High-Yield Neuroanatomy and Stroke Management

Stroke risk factors

The two most important risk factors for stroke (cerebral infarction) on USMLE are hypertension and atrial fibrillation.

Hypertension (HTN)

A strong systolic impulse pounds the carotid arteries, leading to endothelial damage and increased development of atherosclerotic plaques (carotid stenosis), which then launch off to the brain/eye.

Atrial fibrillation (AF)

Results in turbulence and stasis, leading to left atrial mural thrombus, which launches off.

Hypertension prevalence

Hypertension is most common in the population for causing stroke.

Blood pressure control

Blood pressure control is more important than smoking cessation for decreasing stroke risk.

AF vs HTN in stroke

If the USMLE Q gives you a patient who has both AF and HTN, they want AF as the most important risk factor.

Carotid stenosis

Occurs from HTN, where an atheromatous plaque has launched off.

Circle of Willis

A network of arteries at the base of the brain that supplies blood to the brain.

ACA stroke

Anterior cerebral artery stroke leads to motor/sensory abnormalities of contralateral leg.

MCA stroke

Middle cerebral artery stroke leads to motor/sensory abnormalities of contralateral arm + face.

Dominant MCA stroke

Usually left MCA stroke can lead to Wernicke or Broca aphasia.

Non-dominant MCA stroke

Usually right MCA stroke can cause hemispatial neglect (inability to draw clockface).

PCA stroke

Posterior cerebral artery stroke leads to contralateral homonymous hemianopsia with macular sparing.

Prosopagnosia

Inability to recognize faces, associated with PCA stroke.

Lateral medullary syndrome

Also known as Wallenberg syndrome, the answer for dysphagia + ipsilateral Horner syndrome after a stroke.

PICA stroke

Causes dysphagia and is associated with lateral medullary syndrome.

Horner syndrome

Ipsilateral miosis, partial ptosis, anhidrosis, can be caused by Pancoast tumor or lateral medullary syndrome.

Medial medullary syndrome

The answer for ipsilateral tongue deviation after a stroke.

Lateral pontine syndrome

The answer for ipsilateral Bell's palsy after a stroke.

AICA stroke

Causes lateral pontine syndrome, which is associated with Bell's palsy.

Weber syndrome

Midbrain stroke that results in ipsilateral CN III palsy (down and out eye) + contralateral spastic hemiparesis.

Locked-in syndrome

Basilar artery stroke that results in inability to move entire body except for eyes.

Gerstmann syndrome

Stroke of angular gyrus of parietal lobe.

Tetrad

1) agraphia (inability to write); 2) acalculia (cannot do math); 3) finger agnosia (can't identify fingers); 4) left-right disassociation (cannot differentiate between left and right sides of body).

Hemiballismus

Stroke of subthalamic nucleus causing 'ballistic' flailing of contralateral arm and/or leg.

Lenticulostriate strokes

Strokes affecting small lenticulostriate arteries deep within the brain, often leading to lacunar infarcts.

Lacunar infarcts

Ischemia within small vessels leading to necrosis and reabsorption of tissue, resulting in tiny cavities called lacunae.

Charcot-Bouchard microaneurysms

Tiny (<1mm) aneurysms that form within lenticulostriate arteries that can bleed and cause hemorrhagic strokes.

Liquefactive necrosis

The answer for necrosis of nervous system tissue.

Red neurons

Strong eosinophilic (pink) staining seen acutely with ischemic infarction of the CNS.

Microglia

Resident macrophages of the CNS that phagocytose necrotic brain/spinal tissue.

Astrocytes

Glial cells that proliferate and become a glial scar (gliosis) in the CNS.

Wallerian degeneration

Degradation of an axon/myelin sheath distal to the site of injury, with regrowth occurring at a maximum of 1mm/day.

Optic nerve

Considered an extension of the CNS and myelinated by oligodendrocytes; degeneration results in permanent blindness.

Vertebrobasilar insufficiency

Condition related to blood flow issues in the vertebral artery affecting brain perfusion.

Subclavian steal syndrome

Condition caused by narrowing/stenosis of the proximal subclavian artery leading to lower pressure in the vertebral artery.

Dizziness

A potential neuro finding in subclavian steal syndrome due to backflow of blood in the vertebral artery.

Blood pressure difference

A sign of subclavian steal syndrome, where blood pressure is different between the two arms.

Pure motor hemiparesis

A specific syndrome that can manifest from lacunar infarcts.

Pure sensory stroke

Another specific syndrome that can manifest from lacunar infarcts.

Ataxic hemiparesis

A specific syndrome that can manifest from lacunar infarcts.

HTN

Hypertension can cause lipohyalinosis leading to lacunar infarcts.

Lipohyalinosis

A fancy term for microatheroma formation in small lenticulostriate arteries.

CNS

Central Nervous System, where astrocytes and microglia play crucial roles.

PNS

Peripheral Nervous System, where Schwann cells can regenerate myelin.

Oligodendrocytes

Cells in the CNS that do not effectively regenerate myelin post-injury.

CN VII

Cranial nerve associated with Bell's palsy, which has better regenerative potential compared to the optic nerve.

Blood pressure difference between arms

Indicates potential aortic dissection or subclavian steal syndrome.

CT or MR angiography

Next best step in diagnosis for conditions related to blood pressure differences.

Vertebral artery stenosis

Presents with unexplained dizziness without blood pressure differences between arms, caused by atherosclerosis.

Vertebrobasilar insufficiency

A broader term for patients with either subclavian steal syndrome or vertebral artery stenosis.

Vertebral artery dissection

A false lumen in a vertebral artery that can lead to stroke due to clot formation.

Heparin for vertebral artery dissection

Recommended treatment for patients who have experienced posterior stroke due to vertebral artery dissection.

Wernicke aphasia

Fluent aphasia characterized by nonsensical speech and impaired comprehension, caused by L-sided MCA infarct.

Broca aphasia

Non-fluent aphasia with telegraphic speech and normal comprehension, caused by L-sided MCA infarct.

Conductive aphasia

Impaired repetition due to stroke of the arcuate fasciculus connecting Wernicke and Broca areas.

Global aphasia

Combination of Broca and Wernicke aphasias with impaired repetition, caused by stroke affecting Broca, Wernicke areas, and arcuate fasciculus.

Transcortical sensory aphasia

Similar presentation to Wernicke's aphasia but with intact repetition.

Transcortical motor aphasia

Similar presentation to Broca's aphasia but with intact repetition.

Ischemic stroke diagnosis

Non-contrast CT of the head is done to differentiate between ischemic and hemorrhagic stroke.

tPA administration

Given for ischemic stroke within 4.5 hours of symptom onset if no contraindications are present.

4.5-hour window for tPA

Refers to the time since the patient was last confirmed normal before stroke symptoms appeared.

Aspirin for ischemic stroke

Recommended if the 4.5-hour window has elapsed after stroke onset.

185/110

Blood pressure control for tPA: BP should be below ___before administering tPA.

Hemorrhagic stroke treatment

Do not give tPA; first step is to lower blood pressure.

Labetalol, nicardipine, hydralazine

Medications used to lower blood pressure in hemorrhagic stroke.

hemorrhagic

Non-contrast CT findings: Blood appears as bright (hyperdense) areas on CT in cases of __stroke.

Contrast CT

Used for diagnosing conditions like brain abscess and malignancy, not for suspected bleeds.

Stroke of arcuate fasciculus

Leads to conductive aphasia due to impaired repetition.

Frontal lobe stroke

Causes Broca's aphasia.

Temporal lobe stroke

Causes Wernicke's aphasia.

Systolic BP reduction

Reduce BP rapidly to systolic <140 mm Hg.

Anticoagulation reversal

Reverse anticoagulation if the patient is on it (i.e., FFP for patients on warfarin).

Cerebral edema

Correction of hypernatremia too quickly with hypotonic saline can cause cerebral edema.

Central pontine myelinolysis

Correcting hyponatremia too quickly with hypertonic saline causes central pontine myelinolysis.

Osmotic demyelination

Can be described as 'osmotic demyelination.'

Locked-in syndrome

Central pontine myelinolysis causes locked-in syndrome.

Hypercalcemic crisis

Refers to cognitive dysfunction / a delirium-like state in the setting of severe hypercalcemia, often due to malignancy or primary hyperparathyroidism.

Delirium

USMLE wants you to know that high calcium, as well as any sodium disturbance, can cause ___

Treatment for hypercalcemia

First step on USMLE for Tx of hypercalcemia is normal saline.

Bisphosphonate therapy

After normal saline, USMLE wants bisphosphonate therapy (I've seen pamidronate listed on NBME).

Pseudotumor cerebri

Term that refers to increased intracranial pressure in the setting of no clear structural cause.

Papilledema

Q can mention papilledema (optic disc swelling) or absent venous pulsations on fundoscopy (another increased ICP buzzy finding).

Reye syndrome

Cerebral edema and hepatotoxicity seen with administration of aspirin to children (and sometimes adolescents) during a viral infection.

Beta-oxidation impairment

Thought to be due to impairment of beta-oxidation, but USMLE doesn't care.

Diffuse axonal injury

Deceleration injury (e.g., car accident) followed by severe cognitive and/or motor/sensory dysfunction.

MRI findings in diffuse axonal injury

USMLE can show MRI showing scattered hyperintense (white) lesions.

Spinothalamic tract

Pain and temperature sensation from contralateral body.

Decussation point

Cross-over (decussation) point is in spinal cord, meaning if, e.g., the left spinothalamic tract is damaged, we lose pain and temperature on the right side of the body below the lesion.

Corticospinal tract

Motor function from ipsilateral body.

Dorsal columns

Carry vibration + proprioception from ipsilateral body.

Tabes dorsalis

Dorsal column lesion caused by neurosyphilis.

Romberg test

If the dorsal columns are disrupted, patient will have (+) ___ which is where he/she falls over when standing with eyes closed.

Upper motor neuron findings

Lesion of the corticospinal tract presents as hyperreflexia, hypertonia, clonus, Babinski sign.

Lower motor neuron findings

Lesion involving the motor neuron from the anterior horn until the muscle itself presents as hyporeflexia, hypotonia/flaccidity, fasciculations.

Syringomyelia

9/10 Qs will give bilateral loss of pain and temperature due to lesion of anterior white commissure (decussation point for spinothalamic tract).

Corticospinal Tract Involvement

Maybe 1/3 of Qs will also involve corticospinal tract, where you'll see some impaired motor function in addition to the bilateral loss of pain/temperature.

Impaired Motor Function

1/10 Qs will not mention pain/temperature loss but instead just give impaired motor function, where it sounds nothing like syringomyelia, but you're forced to eliminate to get there (on a 2CK Neuro CMS form).

Brown-Sequard Syndrome

Ipsilateral loss of vibration + proprioception (dorsal columns).

Brown-Sequard Syndrome

Ipsilateral loss of motor function (corticospinal tract).