Abstract Details

Title Conduction Block in Charcot-Marie Tooth Neuropathy Type 4J

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P14 - Poster Session 14 (8:00 AM-9:00 AM)

Poster/Presentation
Number 1-013

Objective To demonstrate CMT 4J can present electrophysiologically with conduction block.

Background • Charcot-Marie Tooth (CMT) disease also known as Hereditary Motor Sensory Neuropathy (HMSN) is the most commonly inherited neurological disorder with a prevalence of 1/25001.
• CMT type 4J is a rare demyelinating subtype characterized by recessive mutations in the phosphoinositide phosphatase FIG4 gene.
• Electrographically, inherited demyelinating disorders such as CMT 1, 4, and X present with a homogenously slowed conduction velocity; however we present a case of genetically confirmed CMT type 4J with an unusual electrographic feature characteristic of an acquired demyelinating disorder: Conduction block.
• Literature review reveals one manuscript documenting conduction block and temporal dispersion in a patient with rapidly progressive asymmetric weakness mimicking Chronic Inflammatory Demyelinating Polyneuropathy, but unresponsive to treatment in genetically confirmed CMT type 4J2.
• To date there has not been documentation in the literature of slowly progressive motor sensory decline with conduction block in CMT type 4J.

Design/Methods Left sural nerve and left gastrocnemius muscle biopsy performed at the Montreal Neurological Institute.

Results Figures 1 and 2 show severe demyelinating polyneuropathy with conduction block. No response was obtained from sensory or motor studies performed in the lower extremities bilaterally. The right upper extremity shows severely increased motor latencies, mild to moderately reduced amplitudes, and severely but not uniformly slowed conduction velocities, consistent with an acquired demyelinating polyneuropathy.
Figures 3 and 4 show the waveforms correlating with conduction block.
Figure 5 shows severely prolonged F-waves consistent with demyelination.

Conclusions This unique electrographic finding of conduction block in our patient implicates the need for clinicians to consider CMT type 4J in the differential diagnosis when faced with patients presenting with progressive weakness, sensory loss, diminished reflexes, with electrographic evidence of acquired demyelination that are refractory to immunosuppression.

Authors/Disclosures
Jacqueline Li, MD (Kensington Medical Clinic) PRESENTER	No disclosure on file
Mark G. Stefanelli, MD (Health Sciences Centre/Div of Neuro)	No disclosure on file

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Abstract Details