Horizontal monocular saccadic failure: an unusual clinically isolated syndrome progressing to multiple sclerosis.

This paper describes an unusual clinically isolated syndrome of inflammatory demyelination that was characterized by a right VI nerve palsy and right internuclear ophthalmoparesis (INO), along with an unusual form of dissociated nystagmus. Magnetic resonance imaging (MRI) revealed an isolated lesion within the right dorsomediolateral pontine tegmentum. Four years later, the subject developed a partial sensory transverse myelitis, confirming clinically definite multiple sclerosis (MS). This paper extends the range of isolated syndromes associated with MS.