[Diagnostic importance of electrophysiologic tests in Bell's palsy: report on a longterm follow-up study in 100 cases (author's transl)].

The present study is based upon the results of repeated electrodiagnostic tests carried out in a series of 100 cases of Bell's palsy (Determination of Rheobase and Chronaxy). The first symptoms of denervation can be observed during the second week after the onset of the paralysis. This seems to be the critical period in which the ultimate consequences of the lesion are determined: partial or total recovery or complete irreversible denervation. In cases showing a rapid increase of chronaxy during the 2nd week, prognosis is rather poor because a difference of 240% between the affected and the normal side indicates a progressive denervation. Cases in which the difference of chronaxy values during the 2nd week is increased upto 240% (i.e. partial denervation) recover incompletely in 15% of the cases. Estimation of prognosis in Bell's palsy and timing of a facial nerve decompression must be based on reliable facts, such as the results of repeated electrodiagnostic tests (modified measurement of Rheobase and Chronaxy) carried out at least every secont but preferably every day during the first 3 weeks after the onset of the paresis.