Clinical and neuroradiological studies on internuclear ophthalmoplegia

In this study 14 cases of internuclear ophthalmoplegia (INO) were analysed. The correlation of clinical symptoms with localization of the responsible lesions was studied in these patients. The subjects included 9 patients with CVD, 2 with MS, 1 with Fisher's syndrome, 1 with cranial polyneuritis and one with unknown etiology. Nine patients with unilateral INO are all associated with brainstem infarction. The other 5 patients including 2 MS had bilateral INO. CT showed abnormal findings in brain stem in 7 out of 14 patients. As for MRI an abnormality was found in 5 out of the 8 patients examined. Two of the 7 patients without any abnormality on CT had abnormal signals on MRI. We divided INO into 3 groups based on the clinical symptoms: 1) anterior type in which convergence was involved concomitantly with adduction paralysis, 2) typical type in which dissociated nystagmus was more marked in the abducting eye, and convergence was preserved, 3) posterior type in which abduction is impaired without adduction disturbance. There were 5 cases of anterior type, 9 of typical type, and none of posterior type. On MRI two patients of anterior type had abnormalities in the dorsal midbrain, and one patient had an abnormality in the pons, and two patients of typical type had abnormalities in the upper or middle dorsal pons to the dorsal midbrain. CT failed to demontrate any responsible lesions in 2 patients in whom the responsible legions were clearly identified on MRI. (J.P.N.)