Muscle ultrasound as a key in assisting the diagnosis of neuromyotonia

Abstract

Neuromyotonia or Isaacs syndrome is a rare neuromuscular disorder secondary to hyperexcitable peripheral nerves which fire continuously causing motor unit activation and manifests clinically as cramps, muscle twitches, or visible muscle contraction associated with impaired muscle relaxation. Clinical suspicion and subsequent diagnostic work-up, including electrophysiology, aid in the diagnosis. However, when contractions are not appreciated clinically, there is a high possibility of misdiagnosis. Misdiagnosis may also be attributable to a lack of knowledge of symptoms among physicians and a paucity of diagnostic modalities, hence additional tools have been sought. Here we present the case of 15-year-old girl who presented to us with complaints of painful posturing and stiffness of both hands, which was initially diagnosed and managed as dystonia without symptomatic relief. We suspected the diagnosis of neuromyotonia only after we performed neuromuscular ultrasound, which became the main guiding light to reach the diagnosis.