Diagnosis of psychogenic paralysis: The role of motor evoked potentials

Background In the nineties, there has been evidence that motor evoked poten tial (MEP) studies might improve the diagnosis of psychogenic paralysis. Ob jective To review a series of patients (1986-1999) who finally had a diagno sis of psychogenic paralysis at our Institutions. To detect if, over that p eriod, the time taken to make the diagnosis had changed, and, if so, this h ad any relationship to the diagnostic tests used or to other variables. Met hods We selected a patient sample (n=21) seen by the same team of neurologi sts, whose diagnostic criteria were homogeneously based on the DSM IV, and who were studied with MEPs. We analysed their clinical features, the type a nd timing of the investigations done, and the time taken to make the diagno sis. These variables acted as the dependent factors in a Multivariate Analy sis of Variance (MANOVA) model, in which the year of observation was the fi xed factor. Results The diagnosis was 50 % earlier in the period 1993 to 19 99 (10 patients) than in the period 1986-1992 (11 patients) (F = 28.3, p < 0.0001). The only associated change was an earlier MEP study (F=18.4, p < 0 .0001), which invariably showed normal findings. Conclusion MEP studies con tributed to speed up the diagnosis of psychogenic paralysis. Possibly, norm al MEPs rendered the neurologist confident about the physiological integrit y of motor fibers in the corticospinal tract, anterior roots and plexuses. Such integrity, if nerve trunks and muscles are intact and in the appropria te diagnostic context, implies a psychogenic cause for paralysis.