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SUPPRESSION OF SACCADIC INTRUSIONS IN HEREDITARY ATAXIA BY MEMANTINE

Spinocerebellar ataxia with saccadic intrusions and neuropathy (SCASI) is an autosomal recessive disorder with linkage to chromosome 1p36.1 Affected patients are unable to read because of frequent horizontal saccadic intrusions and hypermetria. We report here therapeutic effects of memantine in SCASI and a possible mechanism.

### Methods.

We studied two brothers with SCASI (ages 54 and 58 years).1 Both had corrected visual acuity of 20/20, but reading was barely possible because of saccadic intrusions and hypermetria. Ten normal subjects, ages 24 to 65 years, served as controls.2 All subjects gave informed consent in accordance with our Institutional Review Board and the Declaration of Helsinki. Eye movements were measured (magnetic search coil technique)3 before and 1 month after increasing memantine to a dose of 20 mg/day. Patients attempted to fixate a target at 1.2 m for 3 minutes in ambient lighting. We also studied saccades and microsaccades, using reported methods for analysis.2,4

### Results.

Prior to treatment, both patients with SCASI had similar inability to hold steady fixation because of horizontal macrosaccadic oscillations, more marked in Patient 1 (figure, A; see supplemental data on the Neurology ® Web site at www.neurology.org). Larger saccades were faster than normal.1 Gain of horizontal saccades was increased in both patients. Treatment with memantine caused sustained improvement in reading in both patients without side effects. Thus, memantine made it possible for Patient 2 to fill out medical insurance forms for the first time. The frequency of saccadic intrusions declined from 154/minute to 69/minute in Patient 1 (figure, A), and from 168/minute to 89/minute in …