Optokinetic nystagmus of Chiari Malfromation. The aim of our study is to determine the special characteristics of disorders of the Optokinetic nystagmus in the early stages of Chiari Malformation

Publication date: March 2016
Source:Clinical Neurophysiology, Volume 127, Issue 3
Author(s): D. Demidenko, V. Viktor
BackgroundDiagnosis and treatment of cochleovestibular dysfunction becomes complicated in case of genetically based combination of pathology. The Chiari Malformation (CM) is a congenital development defect and associated with the caudal displacement of cerebellum and brain stem.The aim of this study is to determine the special characteristics of disorders of the Optokinetic nystagmus in the early stages of CM.At the otorhinolaryngology department of North-West State Medical University named after I.I.Mechnikov (Russia, St Petersburg), 54 cases (patients aged 16–69 ) were studied. All patients showed the symptoms of cochleovestibular dysfunction.MethodsThe Optokinetic nystagmus was taken in a dark-room using VNGULMAR system manufactured by the German company "Heinemann Medizintechnik GmBH" running software developed by the French company Synapsys. The fixed speed horizontal and vertical Optokinetic stimulus on screen (20 o/s) was applied with distracted and focused attention of the patients.All the studies were conducted before the calloric test (CT) and after CT. The intensity of Optokinetic nystagmus was assessed as per SSC (speed of slow component) of nystagmus. Later on the relative asymmetry in Optokinetic nystagmus was calculated for each same name pair of horizontal and vertical Optokinetic reactions.ResultsThe studies showed that in order to diagnose CM in the early stages it is important not only to identify the asymmetry in horizontal and vertical Optokinetic nystagmus but to mark the value and the sign of asymmetry as well. The sign of asymmetry is especially important after CT. Patients with the low placement of cerebellar tonsil Optokinetic reactions are more susceptible to CT.ConclusionsTherefore, in the early stages of CM and "in the risk group", i.e. the patients with low placement of cerebellar tonsil, before the neurological symptoms have taken place and we have only vestibular dysfunction, the videonystagmography with quantitative evaluation of Optokinetic reaction becomes a voluble source of important diagnostic information and an indication for MRI studies.



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