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Licorice consumption-associated thunderclap headache: posterior reversible encephalopathy syndrome or subarachnoid hemorrhage?

Hongliang Zhang12*, Xiao-Feng Wang3 and Jiang Wu1

Author Affiliations

1 Department of Neurology, The First Hospital of Jilin University, Jilin University, Xinmin Street 71#, 130021 Changchun, China

2 NVS, Karolinska Institute, Novum, plan 5, SE 141 86 Huddinge, Stockholm, Sweden

3 College of Public Health, Jilin University, Xinmin Street 1163#, 130021 Changchun, China

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Critical Care 2011, 15:416  doi:10.1186/cc10107

See related research by van Beers et al.,

The electronic version of this article is the complete one and can be found online at:

Published:31 March 2011

© 2011 BioMed Central Ltd


van Beers and colleagues described a 49-year-old woman admitted to hospital for thunderclap headache, blurred vision and hypertension. Based on clinical manifestations, diagnostic work-up and follow-up, the authors diagnosed the case as posterior reversible encephalopathy syndrome (PRES) [1]. We agree that PRES should be considered in this case, while differential diagnosis such as subarachnoid hemorrhage (SAH) requires further investigation and exclusion.

PRES represents a clinicoradiological disease entity arising from failure of cerebrovascular autoregulation and ensuing disruption of the blood-brain barrier upon acuteonset hypertension [2]. The underlying pathogenesis of PRES is vasogenic edema, which requires apparent diffusion coefficient mapping by magnetic resonance imaging for confirmation [3].

In this reported case, the brain computed tomography (CT) showed hemorrhage in the left Sylvian fissure, which was highly suggestive of SAH. The condition of SAH may also present as thunderclap headache, hypertension and reversible cerebral vasoconstriction, appearing as bilateral hypointensity in CT images. Lumbar puncture is needed to identify SAH in suspected cases [4]. As another differential diagnosis, reversible cerebral vasoconstriction may also be associated with licorice [5] and ought to be excluded after performing cerebral angiography.

In summary, PRES and SAH share some clinical similarities. The case reported by van Beers and colleagues merits further investigation, especially to differentiate between PRES and SAH

Authors' response

Eduard J van Beers, Jan Stam and Walter M van den Bergh

We thank Zhang and colleagues for their comment.

We disagree on the need for a lumbar puncture in this case. A diagnostic lumbar puncture in patients with a history suggestive of aneurysmal SAH is only needed if the brain CT scan does not show signs of bleeding [6]. Because of the acute onset of the headache and the finding of subarachnoid blood we did perform CT angiography (available on request), which did not show an aneurysm. CT angiography is an adequate imaging technique for detection of aneurysms and is the study of choice in patients suspected of aneurysmal SAH in our hospital and in other tertiary referral centers [7]. An aneurysmal SAH was excluded in this patient.

We agree that a reversible cerebral vasoconstriction is a remote possibility in this case, which can only be fully excluded by conventional angiography. This vasoconstriction is a very rare condition, however, and was most unlikely in our patient with recent hypertension due to excessive licorice consumption, a favorable course and no signs of cerebral vasospasm on CT angiography.


CT: computed tomography; PRES: posterior reversible encephalopathy syndrome; SAH: subarachnoid hemorrhage.

Competing interests

The authors declare that they have no competing interests.


  1. van Beers EJ, Stam J, van den Bergh WM: Licorice consumption as a cause of posterior reversible encephalopathy syndrome: a case report.

    Crit Care 2011, 15:R64. PubMed Abstract | BioMed Central Full Text OpenURL

  2. Bartynski WS: Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic edema.

    Am J Neuroradiol 2008, 29:1043-1049. PubMed Abstract | Publisher Full Text OpenURL

  3. Zhang HL, Yang Y, Zhou HW, Wu J: Diagnosis of posterior reversible encephalopathy syndrome: does DWI help?

    Lancet Neurol 2010, 9:1046-1047. PubMed Abstract | Publisher Full Text OpenURL

  4. Coats TJ, Loffhagen R: Diagnosis of subarachnoid haemorrhage following a negative computed tomography for acute headache: a Bayesian analysis.

    Eur J Emerg Med 2006, 13:80-83. PubMed Abstract | Publisher Full Text OpenURL

  5. Chatterjee N, Domoto-Reilly K, Fecci PE, Schwamm LH, Singhal AB: Licorice-associated reversible cerebral vasoconstriction with PRES.

    Neurology 2010, 75:1939-1941. PubMed Abstract | Publisher Full Text OpenURL

  6. Vermeulen M, Hasan D, Blijenberg BG, Hijdra A, van Gijn J: Xanthochromia after subarachnoid haemorrhage needs no revisitation.

    J Neurol Neurosurg Psychiatry 1989, 52:826-828. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  7. Velthuis BK, Van Leeuwen MS, Witkamp TD, Ramos LM, Berkelbach van der Sprenkel JW, Rinkel GJ: Computerized tomography angiography in patients with subarachnoid hemorrhage: from aneurysm detection to treatment without conventional angiography.

    J Neurosurg 1999, 91:761-767. PubMed Abstract | Publisher Full Text OpenURL