MRI studies of an individual with DS also revealed the absence of the abducens nerve. Neurophysiologic evidence of neuronal involvement in DS is derived from EMG studies, which show that the medial and lateral recti muscles are electrically active in individuals with DS. However, when individuals with DS attempt to move their eyes inward (ie, adduct it), both of these muscles contract at the same time, causing the eyeball to retract inward and the eye opening (palpebral fissure) to become narrowed. These findings support aberrant innervation of the lateral rectus muscle.
Autop