[Long-term follow-up study on sequelae of carbon monoxide poisoning; serial investigation 33 years after poisoning].

1. We examined 156 patients 33 years after CO poisoning occurred at the Miike Mikawa Mine, Fukuoka, Japan. The subjects were classified according to age as follows: between 55 and 59 years (n = 14), 60 and 69 years (n = 62), 70 and 79 years (n = 60), and 80 and 87 years (n = 18). The mean age was 69.2 years old. Concerning the duration of coma that occurred soon after the accident, 64 remained comatose from 0 to 6 hours, 46 from 6 to 12 hours and 46 from 12 to 48 hours. 2. Subjective symptoms were observed in 96.8% of the patients. Among them, forgetfulness was noted in 89.7%, followed by irritability in 66.7%, headache in 59.6%, insomnia in 55.8%, limb pain in 46.8%, dull head feeling in 42.9% and dizziness in 36.5%. 3. Intellectual disturbances were observed in 68.6% of the patients, including impression disturbance in 58.3%, memory disturbance in 51.9%, calculation disturbance in 63.5%, thinking disturbance in 61.5% and disorientation in 14.1%. 4. Apathy and disorder of volition and interest which were found in 72.4% were included in personality change because all symptoms persisted for many years. Personality change was classified as follows: weakness of emotion and will (hypobulia) in 54.4%, infantilism in 35.2%, hyperactive, talkactive and lack of inhibition in 18.5%, lack of self-possession and unstable temper in 9.6%, depression in 15.3%, neurosis in 7.6% and schizophrenic state in 2.5%. Among these symptoms of personality change, weakness of emotion and will and infantilism were conspicuous among the patients who remained in a coma for more than 6 hours soon after the accident but showed no relationship with age. 5. Neurological symptoms that were found in 48.7% of the patients were classified as sensory disturbance in 25.6%, peripheral nerve symptoms in 16.0%, pyramidal symptoms in 14.1%, ataxia and cranial nerve symptoms in 7.1%, paroxysmal symptoms in 6.4% and focal symptoms in 4.5%, extrapyramidal symptoms in 21.8% (Parkinsonism in 4.5%, tremor in 10.9% and muscle rigidity in 16.0%) and vegetative symptoms in 37.2%. 6. At the time of investigation, 5 CO poisoning patients were classified as serious cases (3.2%), 20 as comparatively serious (12.8%) medium-degree cases, 28 as comparatively mild (17.9%) medium-degree cases, 37 as comparatively serious (23.7%) mild cases, 42 as comparatively mild (26.9%) mild cases, 24 (15.4%) as having symptoms which were not problematic, and 24 (15.4%) as having symptoms that markedly worsened due to complication. 7. A total of 138 (88.4%) cases had complications were classified as follows: 78 cases (50.0%) of hypertension, 62 cases (39.7%) of cerebral infarction, 24 cases (15.4%) of cardiac disturbance, 21 cases (13.5%) of diabetes mellitus, 14 cases (9.0%) of hepatic disturbance and six cases of silicosis (3.8%). 8. Cranial MRI was carried out for 129 cases (82.7%). Of the abnormal findings identified, cerebral atrophy accounted for 72.0% (93 cases), including moderate and severe cases in 47.2% (61 cases), pallidum lesion for 37.9% (49 cases), lacunar infarction (including cerebral infarction) for 52.7% (68 cases), and hippocampal atrophy for 18.6% (24 cases). Many cases of cerebral atrophy and hippocampal atrophy were observed in patients who remained in the initial coma for more than 12 hours and were 80 years of age or old. The cases of pallidum lesion were observed in patients who remained in the initial coma for more than 6 hours, and no relationship with age was found. The other findings, cerebral atrophy and lacunar infarction showed a slight relationship with age. 9. Among the moderate and serious cases of intellectual disturbance, cerebral atrophy constituted to 62.5%, lacunar infarction 68.7% and pallidum lesion 50.0%. Among the moderate and serious cases of personality change, cerebral atrophy constituted 78.5%, lacunar infarction 35.0% and pallidum lesion 50.0%. Moreover, among extrapyramidal symptoms, pallidum lesion constituted 58.6%, cerebral atrophy 55.1% and lacun