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Disorders of Myelination

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A 21-year-old, right-handed female student was working in the photography lab 1 week ago, which required standing all day. After that, she experienced a cold sensation in the left foot and her entire left leg fell asleep. The feeling lasted 4 to 5 days and then slowly went away. Her right lower extremity was fine. Coughing, sneezing, and the Valsalva maneuver did not worsen her symptoms. She had a slight back pain, which she thought was due to using a poor mattress. Past history includes an episode of optic neuritis in the left eye 2 years ago. At that time, she was reportedly depressed and was sleeping constantly. One day, her left eye became blurred and her vision went out. In 1 week, her vision returned to normal. Her vision now is 20/20. She has not had a repeat episode since then. She had a magnetic reasonance imaging (MRI) of her brain, which was normal at that time. She drinks alcohol occasionally and does not use any illicit drugs. Her only medication is birth control pills. Examination is significant for brisk reflexes and sustained clonus at the right ankle. Babinski sign is present on the right. Testing is positive for oligoclonal bands. Which of the following is the most likely diagnosis in this case?

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a. Seizure

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b. Transient ischemic attack

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c. Anaplastic astrocytoma

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d. Multiple sclerosis (MS)

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e. Parkinson disease

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The answer is d. This is a typical history for MS. Multiple sclerosis is a progressive demyelinating disease of the central nervous system. Risk factors include a first-time demyelinating episode such as optic neuritis. Patients are more commonly in the 20 to 30 year age range, with a higher incidence in women. A transient ischemic attack is a brief period of brain ischemia causing neurological deficits that resolve within 24 hours. Patients who have a transient ischemic attack are at increased risk for stroke. A seizure is abnormal rhythmic electrical brain activity with a clinical correlation. There is nothing in the history to suggest that this patient had a seizure or a seizure predisposing factor. Seizure predisposing factors include previous seizure, brain trauma, brain hemorrhage, and encephalitis. An anaplastic astrocytoma is a malignant high-grade brain tumor. These often present with a seizure or hemorrhage. Risk factors include previous brain tumor. Parkinson disease is caused by a loss of dopaminergic neurons. It is characterized by asymmetric slowness, rigidity, and tremor. Risk factors include family history.

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A patient has brought some test results from an outside doctor with her today. One of the results indicates that oligoclonal bands were positive. What are oligoclonal bands?

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