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NEUROSAE 2018 ANNUAL MEETING EDITION (VOLUME 10, ISSUE 3)
QUESTION 83 OF 100
A 56-year-old woman presents with a 4-month history of progressive balance problems, including the inability to walk without looking at the floor or her feet, especially in a poorly lit room, and difficulty showering without holding on to a wall, especially while rinsing her hair. She states her feet feel as though she is constantly wearing socks and reports a similar sensation in her hands. She notes a mild tremor in her hands at times and slightly impaired fine motor dexterity. History includes hypothyroid disease, hypertension, and a “benign” overproduction of protein for which she is referred for hematologic evaluation. Motor strength is normal, except for 3/5 weakness in toe extension and flexion and 1+ reflexes throughout except for an absent Achilles reflex. Sensory examination shows loss of proprioception and vibration in the toes and ankles, decreased light tough to the ankles, and a mild decrease in light touch and vibration in the fingers. She has a low-amplitude postural tremor in the hands bilaterally. Results of a cerebellar examination are normal, and she has a positive Rhomberg sign. Which of the following diagnostic tests is most likely to yield the correct diagnosis?
A. Analysis of CSF
B. Ganglioside GM1 antibody
C. EMG/nerve conduction studies **
D. Myelin-associated glycoprotein antibody
E. 2-hour glucose tolerance test
** = Your answer
Monoclonal gammopathy of undetermined significance (MGUS) is classified as one of three types: IgM MGUS, non-IgM MGUS, and light chain MGUS. MGUS carries a risk of progression to a hematologic malignancy of 1% per year. As many as one third of patients with MGUS have a peripheral neuropathy. IgM MGUS is overrepresented, affecting approximately half of patients with monoclonal gammopathy and peripheral neuropathy. This type often is referred to as IgM neuropathy or distal acquired demyelinating symmetric (DADS) neuropathy and commonly affects men in the sixth to ninth decades. DADS neuropathy is a distal, symmetric, sensory-predominant neuropathy in which patients often present with sensory ataxia. Mild distal weakness may occur, and a mild tremor is common. Approximately 50% of patients have antibodies to myelin-associated glycoprotein. Its positivity can strengthen the association of IgM and peripheral neuropathy; however, no phenotypic or prognostic difference is seen. No proven effective treatments for IgM neuropathy have been found, although rituximab, IVIg, and others may be tried.