Internuclear ophthalmoplegia is a symptom frequently associated with multiple sclerosis (MS), although other etiologies are possible. Some patients do not meet the diagnostic criteria for MS at the time of the internuclear ophthalmoplegia episode but subsequently convert to MS. Studying this specific clinical situation may help enable earlier diagnosis of MS.

The objective is to analyze the proportion of patients with isolated internuclear ophthalmoplegia who convert to multiple sclerosis and to identify factors associated with this conversion.

The study hypothesis is that the presence of internuclear ophthalmoplegia is highly suggestive of multiple sclerosis, particularly when cerebrospinal fluid-specific oligoclonal bands are present.

Inclusion criteria:

• Patients with internuclear ophthalmoplegia listed as a primary or associated diagnosis
• Patients hospitalized in a neurology department

Exclusion criteria:

- Patients under 18 years of age

The extraction of records will be performed through a search using PMSI coding within the medical files of patients hospitalized in a neurology department.