Stroke Syndromes

1. MCA — Middle Cerebral Artery

The most common stroke. MCA supplies the lateral brain surface — motor cortex for face and arm, language areas, and the parietal lobe.

The hallmark: contralateral face and arm weakness with leg spared. 🔑MCA = Most Common Artery, Most of the surface. Face and arm are surface structures. Leg hangs in the fissure where ACA lives.

Dominant hemisphere (usually left): Broca's aphasiaNon-fluent aphasia. Broca's area is in the frontal lobe (superior MCA division). Patient understands you but can't produce fluent speech — short, effortful phrases. "Broca's = Broken speech." Mechanism: motor planning for speech requires intact Broca's area. When it's infarcted, the mouth can move but the brain can't sequence the words. (superior division) or Wernicke's aphasiaFluent but nonsensical speech. Wernicke's area is in the temporal lobe (inferior MCA division). Patient speaks fluently but says gibberish — and doesn't realize it. "Wernicke's = Wordy but Wrong." Mechanism: comprehension requires decoding sounds into meaning via the posterior temporal cortex. Without it, words go in but don't register. (inferior division).

Non-dominant hemisphere (usually right): contralateral neglectThe patient ignores the entire opposite side of their world. Ask them to draw a clock — all numbers crammed on one side. The non-dominant parietal lobe handles spatial awareness for the contralateral space. When damaged, that space ceases to exist for the patient. It's not a visual problem — they can SEE the left side, they just don't attend to it. — patient ignores the opposite side of the world.

2. ACA — Anterior Cerebral Artery

ACA runs along the interhemispheric fissureThe deep groove between the two cerebral hemispheres. The medial brain surface — where the leg motor cortex sits — tucks into this fissure. ACA is the only artery going in there, which is why it's the only one that causes isolated leg weakness. — the medial brain surface. That's where the leg representation on the motor homunculusThe "little man" mapped onto the motor cortex. The body is laid out along the cortical surface: face and arm on the lateral side (MCA territory), leg on the medial side (ACA territory). The leg literally hangs over the top of the brain into the fissure between hemispheres. lives.

The hallmark: contralateral leg weakness with face and arm spared. The exact opposite of MCA.

ACA also supplies medial frontal lobe, so you may see:

• Personality changes — disinhibition or apathy
• AbuliaSevere lack of will or motivation. Patient lies there, barely responds, won't initiate anything — not because they can't, but because the drive is gone. Medial frontal damage disrupts the "motivation circuit" (cingulate cortex). The brain's starter motor is broken. — loss of motivation, akinetic mutism
• Urinary incontinence — medial frontal cortex controls bladder inhibition

3. PCA — Posterior Cerebral Artery

PCA supplies the occipital lobe — the visual cortexPrimary visual cortex (V1) sits at the very back of the brain. ALL visual information from both eyes converges here. PCA is the sole blood supply. Damage = you lose the visual field on the opposite side. The visual pathways cross at the optic chiasm, so right PCA damage = left visual field loss in BOTH eyes.. Nothing motor lives back here.

The hallmark: contralateral homonymous hemianopia — loss of vision on the opposite side in BOTH eyes. No motor weakness whatsoever. "Can't see but can move."

Key detail: macular sparingCentral visual field is often preserved in PCA strokes. Why? The macular area of the visual cortex has dual blood supply — it gets blood from BOTH the PCA AND a small branch of the MCA. So even when PCA is blocked, the macula still gets fed. Patient says: "I can see things right in front of me but everything to the side is gone." — the center of vision is often preserved because the macular cortex has dual blood supply (PCA + MCA collaterals).

4. PICA — Vertebrobasilar / Wallenberg Syndrome

PICA occlusion causes lateral medullary syndromeWallenberg syndrome (Adolf Wallenberg, 1895). The lateral medulla contains: (1) spinal trigeminal nucleus — ipsilateral face pain/temp, (2) spinothalamic tract — contralateral body pain/temp (already crossed below), (3) nucleus ambiguus — swallowing and voice, (4) vestibular nuclei — balance, (5) descending sympathetics — Horner's. One tiny infarct hits ALL five. — Wallenberg syndrome. This stroke pattern is completely different from all others.

The hallmark: CROSSED findings — ipsilateral face + contralateral body. 🔑PICA = Picks Ipsilateral face, Crosses the body Anyway

The full Wallenberg constellation:

• Vertigo, nystagmus — vestibular nuclei damaged
• Dysphagia, hoarseness — nucleus ambiguus (CN IX/X)
• Ipsilateral Horner's syndromePtosis + miosis + anhidrosis on the SAME side as the stroke. Why ipsilateral? Descending sympathetic fibers run through the lateral medulla BEFORE exiting the CNS. They haven't crossed yet. Left medulla damage = left Horner's. Another piece of the "ipsilateral face" pattern. — ptosis, miosis, anhidrosis
• Ipsilateral face — loss of pain/temperature (spinal trigeminal nucleus)
• Contralateral body — loss of pain/temperature (spinothalamic tract already crossed)

5. Lacunar Strokes — Small Vessel Disease

Lacunar strokes hit deep structures — internal capsuleA compact bundle of motor and sensory fibers between the thalamus and basal ganglia. ALL motor fibers from the cortex funnel through here on the way to the spinal cord. A tiny infarct here causes complete contralateral hemiparesis — but because it's below the cortex, there are NO cortical signs., thalamus, basal ganglia, pons. Small perforating arteries, usually from chronic hypertension.

The hallmark: pure motor or pure sensory. One thing. Nothing else. The plainness IS the diagnosis.

Classic lacunar syndromes:

• Pure motor hemiparesis — internal capsule or pons. Face, arm, leg equally weak. No sensory loss.
• Pure sensory stroke — thalamus. Numbness/tingling one side. No weakness.
• Ataxic hemiparesis — weakness + clumsiness same side
• Dysarthria-clumsy handLacunar syndrome from a pontine infarct. Slurred speech + clumsy hand, but NO aphasia. Key distinction from Broca's: Broca's = can't PRODUCE language (cortical). Dysarthria = language is fine but articulation is slurred (subcortical). Broca's = MCA. Dysarthria-clumsy hand = lacunar. — pons

Why It Crosses

Two tracts run through the lateral medulla side by side:

• Spinal nucleus of CN V (trigeminal) — carries face pain/temp. Hasn't crossed yet — stays ipsilateral. Damage = ipsilateral face loss.
• Spinothalamic tract — carries body pain/temp. Already crossed in the spinal cord, far below the medulla. Damage = contralateral body loss.

Same lesion, same side of the brainstem — but the tracts crossed at different levels. That's why you get ipsilateral face + contralateral body.