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Rapid response to:

Clinical Review

Subarachnoid haemorrhage

BMJ 2006; 333 doi: https://doi.org/10.1136/bmj.333.7561.235 (Published 27 July 2006) Cite this as: BMJ 2006;333:235

Rapid Response:

Re: Lumbar puncture for every negative CT scan?

I agree with Dr Coats' Bayesian approach. This mode of thinking is
however not as widespread as it should.

I wonder what a judiciary medical expert, and the judges or jury
would think about "failing to perform lumbar puncture", though , when the
probability the test will unmask a subarachnoid haemorrhage (SAH) ("such a
dreadful disease when left untreated") is "as high as 1/200", or
"nevertheless 1/650". I already can hear the plea about "lumbar puncture
being a simple and dangerless procedure" that can also be painless when
performed with nitrous oxyde/oxygen inhalation, local anaesthesia and a
"non-traumatic" needle.
Well, all right, the odds for this to happen are 1/650 or less.
Another problem is that some physicians are reluctant to perform lumbar
puncture and go straight to angio-MRI ("such a benign test"), thus taking
the risk of unmasking an asymptomatic aneurysm and performing unnecessary
but dangerous treatment of the incidentaloma.
I'd like to read Dr Coat's Bayesian approach about the probability that a
sudden headache might be related to an aneurysm found on MRI angiography
without prior documentation of SAH on CT scan and without performing
lumbar puncture. A situation that may be akin to that of the negative CT-
scan and supposedly traumatic spinal tap leading to MRI angiography.

Competing interests:
None declared

Competing interests: No competing interests

07 August 2006
Axel Ellrodt
Emergency physician
France 92200