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It is well known that exposure to manganese, solvents, or carbon monoxide in an occupational setting may lead to central nervous system damage and parkinsonism. The most important solvents in this respect are methanol, toluene, carbon disulfide, and n-hexane. We describe three patients who had been exposed to various solvents for more than 20 years (25, 34, and 46 years). They presented with parkinsonism, pyramidal signs, mild cognitive decline, and unresponsiveness to levodopa. Two patients had a predominantly axonal and sensory polyneuropathy of the lower legs with fasciculations in one of them. Parkinsonian features were progressive, even after the patients had stopped work. We present clinical data, neuropsychological findings, and results of brain computed tomography or magnetic resonance imaging, electroneuromyography, evoked potentials, single photon emission computed tomography, and positron-emission tomography. There is growing evidence that various organic solvents give rise to a parkinsonism syndrome with pyramidal features in susceptible individuals.

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ABSTRACT. In this note it is shown that for every dynamic vierbein field there is a gauge transformation such that the transformed field satisfies the algebraic gauge condition of Deser and Van Nieuwenhuizen. In this sense there is no Gribov phenomenon for the above gauge condition. guy(P) -~Tabh~(p)hu(P)( 1) where (Tab) = diag (1, -1, -1, -1) is the Minkowski metric, and guy the components of the metric tensor. We shall assume that g is pointwise continuously connected with the Minkowski metric (in the space of four-metrics of Minkowski signature) and has goo > 0. Because of (1) the components of the vierbein may be used instead of the guy to describe the gravitational field. This description, however, is clearly redundant as (1) is invariant under local Lorentz transformations of the vierbeinTo remove this redundancy one imposes a gauge condition on the vierbein by adding a symmetry breaking term to the Lagrangian. Deser and Van Nieuwenhuizen (3) use the background field method and take for the symmetrybreaking term the algebraic expression s -I auvaUVx/_det (guy)where H a is a fixed ('background') vierbein field, g~4~v = ~abH~H~, ha~ is the dynamical vierbein field, ab ab -a b ~ab (H~hv -guv-~abhuhv and auv = Hvhu).