Cerebral amyloid angiopathy (CAA) leads to deposition of amyloid-beta-peptide in leptomeninges and cerebral blood vessels. A β-related angiitis (ABRA) is a severe form of CAA characterized by transmural inflammation and/or, granulomatous inflammation. We report two patients with advanced malignancy presenting with leptomeningeal enhancement (LME) concerning for leptomeningeal metastases, with biopsy demonstrating ABRA.

1. 76-year-old man presented with left facial droop, dysarthria and imbalance. MRI head showed acute infarcts in multiple vascular distributions and diffuse LME. CTA showed bilateral cervical lymphadenopathy, without evidence of vasculitis. CSF analysis demonstrated lymphocytic pleocytosis and negative flow cytometry and cytology. Cervical lymph node biopsy revealed a new diagnosis of metastatic papillary thyroid cancer. Repeat MRI brain one month later showed persistent and worsening cortical LME. Prior to surgery for the thyroid cancer, a brain biopsy was performed for staging. Pathology demonstrated fibrinoid necrosis of vessels walls and foci of thrombosis, consistent with CAA. The patient was treated with corticosteroids followed by cyclophosphamide for ABRA.

2. 78-year-old woman with cognitive impairment and stage IV serous endometrial cancer presented after incidental findings of subarachnoid hemorrhage (SAH) with LME on MRI brain. CSF analysis was normal with negative cytology. Head CTA was negative for aneurysm or vascular malformation. A repeat MRI showed new small SAH in the right superior frontal gyrus and multiple new punctate cerebellar infarcts. Brain biopsy revealed amyloid positivity with congo red staining in cerebellar leptomeningeal vessels, consistent with CAA. She received a 5-day course of IVIG (steroids contraindicated) with plan to start immunosuppressive therapy outpatient.

Our patients presented with LME in the setting of newly diagnosed malignancy, which raised concern for leptomeningeal metastases. The presence of SAH and infarcts are uncommon in leptomeningeal metastatic disease. In these cases, pathologic confirmation of CAA on brain biopsy changed the cancer-related prognosis and treatment plan.