Abstract
Purpose:
Spinocerebellar Ataxia type 3(SCA3) or Machado-Joseph disease is the most common inherited spinocerebellar ataxia. It is the most common SCA associated with diplopia. We aimed to characterize the type of strabismus and ocular motor abnormalities in SCA3.
Methods:
Eye movements and strabismus were clinically assessed in 12 patients with SCA3. The saccadic eye movements and gaze holding was objectively measured with a corneal curvature tracker (Jazz Novo, Ober Consulting, Poland) and Eyelink SR 1000.
Results:
Eight patients had ophthalmoplegia with mild abduction deficit and three patients later developed an upward deficit. Ten patients had strabismus.Three patients had esotropia, one patient had skew deviation,one had a hypotropia accompanying the asymmetric upward deficit, four patients had mild-moderate intermittent exotropia, and one had moderate exophoria. The near point of convergence was normal in the exotropic patients. Eight patients had gaze-evoked nystagmus, eight had saccadic dysmetria, whereas all twelve patients had saccadic pursuit. Two patients had slowing of the saccades and five had microopsoclonus.
Conclusions:
Strabismus and ophthalmoplegia were most common, but saccadic oscillations were also notable in many patients. The type of strabismus could not be explained by the co-existing ophthalmoplegia or vergence abnormalities in our patients with exotropia that comprised 50% of the cohort. It is possible that involvement of the brainstem, the deep cerebellar nuclei and the superior cerebellar peduncle are driving the exotropia in these patients. Brainstem and deep cerebellar nuclei lesion also explains microopsoclonus, while brainstem deficits can describe slow saccades seen in our patients with MJD.