Answer: As a major artery that provides blood to the cortex, a stroke of that affects the middle cerebral artery can result in muscle weakness, paralysis, or aphasia.
Brain tissue colored in red indicates areas innervated by the middle cerebral artery. Image from https://en.wikipedia.org/wiki/Middle_cerebral_artery
The middle cerebral artery (MCA) is one of the three major paired arteries that deliver blood to the cortex of the brain. MCA sends blood predominantly into the temporal lobe, but also into the frontal, parietal, and insular lobes of the cerebrum, as well as some subcortical structures such as the caudate and thalamus. (The two other major paired cerebral arteries are the posterior cerebral artery, the PCA, and anterior cerebral artery, the ACA.)
Anatomically, the MCA is a major branch off the internal carotid artery. It is made up of 4 main branches.
M1, or the sphenoidal segment, is closely associated with the sphenoid bone, the plate of the skull just anterior to the temporal bone. The M1 branch is responsible for delivering blood into the basal ganglia along with branches of the ACA.
M2 is also called the insular segment. It is responsible for bringing oxygenated blood into the insula.
M3, or the opercular segment, also brings blood into the insula.
M4 is the terminal region, and sends blood to the surface of the lateral and ventral aspects of the cortex, reaching out from the lateral sulcus (Sylvian fissure.)
Of the blood vessels in the brain, the MCA is the most clinically significant blood vessel. The middle cerebral artery is often damaged in acute stroke, a cardiovascular injury that could result in occlusion of the blood vessel, depriving neural tissue of oxygenated blood, or rupture of the vessels, leading to blood in the extracellular space, which is also toxic to neurons. Because the different branches of the MCA send blood into so many different brain areas, any stroke of this artery can lead to a wide variety of symptoms.
Weakness or paralysis of the contralateral face or arm. This means that if the stroke occurs in the left MCA, the right half of the face and right arm may experience weakness or paralysis. Accompanying the motor deficits, they often also experience a sensory loss, such as numbness.
When the stroke affects the left MCA, the patient may likely experience some form of aphasia, a deficit of language. Aphasia can range in severity, and manifest in different ways. (Language functions are often lateralized to the left hemisphere, which is why a left hemisphere stroke more often leads to aphasia compared to a right hemisphere stroke. But, for some people, their right half of the brain is more dominant for language.) Aphasias may present as a difficulty in the production of language (also called expressive aphasia, or Broca's aphasia.) Alternatively, aphasia may result in a difficulty to comprehend language (also called receptive aphasia, or Wernicke's aphasia.) Over time, patients with aphasia resulting from stroke are able to restore much of their language function.
Treatment of middle cerebral artery stroke
The most important first step to treatment of a stroke is to identify the nature of the stroke. Even though an initial diagnosis can be made through observation and a neurological exam, further imaging tests such as a CAT scan or an MRI scan will be used to make a more accurate diagnosis.. A stroke may take two different forms.
Ischemic stroke. An ischemic stroke happens when blood flow through the artery is occluded, generally because of a blood clot. These blood clots can form at the site of the artery (called a thrombotic stroke), or they may form outside of the brain, then travel into the artery through the circulatory system (called an embolic stroke). Generally, MCA strokes are embolic ischemic strokes. The treatment regimen for ischemic stroke of the MCA is giving a clot busting drug, such as tissue plasminogen activator (TPA) or blood thinners. These drugs are given under careful clinical supervision. These drugs are most effective when given within a short time window after the onset of stroke symptoms, usually measured in hours (Thrombolysis for Acute Ischemic Stroke in the Extended Time Window). Importantly, the correct diagnosis about the nature of the stroke is critical, since these drugs may worsen the symptoms if the stroke is not ischemic.
Hemorrhagic stroke. In a hemorrhagic stroke, the artery busts open, and blood spills into the brain. Head trauma or chronic hypertension are some common risk factors that can lead to a hemorrhagic stroke. Hemorrhagic strokes are much less common than ischemic strokes, and need to be treated differently. Medications that lower blood pressure may be given here, and depending on the severity of the stroke, emergency surgery may be required to decrease the bleeding and stop the swelling on the brain.