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MRA and ASL perfusion findings in pediatric reversible cerebral vasoconstriction syndrome

Reversible vasoconstriction is rare in the pediatric population. Typically manifesting as peripheral vasoconstriction with variable neurologic symptoms, Reversible cerebral vasoconstriction syndrome is often a diagnosis of exclusion and may not be diagnosed in the absence of angiographic imaging. Shown here are 2 cases of pediatric Reversible cerebral vasoconstriction syndrome with disparate MRI findings and arterial spin labeling perfusion findings.


Introduction
Reversible cerebral vasoconstriction syndrome (RCVS) is a clinicoradiological condition that presents with recurrent severe headaches with or without concurrent focal neurologic signs. Seizures have been described. Calabrese et al established diagnostic criteria for this syndrome in 2007 [1,2] . Most reported cases of RCVS have been in adult patients with predilection for female gender. Some possible triggers of RCVS include pregnancy, the use of serotonin agonist medications, and illicit drug use [3,4] . Most patients initially present with severe headaches, sometimes characterized as "thunderclap" Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Conflict of interest: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. * Corresponding author.
headaches. Imaging findings described in the reported adult cases include multifocal areas of vasoconstriction in the cerebral arteries which are transient in nature.
It is important to rule out other diagnoses including venous sinus thrombosis, pituitary apoplexy, cervical artery dissection, and intraparenchymal hemorrhages [5][6][7] , as these disorders may produce similar headaches. Posterior reversible encephalopathy can share clinical features with RCVS and may share a similar pathophysiology [3,8] .
In contrast to the adult population, RCVS in children is not well-understood with few reported cases in medical literature.

Case report 1
The first patient is a 13-year-old female with a history of headaches who initially presented to the emergency department with throbbing headache, altered mental status, confusion, and slurred speech. The patient localized her headache to left and frontal regions and reported nausea. She described the pain as 8/10. Shortly after the initial onset of cephalgia, she experienced blurred vision in her right eye. She then slept 2 hours. When she awoke, her headache had increased in severity, and her vision had not improved. The patient then began to have slurred and incomprehensible speech. She was confused and not oriented to time, though she was oriented to person and place. Throughout this time, the patient did not experience any frank tonic-clonic activity, eye deviation, spontaneous voiding/defecating, or loss of consciousness. She has no family history of migraines, headaches, hypertension, strokes,  or seizures. CT of the head performed at presentation demonstrated no abnormality. Her complete-blood count, comprehensive metabolic profile, and urine-drug screening results were all unremarkable. She received solumedrol, compazine, zofran, toradol, and a normal-saline bolus.
On the second day of admission, the patient underwent Magnetic Resonance Imaging (MRI) which showed no focal parenchymal signal abnormality. There was no diffusion restriction. Concomitant Magnetic Resonance Angiogram (MRA) of the brain demonstrated multiple areas of narrowing of several peripheral branches of the Circle of Willis includ-ing the right anterior cerebral artery ( Fig. 1 A) as well as the left parieto-occipital artery ( Fig. 1 B). An arterial spin labeling (ASL) perfusion study showed decrease in cerebral blood flow throughout the right cerebral hemisphere ( Fig. 2 A).
After 3 months of verapamil therapy, the patient only reported 2 headaches which were less intense and shorter in duration than her presenting symptoms. The patient denied altered mental status, confusion, and slurred speech. Repeat MRA of the head performed 10 months following initial presentation showed an improved appearance of the multiple arterial stenoses. There was asymmetric hyperperfusion of the  right cerebral hemisphere compared to the left ( Fig. 3 ). There was no focal parenchymal signal abnormality in the brain or diffusion restriction.

Case report 2
The second patient is a 6-year-old male who presented with headache, slurred speech, and left-sided weakness. His past medical history was significant for recurrent headaches and transient right-signed weakness. CT of the head and MRI of the brain performed 7 months prior were unremarkable. MRI of the brain ordered at this presentation was significant for cortically based increased FLAIR signal throughout the right cerebral hemisphere ( Fig. 3 A) with associated diffusion restriction ( Fig. 3 B). MRA demonstrated focal narrowing of a distal branch of the right anterior cerebral artery ( Fig. 4 A) and right middle cerebral artery at the bifurcation ( Fig. 4 B). There was decreased ASL perfusion throughout the right cerebral hemisphere ( Fig. 6 A). After 1 month of verapamil therapy, repeat MRI and MRA showed improvement in vasoconstriction ( Fig. 5 ) with improvement in ASL perfusion ( Fig. 6 B). Coffino and Fryer [3] reviewed the 13 cases of pediatric RCVS that had been reported in the literature as of 2017. Of these 13 children, 11 were male. This represents a striking reversal of sex predominance relative to the adult population in which the female portion of RCVS cases has been reported to be as high as 81% [4] .

Discussion
These 2 cases highlight the unique radiological presentation of RCVS. In the first case, there were no parenchymal imaging findings on MRI despite the stenoses present on the MRA. In the second case, there was diffusion restriction throughout the affected hemisphere accompanying the MRA findings. MRI can show variable findings in the same patient from presentation to presentation. Indeed, review of the second patient's medical record showed prior episodes of headache and transient weakness in the setting of a normal MRI.
Little is known of the relationship between ASL perfusion and RCVS in the pediatric patient. The finding of slightly increased perfusion 10 months following initial presentation in the first patient may suggest a reperfusion hyperemia in response to calcium channel blocker therapy. In the second patient, the follow-up ASL perfusion study may have been performed too recently to observe a similar phenomenon.
RCVS is a transient vasculopathy which can present as a severe headache with distinguishing features on MRA studies of multifocal segment cerebral artery vasoconstriction. Areas of narrowing are typically observed more peripherally ( Fig. 7 ). Focal stenosis of a peripheral artery with subsequent parenchymal hypoperfusion is depicted in the second patient. Calcium channel blocker therapy has been used to improve clinical symptomatology and vasoconstriction.
RCVS is likely underdiagnosed in the pediatric population but should be considered among patients who present with recurrent thunderclap or severe headaches. As such, when neurologic imaging is considered in the approach to headache, MRA and/or ASL perfusion may be important adjuncts to conventional MRI of the brain.