John P. Hammerstad

3-Nitropropionic acid-exogenous animal neurotoxin and possible human striatal toxin.

3-Nitropropionic acid (3-NPA)--a suicide inhibitor of succinate dehydrogenase--is a widely distributed plant and fungal neurotoxin known to induce a damage to basal ganglia, hippocampus, spinal tracts and peripheral nerves in animals. Recent reports from Northern China indicate that 3-NPA is also likely to be responsible for the development of putaminal necrosis with delayed dystonia in children after ingestion of mildewed sugar cane. This article discusses the role of 3-NPA in the causation of the disease in China, its neurotoxic effects in animals and the potential role for this compound as a probe of selective neuronal vulnerability.

Comparison of Pallidal and Subthalamic Nucleus Deep Brain Stimulation for Advanced Parkinson's Disease: Results of a Randomized, Blinded Pilot Study

OBJECTIVE Deep brain stimulation (DBS) of the globus pallidus internus (GPi) and subthalamic nucleus (STN) has been reported to be effective in alleviating the symptoms of advanced Parkinsons disease (PD). Although recent studies suggest that STN stimulation may be superior to GPi stimulation, a randomized, blinded comparison has not been reported. The present study was designed to provide a preliminary comparison of the safety and efficacy of DBS at either site. METHODS Ten patients with idiopathic PD, L-dopa-induced dyskinesia, and response fluctuations were randomized to implantation of bilateral GPi or STN stimulators. Neurological condition was assessed preoperatively with patients on and off L-dopa and on DBS at 10 days and 3, 6, and 12 months after implantation. Patients and evaluating clinicians were blinded to stimulation site throughout the study period. Complete follow-up data were analyzed for four GPi patients and five STN patients. RESULTS When off-L-dopa, both GPi and STN groups demonstrated a similar response, with approximately 40% improvement in Unified PD Rating Scale motor scores after 12 months of DBS. Rigidity, tremor, and bradykinesia improved in both groups. In combination with L-dopa, Unified PD Rating Scale motor scores were more improved by GPi stimulation than by STN stimulation. On-L-dopa axial symptoms were clinically improved in the GPi but not the STN group. L-Dopa-induced dyskinesia was reduced by DBS at either site, although medication requirement was reduced only in the STN group. There were no serious intraoperative complications among patients in either group. CONCLUSION Pallidal and STN stimulation appears to be safe and efficacious for the management of advanced PD. A larger study is needed to investigate further the differences in symptom response and the interaction of L-dopa with stimulation at either site.

Ropinirole for the treatment of early Parkinson's disease

A prospective, randomized, placebo-controlled, double-blind, parallel-group, 6-month study assessed the efficacy and safety of ropinirole, a nonergoline D2-dopamine agonist, in patients with early Parkinsons disease (n = 241; Hoehn & Yahr stages I to III) with limited or no prior dopaminergic therapy. Patients (mean age, 62.8 years), stratified by concomitant use of selegiline, were randomized to ropinirole (n= 116) or placebo (n = 125). The starting dose of ropinirole was 0.25 mg tid with titration to at least 1.5 mg tid (maximum dose, 8 mg tid). Primary efficacy endpoint was the percentage improvement in Unified Parkinsons Disease Rating Scale (UPDRS) motor score. Ropinirole-treated patients had a significantly greater percentage improvement in UPDRS motor score than patients who received placebo (+24% vs -3%; p < 0.001). Ropinirole was well tolerated and patient withdrawals were infrequent. Most adverse experiences were related to peripheral dopaminergic activity. Ropinirole monotherapy is an effective and well-tolerated therapeutic option for treatment of early Parkinsons disease.

Effect of peripheral catechol‐O‐methyltransferase inhibition on the pharmacokinetics and pharmacodynamics of levodopa in parkinsonian patients

Article abstract –Catechol-O-methyltransferase (COMT) metabolizes a portion of administered levodopa and thus makes it unavailable for conversion to dopamine in the brain. In an open-label trial, we examined the effects of entacapone, a peripheral inhibitor of COMT, administered acutely or for 8 weeks, on the pharmacokinetics and pharmacodynamics of levodopa in 15 parkinsonian subjects with a fluctuating response to levodopa. Acutely and chronically administered entacapone similarly decreased the plasma elimination of orally and intravenously administered levodopa. Absorption of levodopa was minimally affected. During chronic entacapone treatment, daily levodopa dosages were reduced by 27% yet mean plasma levodopa concentrations were increased by 23%. Plasma 3-O-methyldopa concentrations were decreased by 60%. Entacapone increased the duration of action of single doses of levodopa by a mean of 56%. The percent of the day “on” after 8 weeks of entacapone treatment was 77%; it dropped to 44% upon withdrawal of entacapone. We conclude that inhibition of COMT by entacapone increases the plasma half-life of levodopa and augments the antiparkinsonian effects of single and repeated doses of levodopa.

DBS and diathermy interaction induces severe CNS damage

Pulse-modulated radiofrequency diathermy treatment to the maxilla produced permanent diencephalic and brainstem lesions and a vegetative state in a patient with PD with implanted subthalamic electrodes for deep brain stimulation.

Functional correlates of pallidal stimulation for Parkinson's disease

We measured regional cerebral blood flow with H215O and positron emission tomography (PET) scanning at rest and during a motor task to study the mechanism of motor improvement induced by deep brain stimulation of the internal globus pallidus in Parkinsons disease. Six right‐handed patients with Parkinsons disease were scanned while performing a predictable paced sequence of reaching movements and while observing the same screen displays and tones. PET studies were performed ON and OFF stimulation in a medication‐free state. Internal globus pallidus deep brain stimulation improved off‐state United Parkinsons Disease Rating Scale motor ratings (37%, p < 0.002) and reduced timing errors (movement onset time, 55%, p < 0.01) as well as spatial errors (10%, p < 0.02). Concurrent regional cerebral blood flow recordings revealed a significant enhancement of motor activation responses in the left sensorimotor cortex (Brodmann area [BA] 4), bilaterally in the supplementary motor area (BA 6), and in the right anterior cingulate cortex (BA 24/32). Significant correlations were evident between the improvement in motor performance and the regional cerebral blood flow changes mediated by stimulation. With internal globus pallidus deep brain stimulation, improved movement initiation correlated with regional cerebral blood flow increases in the left sensorimotor cortex and ventrolateral thalamus and in the contralateral cerebellum. By contrast, improved spatial accuracy correlated with regional cerebral blood flow increases in both cerebellar hemispheres and in the left sensorimotor cortex. These results suggest that internal globus pallidus deep brain stimulation may selectively improve different aspects of motor performance. Multiple, overlapping neural pathways may be modulated by this intervention. Ann Neurol 2001:49:155–164

Patterns of Asymmetry Do Not Change Over the Course of Idiopathic Parkinsonism Implications for Pathogenesis

Article abstract-We investigated the asymmetry of focal deficits of bradykinesia in a cross-sectional study of 198 patients with idiopathic parkinsonism. We have analyzed the difference in Unified Parkinsons Disease Rating Scale (UPDRS) scores between the more and less affected sides in these patients, whose duration of symptoms ranged from 1 to 15 years. There was no significant change in the asymmetry or focality over this period; the deficit for each side progressed faster initially and then approached the normal age-related linear rate of decline. Previous studies indicate that there is an inverse linear relation between the UPDRS bradykinesia score and the nigral dopaminergic cell count. We infer that the rate of death of nigral dopaminergic neurons is predetermined from the time of onset of pathogenesis. The simplest explanation is that a causal event kills some cells and damages others so that they undergo premature death. This sequence of changes could be implemented through environmental (toxic or viral) damage to the genome. Several diverse sources of evidence support this concept. NEUROLOGY 1995;45: 435-439

Interactions between deep brain stimulation and levodopa in Parkinson’s disease

Objective: To quantify the effects of deep brain stimulation (DBS) of globus pallidus interna (GPi) and subthalamic nucleus (STN) on motor fluctuations and dyskinesia in PD and to determine how the response to levodopa was modified by DBS. Background: Patients report that DBS reduces levodopa-induced motor fluctuations and dyskinesia throughout the day, but this has not been objectively measured. Further, the means by which DBS alters the response to levodopa to improve motor fluctuations is unknown. Methods: Twelve subjects, six with bilateral GPi electrodes and six with bilateral STN electrodes, were studied 12 to 33 months after surgery. To quantify motor fluctuations and dyskinesia, subjects were monitored hourly throughout 2 waking days with their usual oral medications, 1 day with DBS on and 1 day with DBS off, with subjects and nurse raters blinded to DBS status. To examine the effects of DBS on levodopa pharmacodynamics, the effects of a 2-hour levodopa infusion were examined, 1 day with DBS on and 1 day with DBS off, again under double-blind conditions. Time course of variations in parkinsonism was evaluated by tapping speed, arising and walking speed, tremor scores, and dyskinesia scores. Results: DBS raised the mean tapping speed and reduced the coefficient of variation during the waking day. This was achieved by increasing the lowest or trough tapping speed between doses of antiparkinson medications. Mean walking speed was modestly increased and mean tremor scores were reduced. DBS increased the drug-off tapping speed, but neither the peak response nor the duration of response to levodopa was affected by DBS. The study was not powered to detect differences between GPi and STN stimulation and the only difference that approached significance was that GPi reduced peak dyskinesia and STN tended to increase peak dyskinesia. Conclusion: DBS objectively reduces motor fluctuations. This is achieved by reduction of drug-off disability and not by alterations in levodopa pharmacodynamics. This finding suggests alleviation of interdose trough disability as an alternative strategy to prolonging the effects of each dose of levodopa as a means to reduce motor fluctuations.

Intracranial calcification in hyperparathyroidism associated with gait apraxia and parkinsonism

Two patients with hyperparathyroidism had symmetric calcification of the brain, including the basal ganglia. In both patients, the neurologic disorder included parkinsonism and gait apraxia. Computerized tomography may help define the prevalence and clinical manifestations of this rare syndrome.

Assessments of axial motor control during deep brain stimulation in parkinsonian patients.

OBJECTIVEWe tested the hypothesis that bilateral deep brain stimulation (DBS) in the globus pallidus internus or the subthalamic nucleus improves various components of postural and oromotor function and that some of the components correlate with changes in the Unified Parkinson’s Disease Rating Scale (UPDRS) in patients with Parkinson’s disease. METHODSSix patients with Parkinson’s disease were evaluated for four postural and two orofacial UPDRS items, and quantitative tests of posture adjustments and oromotor control were performed while the patients were on and off DBS. Measurements of postural adjustments included reactive force and latency before a voluntary step. The oromotor assessments involved velocity and amplitude changes during voluntary jaw movement. RESULTSDBS significantly improved the total UPDRS motor score by an average of 44%, which included improvement of 18 to 54% in the postural and orofacial items. DBS also decreased foot lift-off latency significantly, but it produced a variable response to the preparatory postural force in the swing limb. DBS significantly improved jaw-opening velocity by 14 to 50% and jaw opening amplitude by 5 to 41%. Significant correlations for the percentage change from off and on DBS occurred among a few UPDRS items and foot lift-off latency and jaw-opening velocities. CONCLUSIONDBS in either the globus pallidus internus or the subthalamic nucleus induces improvements in bradykinesia of specific components of postural and oromotor control, which also can be measured by the postural and orofacial UPDRS items. In some Parkinson’s disease patients, DBS results in improvements in force or amplitude control, although these changes are not reflected in changes in UPDRS postural and orofacial items. A battery of quantitative and clinical tests must be used to evaluate the effects of DBS on axial motor control adequately.