A 54-year-old hospitalized man develops new-onset slurring of speech and extremity weakness. Medical history is significant for alcohol abuse. Physical examination reveals confusion, dysarthria, dysphagia, and quadriparesis. MRI of the brain shows symmetric areas of demyelination in the pons. Which of the following most likely predisposed this patient to his current condition?

Question

A 54-year-old hospitalized man develops new-onset slurring of speech and extremity weakness.  Medical history is significant for alcohol abuse.  Physical examination reveals confusion, dysarthria, dysphagia, and quadriparesis.  MRI of the brain shows symmetric areas of demyelination in the pons.  Which of the following most likely predisposed this patient to his current condition?

Quizplus · Accepted Answer

11ec160b_3b03_aabf_9249_8fef0a79e192_MD0001_00 This patient with a history of alcohol abuse has new-onset pseudobulbar palsy (dysarthria, dysphagia, dysphonia) and quadriparesis suggesting a brainstem insult. In association with the focal, symmetric demyelination of the pons noted on MRI, this presentation suggests osmotic demyelination syndrome (ODS), also known as central pontine myelinolysis. Other classic clinical features include a horizontal gaze paralysis, obtundation, and "locked in" syndrome, in which patients are aware but unable to move or communicate verbally. Decreased plasma osmolality from hyponatremia (common in patients with alcohol abuse) results in water flowing across the osmotic gradient into brain cells; if this happens acutely, life-threatening cerebral edema can occur. However, with slowly developing (chronic) hyponatremia, astrocytes and oligodendrocytes excrete osmotically active organic solutes (eg, glutamate, myoinositol) to cause compensatory intracellular water loss and normalization of brain volume. Therefore, chronic hyponatremia can present with minimal neurologic symptoms. However, overly rapid correction of chronic hyponatremia (eg, bolus of normal saline) reverses the osmotic gradient, drawing water from the cells into the plasma. The astrocytes and oligodendrocytes are unable to rapidly re-accumulate the lost organic solutes, resulting in cell shrinkage, dehydration, and apoptosis. The resultant demyelination preferentially affects the pons, possibly because the cells there are less metabolically active and less able to rapidly regenerate organic solutes. (Choice A) Vertebrobasilar atheroma formation can result in a pontine stroke with similar symptoms; however, ischemia (not demyelination) is expected on MRI. (Choice B) Septic emboli (hematogenous spread of bacteria or fungi) are typically associated with endocarditis. Symptomatic brain abscesses can occur (eg, headache, focal neurologic findings), but MRI would demonstrate ring enhancement with vasogenic edema. (Choice C) The administration of glucose-containing fluids to patients with thiamine deficiency (common in patients with alcohol abuse) can cause Wernicke encephalopathy (ie, ataxia, oculomotor dysfunction, encephalopathy). Korsakoff syndrome (chronic memory impairment) can also occur. Mamillary body atrophy is often visible on MRI. (Choice E) Paraneoplastic production of anti-neuronal antibodies can be seen in a variety of malignancies (eg, small cell lung cancer, thymoma), but symptoms are often nonfocal (eg, altered mentation, seizures). Demyelination is unexpected. Educational objective: Osmotic demyelination syndrome results from overly rapid correction of chronic hyponatremia. Clinical features include quadriplegia, pseudobulbar palsy, and reduced level of consciousness. MRI demonstrates focal demyelination of the pons.

A 54-Year-Old Hospitalized Man Develops New-Onset Slurring of Speech and Extremity