Stiff person syndrome: presentation of a case with repetitive complex discharges in electromiograms

Stiff person syndrome is characterized by rigidity of axial and proximal limb muscles, associated with muscle spasms, triggered by unexpected acoustic or somesthetic stimuli. It usually has an autoimmune basis, in which the blood contains antiglutamate decarboxylase antibodies, and is associated with different types of autoimmune diseases. The electromyogram provides evidences of continuous muscular activity.

A 41-year-old woman with a history of diabetes mellitus type I, Hashimoto thyroiditis, vitiligo, and pernicious anemia developed symptoms compatible with stiff person syndrome. In the electromyogram, in addition to continuous muscular activity, there was evidence of complex repetitive activity in the form of doublets and triplets.

Given the absence of clinical or electrophysiological neuropathic affectation, the presence of doublets and triplets in our patient could be due to a subclinical functional alteration of alpha motoneurons. They could produce the complex repetitive discharges when released from the inhibition mediated by GABAergic neurons.