Primary aberrant regeneration and neuromyotonia of the third cranial nerve

A 52-year-old woman presented with episodic diplopia with a duration of 6 months. Between the episodes, infraduction of the right eye was mildly impaired with retraction of the right upper lid on downgaze. On resuming the primary position after prolonged left gaze, she developed a right esotropia and reduced abduction, supraduction, and infraduction of the right eye. There was no history of cranial radiation or previous diagnosis of a brain lesion. Brain imaging results were negative. The interictal infraduction deficit and lid retraction were interpreted as signs of a mild right third cranial nerve palsy with primary aberrant regeneration. The episodic esotropia and ductional deficits were considered to be signs of neuromyotonia. This combination of findings, rarely described before, suggests a link between primary aberrant regeneration and neuromyotonia. Abnormal and excessive conduction triggered by stimulation of a partially damaged nerve probably underlies ocular neuromyotonia.