Divergence Insufficiency in Cerebellar Ataxia

This is a 65-yo woman with complaints of imbalance (progressive over years) and horizontal diplopia at distance. On her exam, there was a small symptomatic esotropia at distance, but only a small esophoria at near. There were no obvious abduction deficits, and the 6 prism diopter ET at distance was comitant in all directions of gaze. Divergence insufficiency was diagnosed. ; Occasionally, this can be a sign of a brainstem or cerebellar lesion, and on her exam, there was also gaze-evoked nystagmus (GEN) and saccadic pursuit in addition to gait ataxia. These features localize best to the cerebellar flocculus, and in fact, esodeviations greater at distance are commonly found in patients with GEN, saccadic pursuit and downbeat nystagmus (flocculus) syndromes (perhaps due to dysfunction of flocculus to medial rectus subnuclei connections). In this patient's case, MRI showed mild cerebellar atrophy, and investigations for causes of reversible/treatable causes of cerebellar ataxia were negative. Spinocerebellar ataxia testing was deferred. She benefited from prisms placed in distance glasses only. ; Alternatively, many patients of advanced age who present with esodeviation greater at distance (without central ocular motor signs and with a normal neurologic exam) probably have the sagging eye syndrome. Sagging eye syndrome or age-related orbital involutional changes cause divergence issues which are characteristically worse at distance, which is due to LR-SR band rupture or distention causing the LR to be at a mechanical disadvantage. A prominent superior sulcus and levator disinsertion with high lid creases are other typical signs seen with sagging eye syndrome.