Between 1985 and 1990, the authors performed stereotactic posteroventral
pallidotomies on 38 patients with
Parkinson's disease whose main complaint was
hypokinesia. Upon re-examination 2 to 71 months after surgery (mean 28 months), complete or almost complete relief of rigidity and
hypokinesia was observed in 92% of the patients. Of the 32 patients who before surgery also suffered from
tremor, 26 (81%) had complete or almost complete relief of
tremor. The
L-dopa-induced
dyskinesias and
muscle pain had greatly improved or disappeared in most patients, and gait and speech volume also showed remarkable improvement. Complications were observed in seven patients: six had a permanent partial
homonymous hemianopsia (one also had transient
dysphasia and facial weakness) and one developed transitory
hemiparesis 1 week after
pallidotomy. The results presented here confirm the 1960 findings of Svennilson, et al., that parkinsonian
tremor, rigidity, and
hypokinesia can be effectively abolished by posteroventral
pallidotomy, an approach developed in 1956 and 1957 by Lars Leksell. The positive effect of posteroventral
pallidotomy is believed to be based on the interruption of some striopallidal or subthalamopallidal pathways, which results in disinhibition of medial pallidal activity necessary for movement control.