Abstract DP362: Cerebellar tonsillar microhemorrhages – A radiological marker for diagnosing primary central nervous system vasculitis?

Introduction: Primary central nervous system vasculitis (PCNSV) is a rare, heterogenous and polymorphic disorder affecting the blood vessels of the CNS. It is a diagnosis of exclusion with no disease specific clinical features, serological or imaging findings. Historically, the presence of hemorrhages was considered rare in PCNSV. However, with the advent of susceptibility weighted imaging (SWI) sequences of MRI, the presence of microhemorrhages has been found to be common despite macrohemorrhages being uncommon. Hypothesis: The presence of microhemorrhages in the cerebellar tonsils on SWI sequences of MRI brain in a patient with an unexplained neurological deficit are indicative of PCNSV. Methods: We retrospectively evaluated our biopsy proven PCNSV patients and patients with hypertensive cerebellar hemorrhage who underwent an MRI (1.5T or 3T) between 2020-2024. All clinic-radiological and histopathological details of these patients were entered into a predesigned proforma. A senior neuroradiologist evaluated the MRI scans for the presence of tonsillar microhemorrhages. Results: Twenty-nine patients of PCNSV (15- granulomatous vasculitis; 14 – lymphocytic vasculitis) and 44 patients with hypertensive cerebellar ICH fulfilled the study criteria. The clinical characteristics of the patients are mentioned in table 1. All PCNSV patients (100%) were found to have tonsillar microhemorrhages along with supratentorial and infratentorial lesions (T2/ FLAIR/ SWI) and 27/29 (93.1%) revealed punctate or linear enhancement of these tonsillar lesions (Figure 1). There was no difference in the microhemorrhage pattern between granulomatous and lymphocytic vasculitis subtypes of PCNSV. In comparison, only 9/44 (20.4%) patients with cerebellar hemorrhage had tonsillar microhemorrhages. Amongst them, all of them had pontine microhemorrhages while 6/9 (66.7%) and 5/9 (55.5%) had concomitant midbrain and medullary microhemorrhages respectively. Most patients with concomitant pontine microhemorrhages had no cerebellar tonsil involvement. Conclusions: Cerebellar tonsillar microhemorrhages in PCNSV may be a marker of its intrinsic microangiopathy. The presence of cerebellar tonsillar microhemorrhages in patients with an unexplained neurological deficit may be an imaging marker for diagnosing PCNSV.