Simultaneous recording of pattern electroretinography and visual evoked potentials in multiple sclerosis. A method to separate demyelination from axonal damage to the optic nerve.

Pattern electroretinograms (P-ERGs) and visual evoked potentials (VEPs) were recorded in 35 patients with multiple sclerosis and in 35 age-matched normal subjects. Four patterns of abnormalities were noted in the group with multiple sclerosis. The most frequent abnormality consisted of the following: normal P-ERG, delayed P100, and prolonged interpeak interval between the b-wave of the P-ERG and P100 (retinocortical time). This pattern indicates demyelination of the optic nerve. A second pattern consisted of absent P-ERG and absent VEP. This pattern was associated with optic atrophy and/or central scotoma, indicating severe optic nerve axonopathy with retrograde degeneration of ganglion cells. A third pattern consisted of normal P-ERG and absent VEP, suggesting a total block of transmission at the optic nerve. A fourth pattern consisted of present but low-amplitude P-ERG, delayed VEP, and prolonged retinocortical time, indicating a demyelinating process with partial axonal involvement. The concomitant use of P-ERG and VEP results in a better classification of the type and severity of dysfunction affecting the optic nerve. The prognostic value of the four patterns for recovery of visual function is discussed.