CORRELATION-ANALYSIS OF SOMATOSENSORY-EVOKED POTENTIAL WAVE-FORMS - CLINICAL-APPLICATIONS

Objective: To assess the validity of the correlation coefficient (CC) as a diagnostic tool in evaluating somatosensory evoked potential (SEP ) waveforms. Design: SEP waveforms were recorded over the spine and sc alp in response to tibial nerve stimulation at the ankle for 30 patien ts. Setting: A general community, ambulatory, private referral center. Patients: Patients were all ambulatory and were selected randomly fro m among existing patient records at the medical. center. Main Outcome Measure: The test for validity uses the CC to verify reproducibility. the test for side-to-side symmetry uses the CC to obtain a measure of similarity between left and right tibial scalp responses. For both tes ts, a table is presented with CCs for normal subjects. If the CC for e ach patient falls below the appropriate critical value from the table, then the CC is taken to be abnormal; p values are provided at specifi c levels in this table. Results: A new data base for the means and cri tical values of CCs with corresponding p values is established for nor mal subjects. Most of the patient data reveal significant CC nonreprod ucibility and lack of symmetry in tibial scalp SEP waveforms. Conclusi on: The CC provides objective and quantitative waveform information th at complements latency and amplitude measurements in the clinical inte rpretation of tibial scalp SEP waveforms. (C) 1998 by the American Con gress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.