Internuclear ophthalmoplegia (ION)is a central oculomotility disorder resulting from dysfunction of the medial longitudinal fasciculus. It is frequently associated with skew deviation and vertical nystagmus. We aimed to determine the incidence of oculomotility disorders associated with ION.Methods
Retrospective chart review of patients diagnosed with ION. Patients were retrieved from the Neuro-Ophthalmology Database of the Hôpital Ophtalmique Jules-Gonin. Patients’ demographics, etiologies, uni-bilaterality, association with other oculomotility disorders were studied.Results
Our study comprised of 69 patients, 38F/31M, aged 16 to 77 years (mean 47 years). Etiologies included multiple sclerosis (MS, 39/69), stroke (20/69), tumor (5/69), and inflammatory/idiopathic (5/69). ION was unilateral in 39 cases and bilateral in 30 cases. Oculomotility disorders other than ION were found in 56 patients : upbeat nystagmus (31/56), downbeat nystagmus (29/56), oculo-cerebellar syndrome (25/56), skew deviation (18/59), VI palsy (7/56), III palsy (6/56), dorsal midbrain syndrome (4/56), and one-and-a-half syndrome (3/56). Stroke was responsible for the majority of skew deviation cases, whereas MS was the predominant cause of all the other oculomotility disturbances.Conclusion
More than 80% of patients with ION exhibited also other central oculomotility disturbances. Vertical nystagmus and oculomotor cerebellar syndrome outnumbered skew deviation. Other disturbances included VI nerve palsy, III nerve palsy, Parinaud’s syndrome and Fisher’s one-and-a-half syndrome. ION is rarely isolated and the spectrum of other oculomotor abnormalities is wide.