Case Report and Technique

A 13-year-old boy presented with subarachnoid haemorrhage (SAH) due to a ruptured left carotid aneurysm treated with endovascular embolization, with underlying presumed CNS vasculitis. This was diagnosed six years previously, following a stroke in the right superficial sylvian territory with left-sided palsy, after which the patient was treated with aspirin. Following rupture of his aneurysm, the patient experienced two episodes of TIA (recurrence of left-sided palsy) within three months, and the treatment was switched to low-molecular-weight heparin at a therapeutic dose (tinzaparin), despite the presence of multiple cerebral aneurysms in the anterior circulation. Although the relationship with management changes was uncertain, no further strokes occurred following instigation of anticoagulation. Diagnosis of presumed CNS vasculitis was made in the context of a familial history of autoimmune disease (multiple sclerosis in an aunt and lupus in another aunt) and the presence of persistent anti-phospholipid antibodies (28 to a maximum of 51 U of IgG). All other inflammatory markers (ESR, native DNA, antib2GPI) were normal, as well as cerebrospinal fluid analysis. At the time of the SAH, angiography showed several aneurysms and a stenosis in the anterior circulation, with posterior circulation sparing (Figure 1).

Steroid (prednisone 8 mg/day, 3 years of treatment) and immunosuppressant therapy (cyclophosphamide 750 mg/m², 13 sessions of treatment; rituximab 375 mg/m², 1 dose) were initiated, without change of vessel wall enhancement on repeated yearly MRI during this time period, even though no new ischaemia-related symptoms occurred. Four years later, control angiography showed posterior circulation involvement, in a similar pattern to the anterior circulation, with development of a saccular basilar tip aneurysm and arterial stenosis (Figure 2). Beginning of dilatation of the basilar tip was retrospectively noted after reviewing the previous MRI. Because of the perceived high risk of ischaemic stroke, burr-hole treatment was performed to improve brain perfusion in case of further progression of the posterior circulation stenosis. Although risk of aneurysmal haemorrhage was still present, treatment of the remaining aneurysms was not undertaken, as procedural risks (either endovascular or surgical) were considered to be too high.

Figure 2 MRI axial T1SE-weighted sequence (level of slices represented as a dotted line in E) performed before (A & C) and after gadolinium injection (B & D) and angiography (E: basilar artery) in frontal view, both performed in December 2011. Persistence of diffuse vessel wall enhancement is demonstrated (B & D: white arrows). Interval development of a similar pattern in the posterior circulation as in the carotid circulation with development of a basilar stenosis (E: arrow) and basilar tip aneurysm (D and E: empty arrow).

The main finding in this case is that vessel wall enhancement preceded the development of arterial aneurysmal dilatation and stenosis, with resultant risk of haemorrhage or ischaemic stroke. Indeed, the patient had severe stenosis of both internal carotid arteries, and the brain was mainly supplied by the vertebrobasilar system. In such cases, we think that short-interval follow-up vessel wall MRI should be performed to adapt further treatment strategies. In our case, we decided to prophylactically treat the patient with transcortical reperfusion in order to improve vascular reserve in case of increasing posterior circulation stenosis.

Vessel wall enhancement on MRI is a known diagnostic sign of cerebral vasculitis.Reference Küker, Gaertner, Nagele, Dopfer, Schoning and Fiehler ^{2 ,} Reference Saam, Habs, Pollatos, Cyran, Pfefferkorn and Dichgans ⁴ In our case, vessel wall enhancement involved large-sized cerebral arteries in the anterior and posterior circulation, with both arterial stenosis and aneurysmal dilatation.

Cerebral arteriopathy, which on luminal imaging appears as arterial stenosis, is common in children with acute ischaemic stroke. Associated risk factors are early school age, sickle cell disease and recent upper respiratory infections.Reference Amlie-Lefond, Bernard, Sébire, Friedman, Heyer and Lerner ¹ In our presentation, the patient did not have any of these risk factors. Moreover, no data are available in the literature regarding arterial dilatations or aneurysms. Although the patient had a presumed CNS vasculitis and had elevated anticardiolipin antibodies, he did not fit the classical presentation of focal cerebral arteriopathy of childhood.Reference Amlie-Lefond, Bernard, Sébire, Friedman, Heyer and Lerner ^{1 ,} Reference Mineyko, Narendran, Fritzler, Wei, Schmeling and Kirton ³

To conclude, we observed that wall enhancement on 2-mm T1SE-weighted sequences in case of cerebral vasculitis was followed by further changes in arteries that appear initially normal on angiography in a patient who was a poor responder to medical treatment. Further studies are needed to explore this relationship and to determine if vessel wall enhancement could predict further appearance of stenosis and/or aneurysmal dilatations in such cases.