Brain electrical activity mapping in adductor spasmodic dysphonia

Brain electrical activity mapping (BEAM) was employed to study ten patients exhibiting adductor spasmodic dysphonia. BEAM is a recent neural imaging technique which utilizes digital signal processing and color graphics capabilities to generate mappings of the scalp distribution of ongoing cortical EEG activity, as well as cortical evoked response amplitudes to sensory stimulation. The technique provides data for EEG eyes open, EEG eyes closed, and auditory, visual and somatosensory evoked potentials. Patient responses were compared with normative data previously established for the BEAM technique, and significance probability mappings of patient-to-normal deviations generated. Results suggest diverse neurophysiologic abnormalities among the spasmodic dysphonic patients. Specific findings varied from patient to patient but included abnormal EEG activity and abnormal evoked responses in a significant proportion of patients tested. Regions of frequent “lesion” overlap were also present. Relationships of BEAM findings with those of other neural imaging techniques, and the possible significance of these findings for neurobiological interpretations of spasmodic dysphonia will be discussed. [Work supported by a grant from NINCDS.]