A Case of Morvan Syndrome Mimicking Amyotrophic Lateral Sclerosis With Frontotemporal Dementia

J Clin Neuromuscul Dis. 2016 Jun;17(4):207-11. doi: 10.1097/CND.0000000000000118.

Abstract

Introduction: Morvan syndrome is a rare autoimmune/paraneoplastic disorder involving antibodies to the voltage-gated potassium channel complex. It is defined by subacute encephalopathy, neuromuscular hyperexcitability, dysautonomia, and sleep disturbance. It may present a diagnostic dilemma when trying to differentiate from amyotrophic lateral sclerosis with frontotemporal dementia.

Methods: A 76-year-old man with a history of untreated prostate adenocarcinoma was evaluated for subacute cognitive decline, diffuse muscle cramps, and hyponatremia.

Results: MRI demonstrated atrophy most prominent in the frontal and temporal regions. Electromyography (EMG) demonstrated diffuse myokymia/neuromyotonia. Polysomnography lacked REM and N3 sleep. Paraneoplastic panel detected antibodies to voltage-gated potassium channel complex (CASPR2 subtype).

Conclusions: It is difficult to differentiate between Morvan syndrome and amyotrophic lateral sclerosis with frontotemporal dementia with examination and neuroimaging alone. There may be a link between Morvan syndrome and prostate adenocarcinoma which could help with screening/diagnosis. The authors found that laboratory and neurophysiological tests are indispensable in diagnosing and treating Morvan syndrome.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Amyotrophic Lateral Sclerosis / diagnosis*
  • Amyotrophic Lateral Sclerosis / diagnostic imaging
  • Amyotrophic Lateral Sclerosis / physiopathology
  • Autoantibodies
  • Brain / diagnostic imaging
  • Diagnosis, Differential
  • Electromyography
  • Frontotemporal Dementia / diagnosis*
  • Frontotemporal Dementia / diagnostic imaging
  • Frontotemporal Dementia / physiopathology
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Muscle, Skeletal / physiopathology
  • Potassium Channels, Voltage-Gated / immunology
  • Syringomyelia / diagnosis*
  • Syringomyelia / diagnostic imaging
  • Syringomyelia / immunology
  • Syringomyelia / physiopathology

Substances

  • Autoantibodies
  • Potassium Channels, Voltage-Gated