distant memories preserved) Visuospatial deficits (eg, lost in own neighborhood) Language difficulties (eg, difficulty finding words) Cognitive impairment with progressive decline Late findings Neuropsychiatric (eg, hallucinations, wandering) Dyspraxia (eg, difficulty performing learned motor tasks) Lack of insight regarding deficits Noncognitive neurologic deficits (eg, pyramidal & extrapyramidal motor, myoclonus, seizures) Urinary incontinence This elderly patient likely has Alzheimer dementia, a neurodegenerative disorder that presents insidiously with memory loss, especially of recent events.  Other cognitive deficits such as word-finding difficulty, executive dysfunction (eg, difficulty planning and organizing) and visuospatial impairment (eg, getting lost in one's own neighborhood) may also occur early in the disease course, whereas behavioral abnormalities and more severe language deficits often manifest later. Classic histopathologic findings of Alzheimer disease include amyloid plaques and neurofibrillary tangles.  Neuritic (senile) plaques are extracellular deposits often found in the medial temporal lobe (eg, hippocampus, amygdala, entorhinal cortex) and are composed of a central amyloid beta (Aβ) core surrounded by dystrophic neurites.  Abnormal accumulation of Aβ is toxic to neurons and is thought to occur secondary to impaired clearance or overproduction of amyloid precursor protein.  Neurofibrillary tangles are found in the neuronal cytoplasm and consist of aggregates of hyperphosphorylated tau protein, which normally mediates microtubule stabilization. (Choice A)  Demyelinated plaques are seen in multiple sclerosis, which typically presents in young to middle-age adults with neurologic deficits disseminated in space and time. (Choice B)  Large intracytoplasmic vacuoles, sometimes described as spongiform, are seen in prion diseases such as Creutzfeldt-Jakob disease.  This condition typically presents with rapidly progressive dementia and myoclonus. (Choice C)  Lewy bodies are intracellular eosinophilic inclusions composed of α-synuclein that are typically seen in patients with Parkinson disease and Lewy body dementia.  Lewy body dementia classically presents with attention deficits, visual hallucinations, and spontaneous parkinsonism (eg, bradykinesia, rigidity, resting tremor). (Choice D)  Multiple lacunar infarcts would be expected in vascular dementia.  Vascular dementia is distinguished from Alzheimer dementia by a step-wise rather than gradual decline in cognitive function, as well as focal neurologic deficits. (Choice E)  Negri bodies are round eosinophilic inclusions seen in the cytoplasm of pyramidal hippocampal neurons and cerebellar Purkinje cells in patients infected with the rabies virus. Educational objective: Alzheimer dementia typically presents insidiously with memory loss (especially of recent events), executive dysfunction, and visuospatial impairment.  Classic histopathologic findings include amyloid plaques (central amyloid beta core surrounded by dystrophic neurites) and neurofibrillary tangles (aggregates of hyperphosphorylated tau protein). all 3 are questions related to alzheimers

​​​​​​​A 65-year-old woman is brought to the clinic by her husband due to worsening memory problems.  She has a medical history significant for long-standing hypertension, type 2 diabetes mellitus, and depression.  Physical examination shows cognitive impairment but no focal neurologic deficits.  Two years later, the patient dies suddenly from a massive myocardial infarction.  Congo red staining of brain samples obtained from the hippocampus and cerebral arterioles reveals patchy red deposits that turn yellow-green under polarized light.  This patient most likely suffered from which of the following conditions? myloid is an abnormally folded (insoluble) fibrillar protein that deposits in the extracellular space of tissues.  When stained with Congo red and viewed under polarized light, these deposits have a characteristic apple-green birefringence due to their β-sheet structure.  Amyloid deposition can affect multiple organ systems, as occurs with plasma cell tumors (eg, amyloid light chain protein [AL]) and chronic inflammatory diseases (eg, amyloid-associated protein [AA]). However, in Alzheimer disease, amyloid deposits are seen exclusively in brain tissue.  These deposits contain beta-amyloid (Aβ), which is formed by cleavage of amyloid precursor protein (a transmembrane glycoprotein).  Early in the disease, neuritic (senile) plaques can be found in the medial temporal lobe (eg, hippocampus, amygdala, entorhinal cortex) and are composed of a central Aβ core surrounded by dystrophic neurites.  Aβ deposition also occurs in the media/adventitia of cerebral vessels (amyloid angiopathy) and may cause vessel weakening with intracranial hemorrhage. (Choice B)  Huntington disease typically presents with dementia, choreiform movements, dystonia, and psychiatric symptoms.  Patients characteristically have atrophy of the caudate and microscopy reveals intranuclear inclusions containing aggregates of huntingtin protein. (Choice C)  Parkinson disease usually presents with bradykinesia, rigidity, and tremor.  Brain biopsy characteristically shows intracellular eosinophilic inclusions composed of α-synuclein (Lewy bodies). (Choice D)  Pick disease (frontotemporal dementia) typically presents with changes in personality/behavior and abnormal speech (eg, aphasia).  Individuals usually have pronounced frontotemporal brain atrophy, and silver staining shows round cytoplasmic inclusions containing aggregates of tau protein (Pick bodies). (Choice E)  Elderly individuals may develop cognitive impairment in association with depression ("pseudodementia"); however, neuritic plaques and amyloid angiopathy would not be seen. (Choice F)  Vascular dementia typically presents with sudden/stepwise cognitive decline in patients with cardiovascular risk factors and ischemic stroke.  The absence of glial scar formation on autopsy makes vascular dementia less likely in this patient. (Choice G)  Vitamin B12 deficiency is common in the elderly and may cause dementia, peripheral neuropathy, and/or subacute combined degeneration; however, neuritic plaques and amyloid angiopathy would not be seen. Educational objective: Amyloid is an abnormally folded (insoluble) extracellular protein that has apple-green birefringence when stained with Congo red and viewed under polarized light.  Alzheimer disease is associated with beta-amyloid deposits in the brain parenchyma (neuritic plaques) and walls of cerebral vessels (amyloid angiopathy). this also i forgot

An 18-year-old woman is brought to the emergency department by her parents for altered mental status that began today.  Two months ago, the patient began restricting her dietary intake due to fear of being overweight.  Since then, she has experienced notable weight loss and has felt weaker overall.  The patient's parents have been encouraging her to eat, and today, she agreed to eat watermelon and pineapple for breakfast.  Afterward, she fell while walking and appeared very somnolent.  The patient is otherwise healthy with no chronic medical conditions and takes no medications.  BMI is 16 kg/m2, decreased from 18.5 kg/m2 a few months ago.  The patient is oriented to name only and has a poor attention span.  Pupils are equal and reactive, but she has nystagmus and lateral gaze palsy.  Strength and sensations are equal in the bilateral extremities.  The patient walks in short steps and has difficulty maintaining her balance.  Abdominal and skin examinations are unremarkable.  Head imaging reveals no hemorrhage.  This patient's clinical findings are most likely due to which of the following? Wernicke encephalopathy Risk factors Chronic alcohol use (most common) Malnutrition (eg, anorexia, gastric bypass surgery) Pathophysiology Thiamine deficiency → impaired glucose metabolism & ATP production → neuronal injury/death (eg, mammillary bodies) May be precipitated by high metabolic demand or high glucose load Clinical findings Encephalopathy Oculomotor dysfunction Ataxia Management & prognosis Thiamine infusion reverses most symptoms. Memory impairment may be chronic/irreversible (Korsakoff syndrome). This patient has anorexia (eg, restricted diet, BMI of 16 kg/m2) and acutely developed encephalopathy, ataxia, and oculomotor dysfunction after ingesting glucose, findings suspicious for Wernicke encephalopathy (WE).  WE is a complication of thiamine (vitamin B1) deficiency and most commonly occurs in patients with chronic malnutrition (eg, chronic alcohol use, anorexia). Thiamine is a cofactor for several enzymes involved in glucose metabolism, and deficiency results in decreased glucose use and impaired ATP production.  In patients with low glucose intake, thiamine deficiency may be asymptomatic.  However, this patient ingested a large quantity of glucose, which likely rapidly depleted her limited thiamine stores. Without thiamine, cerebral energy production is impaired, increasing neuronal susceptibility to oxidative stress and causing disruption of the tight junctions that form the blood-brain barrier.  The resulting neuronal injury primarily affects areas of the brain with the highest metabolic demand and leads to the classic triad of WE: Encephalopathy (mammillary bodies):  somnolence, confusion, inattention Ataxia (cerebellum):  gait and balance disturbances Oculomotor dysfunction:  nystagmus, lateral gaze palsy (Choice A)  Anorexia increases the risk for deficiency of fat-soluble vitamins, such as vitamin E, an antioxidant that protects the cerebellum from reactive oxygen species.  Deficiency may result in ataxia, but encephalopathy and oculomotor dysfunction would not be expected. (Choice B)  Encephalopathy is common in patients with impaired hepatic clearance of ammonia; ataxia and nystagmus can also occur.  However, symptoms are usually insidious, not acute, in onset, and jaundice and asterixis would be expected. (Choice D)  Vitamin K is synthesized by gut microflora and is a cofactor for carboxylase enzymes involved in coagulation factor synthesis.  Patients with vitamin K deficiency are at increased risk for bleeding, such as a hemorrhagic stroke causing focal neurologic findings and/or altered mental status.  However, this patient's lack of hemorrhage on imaging is inconsistent with this diagnosis. (Choice E)  Clostridium botulinum is a spore-forming bacterium that produces a neurotoxin upon germinating which can cause cranial nerve motor dysfunction (eg, lateral gaze palsy) and descending muscle weakness.  However, this patient has normal extremity strength, and spore ingestion is mostly associated with infant botulism. Educational objective: Thiamine is a cofactor for several enzymes involved in glucose metabolism.  A complication of thiamine deficiency is Wernicke encephalopathy (encephalopathy, ataxia, oculomotor dysfunction), which can be precipitated by a high glucose load causing rapid depletion of limited thiamine stores.

​​​​​​​During a genetic study, several members of a family are found to have an abnormality affecting a gene located on chromosome 21.  The gene encodes a cell surface protein that is processed by proteolytic enzyme cleavage.  In the affected individuals, there is an increased number of hydrophobic fragments of the protein, which are prone to aggregation into insoluble fibrils.  Which of the following is the most likely result of the genetic abnormality in these individuals? The amyloid precursor protein (APP) gene (located on chromosome 21) encodes a transmembrane protein that is normally involved in synaptic formation and repair.  APP is processed in 1 of 2 pathways by a series of secretases (proteolytic enzymes): processing via the alpha- and gamma-secretase pathway, which does not result in amyloidogenic proteins, or processing via the beta- and gamma-secretase pathway, which results in the production of beta amyloid. If beta amyloid is not sufficiently cleared by cellular processes, it can form insoluble fibrils and contribute to the generation of extracellular amyloid plaques that accumulate in the brain.  These aggregates of beta amyloid are neurotoxic and associated with the development and progression of Alzheimer dementia, a disease characterized by accelerated neurodegeneration leading to progressive cognitive dysfunction.  As a result, patients who have abnormal APP processing, impaired beta-amyloid clearance, or production of higher levels of APP (eg, trisomy 21 [Down syndrome]) are at increased risk of developing Alzheimer dementia. (Choice A)  Patients with trisomy 21 have an increased risk of hematologic malignancies such as acute lymphoblastic leukemia and acute megakaryoblastic leukemia.  This is thought to be related to the high susceptibility of megakaryocytic and B-cell precursors to increased dosage of chromosome 21 genes. (Choice C)  Erythrocyte membrane distortion most often occurs with abnormalities affecting either the cytoskeleton (eg, spectrin/ankyrin in hereditary spherocytosis) or hemoglobin (eg, beta globin in sickle cell disease). (Choice D)  Pulmonary elastic tissue loss can occur when there is excessive alveolar elastin degradation (eg, alpha-1 antitrypsin deficiency).  Alpha-1 antitrypsin is a serine protease inhibitor that is synthesized in the liver and released into the systemic circulation. (Choice E)  Skeletal myofiber disruption (eg, muscular & myotonic dystrophy) can occur with numerous mutations affecting the internal cytoskeletal system and contractile components (eg, sarcomere, costamere proteins).  However, it is not typically related to impaired proteolytic cleavage and does not result in precipitation of insoluble fibrils. Educational objective: The amyloid precursor protein (APP) gene is located on chromosome 21 and encodes a cell-surface protein that can be degraded into beta amyloid.  Abnormal APP processing, impaired beta-amyloid clearance, and production of higher levels of APP are associated with the increased formation of the neurotoxic plaques that characterize Alzheimer dementia