This is a prospective pilot study to determine the utility of MRI and high resolution intracranial vessel wall imaging for the diagnosis and disease activity assessment of intracranial vasculitis.

This study will evaluate patients with suspected primary angiitis of the central nervous system (PACNS), recruited during initial work-up by our multi-disciplinary team. Given the low incidence of CNS vasculitis and the fact that some patients are routed to a quaternary care center after initial work-up and diagnosis, evaluation of both groups will be useful to maximize the number of participants evaluated and to provide a representative sample of patients typically treated. During the study, participants will ultimately be deemed to have;

1. A specific clinical and pathologic subtype of PACNS,
2. PACNS not otherwise specified (NOS) without pathologic or clinical proof of a specific subtype, or
3. An alternative diagnosis other than PACNS.

Patients will undergo a standardized imaging and clinical examination at presentation and at pre-defined follow-up periods. Imaging examinations will include an MRI of the head, standard magnetic resonance angiogram (MRA) of the head, and intracranial vessel wall imaging without and with IV gadolinium. Patients will receive up to 4 imaging examinations at predefined intervals as part of this study. MRI/MRA/Vessel wall features will be evaluated by 2 neuroradiologists. Imaging findings will be correlated to clinical and any available laboratory or pathologic data. The target accrual is 10 patients for this pilot study.

Inclusion Criteria:

1. The patient is determined to have suspected PACNS upon evaluation by a neurologist or rheumatologist or may have an established diagnosis of PACNS of any duration as determined by a neurologist or rheumatologist.
2. Ability to undergo routine clinical testing, including lumbar puncture performed for PACNS to exclude potential alternative diagnoses (for initial suspected cases).
3. Ability to provide informed consent.

Exclusion Criteria:

1. Less than 18 years of age.
2. Any absolute contraindication to 3 Tesla MRI.
3. Any absolute contraindication to gadolinium.
4. Contraindication to lumbar puncture such as severe coagulopathy.
5. High risk carotid atherosclerotic plaque defined as either greater than 70% stenosis or known high risk plaque features such as intra-plaque hemorrhage.
6. Medium or high risk factors for cardioembolic stroke based on the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria.