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🧠 COMPLETE NEUROLOGY LECTURE - Pages 522 to 529

Imagine you are sitting in a classroom. Let's begin from the very first line and go through everything step by step.

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PAGE 522: SPINAL TRACT ANATOMY AND FUNCTIONS

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The Opening Statement

"Spinothalamic tract and dorsal column (ascending tracts) synapse then cross." "Corticospinal tract (descending tract) crosses then synapses."

• Ascending tracts = wires going UP from body to brain (carrying SENSORY information - what you feel)
• Descending tracts = wires going DOWN from brain to body (carrying MOTOR commands - what you move)

• Ascending tracts (spinothalamic + dorsal column) first SYNAPSE (connect at a relay station), THEN CROSS to the opposite side.
• Descending tract (corticospinal) first CROSSES, THEN SYNAPSES.

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THE THREE TRACTS - Side by Side Comparison

1. SPINOTHALAMIC TRACT (Pain and Temperature Highway)

• Plain English: This tract tells you when something is hot, cold, sharp, or painful. When you touch a hot stove and say "OUCH!" - that's this tract working.

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• Sensory nerve ending = The tiny receptor at your fingertip or skin that first detects the pain/temperature.
• Aδ fibers = Fast pain fibers. Sharp, immediate pain. Like when you prick your finger - the first "ouch."
• C fibers = Slow pain fibers. Dull, burning, aching pain. Like the throbbing that comes after.
• Pseudounipolar neuron = A special type of nerve cell shaped like the letter "T" - it has one long arm going to the skin and another arm going to the spinal cord. "Pseudo" means "fake" - it LOOKS like it has one process but actually has two merged together.
• Dorsal root ganglion = A small bundle (ganglion = cluster of nerve cell bodies) located just outside the spinal cord on the BACK (dorsal) side. Think of it as a mini-relay station sitting right next to your spine. This is where the cell body lives.
• → enters spinal cord = The message arrives at the spinal cord.

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• Posterior horn = The BACK part of the spinal cord's butterfly-shaped gray matter. "Posterior" = back. "Horn" = because it looks like a horn in cross-section.
• Here, the first neuron passes the baton to the second neuron. This handoff is called a SYNAPSE.

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• Decussates = Crosses to the opposite side. Fancy medical word for "crosses." (Remember: "Decussate" comes from the Latin letter "X" = decussation!)
• Anterior white commissure = The "bridge" of white matter (myelinated nerve fibers) at the FRONT of the spinal cord that the fibers use to cross over to the other side.
• Contralaterally = On the opposite side. "Contra" = against/opposite. "Lateral" = side.

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• VPL = Ventral Posterolateral nucleus of the Thalamus. The thalamus is like the brain's "telephone switchboard" - almost all sensory information passes through it before reaching consciousness.
• VPL specifically handles sensory information from the BODY (not the face - that's a different nucleus).

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• 1° (primary) somatosensory cortex = The part of your brain that CONSCIOUSLY feels sensations. Located in the parietal lobe (behind your forehead, near the top of your head).
• This is where the signal finally becomes a CONSCIOUS experience - you actually FEEL the pain.

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2. DORSAL COLUMN (Pressure, Vibration, Fine Touch - "Conscious Proprioception")

• Proprioception = Your body's ability to know where it is in space WITHOUT looking. Close your eyes and touch your nose - that's proprioception. This is why drunk people fail this test - alcohol disrupts this pathway!
• Fine touch = Distinguishing two points close together, feeling texture, reading Braille.
• Vibration = Feeling a tuning fork buzz on your bone.

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• Ipsilaterally = ON THE SAME SIDE. "Ipsi" = same.
• So the first neuron does NOT cross. It goes straight UP on the same side it came in.
• These fibers travel in bundles called:
  • Nucleus gracilis = carries info from LOWER limbs (below T6) - "Grace is slim and goes below" (gracilis = slender)
  • Nucleus cuneatus = carries info from UPPER limbs (above T6) - (cuneate = wedge-shaped)
  • Mnemonic from the book: "grass on the ground, clouds in the sky" - gracilis is like grass (lower), cuneatus is like clouds (upper)

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• Medulla = The lowest part of the brain stem - just above where your spinal cord enters your skull. Think of it as the brain's basement.
• The 1st synapse happens here in the medulla - much higher up than in the spinothalamic tract.

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• Now it crosses - but HIGHER UP in the medulla (not in the spinal cord like the spinothalamic).
• Medial lemniscus = The name of the fiber bundle after it crosses in the medulla. "Lemniscus" comes from Greek for "ribbon."

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CLINICAL PEARL: Why does the crossing level matter?

• Pain/temp (spinothalamic) is lost on the LEFT side (it already crossed in the spinal cord)
• Vibration/proprioception (dorsal column) is lost on the RIGHT side (it hasn't crossed yet - it crosses in the medulla)

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3. CORTICOSPINAL TRACT (Motor - Voluntary Movement)

• 1° motor cortex = Primary motor cortex, in the frontal lobe (front of the brain). This is where the "command" originates. Think of it as the brain's "command center."
• Descends ipsilaterally = Goes DOWN on the SAME side first.
• Posterior limb of internal capsule = A tight corridor of white matter deep in the brain. Very important because strokes here cause massive paralysis (many fibers pass through a small area).
• Cerebral peduncle = "Stalk" of the brain connecting the brain to the brainstem. "Peduncle" = little foot/stalk.
• Decussates at caudal medulla = Crosses at the LOWER part of the medulla.
• Pyramidal decussation = This crossing creates the "pyramids" on the front of the medulla - visible bumps you can see on a dissected brain. THIS is why the corticospinal tract is also called the "pyramidal tract."
• Descends contralaterally = After crossing, goes down on the OPPOSITE side.

• UMN (Upper Motor Neuron) = The neuron from the cortex to the spinal cord. "Upper" because it's higher up in the nervous system.
• LMN (Lower Motor Neuron) = The neuron from the spinal cord to the actual muscle. "Lower" because it's the final messenger to the muscle.
• LMN: leaves spinal cord (goes to the muscle via the NMJ)
• NMJ (Neuromuscular Junction) = Where the nerve meets the muscle. Like a plug socket - nerve is the plug, muscle is the socket.

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PAGE 522-523: CLINICAL REFLEXES

"Reflexes count up in order (main nerve root in bold)"

• Achilles reflex = S1, S2 - Tap the heel tendon → foot points down (plantarflexion). Mnemonic: "buckle my shoe" (1, 2 - buckle my shoe - from nursery rhyme "1, 2 buckle my shoe")
• Patellar reflex = L2, L3, L4 - Tap the knee → leg kicks forward. Mnemonic: "kick the door" (3, 4 - kick the door)
• Biceps and brachioradialis reflexes = C5, C6 - Tap the bicep/brachioradialis tendon → elbow flexes. Mnemonic: "pick up sticks" (5, 6 - pick up sticks)
• Triceps reflex = C6, C7, C8 - Tap the triceps tendon → elbow extends. Mnemonic: "lay them straight" (6, 7, 8 - lay them straight)

• 0 = Absent (like a dead wire - no signal getting through)
• 1+ = Hypoactive (sluggish - signal is weak, LMN problem)
• 2+ = Normal
• 3+ = Hyperactive (exaggerated - the brake is gone, UMN problem)
• 4+ = Clonus (rhythmic, involuntary jerking - severely hyperactive, serious UMN lesion)

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PRIMITIVE REFLEXES

"Primitive CNS reflexes present in healthy infants which disappear within 1st year of life due to inhibition from developing frontal lobe. Absent in neurologically intact adult. May reemerge in adults with frontal lobe lesions → loss of inhibition."

Moro Reflex

• Baby throws arms OUT then brings them back IN when suddenly surprised or feels like it's falling.
• Evolutionary reason: Baby grabbing onto mother.
• When it comes back in adults: frontal lobe damage, dementia.

Rooting Reflex

• Touch a baby's cheek → baby turns toward it with mouth open.
• Evolutionary purpose: Finding the nipple to feed.
• An adult with severe dementia or frontal lobe tumor may show this.

Sucking Reflex

• Touch the palate → baby sucks automatically.
• Again, feeding survival mechanism.

Palmar Reflex

• Stroke the palm → baby grabs your finger.
• You've probably seen babies grip your finger tightly!

Plantar Reflex (BABINSKI SIGN)

• Normal adult: Stroke the bottom of the foot → toes curl DOWN (plantarflexion).
• Abnormal (Babinski positive): Big toe goes UP, other toes fan out.
• Dorsiflexion = bending foot/toe UPWARD.
• A positive Babinski in a walking adult = UMN lesion (brain or upper spinal cord damage). This is one of the most famous signs in all of neurology.

Galant Reflex

• Baby held face-down, stroke along one side of spine → baby bends like a "C" toward that side.
• Tests spinal cord integrity in newborns.

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LANDMARK DERMATOMES

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PAGE 524: COMMON BRAIN LESIONS

Prefrontal Cortex

• Frontal lobe = The "CEO" of the brain. Controls planning, personality, impulse control, emotions.
• Disinhibition = Loss of social brakes. Patient says/does inappropriate things. Like the brain's filter is gone.
• Impulsivity = Acts without thinking.
• Abulia = Lack of motivation or initiative. Patient just sits there, won't initiate actions.
• Mutism = Not speaking.
• Executive function = Higher-order tasks: planning, organizing, decision-making.
• MCA (Middle Cerebral Artery) = The artery that supplies most of the lateral cortex including frontal lobe. The most commonly stroked artery.

Frontal Eye Fields

• Hemiplegia = paralysis of one side of body.
• The frontal eye fields move your eyes toward the OPPOSITE side. So when they're damaged, the eyes drift TOWARD the lesion side.
• Trick: Eyes LOOK AWAY from the paralyzed side (toward the lesion).

Paramedian Pontine Reticular Formation (PPRF)

• The PPRF is in the brainstem (pons). It moves eyes TOWARD its own side.
• When PPRF is damaged, eyes drift to the OPPOSITE side = toward the paralyzed side.
• This is the OPPOSITE pattern from frontal lobe lesions. Key exam distinction.

Dominant Parietal Cortex

• Dominant = Usually the LEFT hemisphere (in right-handed people - controls language and "academic" skills).
• Parietal lobe = Behind the frontal lobe, processes sensory information and spatial orientation.
• Gerstmann syndrome - damage to the LEFT inferior parietal lobe gives FOUR symptoms (all starting with inability):
  • Agraphia = Cannot write ("a" = without, "graphia" = writing)
  • Acalculia = Cannot calculate/do math
  • Finger agnosia = Cannot identify their own fingers when asked ("point to your ring finger" - they can't)
  • Left-right disorientation = Cannot tell left from right

Non-Dominant Parietal Cortex

• Non-dominant = Usually the RIGHT hemisphere.
• Hemispatial neglect = Patient IGNORES everything on the LEFT side of their world.
• Agnosia = Failure to recognize ("a" = without, "gnosis" = knowledge).
• A patient with right parietal damage may only eat from the right side of their plate, only draw the right side of a clock face, or only dress the right side of their body. They're not blind - they just don't "pay attention" to the left side.

Basal Ganglia

• Basal ganglia = Deep brain nuclei that smooth out and coordinate movements. Think of them as the brain's "movement editor."
• Tremor at rest = Shaking when NOT moving (typical of Parkinson's - the "pill-rolling" tremor).
• Chorea = Rapid, random, jerky involuntary movements. ("Chorea" = Greek for dance). Seen in Huntington's.
• Athetosis = Slow, writhing, sinuous involuntary movements. Like a snake moving.

Subthalamic Nucleus

• Subthalamic nucleus = Sits below the thalamus, part of the basal ganglia circuit.
• Hemiballismus = Wild, violent, flinging movements of one arm/leg. "Ballismus" = ball-throwing. Looks like the limb is being thrown around.
• Caused by a stroke in the subthalamic nucleus on the OPPOSITE side.

Mammillary Bodies

• Mammillary bodies = Small round structures at the base of the brain, part of the limbic system (memory circuit).
• Wernicke-Korsakoff syndrome = A severe brain disorder from thiamine (Vitamin B1) deficiency - classically seen in chronic alcoholics.
  • Wernicke's encephalopathy = ACUTE phase: confusion, eye movement problems (ophthalmoplegia), ataxia (unsteady gait) - "the drunk triad"
  • Korsakoff's psychosis = CHRONIC phase: severe memory loss, confabulation (making up memories to fill gaps)
• Bilateral = Both sides. Both mammillary bodies must be damaged.

Amygdala

• Amygdala = The brain's "emotional alarm center." Processes fear, anger, and emotional memory.
• Klüver-Bucy syndrome = Damage to BOTH amygdalae → the emotional brakes are gone:
  • Disinhibition = No fear, no normal social inhibitions
  • Hypersexuality = Inappropriate and excessive sexual behavior
  • Hyperorality = Putting everything in the mouth, examining objects with the mouth
  • Docility = Extreme calmness, no fear
• Seen in Alzheimer's (as it progresses), HSV-1 encephalitis (herpes virus loves the temporal lobe).

Hippocampus

• Hippocampus = The brain's "memory recorder." Critical for forming NEW memories.
• Anterograde amnesia = Cannot form NEW memories AFTER the injury. Old memories are intact but nothing new is recorded. ("Antero" = forward in time).
• Anoxia = Lack of oxygen to the brain. The hippocampus is one of the MOST sensitive areas to oxygen deprivation - it dies quickly.

Dorsal Midbrain

• Dorsal midbrain = Back part of the midbrain.
• Parinaud syndrome = Inability to look upward, plus pupil problems and other eye findings.
• Pineal gland tumors compress the dorsal midbrain from above, pushing down on the structures that control upward gaze.

Reticular Activating System

• Reticular activating system (RAS) = A network in the brainstem that keeps you AWAKE and conscious. It's your brain's "on switch."
• Damage → coma. The lights go out.

Medial Longitudinal Fasciculus (MLF)

• MLF = A bundle of fibers in the brainstem that coordinates both eyes to move TOGETHER.
• Internuclear ophthalmoplegia (INO) = The two eyes can't coordinate. When you look to the right:
  • The right eye goes right (normal)
  • The LEFT eye can't adduct (move inward to the right) properly
  • The left eye shows nystagmus (rhythmic jerking)
• Adduction = Moving eye toward the nose.
• Nystagmus = Rhythmic, involuntary eye movements.
• Classic in multiple sclerosis in young adults. Bilateral INO in a young person = MS until proven otherwise.

Cerebellar Hemisphere

• Cerebellum = The "fine-tuning computer" at the back of the brain. Makes movements smooth and accurate.
• Ipsilateral = SAME side - unlike most of the brain, the cerebellum controls the SAME side of the body.
• Ataxia = Loss of coordination. Walking like a drunk person (wide-based, staggering gait).
• Dysmetria = Can't judge distance accurately. Overshooting or undershooting when reaching for something (finger-nose test is abnormal).
• Intention tremor = Tremor that WORSENS as you approach your target (opposite of resting tremor in Parkinson's).

Cerebellar Vermis

• Vermis = The central strip of the cerebellum ("vermis" = worm-shaped).
• Truncal ataxia = The trunk (core/torso) is unstable. Wide, staggering gait.
• Dysarthria = Slurred, poorly articulated speech (not a language problem - the muscles of speech are uncoordinated). Different from aphasia!
• Chronic alcohol classically destroys the vermis first.

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ABNORMAL MOTOR POSTURING

Decorticate (Flexor) Posturing

• Decorticate = Loss of cortex function ("de" = removal of, "corticate" = cortex).
• Position: Arms FLEXED (bent in, toward chest), legs EXTENDED (straight out).
• Mnemonic: "hands near the CORE/heart" = decortiCATE = CATerpillar position.
• Lesion is ABOVE the red nucleus (in the cerebral cortex/white matter).
• Red nucleus = A structure in the midbrain involved in motor control.
• Rubrospinal tract = From red nucleus downward. In decorticate posturing, this tract is INTACT (lesion is above it), so it drives the arms into flexion.

Decerebrate (Extensor) Posturing

• Decerebrate = Loss of cerebrum and midbrain influence ("decerebrate" = as if no cerebrum).
• Position: BOTH arms AND legs EXTENDED (stiff like a board).
• Lesion is LOWER - between the red nucleus and the vestibular nuclei (in the midbrain or pons).
• Worse prognosis than decorticate. The lower the lesion, the more brainstem is involved, the worse the outcome.
• Mnemonic: decereBRATE = stiff like a board = extension.

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PAGE 525: ISCHEMIC BRAIN DISEASE / STROKE

Opening statement:

• Hypoxia = Insufficient oxygen supply.
• Brain cells are incredibly sensitive - after just 5 minutes without oxygen, they begin to die irreversibly.
• This is why CPR and rapid treatment of stroke are emergencies.

• CA1 region = A specific section of the hippocampus, most sensitive to oxygen deprivation.
• Neocortex = The outer "thinking" layer of the brain.
• Purkinje cells = Large, specialized neurons in the cerebellum that coordinate movement.
• Watershed areas = Regions at the border between two arteries' territories - like a village at the border of two countries. When blood pressure drops, these areas get the least blood. They're "at the end of the line."

• tPA (tissue Plasminogen Activator) = The clot-busting drug given for ischemic stroke. You CANNOT give it if there's bleeding, because it would make bleeding catastrophically worse.
• CT scan = Fast, widely available. Can QUICKLY rule out hemorrhage. But it takes 6-24 hours to SEE the actual infarct (dead tissue).
• Diffusion-weighted MRI (DWI) = More sensitive. Can detect ischemia within 3-30 MINUTES. The gold standard for early stroke detection.

HISTOLOGIC TIMELINE OF STROKE

• Eosinophilic cytoplasm = The neuron's inside turns PINK/RED when stained (eosin = pink dye). This is the "red neuron" of early infarct.
• Pyknotic nuclei = The cell's nucleus shrinks and becomes dark. Sign of cell death.
• Neutrophils = First responders of the immune system - arrive 24-72 hours.
• Macrophages/Microglia = The brain's own cleanup crew. Arrive at day 3-5 to eat dead debris. Microglia are the brain's resident macrophages.
• Reactive gliosis = Astrocytes (brain's support cells) proliferate and form a scar. Like scar tissue after a skin wound, but in the brain.
• Glial scar = The final healed product. The cavity fills with fluid and glial tissue.

Types of Ischemic Stroke (3 types):

1. Thrombotic

• A blood clot forms RIGHT THERE in the brain artery.
• Atherosclerotic plaque = A buildup of fat/cholesterol inside the artery wall - like rust inside a pipe. When it ruptures, a clot forms on top.

2. Embolic

• Embolus = A clot (or other material) that forms SOMEWHERE ELSE and travels through the bloodstream to block a brain artery.
• Atrial fibrillation (AF) = Irregular heart rhythm → blood pools in the heart → clots form → travel to brain. Most common cardiac cause of embolic stroke.
• Carotid artery stenosis = Narrowing of the neck artery → plaques break off → travel to brain.
• DVT (Deep Vein Thrombosis) = Blood clot in leg veins.
• Patent foramen ovale (PFO) = A hole between the two sides of the heart that should close at birth but doesn't in some people. A leg clot can travel through this hole directly to the brain ("paradoxical embolism" - bypasses the lungs).
• Infective endocarditis = Infection of heart valves → infected clumps (septic emboli) travel to brain.

3. Hypoxic

• Not caused by a blocked artery - caused by global LOW blood flow to the whole brain.
• Hypoperfusion = Low blood flow (eg, cardiac arrest, severe shock).
• Hypoxemia = Low oxygen in the blood.
• Affects WATERSHED areas first because they're already getting the least blood.

Treatment:

• tPA must be given within 4.5 hours of stroke onset (window of opportunity).
• Thrombectomy = Physical removal of clot using a catheter (mechanical clot retrieval) - for large vessel blockages.
• Secondary prevention = Aspirin/clopidogrel (blood thinners), controlling risk factors.

CEREBRAL EDEMA (Brain Swelling)

• Parenchyma = The actual functional tissue of the brain (not blood vessels, not supporting tissue).
• ICP (Intracranial Pressure) = Pressure inside the skull. The skull is a rigid box - anything that takes up more space raises pressure. High ICP is dangerous because it compresses the brain.

1. Cytotoxic edema = Water enters cells themselves (intracellular). Caused by Na-K-ATPase pump failure due to oxygen deprivation. The pump that normally keeps water OUT of cells stops working, water floods in. Seen early in ischemic stroke.
2. Vasogenic edema = Breakdown of the Blood-Brain Barrier (BBB) → fluid leaks from blood vessels into brain tissue. Caused by tumors, abscesses, inflammation.
3. Vasogenic edema from high ICP itself can cause pressure to further increase (vicious cycle).

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PAGE 526: EFFECTS OF STROKES BY ARTERY

ANTERIOR CIRCULATION

Anterior Cerebral Artery (ACA)

• The ACA feeds the MEDIAL (inner) surface of the brain, which controls the LEGS and FEET.
• Think of the brain like a homunculus (little man) draped over the cortex - the leg area is at the top/inner surface.
• Contralateral = Opposite side.
• ACA stroke → OPPOSITE leg is weak and numb. Arms are largely spared.
• Urinary incontinence = Loss of bladder control because the area that inhibits bladder emptying is also in this territory.

Middle Cerebral Artery (MCA)

• The MCA is the LARGEST cerebral artery, supplying most of the lateral (outer) brain surface.
• Controls arms and face more than legs.
• Wernicke's area = Posterior temporal lobe - understanding language.
• Broca's area = Inferior frontal lobe - producing language.
• MCA stroke on the LEFT (dominant) side → Aphasia (language problems).
• MCA stroke on the RIGHT (non-dominant) side → Hemineglect (ignoring the left side of the world).
• Wernicke aphasia note: "associated with right superior quadrant visual field defect due to temporal lobe involvement" - the optic radiations (visual pathway) pass through the temporal lobe, so temporal damage can affect the visual field too.

Lenticulostriate Artery

• These are TINY deep arteries branching off the MCA.
• Striatum = Part of the basal ganglia (caudate + putamen).
• Internal capsule = Dense corridor of motor and sensory fibers deep in the brain.
• Causes PURE MOTOR STROKE = Only weakness, no language/neglect/visual problems (because cortex is spared).
• Lacunar infarct = A small, deep stroke in the internal capsule or brainstem, caused by microatheroma or lipohyalinosis (damage to small vessel walls from chronic hypertension).
• Lipohyalinosis = The small vessel wall becomes thick and glassy from years of high blood pressure - like thickened rust inside a small pipe.

POSTERIOR CIRCULATION

Posterior Cerebral Artery (PCA)

• PCA supplies the OCCIPITAL LOBE (primary visual cortex).
• Contralateral hemianopia = Loss of vision in the opposite visual HALF-FIELD. "Hemi" = half, "anopia" = no vision.
• Macular sparing = The central vision (macula) is PRESERVED. This is because the macula gets dual blood supply (from both PCA and MCA collaterals). A unique feature of PCA strokes.
• Alexia without agraphia = Can WRITE but cannot READ. Very strange deficit!
• Splenium of corpus callosum = Back part of the bridge connecting the two brain hemispheres. When damaged, visual information from the right hemisphere can't reach the left (language) hemisphere, so the patient can't read even though their vision is intact.
• Prosopagnosia = Cannot recognize FACES. "Prosopo" = face, "agnosia" = not knowing. They can see fine but can't tell who anyone is. Very specific to right occipital/temporal area.

• CN III (Oculomotor nerve) = Cranial nerve 3, controls most eye movements + eyelid + pupil constriction.
• CN III palsy → Eye looks "down and out" + drooping eyelid + dilated pupil.
• Ipsilateral CN III palsy + contralateral hemiplegia = The characteristic "crossed syndrome" of Weber. The nerve and the motor tract are close but separate, so both are damaged.

Basilar Artery

• RAS (Reticular Activating System) = Keeps you conscious.
• If the RAS is preserved → patient is AWAKE but completely paralyzed = LOCKED-IN SYNDROME (described as "locked in the basement").
• Locked-in syndrome = Patient is fully conscious but cannot move anything except possibly vertical eye movements and blinking. Terrifying condition. They can only communicate by blinking.
• Quadriplegia = Paralysis of all four limbs.

Anterior Inferior Cerebellar Artery (AICA)

• LMN facial nerve lesion = ENTIRE face paralyzed (forehead + lower face). Like Bell's palsy.
• UMN cortical lesion = Only LOWER face paralyzed (forehead is spared because it gets bilateral cortical input).

• Horner syndrome = Damage to sympathetic chain → drooping eyelid (ptosis) + small pupil (miosis) + dry half-face (anhidrosis) on the SAME side as the lesion.

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PAGE 529 (continued): POSTERIOR INFERIOR CEREBELLAR ARTERY (PICA) - LATERAL MEDULLARY SYNDROME

• CN IX (Glossopharyngeal) and CN X (Vagus) control swallowing and voice.
• Dysphagia = Difficulty swallowing.
• Hoarseness = Rough, raspy voice.

• This is the HALLMARK of lateral medullary syndrome: pain/temp loss is crossed - contralateral body BUT ipsilateral face. This is because the face fibers cross at a different level.

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PAGE 528: INTRACRANIAL HEMORRHAGE

Epidural Hematoma

• Epidural = "Epi" = above, "dural" = dura mater (tough outer covering of brain). Blood collects ABOVE the dura.
• Middle meningeal artery = An artery that runs in a groove inside the skull. Very vulnerable to fractures.
• Pterion = The thinnest part of the skull (meeting point of 4 bones at the temple). One punch to the temple can fracture this.
• Classic presentation: Brief loss of consciousness → LUCID INTERVAL (patient wakes up, seems fine) → rapid deterioration as blood accumulates → unconscious again.
• "Lucid interval" = The temporary recovery period. Blood builds up slowly enough that the patient initially seems okay.

Subdural Hematoma

• Bridging veins = Veins that stretch from the brain surface to the venous sinuses. In elderly people with brain atrophy (shrunken brain), these veins are stretched longer and more vulnerable to tearing.
• Subdural = Blood collects BELOW the dura, above the arachnoid.
• Can occur with minimal trauma in elderly/alcoholics.

Subarachnoid Hemorrhage (SAH)

• Subarachnoid = Blood in the space UNDER the arachnoid membrane, around the brain.
• Saccular (berry) aneurysm = A berry-shaped ballooning of a brain artery wall. Rupture causes explosive hemorrhage.
• "Worst headache of my life" = The classic description - sudden, thunderclap headache. A red flag that demands immediate investigation.
• Xanthochromic LP = Lumbar puncture (spinal tap) shows yellow-tinged fluid (xanthochromia = yellow color from blood breakdown products). Confirms SAH even if CT is negative.
• Vasospasm = Blood in the subarachnoid space irritates arteries → they go into spasm → secondary ischemic stroke. Treated with nimodipine (a calcium channel blocker for vasospasm).

Intraparenchymal Hemorrhage

• Intraparenchymal = Bleeding INTO the brain tissue itself.
• Charcot-Bouchard microaneurysms = Tiny aneurysms that form in small vessels from chronic high blood pressure. They rupture and cause this type of hemorrhage.
• Most common locations: putamen, globus pallidus (basal ganglia), pons, and cerebellum.
• Lobar hemorrhages = If the bleed is in the outer part (lobes), think cerebral amyloid angiopathy (in elderly) or AVM.

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PAGE 529: THALAMIC PAIN SYNDROME / PHANTOM LIMB PAIN / DIFFUSE AXONAL INJURY / APHASIA

Thalamic Pain Syndrome

• Neuropathic pain = Pain from nerve damage itself, not tissue injury.
• Allodynia = Non-painful stimuli (like a light touch or breeze) cause PAIN. Imagine a feather touch on your arm feeling like a burn.
• Hyperalgesia = Normally painful things feel EVEN MORE painful.
• Dysesthesia = Abnormal, unpleasant sensations - burning, electric shocks.
• This is notoriously TREATMENT-RESISTANT.

Phantom Limb Pain

• After amputation, the brain's map (somatosensory cortex) doesn't immediately erase the missing limb's area. It "reorganizes" - neighboring areas take over, causing confused signals that feel like they come from the missing limb.
• Very real pain for amputees.

Diffuse Axonal Injury

• Axonal = Involving axons (the long "wires" of nerve cells).
• Shearing = Tearing force - the brain continues moving inside the skull when the head suddenly stops.
• White matter (myelinated axons) is torn throughout.
• Punctate = Tiny, multiple, dot-like hemorrhages on MRI.

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APHASIA TABLE (Language Problems)

• Aphasia = A problem with the CONTENT of language (what is said/understood). The brain's language processing is damaged.
• Dysarthria = A problem with the MOTOR ACT of speech (slurred, poorly coordinated words). Like someone talking with a numb mouth. The language content is normal.

• BROCA = Can't BREAK out words. "Broca = Broken speech." Understands fine but can't speak.
• WERNICKE = Speaks fluent WRONG. "Wernicke = Wordy but no sense." Hears but doesn't understand.

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NEONATAL INTRAVENTRICULAR HEMORRHAGE

• Germinal matrix = A fragile, highly vascular region present in developing fetal brains that normally disappears before term birth.
• Fontanelle = The soft spot on a baby's skull (where bones haven't fused). Bulging = high pressure inside.
• Premature babies can't regulate their own blood pressure well, and their germinal matrix is fragile.

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EXTRACRANIAL INJURIES (Birth Injuries)

Caput Succedaneum

• Common birth swelling. Just fluid accumulation in scalp soft tissue.
• Goes ACROSS suture lines (unlike cephalhematoma).
• Resolves on its own.

Subgaleal Hemorrhage

• Between the skull and the galea (tough scalp layer). Large potential space - can collect significant blood.

Cephalohematoma

• Subperiosteal = Under the periosteum (bone covering).
• Does NOT cross suture lines (opposite of caput succedaneum).
• Can cause jaundice as the blood breaks down.

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Summary: The Big Picture

1. Sensory tracts carry signals UP to the brain - each taking a different route and crossing at different levels.
2. Motor tracts carry commands DOWN from the brain - crossing high up in the medulla.
3. Reflexes tell us which level is damaged.
4. Dermatomes map the skin to spinal levels.
5. Brain lesions each produce characteristic syndromes you can identify by their features.
6. Stroke follows arterial territories - know which artery = know the syndrome.
7. Hemorrhage types differ by location and vessel.
8. Aphasia types depend on which language area is damaged.

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