Introduction Reversible cerebral vasoconstriction syndrome (RCVS) is to be suspected in cases of thunderclap headache particularly when associated with convex subarachnoid haemorrhage without cerebral aneurysm. Angiographic changes and clinical state do not always correlate. We present a case report from the Townsville Hospital.

Case A 49 year old female presented to another hospital with recurrent thunderclap headaches first commencing with exercise. The medical history included idiopathic intracranial hypertension in remission, chronic migraine treated with botulinum toxin, and depression treated with amitriptyline and desvenlafaxine. MR imaging revealed cerebral vertex subarachnoid haemorrhage with normal MR angiogram of the cerebral vessels. The patient was transferred to our institution in a confused and restless state for cerebral digital subtraction angiogram, which was normal. A lumbar puncture revealed elevated white cells of 17×10⁶/L with normal CSF protein and opening pressure of 39 cm H₂O. Nimodipine that had been commenced before the patient became encephalopathic was ceased. Her confusion and headaches resolved but relapsed after three days. A repeat MR brain revealed multiple T2 hyperintensities in bilateral anterior and posterior circulation territories demonstrating diffusion restriction, and MR angiography revealed new segmental strictures and beading of bilateral middle and anterior cerebral arteries. The patient was diagnosed with overlap RCVS/posterior reversible encephalopathy syndrome; desvenlafaxine was ceased, acetazolamide commenced for raised intracranial pressure and a several week course of nimodipine recommenced. The patient was discharged home after resolution of headache and confusion without neurological deficit.

Conclusion This case highlights the dynamic changes of vasoconstriction and that angiographic findings can be discordant from the clinical status. Serial imaging is required to detect abnormalities of RCVS when the clinical suspicion is high. CSF analysis can be normal, however may reveal elevated protein or pleocytosis. The cause of our patient’s RCVS was thought to be the chronic use of desvenlafaxine.