Vessel wall magnetic resonance and arterial spin labelling imaging in the management of presumed inflammatory intracranial arterial vasculopathy

Abstract

Optimal criteria for diagnosing and monitoring response to treatment for infectious and inflammatory medium-large vessel intracranial vasculitis presenting with stroke are lacking. We integrated intracranial vessel wall MRI with arterial spin labelling into our routine clinical stroke pathway to detect presumed inflammatory intracranial arterial vasculopathy, and monitor disease activity, in patients with clinical stroke syndromes. We used predefined standardized radiological criteria to define vessel wall enhancement, and all imaging findings were rated blinded to clinical details. Between 2017 and 2018, stroke or transient ischaemic attack patients were first screened in our vascular radiology meeting and followed up in a dedicated specialist stroke clinic if a diagnosis of medium-large inflammatory intracranial arterial vasculopathy was radiologically confirmed. Treatment was determined and monitored by a multi-disciplinary team. In this case series, 11 patients were managed in this period from the cohort of young stroke presenters (<55 years). The median age was 36 years (interquartile range: 33,50), of which 8 of 11 (73%) were female. Two of 11 (18%) had herpes virus infection confirmed by viral nucleic acid in the cerebrospinal fluid. We showed improvement in cerebral perfusion at 1 year using an arterial spin labelling sequence in patients taking immunosuppressive therapy for >4 weeks compared with those not receiving therapy [6 (100%) versus 2 (40%) P = 0.026]. Our findings demonstrate the potential utility of vessel wall magnetic resonance with arterial spin labelling imaging in detecting and monitoring medium-large inflammatory intracranial arterial vasculopathy activity for patients presenting with stroke symptoms, limiting the need to progress to brain biopsy. Further systematic studies in unselected populations of stroke patients are needed to confirm our findings and establish the prevalence of medium-large artery wall inflammation.

Keywords: ASL; cerebral vasculitis; neuroinflammation; stroke; vessel wall MR.

Graphical abstract

Figure 1

HSV-2 inflammatory intracranial arterial vasculopathy (Patient 7); DWI (A) demonstrates an acute infarct involving the right occipital and medial temporal lobes. ToF MRA (B) shows occlusion of the P1 segment of the right PCA (dashed arrow) and narrowing right MCA with a ‘beaded’ appearance (arrow), as well as diffuse narrowing of the intracranial right ICA. VWI (C) wall thickening and enhancement of the right MCA (double arrow), right P1 segment (dashed arrow) and right intracranial ICA (not shown). ASL (D) shows reduced perfusion in the area of infarction (arrow) and extensive ATAs over the cortical territory of the right MCA (arrowheads), indicating a relative delay in blood arrival. Follow-up imaging after treatment (E-H) shows the right temporo-occipital infarct maturation, with no evidence of new ischaemia on DWI (E). ToF MRA (F) demonstrates partial recanalization of the right PCA (dashed arrow), improvement in the calibre of the right MCA (arrow) and reduced narrowing of the right intracranial ICA. VWI (G) shows near resolution of the wall thickening and enhancement of the right MCA (double white arrows), right P1 segment (dashed arrow) and right intracranial ICA (not shown). ASL (H) shows normalization of perfusion in the corresponding cortical territories of the right MCA and PCA.

Figure 2

Intracranial Takayasu (Patient 10); Intracranial Takayasu arteritis: Axial b1000 DWI image (A) demonstrates an acute right striatocapsular infarct, with fusiform dilatation of the M1 segment of the right MCA on time-of-flight MRA (B). ASL perfusion-weighted image (C) shows the reduced signal intensity of labelled spins in the right peri Sylvian regions, which normalized on follow-up imaging (not shown). Axial-fused (F) ¹⁸FDG PET-CT image demonstrates concentric and increased radiotracer uptake within the wall of the ascending and proximal descending thoracic aorta (solid black arrow). Baseline sagittal VWI (D) shows concentric thickening and enhancement of the vessel wall of the right MCA (dotted black arrow), with interval improvement on subsequent VWI following interim treatment (E).

Figure 3

Presumed inflammatory intracranial arterial vasculopathy ‘Inflam-’ (Patient 6). ToF MRA (A), axial VWI (B + C) and serial perfusion-weighted ASL images at supraganglionic level (D-F) in a 53-year-old male patient undergoing sustained immunosuppressive treatment. Baseline MRA (A) demonstrate irregular narrowing of the distal right ICA (arrow) and right MCA (double arrow), associated with concentric thickening and pathological enhancement of the affected vessel walls on VWI (B + C). Baseline ASL (D) demonstrates ATAs over the right M6 territory (arrow), with an overall ASL perfusion score of 25. ASL at 6 months (E) shows more extensive ATAs (arrowheads) with an overall score of 18, Subsequent ASL imaging performed at 1 year following adjustment to the patient’s treatment regime (F) demonstrates an associated improvement in cerebral normalisation perfusion in the right MCA territory (arrowheads), with an overall perfusion score of 22. ‘Inflam-’; Inflammatory medium–large vessel intracranial vasculitis with no supporting evidence of inflammation from additional testing

Figure 4

Presumed inflammatory intracranial arterial vasculopathy ‘Inflam-’ (Patient 8); Luminal, vessel wall and serial ASL imaging in a 48-year-old female patient without sustained treatment. Baseline ToF MRA (A) demonstrates tapered narrowing of the intracranial portions of the right ICA culminating in high-grade stenosis involving the right terminal ICA segment and T junction. Baseline axial VWI (B + C) demonstrates concentric vessel wall thickening and pathological enhancement of the petrous (not shown), cavernous (B) and supraclinoid (C) segments of the right ICA (double arrows). Baseline ASL (D) demonstrates mild ATAs over the posterior right middle cerebral artery territory, with an overall ASL perfusion score of 26, with only minimal change at 6 months (E). ASL performed at 1 year, following no long-term immunotherapy intervention, demonstrates worsening ATAs over the cortical territory of the right MCA, with a decline in overall perfusion score to 21 (F). ‘Inflam-’; Inflammatory medium–large vessel intracranial vasculitis with no supporting evidence of inflammation from additional testing.