New-Onset Gait Difficulty With Kappa Free Light Chains in Cerebrospinal Fluid

Abstract

A 49-year-old woman sought care for a 9-month history of gait difficulty. She was dragging her right foot when walking and could not walk more than 3 blocks because of right leg weakness. Physical examination showed right-sided weakness of hip flexion and foot dorsiflexion and symmetrical hyperreflexia at the knees and ankles. Magnetic resonance imaging of the brain showed multiple foci of T2 hyperintensity throughout the white matter in both cerebral and cerebellar hemispheres, predominantly in a periventricular distribution. Several small enhancing lesions and mild generalized cerebral volume loss were seen. The appearance and distribution were consistent with a demyelinating process such as multiple sclerosis. Magnetic resonance imaging of the cervical and thoracic spine showed multiple small T2 hyperintensities, including 1 enhancing lesion in the cervical spinal cord. Oligoclonal bands were positive, with 11 unique bands in the cerebrospinal fluid. The concentration of cerebrospinal fluid kappa free light chains was increased, at 0.314 mg/dL. The patient was diagnosed with relapsing-remitting multiple sclerosis. A 5-day course of intravenous corticosteroids was started, after which she noted clinical improvement. At her last follow-up 2 years after initial evaluation, the patient has been stable with no new clinical multiple sclerosis episodes and stable magnetic resonance imaging disease burden with no new lesions. The diagnosis of multiple sclerosis incorporates clinical, imaging, and laboratory evidence. The 2017 revised McDonald criteria state that a finding of cerebrospinal fluid -specific oligoclonal bands can replace the criterion for dissemination in time to make a diagnosis of definitive multiple sclerosis. The standard test for oligoclonal bands is performed using isoelectric focusing electrophoresis and takes more than 3 hours to complete. The case patient had 11 unique cerebrospinal fluid bands. The number of bands is not correlated with disease severity or prognosis.