SPEECH FREEZING IN PARKINSONS-DISEASE - A KINEMATIC ANALYSIS OF OROFACIAL MOVEMENTS BY MEANS OF ELECTROMAGNETIC ARTICULOGRAPHY

Kinematic recordings of orofacial movements by means of electromagneti c articulography were performed in an akinetic-rigid Parkinsonian pati ent presenting with intermittent speech freezing in diadochokinesis ta sks (rapid repetitions of the syllable /ta/). During freezing periods the patient produced a sustained /a/ instead of the required consonant -vowel sequences. The underlying articulatory trajectories were charac terized by repetition rates amounting to 8-10 Hz concomitant with redu ced movement amplitudes. Obviously, the undershooting of articulatory gestures failed to establish a sufficient occlusion of the vocal tract giving rise to the perceived speech freezing. In contrast, preserved diadochokinesis occurred at frequencies of 4-6 Hz. Most probably, the increased articulatory repetition rate reflects a pacing of orofacial movements by released tremor oscillations. Due to slowing of articulat ory movements spastic dysarthrics can also present with missing syllab ic modulation during oral diadochokinesis. The results of the articulo graphic recordings demonstrate the different pathophysiology of Parkin sonian freezing.