CNS vasculitis and vasculopathy: Efficacy and usefulness of diffusion-weighted echoplanar MR imaging
Introduction
Vasculitis is defined as the inflammation of the blood vessel wall [1]. Vasculopathy is a more general term and has been used for any disease of the blood vessel [2]. Vasculopathy usually implies a lesion of unknown etiology or pathologically unproven lesion of the blood vessel. The lesions in some types of CNS vasculitis or vasculopathy are treated with immunosuppressants while those in thrombosis or embolism are treated with anticoagulants. Therefore, a rapid noninvasive test to differentiate in CNS vasculitis and vasculopathy is needed for prompt, appropriate management of patients with neurological signs and symptoms.
CNS vasculitis and vasculopathy often have similar clinical and radiologic characteristics. Both result in reversible ischemia or infarction. Whether the lesions on MRI are reversible or irreversible seems to be related to the size or location of involved vessels and severity of ischemia. Diffusion-weighted MR imaging (DWI) has been useful in early detection of cytotoxic edema in hyperacute or acute infarction, distinguishing it from vasogenic edema or chronic infarction [3]. Vasogenic edema is predominantly seen in some types of vasculitis or vasculopathy [4], [5], [6], [7], [8]. This pictorial essay illustrates the patterns in various vasculitides and vasculopathies on DWI.
Section snippets
Principles and methods
DWI was performed on a Sigma Horizon 1.5 T system equipped with echo–speed gradients (GE Medical Systems, Milwaukee, WI) with the following parameters: TR=5999–10 000 ms, TE=97.2–126 ms, 19–30 cm field of view, 128×128 matrix, 5–7 mm slice thickness and slow rate=120 mT/min/ms.
Diffusion weighting was applied in three orthogonal orientations with b values of 1000 s/mm2, and, therefore, three diffusion-weighted images were generated for each slice location. In addition, b=0 images were also
Vasculitis
The term “vasculitis” encompasses a heterogeneous group of multisystemic disorders characterized pathologically by inflammation and necrosis of the blood vessel wall. CNS vasculitis is classified by the size of the predominantly affected vessel [1]. Conventional catheter angiography and brain biopsy have been the mainstays in the diagnosis. However, conventional catheter angiography has a false-negative rate of 20–30% because small-sized arteries under 100–200 μm are beyond its limit of
Vasculopathy vs. vasculitis
“Vasculopathy” is defined as any disease of the blood vessels, which includes a wide range of conditions: degenerative, metabolic and inflammatory vasculopathies, embolic disease, coagulative disorders and functional causes such as posterior reversible encephalopathy syndrome (PRES) [2]. Vasculopathy can also be used for “vasculitis,” which is not pathologically proven. This presentation focuses on vasculopathy that mimics vasculitis but have no inflammation in the wall of the blood vessel.
Conclusion
In conclusion, there are primarily two patterns of acute or subacute lesions in vasculitides and vasculopathies. First is acute or subacute infarction due to primary or secondary arterial stenosis or occlusion. Second is vasogenic edema due to small vessel vasculitis or vasculopathy, in SLE, Behçet's disease or PRES. DWI may provide the information about the choice of treatment and outcome in patients with CNS vasculitides and vasculopathies.
Acknowledgements
Awarded Magna Cum Laude at the 38th Annual Meeting of the American Society of Neuroradiology, Atlanta, LA, April 2000.
References (23)
- et al.
Diffusion-weighted MR imaging of CNS involvement in systemic lupus erythematosus
Acad Radiol
(2001) - et al.
Encephalopathy complicating Henoch–Schonlein purpura: reversible MRI changes
Pediatr Neurol
(1998) - et al.
Pathogenesis of vasculitis
Semin Neurol
(1994) The spectrum of vasculopathies in the differential diagnosis of vasculitis
Semin Neurol
(1994)- et al.
Discrimination between different types of white matter edema with diffusion-weighted MR imaging
J Magn Reson Imaging
(1993) - et al.
MR imaging of systemic lupus erythematosus involving the brain
AJR, Am J Roentgenol
(1985) - et al.
CNS involvement in neuro-Behçet syndrome: an MR study
AJNR, Am J Neuroradiol
(1999) - et al.
A reversible posterior leukoencephalopathy syndrome
N Engl J Med
(1996) - et al.
Diagnosing intracranial vasculitis: the role of MR and angiography
AJNR, Am J Neuroradiol
(1994) - et al.
CNS vasculitis in autoimmune disease: MR imaging findings and correlation with angiography
AJNR, Am J Neuroradiol
(1999)