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, right-leg 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 conventional 0,1,2,3 Likert scores for the response categories. When a two-point score (present or absent) was used for the GHQ, a cut-off score of 6 or above was the optimal threshold for sensitivity (79.2%) and specificity (79.6%)[11
Lastly, all 27 dental technicians were invited to undergo a neurological examination and provide a detailed occupational history in our clinic.
This study was approved by the local ethical committee, and written consent was obtained from all subjects.
A student's t-test was used for the comparisons. The frequency analysis was performed by means of the chi-square test. A p value of 0.05 was considered statistically significant. All the statistical analyses were carried out by means of SPSS software (Version 13.0).