Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 19-year-old woman is admitted to the hospital because of a 2-week history of bilateral leg weakness and numbness accompanied by urinary incontinence that began after a viral gastrointestinal illness of 3 days’ duration. She has no personal or family medical history of note and takes no medication.

On physical examination, temperature is 36.7 °C (98.1 °F), blood pressure is 96/55 mm Hg, and pulse rate is 66/min. Bilateral leg weakness, loss of sensation below the umbilicus, and hyperreflexia in the lower extremities are noted.

Laboratory studies are as follows:

Vitamin B12	455 pg/mL (336 pmol/L)
HIV antibodies	Negative
Human T-lymphotropic virus antibodies	Negative
Cerebrospinal fluid (CSF)
Leukocyte count	45/µL (45 × 106/L)
Glucose	57 mg/dL (3.2 mmol/L)
Protein	65 mg/dL (650 mg/L)
Polymerase chain reaction	No evidence of herpes simplex virus or varicella zoster virus

A T2-weighted MRI of the thoracic spine reveals hyperintensity in the thoracic cord at the T9 level, which enhances with administration of gadolinium. Cultures for acid-fast bacilli and CSF bacteria are negative.

High-dose intravenous methylprednisolone is administered. After 5 days, symptoms have not improved.

Which of the following is the most appropriate next step in treatment?

A: Glatiramer acetate
B: Increased dosage of methylprednisolone
C: Methotrexate
D: Plasmapheresis

MKSAP Answer and Critique

The correct answer is D: Plasmapheresis. This item is available to MKSAP 16 subscribers as item 9 in the Neurology section.

This patient should undergo plasmapheresis. She has had an episode of postinfectious idiopathic transverse myelitis, as suggested by her examination findings of bilateral leg weakness, loss of sensation below the umbilicus, and hyperreflexia in the lower extremities; her laboratory results showing leukocytosis in the cerebrospinal fluid; and the evidence of inflammation indicated by the contrast enhancement on her MRI. The presence of a sensory spinal cord level and hyperreflexia on examination localize her disorder to the spinal cord, which rules out Guillain-Barré syndrome. Transverse myelitis presumably results from an autoimmune process. First-line treatment for this disorder is high-dose corticosteroids, such as methylprednisolone, to which this patient did not respond. For corticosteroid-refractory transverse myelitis, the best available evidence supports the use of plasmapheresis and/or cyclophosphamide as rescue treatment.

Glatiramer acetate is a disease-modifying agent used in the treatment of multiple sclerosis (MS). Thought to modulate immune responses relevant to MS pathophysiology, glatiramer acetate is well tolerated and reduces the relapse rate by approximately one third. It has no role in the treatment of acute transverse myelitis.

The patient is already receiving a high-dose corticosteroid, and no medical evidence suggests that increasing the dosage would be beneficial.

Although methotrexate has anti-inflammatory effects, it also is not an established treatment for corticosteroid-refractory transverse myelitis.

Key Point

• The best available evidence supports the use of plasmapheresis and/or cyclophosphamide as rescue treatment for corticosteroid-refractory transverse myelitis.

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