Disturbance of cerebral function in people exposed to drinking water contaminated with aluminium sulphate: retrospective study of the Camelford water incident.

OBJECTIVE: To establish whether people exposed to drinking water contaminated with 20 tonnes of aluminium sulphate in the Camelford area of Cornwall in the south west of England in July 1988 had suffered organic brain damage as opposed to psychological trauma only. DESIGN: Retrospective study of affected people. PARTICIPANTS: 55 affected people and 15 siblings nearest in age to one of the group but who had not been exposed to the contaminated water were studied. MAIN OUTCOME MEASURES: Various clinical and psychological tests to determine medical condition and anxiety levels in affected people. Assessment of premorbid IQ (pFSIQ) with the national adult reading test, a computerised battery of psychomotor testing, and measurement of the difference in latencies between the flash and pattern visual evoked potentials in all participants. RESULTS: The mean (SE) pFSIQ was above average at 114.4 (1.1). The most sensitive of the psychomotor tests for organic brain disease was the symbol digit coding (SDC) test (normal score 100, abnormal <85). PARTICIPANTS performed less well on this test (54.5 (6.0)) than expected from their pFSIQ (P<0.0001) and a little less poorly on the averaged less discriminating tests within the battery (86.1 (2.5), P<0.0001). In a comparison with the 15 sibling pairs (affected people's age 41.0 (3.3) years v sibling age of 42.7 (3.1) years (P=0.36) the exposed people had similar pFSIQ (114.7 (2.1)) to their siblings (116.3 (2.1), (P=0.59) but performed badly on the symbol digit coding test (51.8 (16.6)) v (87.5 (4.9) for siblings, P=0.03). The flash-pattern differences in exposed people were greater than in 42 unrelated control subjects of similar age (27.33 (1.64) ms v 18. 57 (1.47) ms, P=0.0002). The 15 unexposed siblings had significantly better flash-pattern differences than their affected siblings (13.4 (2.4) ms v 29.6 (2.9) ms, P=0.0002). No effect of anxiety could be shown on these measurements from the analysis of the anxiety scores of exposed people. CONCLUSION: People who were exposed to the contaminated water at Camelford suffered considerable damage to cerebral function, which was not related to anxiety. Follow up studies would be required to determine the longer term prognosis for affected individuals.

Loss of visual function associated with microalbuminuria in diabetes mellitus: a pilot study.

Visual function loss has been documented in diabetes mellitus in relation to flicker and contrast. However, no direct correlation between the degree of loss in sensitivity and the level of retinopathy has been established. It has been suggested that such non-invasive psychophysical procedures actually reflect metabolic disturbances within the diabetic retina. This study investigates the possibility of whether early nephropathy demonstrated by microalbuminuria, is an indicator of microangiopathy which may be a cause of retinal disturbance leading to a loss of visual function. The visual function of a group of diabetics showing microalbuminuria was studied. Contrast and flicker threshold were measured and the results compared with those obtained with an age-matched control diabetic group. The procedures used effectively separated the two groups and raises the issue of incorporating psychophysics in retinal screening programmes.

Disturbance of cerebral function by aluminium in haemodialysis patients without overt aluminium toxicity.

The psychomotor function of 27 long-term haemodialysis patients with apparently normal cerebral function, who had only mildly raised serum aluminium (mean 59 [SEM 9] micrograms/l), was measured by means of a computerised version of the symbol digit coding test. Compared with those of control subjects matched for age and the patients' estimated premorbid IQ, the patients' response times were significantly longer (2.51 [0.10] vs 1.88 [0.05] s). Abnormalities were also detected in five other computerised tests of psychomotor function. The mean activity of erythrocyte dihydropteridine reductase (DHPR), which is inhibited by aluminium, rose during 3 months' desferrioxamine treatment in most of the 15 patients so treated. Although there was no relation between baseline psychomotor function and either indices of cumulative aluminium exposure or erythrocyte DHPR activity, changes in DHPR induced by desferrioxamine correlated with changes in psychomotor performance (r = 0.62). The flash-stimulated visual evoked potential (measured in 10 patients) was delayed (133.4 [2.4] ms), although the pattern-stimulated visual evoked potential remained normal (101.8 [3.2] ms). The difference between the visual evoked potentials stimulated by flash and pattern was significantly greater in the patients than in the controls (31.6 [4.3] vs 19.4 [2.4] ms) and was significantly related to the symbol digit coding response times and to the oral aluminium intake. The results suggest that much more rigorous exclusion of aluminium from the dialysate and diet of dialysis patients is necessary.

Source derivation of the brain-stem auditory evoked potential.

This study described the results of applying source derivation to the brain-stem auditory evoked potential. Unilateral stimulation gives rise to current sinks, associated with waves I and III, which are located in the vicinity of the ipsilateral mastoid. Waves II and V are associated with a pair of current sinks which appear bilaterally in the vicinity of each mastoid.