Paroxysmal tonic upgaze presenting as a clinical isolated syndrome.

We report a 3.5-year-old boy with sudden onset of episodic upward deviation of the eyes that led to diagnosis of paroxysmal tonic upgaze. Cranial magnetic resonance imaging showed right-hand side dominant bilateral hyperintense lesions in the mesencephalon and the thalamus on T2-weighted images. These lesions suggested a demyelinating pathology. Corticosteroid treatment was started. The episodes of upward eye deviation and the lesions on magnetic resonance imaging completely resolved after 3 days and 3 months, respectively. After 2 years of follow-up, he was symptom-free. Our patient with an isolated brain stem syndrome and no mental status changes was diagnosed as having a clinical isolated syndrome.