May 28, 2015: Brun's nystagmus
May 28, 2015
Brun’s nystagmus is characterized by low-frequency, large-amplitude horizontal nystagmus when looking toward the side of the lesion, and high-frequency, small-amplitude nystagmus when looking away from the lesion. The large-amplitude nystagmus is caused by compression of the ipsilateral pons and is a result of an impaired neural integrator, causing inability to maintain eccentric gaze toward the side of the lesion. The small-amplitude nystagmus is due to damage to the ipsilateral vestibular system, causing a decrease in the tonic firing rate. This leads to a slow phase movement toward the lesion side with compensatory fast beating nystagmus in the contralateral direction which is especially prominent when looking away from the lesion. Brun’s nystagmus localizes to the cerebellopontine angle (CPA) and is most commonly indicative of a mass lesion though stroke has also been reported. A mnemonic for remembering the differential of CPA tumors is SAME: S-schwannoma, A-aneurysm, arachnoid cyst, M-meningioma, metastasis, E-epidermoid cyst, ependymoma.
- Leigh RJ and Zee DS. The Neurology of Eye Movements, 3rd ed. New York: Oxford University Press; 1999.
- Chen JJ, Chang TP, Chen DL, Hsu YC. Acute stroke with Opalski’s syndrome and concomitant Brun’s nystagmus. Neurological Sciences 2014; 34: 1493-1495.
Submitted by Sarah D. Hodges DO, Resident physician, Walter Reed National Military Medical Center Department of Neurology, Bethesda, MD.
The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense or U.S. Government.
Disclosures: Dr. Hodges reports no disclosures.