Azygos ACA fusiform dilatation: embryological insights from co-existing midline lipoma and callosal malformation.

We present a case of a tubulonodular-type lipoma of the corpus callosum (LCC) with hypogenesis of the corpus callosum (CC) accompanied by an azygos anterior cerebral artery (ACA) with fusiform dilatation adjacent to the lipoma in an 85-year-old female that was incidentally found during a transient ischaemic attack (TIA) workup. The patient had no symptoms of LCC or fusiform ACA dilatation. This case highlights the characteristic imaging findings and morphological changes in the adjacent arteries, particularly those associated with LCC. A literature review of 32 reported cases of LCC confirmed that fusiform dilatation of the adjacent vessels is commonly associated with this abnormality. This study suggests that these vascular changes may arise from the abnormal differentiation of the meninx primitiva, affecting both brain structures and blood vessels. Conservative management of fusiform dilatation is recommended as the prognosis appears favourable, with no reported cases of bleeding from such lesions. These findings underscore the importance of understanding the embryological origins of LCC and associated vascular abnormalities.