Failure to confirm neurotoxic impairment using cerebral magnetic resonance imaging on solvent-exposed workers.

OBJECTIVES: The study aimed at assessing signs of nervous system impairment by cerebral magnetic resonance imaging (MRI) among workers with a history of long-term exposure to mixtures of organic solvents. METHODS: Thirty-six workers (mean age 44.1 years) with at least 10 (mean 23.9) years of occupational exposure to solvents and pair-matched referents with no former solvent exposure went through a blind, random-order investigation of cerebral MRI, performed with a 1.5-tesla scanner. RESULTS: Linear measurements of the MRI tomograms showed a slight tendency toward wider ventricles and broader cortical sulci in the reference group. Visual evaluation of the MRI by 2 experienced neuroradiologists showed no significant difference between the groups; however, there was substantial interobserver variability. CONCLUSIONS: The MRI findings of this study do not support the hypothesis that long-term low-level occupational exposure to organic solvents results in the development of brain atrophy, or specific MRI signal changes in the region of the basal ganglia and thalami.

[Treatment with hyperbaric oxygen. Illustrated by the treatment of a patient with retinitis pigmentosa]. / Behandling med hyperbart oksygen. Illustret ved behandling av en pasient med retinitis pigmentosa.

A 26 year old man, who was physically fit and occupationally active but had retinitis pigmentosa and a slight hearing impairment, received hyperbaric oxygen treatment for 97 minutes at a pressure of 240 kPA for five days a week over a period of four weeks. After cessation of the treatment his lateral vision was found to be improved. The patient was examined both prior to and after the hyperbaric oxygen treatment to assess possible adverse effects. The examination consisted of a comprehensive neuropsychological test battery, audiometry and spirometry. The patient showed a reversible reduction in gas diffusion for CO (TLCO). No adverse effects on the central nervous system were found. He achieved higher scores in an intelligence test when retested. The gain was greater than usually found as a practice effect. The article discusses possible indications for hyperbaric oxygen treatment.

Neuropsychological findings in a non-clinical sample of workers exposed to solvents.

The risk of long-term damage to the CNS after exposure to mixed solvents in work environments is controversial. Thirty-six workers were studied who had been exposed to organic solvents for more than 10 years (mean 24.5 years) in a working environment. The workers and unexposed controls were studied with a battery of neuropsychological and cognitive tests. Significant group differences were observed for the Wechsler adult intelligence scale (WAIS) digit span and symbol digit substitution, and on paired associate learning and continuous word recognition. The results suggest that long-term work-related exposure to organic solvents may have chronic toxic effects.

Regional cerebral blood flow after long-term exposure to carbon disulfide.

Sixteen former rayon viscose workers were investigated four years after the exposure to carbon disulfide was discontinued. Median age was 58 years (range 43-65 years), median exposure time was 17 years (range 10-35 years). Encephalopathy was diagnosed in altogether 14 workers. To further explore pathophysiological mechanisms, cerebrovascular investigations were employed. Doppler ultrasound examination of the precerebral vessels in 15 workers showed a slight stenosis of the left internal carotid artery in one. Regional cerebral blood flow investigation (rCBF) with single photon emission computerized tomography (SPECT) with Xenon-133 gas was performed in 14. There was no significant difference from a control group. Regional side-to-side asymmetries beyond reference limits were demonstrated in eight workers. The abnormalities were modest, but may indicate a tendency toward focal blood flow disturbances in workers with long-term exposure to carbon disulfide.

Brain damage caused by hydrogen sulfide: a follow-up study of six patients.

Hydrogen sulfide (H2S) poisoning involves a risk of hypoxic brain damage. Six patients who lost consciousness due to H2S poisoning are described. The symptoms varied from anosmia in the patient with the shortest but highest exposure to delayed neurological deterioration in the patient with the longest exposure. The two patients with the most serious symptoms developed pulmonary edema, which may have prolonged the hypoxia. The patients were reexaminated 5 years or more after the poisoning. The five patients who had been unconscious in H2S atmosphere for from 5 to 15-20 min showed persisting impairment at neurological and neuropsychological re-examination. Memory and motor function were most affected. One patient was seriously demented. Recent reports of large groups of H2S-poisoned workers probably underestimate the risk of sequelae, due to the inclusion of cases with exposure of short duration and lack of follow-up.

Vibration sensitivity thresholds: methodological considerations.

Vibration sensitivity thresholds were studied in 12 healthy volunteers using 25, 50, 100 and 250 s-1 stimulus frequencies from an instrument with automated and manual modes ('Vibra Mk II'). For the automated mode, a forced choice principle was adopted. All measurements were performed from both the knuckle of the IInd metacarpophalangeal joint and the medial malleolus on four successive days. In addition, a conventional tuning fork method for vibration sensitivity was applied. The results show high interindividual and intraindividual variation in all measurements. The threshold values measured by the automated system were significantly lower than those by manual system at all frequencies. The largest variation was seen at 250 s-1 and the most uniform values at 100 s-1. There was a clear difference between the values from knuckle and medial malleolus, the values in the foot being lower. There was no learning effect. Clear age-related increase in vibration thresholds was observed. Conventional tuning fork-method showed clear differences in vibration sensitivity between hand and foot, in accordance with computer assisted method. The higher sensitivity of the automated method compared to the manual makes this the method of choice, although further investigations to finish the method and to build up a broader reference material is desirable.

Carbon disulfide exposure and neurotoxic sequelae among viscose rayon workers.

In Norway's only viscose rayon plant, carbon disulfide (CS2) concentrations in ambient air usually were between 30 and 50 mg/m3 during the first 23 years of production. From 1970/1971 until the factory was closed in 1982, corresponding values were 10-25 mg/m3. Through all of these years, high peak exposures of CS2 and H2S occurred. In 1986, 16 of the 24 men still at work in 1982 and with at least 10 years' experience in the spinning room agreed to participate in this study. Clinical neurological examination demonstrated abnormalities in 15; neuropsychological tests showed impairments of probable organic origin in 14. Thirteen had cerebral atrophy demonstrated by cerebral computed tomography (CT). Electromyography (EMG) was abnormal in six, neurography in 11. Regional cerebral blood flow measurements indicated flow asymmetries in eight, whereas Doppler investigation of the extracranial carotid and vertebral arteries, electroencephalography (EEG), and evoked response investigations were mostly normal. Based on these results and the exposure data, a diagnosis of CS2-induced encephalopathy was reached in eight workers; another six had an encephalopathy in which CS2 exposure was regarded as a partial cause. Correspondingly, seven had a neuropathy probably caused by CS2 exposure alone; in three others, CS2 was found to be the partial cause of a neuropathy. This indicates that long-term, relatively moderate exposure to CS2 in association with high peak exposures to CS2 and H2S involves a substantial risk of developing neurotoxic disease.

[H2S poisoning and nervous system damage]. / H2S-forgiftning og skader i nervesystemet.

H2S (hydrogen sulfide) is a very toxic gas. Even brief exposure to high concentrations may be fatal. Unconsciousness may occur without warning. Those who try to help are often poisoned too. In Norway, most poisonings have been described in connection with the herring oil and fish meal industry, farmers handling manure, and sewage work. The risk of hypoxic damage to the nervous system is considerable. The clinical picture varies, and the connection between the patients' symptoms and the poisoning is easily overlooked, especially with delayed sequelae, which may occur several weeks after the acute poisoning. The risk of damage depends on both the exposure time and the concentration of H2S, and a thorough anamnesis, noting the course of events, is important in order to achieve a correct diagnosis.

Neurological examination, computerized tomography, cerebral blood flow and neuropsychological examination in workers with long-term exposure to carbon disulfide.

Sixteen males, formerly exposed to carbon disulfide (CS2) for at least 10 years (mean 20 years), were administered a neurological examination, cerebral computerized tomography (CT), regional cerebral blood flow (rCBF) examination and neuropsychological examination. The clinical neurological examination revealed abnormalities in 15; cerebral CT showed signs of atrophy in 13; and neuropsychological examination indicated brain organic changes in 13. With the rCBF examination, slight abnormalities were found in 8. The findings indicate that long-term exposure to CS2 involves a risk of developing toxic encephalopathy, demonstrable on both neurological and neuropsychological examination. Furthermore, structural changes in the brain may be demonstrable by cerebral CT.

Functional cervical myelography with iohexol.

Thirty patients underwent functional cervical myelography, i.e. radiographs in the lateral view were obtained in extension as well as in flexion of the neck. Sagittal tomography was performed in both positions. Widening of the subarachnoid space and decreased sagittal diameter of the spinal cord due to shortening were demonstrated in the lateral view in flexion. In some cases with advanced narrowing or spinal block in extension, such widening in flexion resulted in better diagnostic images by providing passage of the contrast medium caudally. Although iohexol (Omnipaque, Nyegaard & Co., Oslo) was regularly forced into the posterior cranial fossa by the movements, the frequency of side effects was approximately the same as in our former trials with iohexol in conventional cervical myelography. EEG changes occurred in two patients (7%). A sitting position for 3-4 min after the examination followed by an elevated head end of the bed was probably important for preventing side effects from the contrast medium. Specific questioning revealed twice as many subjective side effects as reported after general questions alone.

Cervical myelography with iohexol.

An open study with iohexol (Omnipaque) in cervical myelography has been performed in 20 patients to evaluate the properties and neurotoxicity of this new water soluble contrast medium. The image quality was good (30%) or excellent (70%) in all cases. The frequency of headache was 25%. No EEG changes were severe and the total frequency was 20%. We conclude that this study supports other reports of iohexol having a low neurotoxicity and is well suited for intrathecal use.

Iohexol compared to metrizamide in cervical and thoracic myelography. A randomized double blind parallel study.

A randomized double blind study with iohexol (Omnipaque) and metrizamide (Amipaque) in cervical myelography was performed in 50 patients, 29 with iohexol and 21 with metrizamide. The myelographies were performed either with lumbar or with C1-C2 puncture in about equal groups, using 300 mg I/ml and 240 mg I/ml of the contrast media respectively. The image quality was equal with both contrast media, excellent in about 4/5 and good in 1/5 of the examinations. Subjective side effects were twice as frequent with metrizamide as with iohexol. The most frequent side effect was headache, occurring in 34% with iohexol and in 67% with metrizamide. Altogether 24% or the patients had EEG changes after iohexol as compared to 47% after metrizamide. All EEG changes were slight dysrythmia-except in three patients with spike activity after metrizamide. These were the only ones with mental reactions as well. It can be concluded that in this trial iohexol was better suited for cervical myelography than metrizamide.

Iohexol compared to meglumine-Ca-metrizoate in common carotid angiography. A randomized double blind cross-over study in man.

A randomized double blind cross-over study with iohexol (Omnipaque) and meglumine-Ca-metrizoate (Isopaque cerebral) was performed to answer questions concerning subjective side effects and tolerability that arose from a double blind parallel study with the same two media. The cross-over study design, with injection of the contrast media under identical conditions in the same artery, seems to be the most practical method of comparison of two well tolerated media. Iohexol showed significantly less side effects than meglumine-Ca-metrizoate. The routine premedication with atropine was neglected in this study to evaluate effects on heart rate due, for example, to the toxicity of the media. Small tachycardial and bradycardial reactions were equally divided between the media. However, a short asystolic period following the injection of meglumine-Ca-metrizoate in two different patients may indicate a higher toxicity of this medium.

Functional lumbar myelography with iohexol.

The results of 25 functional lumbar myelographies with iohexol are reported. The image quality was good or excellent in all. The side effects were mostly mild and showed the same frequency as reported in lumbar and thoracic myelographies with metrizamide. A slight increase in the frequency of side effects was found in 13 patients with spinal repuncture 6 or 24 hours after the myelography. Vacuolized monocytes in ultracentrifuged CSF following repuncture was found in 5 patients. No EEG changes or serious complications were found. Iohexol is considered safe in intrathecal use.

Cerebral angiography with the non-ionic water-soluble contrast medium iohexol and meglumine-Ca-metrizoate. A randomized double blind parallel study in man.

A double blind study was carried out to evaluate safety, tolerability and visualization quality of the non-ionic contrast medium Iohexol compared to Meglumine-Ca-Metrizoate (Isopaque Cerebral) for cerebral angiography. The two contrast media were found equal in most respects. A slight increase in systolic blood pressure following Meglumine-Ca-Metrizoate injections and a slight decrease in diastolic blood pressure following Iohexol were statistically significant. Tachycardia following injections of Meglumine-Ca-Metrizoate in the aortic arch was also significant and may indicate more discomfort from this medium, although no difference was found in patient interviews. The changes in blood pressure and heart rate were small and of no clinical importance.