A 65-year-old woman is found dead in her house.  The family notes that she had difficulty walking over the past few months.  The woman had a history of atrial fibrillation treated with anticoagulation therapy.  Autopsy reveals bruising of the scalp.  Intracranially, there is a large epidural hemorrhage with brain herniation.  In addition, the spinal cord shows symmetric myelin layer vacuolization and axonal degeneration involving the posterior columns and the lateral corticospinal tracts.  Which of the following is the most likely cause of this woman's spinal cord findings? s woman with recent gait impairment likely died due to a head injury from a fall (scalp bruising); her anticoagulation therapy placed her at increased risk for intracranial hemorrhage and subsequent brain herniation.  Evidence of myelin degeneration in the dorsal columns and lateral corticospinal tracts on autopsy is suspicious for vitamin B12 deficiency, the likely cause of her ataxia. Vitamin B12 deficiency is classically associated with megaloblastic anemia due to impaired DNA synthesis in rapidly dividing hematologic cells.  However, vitamin B12 is also essential for myelin generation and maintenance (via methylation of myelin basic protein); deficiency often results in neurologic symptoms due to impaired myelination in the following regions: Dorsal columns:  diminished tactile/vibratory sensation and proprioception, resulting in sensory ataxia (eg, Romberg sign) Lateral corticospinal tracts:  upper motor neuron signs (eg, muscle weakness, spastic paresis), Babinski reflex Spinocerebellar tracts:  ataxia (loss of unconscious proprioception) Peripheral nerves:  numbness, paresthesia, hyporeflexia The pattern of spinal cord damage is referred to as subacute combined degeneration, given the degeneration of both ascending (dorsal columns, spinocerebellar tracts) and descending (lateral corticospinal tracts) pathways. (Choice A)  Amyotrophic lateral sclerosis is a neurodegenerative disorder that affects upper and lower motor neurons.  Damage to the lateral corticospinal tract occurs, but anterior horn damage is also characteristic and not seen in this woman.  Moreover, sensory pathways are usually spared, so dorsal column damage would not be expected. (Choice B)  Multiple sclerosis is marked by asymmetric, focal areas of CNS demyelination.  This woman's symmetric damage to specific spinal cord tracts would be atypical. (Choice C)  Syringomyelia, a cyst within the spinal cord, can lead to central spinal cord injury involving crossing fibers from the spinothalamic tracts within the anterior white commissure.  This woman's autopsy did not reveal a cyst, and extensive dorsal column damage would be unusual. (Choice D)  Tabes dorsales (neurosyphilis) is associated with damage to the dorsal columns and dorsal nerve roots; however, the lateral corticospinal tracts are generally not affected. (Choice E)  Thiamine deficiency causes Wernicke encephalopathy (ataxia, confusion, oculomotor dysfunction).  Unlike in this woman, histopathology shows demyelination in the brain (eg, mammillary bodies, thalamus), not the spinal cord. Educational objective: Vitamin B12 (cobalamin) deficiency can cause subacute combined degeneration due to impaired myelination in the ascending dorsal columns and spinocerebellar tracts (diminished position/vibration sense, ataxia), as well as the descending lateral corticospinal tracts (eg, muscle weakness, spastic paresis). 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. ( USMLE SSTEP 1 oriented)

i dont want table style distractor normal lines and dont seperate every text according to number with line

perefect continue like this for all patterns next

A 16-year-old boy is being evaluated for difficulty walking.  On physical examination, he has thoracic scoliosis and multiple small scars on his hands.  When asked about these, the boy replies, "I frequently burn my hands by accident because I can't feel the heat."  Neurologic examination reveals 1+ biceps reflexes and 3+ patellar reflexes bilaterally, as well as decreased muscle strength in the bilateral upper and lower extremities.  His hand muscles are atrophic, and position and vibration senses in the feet are also impaired.  Which of the following is the most likely cause of this patient's problems? his patient has chronic loss of upper extremity pain and temperature sensations, upper extremity weakness and hyporeflexia, lower extremity weakness and hyperreflexia, and kyphoscoliosis.  These findings are consistent with syringomyelia. In syringomyelia, a central cystic dilation in the cervical spinal cord (a syrinx) slowly enlarges, characteristically causing damage to the ventral white commissure and anterior horns.  The ventral white commissure is the site of decussation of second-order lateral spinothalamic tract neurons, and the ventral horns are the site of lower motor neuron cell bodies.  The syrinx is most commonly situated at the C8-T1 cord levels and may extend rostrally, caudally, and centrifugally.  Further expansion within the cervical cord in later stages of the disease can produce lower extremity weakness and hyperreflexia (an upper motor neuron defect) by affecting the lateral corticospinal tract and can also lead to loss of position and vibration senses in the feet due to involvement of the posterior columns.  Scoliosis can occur due to paresis of paravertebral muscles. (Choice A)  Amyotrophic lateral sclerosis is a progressive degenerative disease of upper and lower motor neurons only; it does not cause sensory loss. (Choice B)  Guillain-Barré syndrome is a peripheral nervous system autoimmune demyelinating polyneuropathy that typically causes lower motor neuron manifestations (eg, areflexia, weakness) in a symmetric ascending pattern. (Choice C)  Medulloblastoma is the most common malignant central nervous system (CNS) tumor in children, with pilocytic astrocytoma, a low-grade astrocytoma, being the most common CNS tumor overall.  Medulloblastoma is a posterior fossa tumor that causes symptoms related to obstructive hydrocephalus. (Choice D)  Multiple sclerosis is an autoimmune CNS demyelinating disorder that presents with episodic neurologic symptoms reflecting defects in various white matter tracts. (Choice E)  Normal pressure hydrocephalus is characterized by gait ataxia and urinary incontinence.  It is rare in patients age <60.  Defective cerebrospinal fluid resorption by the arachnoid granulations gives rise to the secondary form of this disease. Educational objective: The combination of fixed segmental loss of upper extremity pain and temperature sensations, upper extremity lower motor neuron signs, and/or lower extremity upper motor neuron signs in the setting of scoliosis suggests syringomyelia.

A 26-year-old man is brought to the emergency department after a high-speed motorcycle collision.  The patient was thrown several feet after his motorcycle collided with a car.  On arrival, he is profoundly comatose.  A CT scan of the head performed within an hour of the event shows no abnormalities.  The patient dies several hours later, and autopsy examination is performed.  Brain histopathology shows widespread axonal swelling, predominantly at the gray-white junction.  Immunohistochemical staining of these axons reveals accumulation of alpha-synuclein and amyloid precursor proteins.  Which of the following is the most likely cause of these observed findings? is patient has histopathologic findings of diffuse axonal injury (DAI), a type of severe traumatic brain injury that can occur from direct blunt force injury (eg, head hitting windshield) or abrupt changes in acceleration-deceleration (eg, restrained passenger coming to sudden stop after a collision).  Transfer of force can result in immediate shearing of the white matter tracts or induce secondary biochemical changes leading to degradation of the axonal cytoskeleton with subsequent axon breakage.  Normal axonal transport is inhibited, leading to accumulation of axonally transported proteins (eg, amyloid precursor, alpha-synuclein) within axonal swellings at the point of injury (eg, axonal bulb formation). Presentation varies based on the extent of injury; most patients are comatose (Glasgow Coma Score <8); however, those with very mild DAI may have only concussive symptoms (eg, headache, amnesia).  CT scan has low sensitivity for diagnosis and is often normal, but MRI may demonstrate lesions at the gray-white junction.  Microscopically, DAI is visible as widespread axonal swelling, most pronounced at the gray-white matter junction.  Prognosis is poor, with up to 25% of cases resulting in death. (Choices A and C)  Diffuse cerebral hypoperfusion typically occurs in the setting of systemic hypotension or cardiac arrest.  Watershed zone infarctions or diffuse edema with blurring of the gray-white junction are often visible on imaging.  Ischemic neurons can release glutamate, leading to overactivation of the NMDA receptor with continuous membrane depolarization.  This results in neuronal damage in a process known as excitotoxicity.  Red neurons with intensely eosinophilic cytoplasm are seen on histopathology. (Choice B)  Disruption of the bridging cortical veins results in subdural hematoma; the elderly are at increased risk due to cerebral atrophy (stretching of the bridging veins increases the risk of tear).  Subdural hematomas are visible on imaging as crescent-shaped hyperdensities that cross suture lines. (Choice E)  Subarachnoid hemorrhages are typically caused by rupture of saccular aneurysms but may be associated with trauma (typically with associated brain contusions); head CT scan demonstrates blood within the subarachnoid space. Educational objective: Diffuse axonal injury (DAI) is a type of traumatic brain injury that results from disruption of the white matter tracts.  Microscopically, DAI is visible as widespread axonal swelling, most pronounced at the gray-white matter junction, with accumulation of transport proteins (eg, amyloid precursor, alpha-synuclein) at the site of injury.

A 45-year-old man is brought to the emergency department after sustaining a traumatic head injury in a motor vehicle collision.  The patient was found unresponsive and had several generalized tonic-clonic seizures during transport.  Medical history includes hypertension as well as alcohol and cocaine misuse.  Temperature is 36.7 C (98.1 F), blood pressure is 170/96 mm Hg, pulse is 50/min, and respirations are 10/min.  Pulse oximetry shows 98% on mechanical ventilation with 50% oxygen.  On examination, the patient is comatose with midpositioned and fixed pupils and rigid extension of the upper and lower extremities.  Noncontrast CT scan of the head is shown in the image below: his patient who sustained a traumatic head injury has an extensive intraparenchymal hemorrhage that is likely complicated by brain herniation.  Intracranial (eg, intraparenchymal) hemorrhage can cause significant mass effect and increase intracranial pressure, which can manifest with seizures and Cushing triad (hypertension, bradycardia, bradypnea).  With further hemorrhagic expansion, horizontal shifts in midline structures or brain herniation may occur. Progressive pupillary abnormalities are common in herniation.  Uncal herniation initially disrupts the ipsilateral oculomotor nerve (CN III) leading to a fixed dilated pupil; however, as the brainstem becomes inferiorly displaced (ie, central herniation), damage to the midbrain and upper pons typically results in bilateral midpositioned and fixed pupils due to loss of both sympathetic and parasympathetic innervation. Brain herniation also causes abnormal posturing from disruption of descending tracts (eg, rubrospinal, vestibulospinal) typically involved in reflexive and postural movements.  The vestibulospinal tract maintains extensor tone and originates from vestibular nuclei at the pontomedullary junction.  The rubrospinal tract regulates upper extremity flexor tone and originates from the red nuclei in the rostral midbrain; it is inhibited by descending cortical input from the cerebral cortex. Damage above the red nucleus (eg, cerebral hemisphere, internal capsule) typically results in decorticate (flexor) posturing due to loss of descending inhibition of the red nucleus and subsequent hyperactivity of upper limb flexors (Choices B and D). Damage below the red nucleus (eg, pons) or to the nucleus itself (eg, midbrain) often causes decerebrate (extensor) posturing due to loss of descending excitation to the upper limb flexors (via the rubrospinal tract) and extensor predominance (due to unopposed vestibulospinal tract output). (Choice A)  Damage to the cerebellar vermis usually affects balance and coordination of the axial/proximal limb muscles, resulting in gait and truncal ataxia.  Cerebellar vermis injury may also result in nystagmus and vertigo due to this structure's role in vestibular function. (Choice C)  The cervical spinal cord is commonly damaged in the setting of closed-head injury, which may lead acutely to flaccid quadriplegia/spinal shock (ie, absence of flexor and extensor motor tone) due to loss of excitatory input from the descending motor pathways. (Choice F)  Damage to the substantia nigra can result in excessive inhibition of the thalamus with subsequent decrease in excitation of the motor cortex.  This leads to motor features of Parkinson disease (eg, rigidity, bradykinesia, tremor). (Choice G)  The thalamus is a major relay station for motor and sensory information and also help regulate alertness and consciousness.  Although bilateral damage to the thalamus may result in coma, flexor/extensor posturing is not characteristic of thalamic injury. Educational objective: Brain herniation causes abnormal posturing due to disruption of descending motor tracts (eg, rubrospinal, vestibulospinal).  Damage above the level of the red nucleus (eg, cerebral hemispheres, internal capsule) typically results in decorticate (flexor) posturing.  Damage at or below the red nucleus (eg, midbrain to pons) typically results in decerebrate (extensor) posturing

A 28-year-old woman with a history of type 1 diabetes mellitus comes to the emergency department due to abdominal pain, nausea, and vomiting.  Laboratory testing reveals severe hyperglycemia, high anion gap metabolic acidosis, and an elevated beta-hydroxybutyrate level.  While being evaluated in the emergency department, the patient develops involuntary, rhythmic jerking of her right upper extremity that lasts for about a minute.  She remains fully alert during and after the event.  The patient has never had similar symptoms in the past and has no other medical conditions.  Physical examination shows no weakness or sensory loss in the right upper extremity.  Which of the following is the most likely diagnosis? Seizure types Medication Generalized onset (both hemispheres) Tonic-clonic LOC & postictal state Diffuse contraction (tonic) → jerking (clonic) Broad spectrum*: levetiracetam, valproic acid Myoclonic No LOC & no postictal state Brief jerking movements Atonic Sudden loss of muscle control → drop to floor Absence Brief staring episodes Automatisms may be present No postictal state Ethosuximide (only for absence) Focal onset (single hemisphere) Aware Aware during the event & no postictal state Motor (eg, head turn) or sensory (eg, smell) Narrow spectrum: phenytoin,** carbamazepine, gabapentin Impaired awareness Appears awake but consciousness is altered Automatisms present (eg, lip smacking) Postictal state *Can be used for both generalized & focal seizures. **Can be used for management of status epilepticus. LOC = loss of consciousness. This patient with abdominal pain, vomiting, hyperglycemia, anion gap metabolic acidosis, and elevated beta-hydroxybutyrate has diabetic ketoacidosis.  Metabolic derangements (eg, hyperglycemia, acidosis) in patients with diabetic ketoacidosis may cause neurologic dysfunction manifesting as altered mental status, focal neurologic deficits, and/or seizures. Seizures occur due to abnormal, synchronous discharges of neurons in the cerebral cortex.  They are classified as focal onset if they originate from a localized region of a single cerebral hemisphere or generalized if they involve both hemispheres at onset.  Focal seizures can be subclassified based on level of consciousness. Focal seizures with retained awareness:  Patients remain awake and interactive. Focal seizures with impaired awareness:  Patients appear awake but do not interact appropriately (eg, blank stare).  A postictal state (eg, confusion, sedation) is common. The manifestations of focal seizure depend on the brain region in which the seizure activity is occurring.  This patient's episodic right upper limb rhythmic jerking suggests a focal seizure with retained awareness originating in the contralateral motor cortex. (Choice A)  Acute dystonia is a sustained, involuntary muscle contraction resulting in painful, abnormal posturing (eg, torticollis).  It can be idiopathic or provoked by exposure to dopamine antagonists (eg, haloperidol, prochlorperazine, metoclopramide).  Rhythmic jerking is more consistent with seizure activity. (Choice C)  Generalized absence seizure involves both hemispheres at onset and presents as a brief (<10 sec) staring spell with impaired consciousness.  It typically occurs in children, and patients may have hundreds of episodes in a day. (Choice D)  Generalized tonic-clonic seizure is characterized by loss of consciousness with diffuse, bilateral muscle contractions of the limbs followed by rhythmic jerking.  Associated features may include tongue biting and urinary/bowel incontinence. (Choice E)  Hemiballism is characterized by involuntary, unilateral movements that are nonrhythmic and have a large amplitude; they often appear as dramatic, random (eg, unpredictable) arm flinging or kicking.  Hemiballism is considered an extreme form of chorea and can occur in Huntington disease or after a stroke in the subthalamic nucleus. (Choice F)  Motor tics are sudden, brief movements that may include arm jerking but are characterized by an overwhelming urge to perform the movement followed by feelings of relief.  They can be voluntarily suppressed for brief periods. Educational objective: Seizures are classified as focal onset if they originate from a localized region of a single cerebral hemisphere or generalized if they involve both hemispheres at onset.  Focal seizures can be subclassified as retained awareness (patients remain interactive) or impaired awareness (patients appear awake but do not interact appropriately).  Manifestations of a focal seizure depend on the brain region in which the seizure activity occurs.