Q&A: Evaluation of Cerebral Ischaemia

The symptoms of brain ischemia may be transient, lasting seconds to minutes, or may persist for longer periods of time. Symptoms and signs remain indefinitely if the brain becomes irreversibly damaged and infarction occurs. Unfortunately, neurologic symptoms do not accurately reflect the presence or absence of infarction, and the tempo of the symptoms does not indicate the cause of the ischemia. This is a critical issue because treatment depends upon accurately identifying the cause of symptoms.

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This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Brain and Nerve articles more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Classification of stroke
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Classification of stroke

Cerebrovascular disease is caused by one of several pathophysiologic processes involving the blood vessels of the brain:

• The process may be intrinsic to the vessel, as in atherosclerosis, lipohyalinosis, inflammation, amyloid deposition, arterial dissection, developmental malformation, aneurysmal dilation, or venous thrombosis.
• The process may originate remotely, as occurs when an embolus from the heart or extracranial circulation lodges in an intracranial vessel.
• The process may result from inadequate cerebral blood flow due to decreased perfusion pressure or increased blood viscosity.
• The process may result from rupture of a vessel in the subarachnoid space or intracerebral tissue.

The first three processes can lead to transient brain ischemia (transient ischemic attack [TIA]) or permanent brain infarction (ischemic stroke), while the fourth results in either subarachnoid hemorrhage or an intracerebral hemorrhage (primary hemorrhagic stroke). Approximately 80 percent of strokes are due to ischemic cerebral infarction and 20 percent to brain hemorrhage.

MCQ exam: clinical scenario

A 70 year old known hypertensive man presents to the general practitioner complaining of sudden onset of a drooping right eyelid and slurred speech. Examination revealed the tongue deviated to the right. A Horner's syndrome on the right was diagnosed. Further examination showed a loss of pain sensation of the left side. The physician also noted a poor visual acuity from both eyes.

What area of the brain is involved in ischaemia?

a) spinal cord at the level of C2
b) dorsolateral medulla
c) anterior pons
d) right side of midbrain
e) left side of midbrain

MCQ exam: answer

The correct answer is B.

MCQ exam: explanation

This patient's clinical condition suggests ischemia of the dorsolateral medulla. Involvement of the ninth and tenth cranial nerve nuclei result in ipsilateral tongue deviation to the right and ipsilateral palatal weakness, respectively. Involvement of the central sympathetic pathway results in an ipsilateral Horner's syndrome. Damage to the lateral spinothalamic tract results in contralateral loss of pain and temperature sensation. The poor visual acuity in this case was irrelevant and an incidental finding - this was corrected with reading glasses.

Reference(s)
1). UpToDate: Overview of the evaluation of stroke. Available online: https://www.uptodate.com/contents/overview-of-the-evaluation-of-stroke