Magnetic resonance imaging (MRI) of the optic nerves using the STIR (short inversion time inversion recovery) sequence was performed in 37 adult patients with a recent or past attack of optic neuritis. MRI revealed high-signal regions in 84% of symptomatic and 20% of asymptomatic nerves. The mean longitudinal extent of lesions was 1 cm. Slow or poor visual recovery was associated with more extensive lesions, or lesions within the optic canal. Disk swelling was usually associated with anterior lesions but also occurred with lesions in the canal. Visual evoked potentials were even more sensitive than MRI in detecting lesions and are still the investigation of choice in suspected demyelinating disease involving the optic nerve.

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Two tests of binaural hearing, namely intensity discrimination of alternating monaural clicks and interaural time difference (IATD) discrimination of binaural clicks, were performed in 28 patients with definite multiple sclerosis (MS) and 12 with an isolated brainstem lesion compatible with demyelination. Intensity discrimination defects were found in 53.5% and IATD defects in 82% of definite MS cases, although no overt auditory symptoms were reported and pure tone audiology was unremarkable. Corresponding figures in the isolated lesion group were 25% and 33%. Defects were manifested either by an abnormal 'bias' in favour of one ear or by a broadened 'spread' of responses (i.e., greater range of uncertainty). Brainstem auditory evoked potentials (BAEPs) were abnormal in 75% of the definite MS cases but only in 8% of the isolated lesion group. BAEP abnormalities involving component III on one or both sides were invariably associated with a defect of IATD discrimination. This is consistent with disruption of input to the superior olivary complex, the most peripheral structure where binaurally responsive units are sensitive to IATD. Lesions causing abnormality of component V alone less frequently resulted in impaired IATD discrimination, possibly because at rostral levels the IATD is encoded by the location rather than the timing of neuronal activity. In magnetic resonance imaging (MRI), abnormalities of the medulla, pons or midbrain were demonstrated in all MS patients tested and 45% of those with isolated brainstem lesions. The correlation with BAEP abnormalities was plausible in some patients but apparently anomalous in others. More severe BAEP abnormalities than would have been expected on the basis of MRI may have been due to small unresolved lesions, while the more frequent finding of normal or mildly abnormal BAEPs in conjunction with extensive MRI abnormalities may have been due to the fact that areas of abnormal signal reflect an increase in the water content of the tissue rather than demyelination per se.

SUMMARY A group of 53 patients who had suffered an attack of unilateral (n=45) or bilateral (n=8) optic neuritis more than six months before were subjected to a battery of tests to determine their spatial contrast sensitivity, visual field, and colour vision. The 106 eyes investigated were classified according to their clinical status and visual acuity at the time of the study into unaffected (n=45), recovered (n=33), and non-recovered (n=28). At least one of the three tests gave an abnormal result in 67%, 88%, 100% of the three groups respectively. The results obtained with these three tests showed a significant statistical association.