Spinal muscular atrophy type I mimicking critical illness neuropathy in a paediatric intensive care neonate: Electrophysiological features

We report the case of a neonate with spinal muscular atrophy type I (SMA type I or Werdnig–Hoffman disease) who was initially misdiagnosis as having critical illness neuropathy. Electromyography (EMG) showed a moderate loss of voluntary and motor unit potentials of both neurogenic and myopathic appearance. Nerve conduction studies revealed the presence of a severe sensory–motor axonal neuropathy. Finally, a biopsy of quadriceps was compatible with the diagnosis of SMA type I. A genetic study confirmed the existence of a homozygous absence of exons 7 and 8 of the telomeric supervival motoneuron gene (SMN1 gene).