Marquardt et al describe the clinical course and long term outcome of 21 patients they diagnosed as having a perimesencephalic haemorrhage.1 The paper raises two questions.

The first is an impression of an “emperor's new clothes syndrome” given by the first figure of the publication. This figure shows a slice of the CT made shortly after the initial episode of headache in the patient reported to have a recurrent episode of perimesencephalic haemorrhage. The legend of the figure states that the CT shows extravasated blood in the perimesencephalic subarachnoid space, but we fail to see any blood at all. Thanks to the electronic availability of the Journal we were able to review not only the paper version of the figure, but also an enlarged version on screen. Even after enlargement no blood was seen; the slice nicely shows the tentorium adjacent to the ambient cisterns, the proximal parts of the posterior cerebral arteries, and perfectly clear CSF in the perimesencephalic (chiasmatic and partly the ambient and quadrigeminal) cisterns and in the frontal interhemispheric and sylvian fissures.

There are several explanations for this diagnostic mystery. Firstly, the authors may have submitted an inappropriate slice of the CT. In some patients with perimesencephalic haemorrhage, the prepontine cistern is the only site where CT shows blood.2 If blood was visible in the prepontine cistern in this particular patient, the authors have indeed found a patient with a perimesencephalic, non-aneurysmal haemorrhage with a recurrent haemorrhage. Given the unique character of this sequence of events, it would be fair to provide the appropriate slice to convince readers of theJournal.

Secondly, if no evidence of blood is found even in the prepontine cistern, the patient may have had a CT negative subarachnoid haemorrhage. In patients with ruptured aneurysms CT can be …

Dr G Marquardt