[Effect of deep brain stimulation on glottal phonation in patients with Parkinson's disease and multiple sclerosis].

The present study examines the effect of neurostimulatory operations on glottal phonation of 3 parkinsonian patients and 3 patients with multiple sclerosis. With the help of two voice analysis programs (MDVP from Kay Elemetrics and EEG Program by Marasek) for the acoustic and electroglottographic definition of voice characteristics, vowel productions of the patients, which were recorded under two conditions (with and without stimulation), were analysed. In a first step, significantly different intrasubject means in the two conditions indicate the effect of neurostimulation. The strength of the effect differs among subjects, particularly in the case of patients with Parkinson's disease. In a second step, a gender-differentiated comparison of the individual patient's data (recorded with and without stimulation) with a group of normal voice speakers (150 male and 150 female speakers) is carried out. This intersubject comparison proves useful in that it relativizes the results from the intrasubject comparison. It is shown for the parkinsonian patients that stimulation causes a relative deterioration of the glottal cycle, while for the patients with multiple sclerosis a tendency for hyperfunctional phonation is observed. In the latter case, the results suggest the need for long-term monitoring of phonation behaviour during chronic electrical stimulation.