Ocular Motor Apraxia Type 1

Ocular motor apraxia type 1 (AOA1) is an autosomal recessively inherited disease caused by mutations in the APTX gene. The encoded protein Aprataxin has been identified as being involved in DNA-single-strand break repair and defects probably lead to an accumulation of DNA damage in cells ultimately causing cell death.

Signs and Symptoms

AOA1 initially presents itself between ages 2-10 years with progressive gait imbalance, dysarthria and upper-limb dysmetria with intention tremor. 

Ocular motor apraxia can usually be observed a few years after onset of the disease.

Diagnosis

Clinical findings, family history and MRI to detect cerebellar atrophy form the basis for the diagnosis of AOA1. Axonal neuropathy can be detected in all patients with AOA1 using electromyography (EMG). Ocular motor examinations reveal prolonged saccades that may imitate slow saccades but that are in fact hypometric.

Observable ocular motor disorders

  • Hypometric saccades

References

Strupp M, et al. (2014) Central ocular motor disorders, including gaze palsy and nystagmus. J Neurol 261(2):542-558. PubMed

GeneReviews: Ataxia with Oculomotor Apraxia Type 1, Paula Coutinho, Clara Barbot, last update June 22, 2010. http://www.ncbi.nlm.nih.gov/books/NBK1456/.