A 61-year-old man is brought to the emergency room with slurred speech. According to the patient's wife, they were watching a movie together when he developed a minor headache. He soon developed difficulty speaking in complete sentences, at which point she decided to take him to the emergency room. His past medical history is notable for hypertension and hyperlipidemia. He takes aspirin, lisinopril, rosuvastatin. The patient is a retired lawyer. He has a 25-pack-year smoking history and drinks 4-5 beers per day. His father died of a myocardial infarction, and his mother died of breast cancer. His temperature is 98.6°F (37°C), blood pressure is 143/81 mmHg, pulse is 88/min, and respirations are 21/min. On exam, he can understand everything that is being said to him and is able to repeat statements without difficulty. However, when asked to speak freely, he hesitates with every word and takes 30 seconds to finish a short sentence. This patient most likely has an infarct in which of the following vascular distributions?

Superior division of the middle cerebral artery

Proximal middle cerebral artery

Inferior division of the middle cerebral artery

Middle cerebral artery and posterior cerebral artery watershed area

Anterior cerebral artery and middle cerebral artery watershed area

A 76-year-old woman with hypertension and coronary artery disease is brought to the emergency department after the sudden onset of right-sided weakness. Her pulse is 83/min and blood pressure is 156/90 mm Hg. Neurological examination shows right-sided facial drooping and complete paralysis of the right upper and lower extremities. Tongue position is normal and she is able to swallow liquids without difficulty. Knee and ankle deep tendon reflexes are exaggerated on the right. Sensation to vibration, position, and light touch is normal bilaterally. She is oriented to person, place, and time, and is able to speak normally. Occlusion of which of the following vessels is the most likely cause of this patient's current symptoms?

Contralateral lenticulostriate artery

Ipsilateral anterior cerebral artery

Contralateral middle cerebral artery

Ipsilateral posterior inferior cerebellar artery

A 78-year-old right-handed man with hypertension and hyperlipidemia is brought to the emergency department for sudden onset of nausea and vertigo one hour ago. Physical examination shows 5/5 strength in all extremities. Sensation to light touch and pinprick is decreased in the right arm and leg. A CT scan of the brain shows an acute infarction in the distribution of the left posterior cerebral artery. Further evaluation of this patient is most likely to show which of the following findings?

Right-sided homonymous hemianopia

Right-sided superior quadrantanopia

A 75-year-old woman presents with sudden loss of vision. She says that she was reading when suddenly she was not able to see the print on half of the page. Her symptoms started 4 hours ago and are accompanied by a severe posterior headache. Vital signs reveal the following: blood pressure 119/76 mm Hg, pulse 89/min, SpO2 98% on room air. The patient was unable to recognize her niece when she arrived to see her. A noncontrast CT of the head shows no evidence of hemorrhagic stroke. What is the most likely diagnosis in this patient?

Posterior cerebral artery stroke

A 65-year-old man presents with facial weakness. He says he noticed that his face appeared twisted when he looked in the bathroom mirror this morning. He is otherwise well and does not have any other complaints. He denies any facial pain or paresthesia. No significant past medical history. The patient is afebrile and vital signs are within normal limits. Neurological examination reveals difficulty shutting the right eye tight and inability to bring up the right corner of his mouth when asked to smile. Remainder of the exam, including the left side of the face, is unremarkable. Which of the following is the most likely diagnosis in this patient?

Left middle cerebral artery stroke

A 36-year-old woman, gravida 1, para 1, has back pain and numbness in her lower extremities after an emergency cesarean delivery of a healthy 3856-g (8-lb, 8-oz) newborn male. She had a placental abruption and lost approximately 2000 ml of blood. During the procedure, she received two units of packed red blood cells and intravenous fluids. She has no history of serious illness and takes no medications. She is sexually active with one male partner, and they use condoms inconsistently. She is alert and oriented to person, place, and time. Her temperature is 37.2°C (98.9°F), pulse is 90/min, respirations are 15/min, and blood pressure is 94/58 mm Hg. Examination shows decreased sensation to temperature and pinprick below her waist and 0/5 muscle strength in her lower extremities. She feels the vibrations of a tuning fork placed on both of her great toes. Deep tendon reflexes are absent in the lower extremities and 2+ in the upper extremities. Which of the following is the most likely diagnosis?

Anterior spinal artery syndrome

Posterior spinal artery syndrome

Middle cerebral artery territory for USMLE Step 2 CK: High-Yield Anatomy Lessons

MCA Anatomy - The Brain's Superhighway

Origin: Largest terminal branch of the Internal Carotid Artery (ICA).
Course: Travels laterally through the Sylvian fissure to the cerebral convexity.

Circle of Willis and major arteries

Segments & Branches:
- M1 (Sphenoidal): Gives off critical lenticulostriate arteries supplying deep structures.
- M2 (Insular): Branches run over the insular cortex.
- M3 (Opercular): Emerges from the Sylvian fissure.
- M4 (Cortical): Fans out to supply the lateral cerebral cortex.

⭐ The lenticulostriate arteries arising from the M1 segment are thin-walled end-arteries, making them a common site for lacunar infarcts in chronic hypertension.

MCA Supply Zones - Prime Real Estate

Lateral Cortical Surface: As the largest cerebral artery, it perfuses the majority of the lateral hemisphere.
- Frontal Lobe: Primary motor cortex (contralateral face & upper limb), Broca's expressive speech area (dominant hemisphere).
- Parietal Lobe: Primary somatosensory cortex (face & upper limb), angular and supramarginal gyri (language processing).
- Temporal Lobe: Primary auditory cortex and Wernicke's receptive speech area (dominant hemisphere).
Deep Penetrating Branches (Lenticulostriate Arteries):
- These small, thin-walled vessels supply deep structures: basal ganglia (putamen, globus pallidus) and the internal capsule.

⭐ The lenticulostriate arteries are "arteries of stroke." As end-arteries lacking collaterals, they are highly vulnerable to hypertensive damage, causing lacunar infarcts in the basal ganglia and internal capsule.

MCA Stroke - When the Highway Closes

Cortical vascular territories of cerebral arteries

The MCA is the most commonly affected vessel in ischemic stroke. Clinical signs are contralateral and depend on the hemisphere involved and superior/inferior divisions.

Dominant Hemisphere (Left MCA)
- Aphasia: Broca's (expressive, inferior division), Wernicke's (receptive, superior division), or Global.
- Contralateral hemiparesis & sensory loss (face and arm > leg).
- Contralateral homonymous hemianopia.
Non-Dominant Hemisphere (Right MCA)
- Hemispatial Neglect: Ignoring the contralateral side of the body and space.
- Anosognosia: Unawareness of the deficit.
- Contralateral hemiparesis & sensory loss (face and arm > leg).

⭐ Gerstmann syndrome (acalculia, agraphia, finger agnosia, left-right disorientation) can occur with dominant parietal lobe involvement.

📌 Mnemonic (FAST): Face drooping, Arm weakness, Speech difficulty, Time to call 911.

High‑Yield Points - ⚡ Biggest Takeaways

The MCA is the most common artery involved in an ischemic stroke.

Occlusion causes contralateral paralysis and sensory loss, affecting the face and upper limb more than the lower limb.

Dominant hemisphere (usually left) strokes often lead to aphasia (Broca's or Wernicke's).

Non-dominant hemisphere (usually right) strokes can cause contralateral hemineglect.

Visual deficits include contralateral homonymous hemianopia.

Lenticulostriate branches supply deep structures like the basal ganglia and internal capsule.

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