Saccades and saccadic adaptation in children with spina bifida and Arnold-Chiari type II malformation.
Published: 2004
Language: eng
Number of pages: 349
Description: Results. The vermis area was significantly larger (p &lt; 0.0001), although the posterior fossa area was significantly smaller (p &lt; 0.003), in ACII than in control participants. Saccade gains, latencies, and adaptation did not differ significantly between the two groups. Saccadic adaptation was achieved in 67% of control participants who had 13.3% reduction in gain, and in 57% of ACII participants who had 11.6% reduction in gain. Regression analyses revealed no effects of MRI measurements, spinal lesion level, number of shunt revisions, and presence of nystagmus on saccadic gains, latencies, and adaptation.Introduction. Spina bifida myelomeningocele (SB) is associated with Arnold-Chiari type II malformation (ACII), which is a congenital developmental anomaly of the cerebellum and brainstem. Saccades are fast orienting eye movements. Saccadic adaptation is a form of motor learning. The cerebellum regulates saccade amplitude and participates in saccadic adaptation. The study aims were to quantify the dysmorphology of ACII; to investigate the effects of ACII on saccades and saccadic adaptation; and to correlate saccadic function with measures of cerebellar dysmorphology of ACII, spinal lesion level, number of shunt revisions, and presence of nystagmus.Methods. The dysmorphology of ACII was quantified on midsagittal MRI in 68 children with ACII and 28 typically developing children, aged 8--19 years. An infrared eye tracker measured saccades and saccadic adaptation in 39 typically developing children, and 21 children with ACII, aged 8--19 years. Participants made saccades to steps in a visual target. Saccadic adaptation was induced experimentally using a target back-step paradigm. The outcomes of interest were saccadic gains, latencies, percentage of children adapting, and percentage reduction in amplitude gain. Student t-tests and regression models were used to analyze the data.Conclusion. The enlargement of midsagittal vermis area, which involves all of the vermis lobules, is attributed to compressive displacement of midline structures in ACII within the confines of small posterior fossa. Neural coding of saccades and their adaptation is robust and not affected by the dysmorphology of ACII, despite compression of the ocular motor vermis. Normal motor learning and accuracy in the saccadic system signifies functional integrity of the ocular motor vermis.
Notes: Advisers:  M.  Dennis; J. A. Sharpe.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-05, Section: B, page: 2281.