A 62-year-old man comes to the physician with gait instability. One week ago, he suddenly developed nausea, vomiting, and dizziness. In the past 2 days, he has been "seeing double" and has fallen several times due to problems with balance. His review of systems is positive for unintentional weight loss over the last 3 months. The patient uses alcohol occasionally and has a 60-pack-year smoking history.
He is afebrile and vital signs are normal. Physical examination shows horizontal nystagmus, dysarthria, and unsteady gait.
Chest x-ray shows a right upper lobe lung mass. MRI of the brain with and without contrast is normal.
Which of the following is the most likely cause of this patient's gait disturbance?

Question

A 62-year-old man comes to the physician with gait instability.  One week ago, he suddenly developed nausea, vomiting, and dizziness.  In the past 2 days, he has been "seeing double" and has fallen several times due to problems with balance.  His review of systems is positive for unintentional weight loss over the last 3 months.  The patient uses alcohol occasionally and has a 60-pack-year smoking history.
He is afebrile and vital signs are normal.  Physical examination shows horizontal nystagmus, dysarthria, and unsteady gait.
Chest x-ray shows a right upper lobe lung mass.  MRI of the brain with and without contrast is normal.
Which of the following is the most likely cause of this patient's gait disturbance?

Quizplus · Accepted Answer

This patient's presentation is consistent with likely paraneoplastic cerebellar degeneration (PCD). PCD is most commonly associated with lung, gynecologic, and breast cancer. Patients classically present with the acute onset of dizziness with nausea/vomiting, followed by cerebellar signs, dysarthria, and diplopia several days later. Symptoms may progress over weeks to months and often precede a cancer diagnosis by years. Diagnostic studies are mostly nonspecific and can be useful in excluding alternate conditions. MRI may initially be normal but can demonstrate cerebellar atrophy with prominent cerebellar folia several months after symptom onset. Cerebrospinal fluid analysis may show mild pleocytosis and elevated protein. Paraneoplastic antibodies (eg, anti-Yo, anti-Hu, anti-Ri) are helpful in confirming PCD, but negative results do not exclude the diagnosis. Patients without a diagnosis of cancer should undergo workup for occult malignancy. cerebellar atrophy (Choice B) Cerebellar infarction can present with the sudden onset of cerebellar signs (eg, dizziness, gait ataxia, horizontal nystagmus) but is less likely in the setting of a normal brain MRI. (Choice C) Spinal cord compression due to metastasis usually presents with back pain at the site of spinal involvement, followed by progressive myelopathy below the level of involvement (eg, spastic paresis, sensory loss, hyperreflexia). Cerebellar symptoms/signs are not characteristic. (Choice D) Viral encephalitis can produce focal neurologic abnormalities; however, this patient's lack of fever and altered mental status makes the diagnosis unlikely. (Choice E) Neurologic complications of vitamin B12 deficiency typically include sensory polyneuropathy, subacute combined degeneration, and dementia. Cerebellar ataxia may also occur, but isolated cerebellar ataxia in the absence of sensory or neurocognitive abnormalities makes the diagnosis less likely. Educational objective: Paraneoplastic cerebellar degeneration typically presents with the subacute onset of cerebellar symptoms and often precedes the diagnosis of malignancy (eg, lung, gynecologic, breast) by years. Paraneoplastic antibodies (eg, anti-Yo, anti-Hu, anti-Ri) can help confirm the diagnosis. __________ References: Paraneoplastic cerebellar degeneration. (http://www.ncbi.nlm.nih.gov/pubmed/21827891)

A 62-Year-Old Man Comes to the Physician with Gait Instability