The effects of pallidotomy on speech have been assessed in several studies. Schulz et al. (102) assessed six PD patients after pallidotomy and found all six to have positive changes in at least one acoustic measure. In another study, Schulz et al. (103) assessed changes in vocSPL following unilateral pallidotomy in 25 hypokinetic dysarthric individuals with PD. They found that mildly dysarthric individuals had significantly greater increases in vocSPL following pallidotomy, whereas moderately or severely dysarthric individuals had decreases in vocSPL. Uitti et al. (104) assessed 57 PD patients after pallidotomy and found that speech intelligibility was preserved, with a tendency to decline mildly in one-third of patients. Scott et al. (105) compared the effects of unilateral and bilateral pallidotomy three months after surgery and reported a fall in speech diadochokinetic rates and self-perceived worsening of pre-existing dysarthria, hypophonia, and hypersalivation/drooling following bilateral pallidotomy.
Nagulic et al. (106) used acoustic analyses to assess the effects of stereotactic thala-motomy in seven male patients with PD and found that the mean vocSPL during the initial segment of the speech signal and the voice F0 increased after thalamotomy. The voice formants F1 and F2 shifted to the higher energy and frequency regions. Parkin et al. (107) studied the effects of bilateral subthalamotomy for PD and reported speech disturbance as one of three major complications.
Farrell et al. (108) studied the effects of various neurosurgical procedures (pallidotomy, thalamotomy, DBS) on perceptual speech characteristics, speech intelligibility, and oromotor function in 22 individuals with PD. The surgical group was compared with a group of 16 participants with PD who did not undergo neurosurgery and 25 neurologically healthy individuals matched for age and sex. Results indicated that none of the neurosurgical interventions significantly changed perceptual speech dimensions or oromotor function, in spite of significant postoperative improvements in general motor function.
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