Vestibulo-ocular Reflexes: Effects of Vestibular Nuclear Lesions

Recent studies have shown that primary afferent fibers from the semicircular canals and otolith organs end in portions of the vestibular nuclei, which are largely separate from each other. This suggests that activity from the semicircular canals and otolith organs may be integrated in different parts of the vestibular nuclei. There is little information on this subject, which is of clinical and of physiological interest. There are no studies to our knowledge, which describe changes in otolith-ocular reflexes after discrete vestibular nuclei lesions. There were changes in caloric nystagmus after medial vestibular nucleus lesions, but there is little detail about exactly what these hancges might be. Caloric nystagmus was reported to be unaffected when the descending vestibular nucleus was destroyed in the cat. There is also relatively little detail about spontaneous nystagmus after vestibular nuclei lesions. Contralateral nystagmus has been described after lesions of the vestibular complex, or after lesions of the medial, or descending vestibular nuclei. After lesions of the supramedullary portion of the juxtarestiform body, nystagmus was to the ipsilateral side. In earlier studies, vestibular testing was generally inadequate by present standards, and there was little attempt at quantitation. Because vestibular response can be strongly inhibited in light, testing should be done in darkness using recording techniques such as electrooculography (EOG) or electronystagmography (ENG).