The value of elecromyography in the aetiological diagnosis of hypotonia in infants and toddlers

IntroductionDuring the first two years of life, hypotonia may be the only symptom of a central or peripheral nervous system disorder. We propose to assess the sensitivity of electroneuromyography (ENMG) in the aetiological diagnosis of hypotonia of neuromuscular origin in infants and toddlers.MethodThis is a retrospective, single-centre study with revision of the files of the 37 children aged between zero and 24 months who, between 1994 and 2006, underwent an ENMG in the etiological approach of their hypotonia and had a final diagnosis of neuromuscular disease.ResultsAll the 13 patients with spinal muscular atrophy or Charcot Marie-Tooth disease displayed neurogenic alterations on the electromyography (EMG). Among the 24 children ultimately diagnosed with myopathies, five only displayed myogenic alterations when tested before the age of two. Sixteen had normal EMG results and three showed neurogenic alterations.Discussion and conclusionIn infants presenting with hypotonia, ENMG is useful for the diagnosis of peripheral neuropathy. Normal ENMG is relatively common for confirmed muscle disorders in infants whereas myogenic alterations seem more unusual, so that muscle biopsy appears unquestionable. In a few cases, early onset myopathies may present with a neurogenic ENMG pattern. Such a result should not invalidate the clinically presumed diagnosis of myopathy and would indicate on the contrary the need for a muscle biopsy.