Oculomotor deficits affect neuropsychological performance in oculomotor apraxia type 2

Ataxia with oculomotor apraxia type 2 is a rare and early-disabling neurodegenerative disease, part of a subgroup of autosomal recessive cerebellar ataxia, in which oculomotor symptoms (e.g., increased saccade latency and hypometria) and executive function deficits have been described. The aim of this study was to evaluate the impact of oculomotor symptoms on cognitive performance and, in particular, over reading in 2 Italian siblings affected by ataxia with oculomotor apraxia type 2.

The neuropsychological profiles and the oculomotor patterns during nonverbal and verbal tasks were recorded and analyzed.

Saccadic intrusions and/or nystagmus were observed in all eye movement tasks. The neuropsychological profiles were substantially preserved, with only subtle deficits that affected visuomotor integration and attention. Reading ability decreased and became impaired. The reading scan was disturbed by saccadic intrusions and/or nystagmus. However, an ad hoc reading task demonstrated that deficits appeared only when the items that were displayed enhanced oculomotor requests. The preservation of lexical-semantic processes confirmed that the reading disability was caused by oculomotor deficits, not cognitive problems.

Present findings indicate that in patients who are affected by ataxia with oculomotor apraxia type 2, performance on neuropsychological tests, especially those that require rapid performance and eye or hand-eye control, must be analyzed with respect to oculomotor components.