Ocular Motor Apraxia
Ocular motor apraxia, also known as saccadic initiation failure, is a rare supranuclear disorder of ocular motility, sometimes including strabismus. The congenital form may be familial, most commonly autosomal dominant.
This condition has been associated with premature birth and developmental delay. Bilateral lesions of the frontoparietal cortex, agenesis of the corpus callosum, hydrocephalus, and Joubert syndrome (abnormal eye movements, developmental delay, microcephaly, hypoplasia of the cerebellar vermis, and retinal dysplasia, among several anomalies) also have been associated with the condition, as have type 3 Gaucher disease and ataxia-telangiectasia. Several case reports have identified mass lesions of the cerebellum that compress the rostral part of the brainstem. Neurodevelopmental evaluation and imaging of the brain are advisable for assessment of children with ocular motor apraxia, especially if there is an associated vertical apraxia. The differential diagnosis of acquired ocular motor apraxia includes conditions that affect the generation of voluntary saccades, including metabolic and degenerative diseases such as Huntington chorea.
In ocular motor apraxia, normal voluntary horizontal saccades cannot be generated. Instead, changes in horizontal fixation are accomplished by a head thrust that overshoots the target, followed by a rotation of the head back in the opposite direction once fixation is established. The initial thrust serves to break fixation; an associated blink serves the same purpose. Vertical saccades and random eye movements are intact, but horizontal vestibular and optokinetic nystagmus are impaired. The head thrust may improve in late childhood. See also BCSC Section 5, Neuro-Ophthalmology.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.