BACKGROUND: Chiari type II malformation (CII) is a developmental anomaly of the cerebellum and brainstem, which are important structures for processing the vestibulo-ocular reflex (VOR). We investigated the effects of the deformity of CII on the angular VOR during active head motion. METHODS: Eye and head movements were recorded using an infrared eye tracker and magnetic head tracker in 20 participants with CII [11 males, age range 8-19 years, mean (SD) 14.4 (3.2) years]. Thirty-eight age-matched healthy children and adolescents (21 males) constituted the control group. Participants were instructed to 'look' in darkness at the position of their thumb, placed 25 cm away, while they made horizontal and vertical sinusoidal head rotations at frequencies of about 0.5 Hz and 2 Hz. Parametric and non-parametric tests were used to compare the two groups. RESULTS: The VOR gains, the ratio of eye to head velocities, were abnormally low in two participants with CII and abnormally high in one participant with CII. CONCLUSION: The majority of participants with CII had normal VOR performance in this investigation. However, the deformity of CII can impair the active angular VOR in some patients with CII. Low gain is attributed to brainstem damage and high gain to cerebellar dysfunction.
BACKGROUND:Chiari type II malformation (CII) is a developmental anomaly of the cerebellum and brainstem, which are important structures for processing the vestibulo-ocular reflex (VOR). We investigated the effects of the deformity of CII on the angular VOR during active head motion. METHODS: Eye and head movements were recorded using an infrared eye tracker and magnetic head tracker in 20 participants with CII [11 males, age range 8-19 years, mean (SD) 14.4 (3.2) years]. Thirty-eight age-matched healthy children and adolescents (21 males) constituted the control group. Participants were instructed to 'look' in darkness at the position of their thumb, placed 25 cm away, while they made horizontal and vertical sinusoidal head rotations at frequencies of about 0.5 Hz and 2 Hz. Parametric and non-parametric tests were used to compare the two groups. RESULTS: The VOR gains, the ratio of eye to head velocities, were abnormally low in two participants with CII and abnormally high in one participant with CII. CONCLUSION: The majority of participants with CII had normal VOR performance in this investigation. However, the deformity of CII can impair the active angular VOR in some patients with CII. Low gain is attributed to brainstem damage and high gain to cerebellar dysfunction.
Authors: Maureen Dennis; Jack M Fletcher; Tracey Rogers; Ross Hetherington; David J Francis Journal: J Int Neuropsychol Soc Date: 2002-01 Impact factor: 2.892
Authors: M I Van Allen; D K Kalousek; G F Chernoff; D Juriloff; M Harris; B C McGillivray; S L Yong; S Langlois; P M MacLeod; D Chitayat Journal: Am J Med Genet Date: 1993-10-01
Authors: Michael S Salman; Linda Lillakas; Maureen Dennis; Martin J Steinbach; James A Sharpe Journal: Childs Nerv Syst Date: 2007-08-21 Impact factor: 1.475
Authors: G Worley; C W Erwin; J M Schuster; Y Park; O B Boyko; M L Griebel; E R Weidman; R A Radtke; W J Oakes Journal: Dev Med Child Neurol Date: 1994-08 Impact factor: 5.449