Postural headache

Sir

With reference to the endgame titled ‘Postural Headache’ (BMJ
2009;338:b911) we would like to point out several inaccuracies in the case
presentation and discussion that can be potentially misleading.

There are a few minor inaccuracies in the captions of the figures;
figure 1 is a fluid attenuation inversion recovery (FLAIR) sequence rather
than T2 weighted sequence (i.e designed to suppress the normal CSF) and
figure 2 is a T1 weighted sequence rather than T2 weighted (in a normal T2
weighted sequence the CSF is bright).

Although spontaneous intracranial hypotension is characteristically
associated with subdural collections, most patients have subdural hygromas
rather than haemorrhages.(1-3). The subdural collections present in this
case (figure 1) would be better characterised as subdural effusions with
the bright signal on FLAIR due to the characteristic proteinacious
content.

Pachymeningeal enhancement appears to be the most common feature on
MRI (4). The venous engorgement is difficult to evaluate on the images
supplied and without contrast. Certainly most radiologists wouldn’t have
characterised the superior sagittal sinus in figure 1 as engorged. The
venous engorgement is often easier to appreciate in the spinal epidural
venous plexus (5).

Downwards displacement of the brain is radiologically identified when
the position of the iter (opening of the aqueduct) lies below the
incisural line (connecting the anterior clinoid process and the venous
confluence) or when the tonsillar position lies more than 5mm below the
foramen magnum. Although there is sagging of the midbrain and there may be
some pontine flattening, the cerebellar tonsils are not protruded through
the foramen magnum on the image given (figure 2).

Finally, regarding the investigation of suspected cases, MRI would be
the examination of choice in most centres (as supplied by the authors of
the article – figure 3). CT myelography is invasive and not commonly
performed as the investigation of choice in order to find the CSF leak in
the UK. An MRI with or without intrathecal contrast or a radionuclide
cisternography may also be used as second line investigation (6).

It would be most valuable to entrust image interpretation to experts
when submitting teaching material with a major radiological content. We
would advocate consulting a radiologist to proof read submissions
involving radiological images and to consider having a radiologist as an
author if the article is centered around radiological images.

1. Schievink WI. Spontaneous spinal cerebrospinal fluid leaks and
intracranial hypotension. JAMA 2006;295:2284-96

2. Schievink WI, Maya MM, Moser FG, Tourje J Spectrum of subdural
fluid collections in spontaneous intracranial hypotension. J Neurosurg.
2005 Oct;103(4):608-13.

3. Lai TH, Fuh JL, Lirng JF, Tsai PH, Wang SJ. Subdural haematoma in
patients with spontaneous intracranial hypotension. Cephalalgia. 2007
Feb;27(2):133-8.

4. Su CS, Lan MY, Chang YY, Lin WC, Liu KT Clinical features,
neuroimaging and treatment of spontaneous intracranial hypotension and
magnetic resonance imaging evidence of blind epidural blood patch. Eur
Neurol. 2009;61(5):301-7

5. Wolfe SQ, Bhatia S, Green B, Ragheb J Engorged epidural venous
plexus and cervical myelopathy due to cerebrospinal fluid overdrainage: a
rare complication of ventricular shunts. Case report. J Neurosurg. 2007
Mar;106(3 Suppl):227-31

6. Liong WC, Constantinescu CS, Jaspan T Intrathecal gadolinium-
enhanced magnetic resonance myelography in the detection of CSF leak.
Neurology. 2006 Oct 24;67(8):1522

Competing interests:
None declared