What deficit is seen in left inferior division Middle Cerebral Artery (MCA) infarcts?

Left Inferior Division MCA Infarct Deficits

Left inferior division MCA infarcts characteristically produce Wernicke's aphasia (receptive aphasia with impaired comprehension), right homonymous hemianopsia, and right hemisensory loss, without significant motor deficits. 1

Primary Language Deficit

• Wernicke's aphasia is the hallmark deficit, presenting as fluent speech with impaired comprehension, paraphasic errors, and poor repetition. 1
• Superselective angiographic testing of the inferior division of the left MCA consistently produces dense Wernicke's aphasia, confirming this territory's critical role in language comprehension. 1
• The severity of word comprehension impairment correlates directly with the magnitude of perfusion delay in Wernicke's area (Brodmann area 22), which is supplied by the inferior division. 2
• Lexical-semantic deficits (impaired understanding of word meaning) are the core feature, distinguishing this from Broca's aphasia seen in superior division infarcts. 2

Visual Field Deficits

• Right homonymous hemianopsia occurs due to involvement of the optic radiations coursing through the temporal and parietal lobes supplied by the inferior division. 3
• This visual field cut affects the right visual field in both eyes and is a consistent finding in posterior MCA territory involvement. 4

Sensory Deficits

• Right hemisensory loss affecting the face, arm, and leg can occur, though typically less severe than in complete MCA territory infarcts. 3
• The sensory deficit may be more prominent in the face and arm compared to the leg due to the somatotopic organization of sensory cortex. 3

Critical Distinguishing Features

• Motor function is typically preserved or minimally affected, as the motor cortex and corticospinal tract are supplied by the superior division of the MCA, not the inferior division. 1
• This absence of significant hemiplegia distinguishes inferior division infarcts from superior division or complete MCA territory infarcts. 1, 5
• Patients maintain the ability to move the right arm and leg, which differentiates this presentation from the dense hemiplegia seen in superior division or complete MCA strokes. 5

Additional Neuropsychological Deficits

• Right-sided neglect may occur but is less prominent than in right hemisphere strokes. 3
• Visual-spatial processing deficits are generally absent, as these functions are predominantly right hemisphere-mediated. 4

Clinical Pitfall

• The preserved motor function can lead to underestimation of stroke severity, particularly when language deficits are attributed to confusion rather than aphasia. 4
• Clinicians must specifically test comprehension (not just speech fluency) and visual fields to avoid missing this diagnosis. 2