Reversal of vision metamorphopsia: clinical and anatomical characteristics.

BACKGROUND

Metamorphopsia is a visual illusion that distorts the size, shape, or inclination of objects. Reversal of vision metamorphopsia (RVM) is a rare transient form of metamorphopsia described as an upside-down, 180 degrees rotation of the visual field in the coronal plane. The pathophysiological characteristics of RVM remain unclear.

DESIGN

Patients with RVM had a complete neurologic examination during or shortly after an episode of metamorphopsia, with particular emphasis on gaze disorders, visual fields, visually guided hand movements, and perceptual or cognitive deficits. Workup included imaging studies, visual field examinations, and brainstem auditory and visual evoked response.

SETTING

Department of Neurology, Hadassah University Hospital, Hebrew University-Hadassah Medical School, Jerusalem, Israel.

PATIENTS

Six consecutive patients were evaluated from 1991 to 1996.

RESULTS

Five patients had parieto-occipital brain insult sparing the primary visual cortex, and 3 also had evidence of a concomitant brainstem or cerebellar syndrome. One patient had pure brainstem syndrome underlying the RVM. Three patients had complete RVM as well as oblique RVM of less than 180 degrees.

CONCLUSIONS

These cases imply a possible anatomical localization of the central integrator of visual extrapersonal orientation. Our observations suggest that a separate central mechanism of visual orientation might exist in each cerebral hemisphere and that occipital and parietal lesions that spare the optic radiations may account for the oblique and complete RVM. We postulate that failure to perceive space in an allocentric coordinate frame, particularly in the coronal roll plane, is potentially the critical event underlying RVM.