312 is
being given to this idea by specialist advisory comsome (including orthopaedics and otorhinolaryngology) have already decided to adopt a formal oral test before the end of higher surgical training. This is hardly accreditation by rubber stamp. Changes in surgical training have always been encouraged by the older Colleges and the contributions now coming from now
mittees, and
Professor Jennett and Dr Strang appeal for the increased of skull radiographs in the hope of detecting otherwise silent skull fractures. This would further decrease the already very low positive yield from this investigation. We feel that the blanket use of skull radiographs in cases of skull trauma should be replaced by a more discriminating request for this examination. use
the Antipodes will be examined with interest. Sefton General Hospital, Liverpool L15 2HE
Department of Surgery, Dudley Road Hospital, Birmingham B18 7QH
P. GILROY BEVAN
Department of Surgery, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP
METHYL MERCURY IN BLOOD OF DENTISTS
IVAN D. A. JOHNSTON
SKULL X-RAY POLICY
SIR,-One crucial statistic was not declared in Dr Evans reappraisal of the value of post-traumatic skull X-rays (July 8, p. 85). What followed when a skull X-ray revealed a fracture in a patient with no symptoms and no other signs? Watford General Hospital, Herts. WD1 7HH
N.
Watford,
SIR,-Our report of 3035 attenders
at
J. C. SARKIES
accident/emergency
departments and 1181 hospital admissions after recent head injury, based on a structured sample from all Scottish hospitals,l had several similarities to the findings of Dr Eyes and Dr Evans. Skull fractures were found in 3% of attenders who were X-rayed, and in 7% of those admitted; of those attending, 23% were admitted. But only 58% of attenders had skull X-rays. Of 82 patients with skull fractures a third had no symptoms or signs, and their fractures would have been overlooked if they had not been X-rayed. The importance of detecting a skull fracture, as a means of anticipating serious complications, has been emphasised by several studies from this institute.2-6
Delayed diagnosis treatment
of open
SiR,—The biological transformation of inorganic mercurials into organic compounds, which are much more toxic, has been studied by many workers since Minamata disease came to notice some 25 years ago. The water of Minamata Bay was contaminated by methyl mercury in factory eflluent; there were many illnesses, some fatal, as the result of eating fish caught in the bay. Subsequent reports of the presence of mercury in tuna fish, caught in deep waters not thought to be polluted, generated public alarm, but it was afterwards found that methyl mercury occurs naturally in deep-sea fish. Inorganic mercury, released from the earth by volcanic and industrial activity, is washed away by rain and reaches the sea bed where it is converted by bacteria into methyl and dimethyl mercury. These compounds rise to the surface (some being ingested by fish) and are broken down in the atmosphere, yielding metallic mercury which is recycled. The role of methylcobalamin in the methylation of 1mercury in biological systems has been demonstrated in vitro.
of intracranial hxmatoma and delayed injuries are the price paid for missing skull
fractures. Eyes and Evans comment that discovery of a skull fracture seldom leads to "active" treatment. Admission for observation may not be regarded by them as "treatment", but it is a useful, if expensive, method of management. If resources are to be properly deployed admission should be selective; one important criterion for admission is a skull fracture. We shall be publishing further data in support of the view that, if avoidable mortality and morbidity from head injury are to be reduced, and unnecessary admissions to hospital avoided, there will be need, in accident/emergency departments, for more skull X-rays, of better quality, and more re-
liably interpreted. Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF
***These letters have been shown whose reply follows.-ED.L.
.
BRYAN JENNETT IAN STRANG
to
Dr
Eyes and
Dr
Evans,
SiR,—The three symptom-free patients Dr Sarkies mentions observed in hospital and discharged without incident. No signs or symptoms referable to central-nervous-system injury developed. The patients had been referred for skull radiographs because of scalp lacerations and/or haematoma. were
Injury Management Study in Scottish Hospitals. Lancet, 1977, ii, 696. 2. Jennett, B., Miller, J. D. J. Neurosurg. 1972, 36, 333. 3. Galbraith, S. Br. med. J. 1976, i, 1438. 4. Jennett, B. ibid. p. 1383. 5. Rose, J., Valtonen, S., Jennett, B. ibid. 1977, ii, 615. 6. Jennett, B. Carlin, J. Injury. (in the press). 1. Scottish Head
B. E. EYES A. F. EVANS
Magnaval et al.,2 reviewing mercury hazards in dentists, methyl mercury in the blood of four dentists and suggested that the levels were higher than in a control group, though the difference was not statistically significant. We now report experiments showing that mercury vapour inhaled by dentists is partially converted to methyl mercury in the body. Blood-samples (10 ml) were obtained from eleven dentists working in the conservation department of a hospital and from seventeen people not occupationally exposed to mercury. 2 ml heparinised whole blood was freeze dried and its total mercury content measured by neutron-activation analysis. Methyl mercury was estimated in 4 ml samples by gas-liquid chromatography. measured
The results are summarised in the table. The differences between the dentists and the controls are highly significant (p Wilcoxon rank-sum test) for total mercury, methyl
being given to this idea by specialist advisory comsome (including orthopaedics and otorhinolaryngology) have already decided to adopt a formal oral test before the end of higher surgical training. This is hardly accreditation by rubber stamp. Changes in surgical training have always been encouraged by the older Colleges and the contributions now coming from now
mittees, and
Professor Jennett and Dr Strang appeal for the increased of skull radiographs in the hope of detecting otherwise silent skull fractures. This would further decrease the already very low positive yield from this investigation. We feel that the blanket use of skull radiographs in cases of skull trauma should be replaced by a more discriminating request for this examination. use
the Antipodes will be examined with interest. Sefton General Hospital, Liverpool L15 2HE
Department of Surgery, Dudley Road Hospital, Birmingham B18 7QH
P. GILROY BEVAN
Department of Surgery, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP
METHYL MERCURY IN BLOOD OF DENTISTS
IVAN D. A. JOHNSTON
SKULL X-RAY POLICY
SIR,-One crucial statistic was not declared in Dr Evans reappraisal of the value of post-traumatic skull X-rays (July 8, p. 85). What followed when a skull X-ray revealed a fracture in a patient with no symptoms and no other signs? Watford General Hospital, Herts. WD1 7HH
N.
Watford,
SIR,-Our report of 3035 attenders
at
J. C. SARKIES
accident/emergency
departments and 1181 hospital admissions after recent head injury, based on a structured sample from all Scottish hospitals,l had several similarities to the findings of Dr Eyes and Dr Evans. Skull fractures were found in 3% of attenders who were X-rayed, and in 7% of those admitted; of those attending, 23% were admitted. But only 58% of attenders had skull X-rays. Of 82 patients with skull fractures a third had no symptoms or signs, and their fractures would have been overlooked if they had not been X-rayed. The importance of detecting a skull fracture, as a means of anticipating serious complications, has been emphasised by several studies from this institute.2-6
Delayed diagnosis treatment
of open
SiR,—The biological transformation of inorganic mercurials into organic compounds, which are much more toxic, has been studied by many workers since Minamata disease came to notice some 25 years ago. The water of Minamata Bay was contaminated by methyl mercury in factory eflluent; there were many illnesses, some fatal, as the result of eating fish caught in the bay. Subsequent reports of the presence of mercury in tuna fish, caught in deep waters not thought to be polluted, generated public alarm, but it was afterwards found that methyl mercury occurs naturally in deep-sea fish. Inorganic mercury, released from the earth by volcanic and industrial activity, is washed away by rain and reaches the sea bed where it is converted by bacteria into methyl and dimethyl mercury. These compounds rise to the surface (some being ingested by fish) and are broken down in the atmosphere, yielding metallic mercury which is recycled. The role of methylcobalamin in the methylation of 1mercury in biological systems has been demonstrated in vitro.
of intracranial hxmatoma and delayed injuries are the price paid for missing skull
fractures. Eyes and Evans comment that discovery of a skull fracture seldom leads to "active" treatment. Admission for observation may not be regarded by them as "treatment", but it is a useful, if expensive, method of management. If resources are to be properly deployed admission should be selective; one important criterion for admission is a skull fracture. We shall be publishing further data in support of the view that, if avoidable mortality and morbidity from head injury are to be reduced, and unnecessary admissions to hospital avoided, there will be need, in accident/emergency departments, for more skull X-rays, of better quality, and more re-
liably interpreted. Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF
***These letters have been shown whose reply follows.-ED.L.
.
BRYAN JENNETT IAN STRANG
to
Dr
Eyes and
Dr
Evans,
SiR,—The three symptom-free patients Dr Sarkies mentions observed in hospital and discharged without incident. No signs or symptoms referable to central-nervous-system injury developed. The patients had been referred for skull radiographs because of scalp lacerations and/or haematoma. were
Injury Management Study in Scottish Hospitals. Lancet, 1977, ii, 696. 2. Jennett, B., Miller, J. D. J. Neurosurg. 1972, 36, 333. 3. Galbraith, S. Br. med. J. 1976, i, 1438. 4. Jennett, B. ibid. p. 1383. 5. Rose, J., Valtonen, S., Jennett, B. ibid. 1977, ii, 615. 6. Jennett, B. Carlin, J. Injury. (in the press). 1. Scottish Head
B. E. EYES A. F. EVANS
Magnaval et al.,2 reviewing mercury hazards in dentists, methyl mercury in the blood of four dentists and suggested that the levels were higher than in a control group, though the difference was not statistically significant. We now report experiments showing that mercury vapour inhaled by dentists is partially converted to methyl mercury in the body. Blood-samples (10 ml) were obtained from eleven dentists working in the conservation department of a hospital and from seventeen people not occupationally exposed to mercury. 2 ml heparinised whole blood was freeze dried and its total mercury content measured by neutron-activation analysis. Methyl mercury was estimated in 4 ml samples by gas-liquid chromatography. measured
The results are summarised in the table. The differences between the dentists and the controls are highly significant (p Wilcoxon rank-sum test) for total mercury, methyl
