Alteration of orbicularis oculi reflex by posterior fossa tumors

✓ The orbicularis oculi reflex response to electrical stimulation of the supraorbital nerve was studied in 14 cases of intrinsic brain stem lesions (2 mesencephalic, 6 pontine, and 4 medullary neoplasms, and 2 pontine syrinxes) and 20 cases of lesions extrinsic to the brain stem (6 cerebellar and 14 cerebellopontine angle tumors). The early reflex was abnormal in all but three cases of medullary tumors and one case of cerebellar tumor. Alteration of the early reflex by posterior fossa tumors reflects either delayed conduction through the pons due to intrinsic pontine lesions or extrinsic compression of the pons, or indicates trigeminal or facial nerve involvement by tumor. The late reflex with its direct and consensual components is useful in distinguishing afferent from efferent delay (or block). Mixed patterns suggest combined involvement of the trigeminal and facial nerves or a relatively widespread brain-stem lesion. This simple technique appears to be a useful addition to clinical observation in assessment of posterior fossa tumors.