A case of eight-and-a-half syndrome due to malignant lymphoma of the brainstem

Abstract

　Purpose: To discuss the mechanism of development of eight-a-half syndrome in a case with a pontine lesion.

　Case: A 60-year-old man presented with left facial palsy and abnormal eye movements. Neuro-ophthalmologic examination showed conjugate leftward gaze palsy, impaired left eye adduction, rightward gaze-evoked nystagmus of the right eye on looking rightward, and upward gaze-evoked nystagmus. Vergence movements of the eyes were preserved. Contrast-enhanced MRI revealed an approximately 3-cm lesion in the dorsal paramedial pons. Histopathology revealed diffuse large-cell malignant lymphoma. He was diagnosed as having eight-a-half syndrome due to malignant lymphoma of the pons. Eight-a-half syndrome is one-and-a-half syndrome, characterized by impairment of both the medial longitudinal fasciculus (MLF) and paramedian pontinereticular formation (PPRF), accompanied by facial palsy. Ipsilateral facial palsy can be associated with one-and-a-half syndrome, because the facial nuclei and nerve are adjacent to the MLF, PPRF, and the abducens nucleus.

　Conclusion: In a patient with the eight-and-a-half syndrome, neurophysiologic information would be useful to speculate the extent of the lesion.