Faculty Bibliography

Eighteen patients with medically intractable Parkinson's disease that was characterized by bradykinesia, rigidity, and marked 'on-off' fluctuations underwent stereotactic ventral pallidotomy under local anesthesia. Targeting was aided by anatomic coordinates derived from the MRI, intraoperative cell recordings, and electrical stimulation prior to lesioning. A nonsurgically treated group of seven similarly affected individuals was also followed. Assessment of motor function was made at baseline and at 3-month intervals for 1 year. Following the lesioning, patients improved in bradykinesia, rigidity, resting tremor, and balance with resolution of medication-induced contralateral dyskinesia. When compared with preoperative baseline, all quantifiable test scores after surgery improved significantly with the patients off medications for 12 hours: UPDRS by 65%, and CAPIT subtest scores on the contralateral limb by 38.2% and the ipsilateral limb by 24.2%. Walk scores improved by 45%. Medication requirements were unchanged, but the patients who had had surgery were able to tolerate larger doses because of reduced dyskinesia. Ventral pallidotomy produces statistically significant reduction in parkinsonism and contralateral 'on' dyskinesia without morbidity or mortality and with a short hospitalization in Parkinson's disease patients for whom medical therapy has failed

Our ongoing study of ventral pallidotomy for the control of Parkinson's disease in selected patients has provided the opportunity to explore the topographical and somatotopic organization of the human globus pallidus. Utilizing microelectrode techniques we have obtained recordings which were correlated with data from MPTP-parkinsonian primates. In addition, we performed pre- and post-operative FDG/PET scans in these patients. Our studies reveal similarities between the MPTP-parkinsonian primate model and human Parkinson's disease in terms of physiologic recordings and responses. However, we have encountered significant differences between dominant and non-dominant hemisphere representations, particularly for the hand, in the human. In addition, our PET studies confirmed, as in previous parkinsonian primate models, glucose hypermetabolism in the lenticular area of Parkinson's disease patients. This hypermetabolism is dramatically altered by creation of a lesion in the globus pallidus medialis. This is demonstrated by follow-up PET scans which reveal not only a decrease in metabolism of the operated lenticular region, but also in the frontal cortical projections. These combined observations of the cellular activity in the globus pallidus and the observed changes in PET metabolism support the selection of the pallidum for lesioning and control of Parkinson's disease, and offer insight into the underlying physiology of this disorder. The above physiological and PET data will be clinically correlated with our ongoing series of 35+ patients

dl-threo-Methylphenidate (Ritalin) was labeled with carbon-11 (t1/2:20.4 minutes) in order to measure its pharmacokinetics, to evaluate it as a radiotracer for the presynaptic dopaminergic neuron, and to examine its sensitivity to the loss of dopaminergic neurons. Positron emission tomographic (PET) studies were carried out in the baboon to determine specificity for the presynaptic dopaminergic neuron and in humans to assess sensitivity to neuronal loss. Studies with [11C]dl-threo-methylphenidate ([11C]MP) in baboon demonstrated high regional uptake in the striatum. Peak uptake (0.04%/cc) occurred at 5-15 minutes post-injection. The half-time for clearance from peak uptake for [11C]MP was 60 minutes and the ratio between the radioactivity in the striatum and that in the cerebellum (ST/CB) ranged from 2.2 to 2.6 at 40 minutes. Repeated measures in the same baboon showed < or = 8% variability in the ST/CB ratio. Pretreatment with unlabeled methylphenidate (0.5 mg/kg) or GBR12909 (1.5 mg/kg) 30 minutes prior to [11C]MP injection markedly reduced the striatal but not the cerebellar uptake of [11C]MP, demonstrating the saturable and specific binding of [11C]MP to a site on the dopamine transporter in the brain. In both cases, the ratio of striatum to cerebellum (ST/CB) after pretreatment was reduced by about 43%. The ratios of distribution volumes at the steady-state for the striatum to cerebellum (ST/CB) for these two separate studies in the same baboon were reduced by 37 and 38%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

L-Deprenyl (Selegeline) is an enzyme-activated irreversible inhibitor of monoamine oxidase B (MAO B; EC 1.4.3.4). It is used to treat Parkinson's disease at a dose of 5 mg twice a day. Since enzyme inhibition is irreversible, the recovery of functional enzyme activity after withdrawal from L-deprenyl requires the synthesis of new enzyme. We have measured a 40 day half-time for brain MAO B synthesis in Parkinson's disease and in normal subjects after withdrawal from L-deprenyl. This is the first measurement of the synthesis rate of a specific protein in the living human brain. L-Deprenyl is currently used by 50,000 patients with Parkinson's disease in the United States and its use is expected to increase with reports that it may be beneficial in Alzheimer's disease. The slow turnover of brain MAO B suggests that the current clinical dose of L-deprenyl may be excessive and that the clinical efficacy of reduced dosing should be evaluated. Such an evaluation may have mechanistic importance as well as an impact on reducing the side effects and the costs arising from excessive drug use

Neuronal properties of the human globus pallidus (GP) are not known. Since GP is the major output of the basal ganglia, it may be involved in the pathophysiology of Parkinson's disease. We studied 12 patients with medically resistant Parkinson's disease by using single cell recording of the GP during stereotaxic pallidotomy to define neuronal firing rate and its modulation during active and passive movements. Different frequency and pattern of single cell activity was found in globus pallidus externus compared with globus pallidus internus. Discharge rates of 19% of GP cells were modulated by passive contralateral movements. Pallidal units were most often related solely to single joint movement. Different patterns of activity in relation to the two different movements of the same joint were often observed. We identified somatotopically arranged cell clusters that alter discharge rate with related movements. These findings suggest at least a partial somatotopic organization of the human GP and similarity with experimental results in both healthy and MPTP monkeys, providing a rationale for surgical or pharmacological targeting of GP for treating Parkinson's disease