Electrophysiology and avoidance of invasive neuroradiology in multiple sclerosis

A prospective study of "undiagnosed" isolated myelopathy: I. Case selection and clinical features

We aimed to carry out a study of isolated, unexplained myelopathy which avoided as far as possible selection and referral bias. We used a prospective design with case ascertainment from both neurological and neurosurgical referrals. We wanted to establish the sensitivity, predictive value and possible redundancy of currently available tests as assessed by the proportion of such patients who finally developed clinically definite multiple sclerosis at follow up. Although MRI scanning of the spinal cord is now the investigation of choice for myelopathy, the case ascertainment for the present studies was completed, and follow-up commenced, before MRI became available to patients in our catchment region. We believe that this was an important factor in the ascertainment of a representative sample of undiagnosed myelopathies. Of 2104 patients having myelography in a 36-month period, 473 had signs of a myelopathy without lower motor neurone involvement Sixty-nine of these 473 patients (15%, 95% CI 11.8-18.2) eventually satisfied the entry criteria for the prospective trial. Fourteen of the 69 patients (20%) presented with acute or subacute cord syndromes, while 55 (80%) had chronic symptoms of more than 3 months duration. Approximately two-thirds of the chronic cases were progressive and one-third relapsing and remitting. Overall there was a female predominance (3:2) and a significant excess of HLA-DR2 antigen compared with a healthy control population (p < 0.0001). In this series the patients with chronic unexplained myelopathy were younger and had shorter symptom durations (mean 46.5 months) and less disability (mean EDSS 3.0) than cases in other comparable published series. The neurological findings, sex distribution and HLA characteristics were similar to those found in patients with clinically definite MS.

The incidence of abnormal pattern electroretinography in optic nerve demyelination

This report describes the pattern electroretinogram (PERG) findings in 141 patients with optic nerve demyelination in one or both eyes. The overall incidence of PERG abnormality in the 199 eyes with abnormally delayed pattern visual evoked potential (PVEP) P100 component was 39.2%, with 84.6% of these PERG abnormalities being confined to the N95 component. The incidence of abnormal PERG was greater (53.3%) in those eyes with a history of retrobulbar neuritis than in those with sub-clinical demyelination (22.8%). The importance of stimulus parameters is noted. The value of the PERG in the improved interpretation of an abnormal PVEP is discussed.

Pattern electroretinography in patients with delayed pattern visual evoked potentials due to distal anterior visual pathway dysfunction

Between March 1983 and January 1988 delayed pattern visual evoked potentials (PVEP) were observed in 67 patients with distal visual pathway dysfunction. Many of these patients had been referred for neurophysiological examination because of possible optic nerve dysfunction. These patients also had pattern electroretinography (PERG) performed which in all cases showed an abnormality of the main positive P50 component. None of these patients had an abnormality confined to the negative N95 component, the type of abnormality usually found if the PERG is abnormal in optic nerve disease. It is suggested that PERG recording should now be a routine adjunct to the PVEP in the assessment of anterior visual pathway dysfunction.

Value of visual evoked response and oligoclonal bands in cerebrospinal fluid in diagnosis of spinal multiple sclerosis

To assess the predictive value of prolongation of visual evoked response (VER) plus the presence of oligoclonal bands in the cerebrospinal fluid (CSF) in the diagnosis of multiple sclerosis (MS) in patients with isolated cord lesions, the false-positive rate for the two tests combined was determined by a prospective analysis of 42 patients with a structural spinal cord lesion. The false-positive rate for the combination of VER and CSF abnormalities was zero, but the individual false-positive rates were 10% for VER and 12% for CSF protein oligoclonal bands. According to Bayes' theorem, and taking into account the false-positive rates of the tests in the population studied and the prevalence of MS and the true-positive rates for the tests as derived from published reports, abnormalities of VER and CSF protein together gave a probability of MS of 100%. However, if only either the VER or the CSF were abnormal, the probability of MS was 44% or 49%, respectively. An abnormal result for both tests thus indicates a sufficiently high probability of MS to exclude myelography, but a positive result in only one test warrants the procedure.

Diagnostic techniques in multiple sclerosis

Although multiple sclerosis (MS) has been an area of great interest and effort in numerous scientific disciplines, its etiology, pathogenesis and therapy remain mysterious. Perhaps the most significant advances have resulted from the ability to be more precise in establishing the diagnosis of MS. Among the most important of the new diagnostic tools are electrophysiological techniques for examination of the visual and oculomotor systems. Tests such as the visually evoked potential (VEP) can confirm the existence of clinically suspected lesions and document the presence of asymptomatic ones. Various electrophysiological techniques for detection and evaluation of MS, as well as CSF analysis, psychological and neuroradiological procedures, and immunological observations are described. The relationship between optic neuritis and MS is reviewed, as are therapeutic regimens in use and under study.