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March 1990

Convergence Nystagmus Associated With Arnold-Chiari Malformation

Author Affiliations

From the Medical Research Council Neuro-Otology Unit, Institute of Neurology (Drs Mossman, Bronstein, Gresty, and Rudge), and the Department of Radiology (Dr Kendall), National Hospital, London, England.

Arch Neurol. 1990;47(3):357-359. doi:10.1001/archneur.1990.00530030139030

• A case of convergence nystagmus associated with an Arnold-Chiari type I malformation is presented. The nystagmus appeared in the absence of fixation, was provoked during Valsalva's maneuver and neck flexion and extension, and attenuated on deep inspiration. Sagittal magnetic resonance images showed that the diameter of the cerebral aqueduct increased with the neck in full flexion and in full extension. Surgical foramen magnum decompression considerably reduced the nystagmus and abolished the postural variation of aqueduct diameter. It is postulated that this nystagmus was due to a combination of mechanical distortion and abnormal transmission of cerebrospinal fluid pressure to the aqueductal region.