A resurgence of interest in the surgical treatment of Parkinson's disease (PD) came with the rediscovery of posteroventral pallidotomy by Laitinen in 1985. Laitinen's procedure improved most symptoms in drug-resistant PD, which engendered wide interest in the neurosurgical community. Another lesioning procedure, ventrolateral thalamotomy, has become a powerful alternative to stimulate the nucleus ventralis intermedius, producing high long-term success rates and low morbidity rates. Pallidal stimulation has not met with the same success. According to the literature pallidotomy improves the “on” symptoms of PD, such as dyskinesias, as well as the “off” symptoms, such as rigidity, bradykinesia, and on-off fluctuations. Pallidal stimulation improves bradykinesia and rigidity to a minor extent; however, its strength seems to be in improving levodopa-induced dyskinesias. Stimulation often produces an improvement in the hyper- or dyskinetic upper limbs, but increases the “freezing” phenomenon in the lower limbs at the same time. Considering the small increase in the patient's independence, the high costs of bilateral implants, and the difficulty most patients experience in handling the devices, the question arises as to whether bilateral pallidal stimulation is a real alternative to pallidotomy.
Parkinson Disease: Top 25 Cited Articles
Volker M. Tronnier, Wolfgang Fogel, Martin Kronenbuerger, and Sarah Steinvorth
Alim Louis Benabid, Pierre Pollak, Dongming Gao, Dominique Hoffmann, Patricia Limousin, Emmanuel Gay, Isabelle Payen, and Abdhelhamid Benazzouz
✓ Tremor was suppressed by test stimulation of the thalamic ventralis intermedius (VIM) nucleus at high frequency (130 Hz) during stereotaxy in nonanesthetized patients suffering from Parkinson's disease or essential tremor. Ventralis intermedius stimulation has since been used by the authors over the last 8 years as a treatment in 117 patients with movement disorders (80 cases of Parkinson's disease, 20 cases of essential tremor, and 17 cases of various dyskinesias and dystonias including four multiple sclerosis). Chronic electrodes were stereotactically implanted in the VIM and connected to a programmable stimulator. Results depend on the indication. In Parkinson's disease patients, tremor, but not bradykinesia and rigidity, was selectively suppressed for as long as 8 years. Administration ofl-Dopa was decreased by more than 30% in 40 Parkinson's disease patients. In essential tremor patients, results were satisfactory but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their tremor. In other types of dyskinesias (except multiple sclerosis), results were much less favorable. Fifty-nine patients underwent bilateral implantation and 14 other patients received implantation contralateral to a previous thalamotomy. Thirty-seven patients (31.6%) experienced minor side effects, which were always well tolerated and immediately reversible. Three secondary scalp infections led to temporary removal of the implanted material. There was no permanent morbidity. This tremor suppression effect could be due to the inhibition or jamming of a retroactive loop. Chronic VIM stimulation, which is reversible, adaptable, and well tolerated even by patients undergoing bilateral surgery (74 of 117 patients) and by elderly patients, should replace thalamotomy in the regular surgical treatment of parkinsonian and essential tremors.
Andres Lozano, William Hutchison, Zelma Kiss, Ronald Tasker, Karen Davis, and Jonathan Dostrovsky
✓ Methods for localizing the posteroventral globus pallidus internus are described. The authors' techniques include the use of microelectrodes to record single-unit activity and to microstimulate in human pallidum and its surrounding structures. This technique allows a precise determination of the locations of characteristic cell types in sequential trajectories through the external and internal segments of the pallidum. The location of the optic tract can be determined from microstimulation-evoked visual sensations and recordings of flash-evoked potentials. In addition, microstimulation-evoked motor and sensory responses allow the internal capsule to be identified. The data collected using this technique are an important adjunct to selecting optimum sites to place electrocoagulation lesions for stereotactic posteroventral pallidotomy for refractory Parkinson's disease.
Lauri V. Laitinen, A. Tommy Bergenheim, and Marwan I. Hariz
✓ 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.
Mark W. Fox, J. Eric Ahlskog, and Patrick J. Kelly
✓ Thirty-six patients with Parkinson's disease and medically refractory tremor underwent stereotactic ventrolateralis thalamotomy at the Mayo Clinic between 1984 and 1989. All patients had been or were being treated with carbidopa/levodopa but with unsatisfactory tremor control. Modern stereotactic techniques, including microelectrode recording, were used to treat 36 patients, of whom 31 (86%) had complete abolition of tremor and three patients (5%) had significant improvement. Tremor recurred in two patients within 3 months of surgery; however, the remaining patients suffered no recurrence of tremor during follow-up periods ranging from 14 to 68 months (mean 33 months). Persistent complications (arm dyspraxia, dysarthria, dysphasia, or abulia) were noted in five patients but were a source of disability in only two. It is concluded that thalamotomy in carefully selected patients is a beneficial operation for the control of medically refractory parkinsonian resting tremor.