Neuro Pathophysiology - Stroke Syndromes

Let's do a little discussion on Stroke syndromes. If you want to learn about the introduction to strokes, you should do well you check my blog posts, I have written posts on strokes, and you can also do brief readings on other sites for a general understanding of strokes. Today, I will be discussing the neuro deficit presentation of patients with certain ischemic strokes and I will start by explaining the vessels that supply the brain I will be looking at some areas of the brain and the clinical manifestations that would be displayed.

Starting with the Middle Cerebral Artery, which is the artery that supplies the frontal lobe, the lateral side of the parietal lobe, and the lateral side of the temporal lobe. At the frontal lobe, the Middle Cerebral Artery supplies the primary motor cortex, so an occlusion or a blockage to the artery would mean blood won't get to the primary motor cortex which means that there will inability to move the contralateral part of the body where the Primary motor cortex locates. If the left primary motor cortex isn't supplied, then the right upper part side of the body will be paralyzed. This will lead to Contralateral Hemaplegia of the face and the upper extremities. The primary somatosensory cortex can also lack blood leading to a contralateral lack of senses, causing sensory loss of the face and the upper extremities. When the Middle Cerebral Artery that supplies the Frontal lobe is affected, it would affect the frontal eye fields, causing an Ipsilateral gaze deviation of the eye. The Middle Cerebral Artery also supplies the Wernickes area at the temporal lobe. The Wernicke area is responsible for the understanding of language both auditory and non-auditory, either passing through the auditory cortex, or the visual cortex to the Wernicke's area. If there is an occlusion to the inferior division of the Middle Cerebral Artery affecting the Wernicke's area, then there will be difficulty with the comprehension of language and also there will be an obstruction with its communication with the Broca's area thereby preventing expression of language. The occlusion of the MCA to the Wernicke's area would lead to Aphasia. An MCA lesion that affects the inferior region can affect the Optic radiation through the temporal lobe as well as the parietal lobe causing optic dysfunctions such as contralateral visual field loss (contralateral homonymous hemianopia). If there is an occlusion or lesion towards the right Middle Cerebral Artery (MCA), which is the less dominant hemisphere, it can lead to aplasia.^{, ,}

Another syndrome after the Middle Cerebral Artery syndrome, is the Anterior Cerebral Artery syndrome (ACA syndrome). The medial frontal and the medial parietal lobe are supplied by the Anterior Cerebral Artery, thereby supplying the medial portion of the primary somatosensory cortex and the primary motor cortex. A lesion of the Anterior Cerebral Artery, at the medial region of the same regions of the Medial Cerebral artery, it would affect the lower extremities, and contralateral sensory loss of the lower extremities. When it affects the paracentral lobule there will be urinary incontinence and fecal continence. When it affects the prefrontal cortex, which is responsible for emotions, personalities, decisions, behavior, and the anterior cingulate cortex which is responsible for memory and the limbic system, it will lead to Abulia (reduction in response to stimuli and decrease willingness, and desire to perform activity), and akinetic mutism.^{, ,}

In cases of Middle Cerebral Artery and Anterior Cerebral Artery watershed zone where both arteries meet, if there is a lesion at that point then it will cause a defect in the proximal upper extremities and the proximal lower extremities which includes motor and sensory loss of both extremities.^,

The Internal Carotid Artery (ICA) syndrome would occur when there is a lesion in the internal carotid artery. The internal carotid artery branches to give the common carotid arteries which then give the Middle Cerebral Artery Anterior Cerebral Artery, and the ophthalmic artery. The Internal Carotid Artery Feeds the anterior circulation of the circle of Willis. If there is an occlusion or obstruction to the ICA, then there will be a decrease of blood or lack of blood flow to the Middle Cerebral Artery and the Anterior Cerebral Artery. This will present with both Middle Cerebral Artery and Anterior Cerebral Artery clinical conditions.^{, ,}

The Posterior Cerebral Artery supplies the brain stem (midbrain), the occipital lobe, and the thalamus. When there is a lesion to the Posterior Cerebral Artery in the midbrain affecting the third nerve and the cortical spinal tract, it would lead to Weber syndrome. If the third nerve is affected, it would lead to Ipsilateral third nerve palsy, as well as contralateral hemiplegia. If the Posterior Cerebral Artery lesion affects the red nucleus, then it will lead to Claude syndrome. This would cause Contralateral ataxia and ipsilateral third nerve palsy. If the Posterior Cerebral Artery lesion occurs affecting the red nucleus, the third nerve, and the corticospinal tract causing both Weber and Claude syndrome, then it is referred to as Benedict syndrome. ^,

Just like the Middle Cerebral Artery and Anterior Cerebral Artery watershed, there is a Middle Cerebral Artery and Posterior Cerebral Artery watershed zone where both arteries meet and when this area is destroyed or there is a lesion, the patient exhibits conditions such as Prosopagnosia which causes the inability to recognize, analyze and identify faces and objects. Patients can also have balance syndrome, optic ataxia, or ocular motor apraxia.

The Basilar artery supplies the medial pons, the superior, anterior, and inferior parts of the cerebellum. A lesion of the basilar artery affecting the medial pons would lead to loss of gaze ipsilaterally. If it affects the medial lemniscus that deals with discriminative touch, proprioception, and vibration, then there will be a loss of sensations contralaterally to the upper and the lower extremity trunk.^{, , ,}