A 65-year-old man comes to the emergency department with right upper and lower extremity weakness and slurred speech. The patient went to bed in his usual state of health and woke up with these symptoms. His medical problems include type 2 diabetes mellitus, hypertension, and hyperlipidemia. He takes atorvastatin, metformin, lisinopril, and low-dose aspirin. The patient has smoked a pack of cigarettes daily for the past 40 years. His temperature is 36.7 C (98 F), blood pressure is 160/90 mm Hg, and pulse is 118/min. He is mildly dysarthric with a right lower facial droop and right-sided hemiparesis. A noncontrast head CT is normal. Brain MRI reveals an acute subcortical infarct in the left internal capsule. Six months later, which of the following findings is most likely to be observed in the affected pyramidal tracts of this patient?

Question

A 65-year-old man comes to the emergency department with right upper and lower extremity weakness and slurred speech.  The patient went to bed in his usual state of health and woke up with these symptoms.  His medical problems include type 2 diabetes mellitus, hypertension, and hyperlipidemia.  He takes atorvastatin, metformin, lisinopril, and low-dose aspirin.  The patient has smoked a pack of cigarettes daily for the past 40 years.  His temperature is 36.7 C (98 F), blood pressure is 160/90 mm Hg, and pulse is 118/min.  He is mildly dysarthric with a right lower facial droop and right-sided hemiparesis.  A noncontrast head CT is normal.  Brain MRI reveals an acute subcortical infarct in the left internal capsule.  Six months later, which of the following findings is most likely to be observed in the affected pyramidal tracts of this patient?

Quizplus · Accepted Answer

11ec160b_39cc_d8dd_9249_1b45c08d5f9f_MD0001_00 Wallerian degeneration refers to the process that occurs when an axon is damaged, resulting in axonal degeneration and breakdown of the myelin sheath distal to the site of injury. Degeneration of the axon usually begins within a few days after lesion onset. In the peripheral nervous system, Schwann cells sense the axonal degeneration and begin to degrade their myelin and secrete cytokines and chemokines that recruit macrophages. This allows effective clearance of myelin debris which, along with trophic factor secretion by Schwann cells, stimulates formation of a growth cone from the stump of the proximal axon and facilitates nerve regeneration. In the central nervous system, phagocytic macrophages/microglia are recruited more slowly because of the blood-brain barrier. Myelin-producing oligodendrocytes also become inactive or undergo apoptosis and do not assist with phagocytosis. This slows removal of the myelin debris, which can persist for years in the degenerating tracts and suppress axonal growth via myelin-associated inhibitory factors. Astrocytes also release inhibitory molecules and proliferate in the weeks to months following injury, forming a glial scar that acts as a barrier to axon regeneration. (Choice A) Calcification of an ischemic infarction may occur months to years after the event; however, this is a rare occurrence. Brain calcification is most commonly seen with certain neoplasms (eg, oligodendroglioma), infections (eg, neurocysticercosis), and vascular malformations. (Choices B and G) Cytotoxic and vasogenic edema typically occur in the acute setting after ischemic neuronal injury. Cytotoxic edema is a type of intracellular edema caused by impaired function of ATP-dependent sodium/potassium pumps on neuronal cell membranes. In contrast, vasogenic edema is a type of extracellular edema caused by increased vascular permeability due to the effects of pro-inflammatory cytokines. (Choice C) In the first 12-24 hours after ischemic stroke, affected neurons classically shrink and develop intense cytoplasmic eosinophilia (red neurons) with pyknosis of the nucleus. (Choice D) Embolic ischemic strokes have a high risk of undergoing acute hemorrhagic transformation within the first 7 days following the ischemic event. (Choice E) Neutrophilic infiltration progressively increases up to 48 hours after ischemic stroke and then diminishes. Educational objective: Wallerian degeneration refers to the process of axonal degeneration and breakdown of the myelin sheath that occurs distal to a site of injury. Axonal regeneration does not occur in the central nervous system due to the persistence of myelin debris, secretion of neuronal inhibitory factors, and development of dense glial scarring. __________ References: Histopathological changes in acute ischemic stroke. (http://www.ncbi.nlm.nih.gov/pubmed/19690757) Wallerian degeneration: gaining perspective on inflammatory events after peripheral nerve injury. (http://www.ncbi.nlm.nih.gov/pubmed/21878126) Wallerian degeneration of the corticospinal tracts: postmortem MR-pathologic correlations. (http://www.ncbi.nlm.nih.gov/pubmed/17611880)

A 65-Year-Old Man Comes to the Emergency Department with Right