From the comparison we have made between PD and manganism, we draw the following conclusions: 1. There are similarities between PD and manganism, notably the presence of (a) generalized bradykinesia and (b) widespread rigidity. 2. There are also dissimilarities between PD and manganism, notably the following in manganism: (a) less-frequent resting tremor, (b) more frequent dystonia, (c) a particular propensity to fall backward, (d) failure to achieve a sustained therapeutic response to levodopa, and (e) failure to detect a reduction in fluorodopa uptake by PET. Further studies are likely to yield more discriminants between PD and manganism. For example, PET with raclopride may be useful in early cases of manganism, and MRI may be helpful in patients with advanced manganism.

We report a longitudinal follow-up study on six patients with chronic manganese-induced parkinsonism following cessation of manganese exposure. Compared with the 1987 study, their parkinsonian symptoms showed a slow progression, particularly in gait disturbances such as freezing during turning and walking backward with retropulsion. The mean disability scores on the King's College Hospital Rating Scale were 15.0 +/- 4.2 in 1987 and 28.3 +/- 6.7 in 1991 (p = 0.003, paired t test). Review of the video records also confirmed a worsening of parkinsonism, especially in difficulty turning. Three of six patients receiving levodopa treatment had an initial improvement. The response decreased after 2 to 3 years. During the therapy, they did not develop on-off fluctuation or dyskinesia. We conclude that patients with manganese-induced parkinsonism may develop increasing neurologic dysfunction long after cessation of exposure and that their responses to levodopa are different from those of patients with Parkinson's disease.

No abstract

Betel chewing has been claimed to produce a sense of well-being, euphoria, heightened alertness, sweating, salivation, a hot sensation in the body and increased capacity to work. Betel chewing also leads to habituation, addiction and withdrawal. However, the mechanisms underlying these effects remain poorly understood. Arecoline, the major alkaloid of Areca nut, has been extensively studied, and several effects of betel chewing are thought to be related to the actions of this parasympathomimetic constituent. However, betel chewing may produce complex reactions and interactions. In the presence of lime, arecoline and guvacoline in Areca nut are hydrolyzed into arecaidine and guvacine, respectively, which are strong inhibitors of GABA uptake. Piper betle flower or leaf contains aromatic phenolic compounds which have been found to stimulate the release of catecholamines in vitro. Thus, betel chewing may affect parasympathetic, GABAnergic and sympathetic functions. Betel chewing produces an increase in heart rate, blood pressure, sweating and body temperature. In addition, EEG shows widespread cortical desynchronization indicating a state of arousal. In autonomic function tests, both the sympathetic skin response and RR interval variation are affected. Betel chewing also increases plasma concentrations of norepinephrine and epinephrine. These results suggest that betel chewing mainly affects the central and autonomic nervous systems. Future studies should investigate both the acute and chronic effects of betel chewing. Such studies may further elucidate the psychoactive mechanisms responsible for the undiminished popularity of betel chewing since antiquity.

Betel quid chewing has been claimed to produce a sense of well-being, euphoria, warm sensation of the body, sweating, salivation, palpitation, heightened alertness and increased capacity to work. These effects suggest that betel quid chewing affects predominantly the central and autonomic nervous systems. Several studies have been conducted to elucidate the central and autonomic effects of betel quid chewing. The results are: (1) betel quid chewing increased the heart rate with onset within 2 minutes, maximal effect within 4-6 minutes and an average duration of 16.8 minutes. The cardio-acceleratory response was more prominent for fresh and occasional chewers than for habitual chewers; (2) betel quid chewing increased the skin temperature with onset and duration similar to a cardio-acceleratory response. The hyperthermic effect was abolished by atropine and partly inhibited by propranolol. (3) Betel quid chewing had no effect on simple reaction time but shortened the choice reaction time. (4) Betel quid chewing produced widespread cortical desynchronization of EEG. (5) Chewing of one or two betel quids attenuated the sympathetic skin response while continued consumption of more than two betel quids affected the RR interval variation. (6) Plasma concentrations of noradrenaline and adrenaline were elevated during betel quid chewing. These studies have confirmed several effects claimed by betel quid users. The effects of betel quid chewing appeared to be habit-related and dose-dependent. Although arecoline has been thought to be responsible for several effects of betel quid chewing, the present data suggest a role also played by sympathetic activation.