Partial MCA syndromes occur due to the following
- Cortical collateral blood flow
- Differing arterial configurations
- Partial syndromes can also occur due to emboli that enter the proximal MCA without complete occlusion, occlude distal MCA branches, or fragment and move distally.
Partial syndromes due to embolic occlusion of a single branch results in
- Hand, or arm and hand, weakness alone (brachial syndrome)
- Facial weakness with nonfluent (Broca) aphasia with or without arm weakness (frontal opercular syndrome).
- A proximal superior division occlusion of dominant lobe- A combination of sensory disturbance , motor weakness, nonfluent aphasia suggests that an embolus has occluded the proximal superior division and large portions of the frontal and parietal cortices is infarcted
- Inferior division occlusion dominant hemisphere- a fluent (Wernicke’s) aphasia without weakness, the inferior division of the MCA that supply the posterior part (temporal cortex) of the dominant hemisphere is probably involved. Jargon speech and an inability to comprehend written and spoken language are prominent features. It is often accompanied by a contralateral, homonymous superior quadrantanopia.
- inferior division of the MCA in the nondominant hemisphere -Hemineglect or spatial agnosia without weakness indicates that the inferior division of the MCA in the nondominant hemisphere is involved.
Occlusion of a lenticulostriate vessel from MCA produces small-vessel (lacunar) stroke within the internal capsule.
This will result in
- Pure motor stroke
- Sensory-motor stroke contralateral to the lesion.
- Ischemia within the genu of the internal capsule produce
- Primarily facial weakness followed by arm then leg weakness as the ischemia extends posteriorly within the capsule.
- The contralateral hand may become ataxic and dysarthria will be prominent (clumsy hand, dysarthria lacunar syndrome).
- Lacunar infarction affecting the globus pallidus and putamen has only few clinical signs such as parkinsonism and hemiballismus
