Multi-channel visual evoked potential as an ancillary tool to diagnose intraorbital optic nerve lesions

Multi-channel visual evoked potential (MVEP) recording method was used to assist in diagnosing a 4-month-old Chinese Albino rabbit with an intraorbital mass. Subcutaneous MVEP of its both eyes were recorded simultaneously using 16 electrodes (4 x 4) multi-channel array. Analysis of the cortical potential landscapes (CPL) showed that the conduction function of right eye was remarkably impaired in terms of decreased amplitudes and prolonged latencies. Specific side-dominant distribution asymmetry of the decreased MVEP amplitudes indicated that the temporal side of the optic nerve (ON) was severely involved. Overall prolonged latencies of the CPL without side differences suggested that the functional impairment could have been caused by the mechanical compression exerted by an intraorbital mass. Surgical removal procedures confirmed that the mass was located temporally to the ON. Pathological examination provided a final diagnosis of a giant polycystic mucocele. Beyond its significance as a standard tool to assess functional changes of the visual pathway, MVEP recordings might assist locating intraorbital lesions that involve the ON by careful analysis of abnormal CPLs.