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Repetitive compound muscle action potential: a characteristic diagnostic clue
  1. Ahmed Abbas,
  2. Rajdeep Jain
  1. Department of Clinical Neurophysiology, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
  1. Correspondence to Ahmed Abbas, Department of Clinical Neurophysiology, Queen Elizabeth Hospital Birmingham, Birmingham, UK; ahmed.abbas4{at}

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A 27-year-old woman complained of gradually deteriorating symmetrical weakness of finger extension over 18 months since the start of her first pregnancy. She had no other neurological symptoms but did recall a previously stable history of very mild and non-progressive hand weakness, first noticed in early childhood. Also, her mother had long-standing, although much milder, unexplained weakness affecting the hands.

There was symmetrical grade 3 weakness of finger and wrist extension, and grade 4 weakness involving flexion and abduction of fingers and thumbs. More proximal upper limb, neck and lower limb strength was normal. Her deep tendon reflexes, coordination, sensation and cranial nerve examination were normal. Serum creatine kinase was normal.

The differential diagnosis included a distal myopathy, upper-limb-predominant distal hereditary motor neuropathy (eg, type V) or multifocal motor neuropathy. We performed nerve conduction studies to evaluate these possibilities. All four limbs showed sensory and motor nerve responses that were within normal absolute …

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  • Contributors All authors contributed equally to the manuscript. Conception and drafting of manuscript, final approval of revised submission and agreement to be accountable for all aspects of the work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned. Externally peer reviewed by Nick Kane, Bristol, UK.

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