Subarachnoid haemorrhageBMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b2874 (Published 21 August 2009) Cite this as: BMJ 2009;339:b2874
All rapid responses
Hankey and Nelson highlight the importance of lumbar
puncture (LP) in the investigation of subarachnoid
haemorrhage (SAH) if computed tomography (CT) brain scan is
normal . Despite this being well recognised in the
literature for at least a decade , there is evidence that
in up to 50% of patients this is not followed . This is
concerning as missed SAH carries a worse prognosis  and
3% of patients with negative CT examination show
angiographic evidence of SAH .
We sought to investigate current practice in our District
General Hospital. We retrospectively identified 50 cases
over a 2-month period where urgent head CT scanning was
performed specifically questioning the diagnosis of SAH. Of
these, only one radiological examination was positive for
SAH. Of the remaining 49 patients with negative CT, 34 had
LP. Two LPs were suggestive of SAH, 31 were negative and
one sample was inadequate.
In 15 cases LP was not performed in the context of a
negative CT. Two patients’ clinical pictures altered,
making SAH no longer a likely diagnosis. Four patients self
discharged or withdrew consent before a lumbar puncture
could be completed. The remaining nine patients were
discharged with only a negative CT examination to exclude
Whilst our snap-shot is not as concerning as previously
published results , it is still a worry that 28% did not
have further investigation following a negative CT. As
Hankey and Nelson suggest, this may reflect a failure of
clinicians to understand the limitations of CT. However, it
is possible that our findings reflect use of CT in cases
where the true index of suspicion of SAH is not high.
Alternatively, they may demonstrate a trend towards medical
practice where something is seen to have been done, with a
CT examination being quicker and less painful for both the
patient and the clinician!
John D Tuckett, Bhaskar Ganai
Northern Deanery Clinical Radiology Rotation
1 Hankey GJ, Nelson MR. Subarachnoid haemorrhage. BMJ 2009;
339: b2874 (5 September.)
2 Caplan LR. Avoiding pitfalls in the diagnosis of
subarachnoid haemorrhage. N Engl J Med 2000;342:29-36.
3 O’Neill J, McLaggan S, Gibson R. Acute headache and
subarachnoid haemorrhage: a retrospective review of CT and
lumbar puncture findings. Scott Med J 2005; 50: 151–53.
4 Van Der Wee N, Rinkel GJE, Hasan D, van Gijn J. Detection
of subarachnoid haemorrhage on early CT: is lumbar puncture
still needed after a negative scan? J Neurol Neurosurg
Psychiatry 1995; 58: 357–59.
Competing interests: No competing interests