High prevalence of extrapyramidal signs and symptoms in a group of Italian dental technicians

BMC Neurology High prevalence of extrapyramidal signs and symptoms in a group of Italian dental technicians Edito Fabrizio 1 Nicola Vanacore 0 Marcella Valente 1 Alfonso Rubino 1 Giuseppe Meco 1 0 National Centre of Epidemiology, National Institute of Health , Via Giano della Bella 34, 00161 Rome , Italy 1 Department of Neurological Sciences, "La Sapienza" University , Viale Universita 3000185 Rome , Italy Background: Occupational and chronic exposure to solvents and metals is considered a possible risk factor for Parkinson's disease and essential tremor. While manufacturing dental prostheses, dental technicians are exposed to numerous chemicals that contain toxins known to affect the central nervous system, such as solvents (which contain n-hexane in particular) and metals (which contain mercury, iron, chromium, cobalt and nickel). Methods: We performed an epidemiological and clinical study on all 27 dental technicians working in a school for dental technicians. We asked all the technicians to fill in a self-administered questionnaire on extrapyramidal symptoms, and the General Health Questionnaire (GHQ), a selfadministered screening instrument, to detect any psychiatric disorders. Moreover, we invited all 27 dental technicians to undergo a neurological examination and provide a detailed occupational history in our clinic. Results: Of the 14 subjects who underwent the neurological examination, four had postural tremor and one had a diagnosis of Parkinson's disease. Conclusion: We found a high prevalence of extrapyramidal signs and symptoms in this group of male dental technicians working in a state technical high school in Rome. We believe that this finding may be due to the presence of toxins in the dental technician's work. - Numerous case-control studies point to a role of these environmental toxins in the etiopathogenesis of PD. One study performed on 144 PD cases and 464 controls revealed a higher incidence of PD among subjects with more than 20 years' exposure to lead-iron (OR = 2.83; 95CI% 1.077.50) and iron-copper (OR = 3.69; 95 CI% 1.409.71) combinations [1]. Another study, conducted on 341 cases and 357 controls, revealed that the incidence of PD was associated with Yet another analytical epidemiological study indicated a possible association between exposure to mercury and PD [3]. Moreover, some case reports point to a link between parkinsonism and exposure to n-hexane and mercury [4,5]. An epidemiological review of this topic has been published [6]. Other case-control studies report contrasting results regarding a possible link between occupational exposure to metals and solvents and essential tremor (ET) [7,8]. Dental technicians are exposed to dust and vapour during the manufacture of dental prostheses from the negative impression of the patients' teeth provided by the dentist. Dental production entails exposure to various chemical hazards, including solvents, mineral acids, gases and vapours released during polymerisation, metal casting and porcelain baking, as well as to dust from plaster, metal alloys, ceramics and acrylic resins [9]. Moreover, during the processing of resins, particles of dust of methacrylate compounds are worked with oxidative substances that release free radicals. The dust also contains inorganic pigments such as mercury sulphide. Dental technicians are consequently exposed during the manufacture of dental prostheses to numerous chemicals that contain toxins known to affect the central nervous system, such as solvents (which contain n-hexane in particular), metals (which contain mercury, iron, chromium, cobalt and nickel) and bisphenol-A [9]. In this study, we found a high prevalence of extrapyramidal symptoms in a group of male dental technicians working in a state technical high school in Rome. Methods and population A 47-year-old, right-handed male was referred to our specialized centre for the diagnosis and treatment of PD and other extrapyramidal diseases. The neurological symptoms in this patient, consisting of heaviness in the right arm, had first appeared at the age of 44 years. At the clinical examination, the patient scored 13 in the UPDRS motor scale, (speech 1, facial expression 2, right-arm postural tremor 1, neck rigidity 1, right-arm rigidity 2, rightleg rigidity 1, right-hand finger taps 1, right-hand movements 1, right-hand rapid alternating movements 2, gait 1). The patient's anamnesis did not reveal a family history of either parkinsonism or ET. Magnetic resonance images of the encephalon, the electromyography, sensorimotor nerve conduction, motor evoked potential, serum copper and serum ceruloplasmin were all normal. An acute L-dopa test, in which the patient took one tablet of levodopa and carbidopa at dosages of 250 and 25 mg, respectively, improved the UPDRS motor score after two hours by 46%, reducing it from 13 to 7. The patient is now 50 years old and, 7 years after the onset of symptoms, and 3 years after first coming to our observation, during which the disease has remained clinically stable, the parkinsonism continues to be strictly lateralized on the right side (UPDRS motor score of 12). He has, for the last 16 months, been taking antiparkinsonian drugs; he is currently on pramipexole and selegiline at dosages of 2.1 mg/day and 5 mg/day, respectively. Although he has had a right hemiparkinsonism for 7 years, our patient's other clinical features meet the UK Brain Bank clinical diagnosis criteria for probable PD. He is a dental technician who had been teaching in a state school for dental technicians in Rome. He had, for the previous 30 years, always worked in an environment in which numerous toxic substances, such as mercury sulphate, metals and solvents, were used. The patient had never used any protective clothing, nor had he ever undergone any biochemical tests to assess his level of exposure to solvents and metals. Moreover, the patient referred that many of his colleagues had similar symptoms. We performed an epidemiological and clinical study on all 27 dental technicians (including the above patient) working in the same school for dental technicians. We asked all the technicians to fill in a self-administered questionnaire on extrapyramidal symptoms, which is used as a screening instrument to detect parkinsonism cases in the general population [10]. This questionnaire contained nine questions on symptoms (presence or absence of a symptom) and two questions regarding the diagnosis and treatment of PD. Using a cut-off of four positive answers, this questionnaire achieves a sensitivity of 90% and a specificity of 94% [10]. We also used the General Health Questionnaire (GHQ), a self-administered screening instrument, to detect any psychiatric disorders [11]. The GHQ is designed to cover four identifiable elements of distress: depression, anxiety, social impairment and hypochondriasis (indicated above all by organic symptoms). We used a GHQ-28 item version. Items were scored using con (...truncated)