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Investigating the Deployment of Visual Attention Before Accurate and Averaging Saccades via Eye Tracking and Assessment of Visual Sensitivity
Published on: March 18, 2019
The syndrome of infantile-onset saccade initiation delay
Michael S Salman1, Kristin M Ikeda
1Section of Pediatric Neurology, University of Manitoba, Winnipeg, Manitoba, Canada. msalman@hsc.mb.ca
Insights
Infantile-onset saccade initiation delay (ISID) often involves abnormal reflexive saccades and is frequently linked to developmental delays, hypotonia, and ataxia. These findings suggest a broader neurological impact beyond just saccadic dysfunction.
Area of Science:
- Ophthalmology
- Neurology
- Pediatrics
Background:
- Infantile-onset saccade initiation delay (ISID), or congenital ocular motor apraxia, is a condition characterized by the inability to initiate voluntary horizontal eye movements.
- Associated neurological abnormalities such as developmental delay and ataxia are known but their frequency is not well-established.
Purpose of the Study:
- To conduct a comprehensive review of the medical literature to quantify the prevalence of various clinical features in patients with ISID.
- To better understand the spectrum of neurological deficits associated with ISID.
Main Methods:
- A systematic search of English medical literature from 1952 to 2010 was performed for studies on ISID.
- Patients with acquired saccade initiation delay, Joubert syndrome, or neurodegenerative conditions were excluded.
- The minimum prevalence of each reported abnormality was calculated based on the included studies.
Main Results:
- Analysis of 66 articles involving 288 patients revealed frequent abnormalities in reflexive saccades (84.7% used head thrusts).
- Associated neurological deficits were common: global developmental delay (41.3%), motor delay (48.6%), and ataxia (49.3%).
- Neuroimaging showed abnormalities in 60.9% of patients, frequently involving the cerebellum.
Conclusions:
- ISID is commonly associated with impaired reflexive saccades and less frequently with abnormal smooth pursuit.
- The high prevalence of developmental delay, hypotonia, and ataxia indicates that ISID is often part of a more global brain impairment, not solely an ocular motor disorder.
Introduction:
Infantile-onset saccade initiation delay (ISID), also known as congenital ocular motor apraxia, is characterized by the inability to initiate volitional horizontal saccades. Other abnormalities including developmental delay and ataxia have been reported. The frequency of these abnormalities is unknown. We performed a detailed review of the medical literature to quantify features of ISID.
Methods:
We searched the English medical literature for articles related to ISID from 1952 to 2010. Whenever possible, patients were excluded if they had acquired SID, Joubert syndrome or neurodegenerative conditions. The minimum prevalence was calculated for each abnormality.
Results:
Sixty-six articles with information on 288 patients were included in the analysis. Head thrusts were reported in 84.7%. Blinks without head thrusts were used to initiate saccades in 41%. The fast phases of the optokinetic response and vestibulo-ocular reflex were impaired in 69.8% and 34.4% respectively. Smooth ocular pursuit was abnormal in 33%. Global developmental delay occurred in 41.3%, speech or language delay in 36.5%, cognitive delay in 17%, hypotonia in 35.8%, motor delay in 48.6%, and ataxia/clumsiness in 49.3% of patients. Neuroimaging was performed on 197 patients and was normal in 39.1%. Abnormalities involved the cerebellum (24.9%), cerebrum (15.7%), other infratentorial structures (11.7%), and corpus callosum (6.1%).
Conclusions:
Infantile-onset saccade initiation delay is frequently associated with deficits in reflexive saccades and less frequently with impaired smooth ocular pursuit. Developmental delay, hypotonia, and ataxia occur frequently in ISID, suggesting more global brain impairment and not just a saccadic disorder.
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