Neuro-Otological Study of Bilateral Lesions of Medial Longitudinal Fasciculus

Abstract

A 64-years-old female with symptoms of bilateral lesion of medial longitudinal fasciculus (MLF) syndrome was examined by neuro-otological study using electronystagmography (ENG). The neurological studies at the first examination demonstrated left blepharoptosis and abduction of left eye position in the midline gaze.
Abnormal findings on eye movement were as follows: paralysis of bilateral ocular abduction, nystagmus in the bilateral abducted eye during horizontal gaze, disturbance of convergence, disturbance of bilateral rapid upward gaze, and nystagmus to upward and downward gaze direction. These findings suggest lesion of bilateral MLF and left oculomotor nuclei and this lesion belongs to the anterior type of Cogan's classification. Moreover, the MRI study disclosed the same focus as the infarction. When the disturbance of upward gaze remained, upbeat nystagmus was developed by the caloric test with bilateral chilling stimulation. It may disclose that there was tract of vestibuloocular reflex (VOR) in the vertical direction other than the MLF tract.