Ocular-Motor Profile and Effects of Memantine in a Familial Form of Adult Cerebellar Ataxia with Slow Saccades and Square Wave Saccadic Intrusions

This study [here] suggests that memantine may have some general suppressive effect on saccadic intrusions, including both square wave intrusions (SWI)  and macrosaccadic oscillations (MSO), thereby restoring the capacity of reading and visual attention in these and in other recessive forms of ataxia, including Friedreich’s, in which saccadic intrusions are prominent.  

Two patients (two sisters with identical phenotype) with an unrecognized, probably recessive hereditary form of adult-onset cerebellar ataxia clinically characterized by axonal sensory neuropathy, cerebellar atrophy, slow saccades and prominent square wave intrusions, have been treated with the drug memantine, which is an uncompetitive antagonist of the NMDA-receptor (NMDAR) [1]. The aim was to suppress frequent and large saccadic intrusions. 

Fixation instability due to saccadic intrusions is a feature of autosomal recessive spinocerebellar ataxias, and SWI and MSO. A recent report suggested that the non-competitive antagonist of NMDA receptors, memantine, could decrease MSO and improve fixation in patients with spinocerebellar ataxia with saccadic intrusions (SCASI). 

Horizontal visually guided saccades (10°–18°) and three minutes of steady fixation in each patient and in thirty healthy controls have been tested.
Both patients showed a significant reduction of peak and mean velocity compared with control subjects. Large SWI interrupting steady fixation were prominent during steady fixation and especially following visually guided saccades. Eye movements were recorded before and during the treatment with memantine, 20 mg/daily for 6 months. 

The treatment with memantine reduced both the magnitude and frequency of SWI (the former significantly), but did not modified neurological conditions or saccade parameters. 





1. Johnson JW, Kotermanski SE (2006) Mechanism of action of memantine. Curr Opin Pharmacol 6: 61–7. doi: 10.1016/j.coph.2005.09.007.

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