Brain Stem and Audio-Vestibular Regulation
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The central pathologies present with perverted auditory perception and compromised postural control. Considering the existing controversy this study involves assessments of 100 cases of post fossa tumefactions in which a detailed clinical and neuro-otological (pure tone audiometry, electronystagmography, brainstem evoked response audiometry) profile is compared with their imaging patterns. The CP angle schwannomas (N = 26) presented with abnormal speech tests (N = 18), abnormal auditory adaptation (N = 7) and ABR with pathologically increased latency of wave V (N = 32), poor formation of wave I (N = 31) along with abnormal inter-wave interval (N = 32). In lesions (N = 32) compressing deeper nuclei, vermis and axial parts of brain stem, a gross truncal ataxia, incoordination, nystagmus, speech defects, subtotal deafness and bilateral ABR abnormalities were observed. The abnormal optomotor activities were seen as saccadic (N = 44) and deformed slow pursuit eye movements (N = 20). Inability to sustain holding function resulted in gaze nystagmus (N = 71), and poor timing manifested as fixation overshoots (N = 42). The midline cerebellar and upper brain stem lesions revealed bilateral OKN abnormalities whereas paramedian pathology showed only ipsilateral distortion. Caloric tests revealed culmination frequency as the most sensitive parameter for assessment of the hypo-reflexia in diffuse cerebellopathies while slow phase velocity in cases of posterior fossa lesion. The caloric hypo-activity appears to be of a better localizing value than the directional preponderance. The slow pursuit tracking revealed Type III curve perhaps due to defective regulation of slow movements in partially intact cerebellum (N = 15), while gross cerebellar dysfunctioning resulted into Type IV curve (N = 5).
KeywordsBrainstem Cerebellum Audiovestibulopathy
AM would like to acknowledge Professor. Dr. Girish Kumar Shukla and Professor Dr. Devika Nag for their time to time guidance.
AM in this Masters thesis project of his was the key person to recruit the patients from the departments of Neurology, Medicine and Otorhinolaryngology. He also conducted the basic anamnesis, otolaryngological examination, data entry and collection of references. The original idea of this work and design of study was framed by SCM who was the guide and supervisor of AM for his Masters thesis project of Otolaryngology. SCM was the final authority to decide the results of vestibular examination in situations of divided opinions if any. AM was also the main person to draft the manuscript (along with SCM) and obtaining inputs from the statistician. SCM was instrumental in assisting AM in vestibular assessment of the patients as well as providing important inputs for manuscript writing. Both the authors read and approved the final manuscript.
Conflict of interest
The authors declare that they have no competing interests.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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