Meningeal abnormalities: a radiologist's guide to comprehensive imaging and differential diagnosis

Meningeal abnormalities encompass a wide spectrum of pathological conditions affecting the protective layers of the central nervous system the dura mater, arachnoid mater, and pia mater. These abnormalities may arise from infectious, neoplastic, inflammatory, traumatic, or post-surgical origins and often present with non-specific clinical symptoms such as headache, seizures, or altered mental status. As such, neuroimaging plays a pivotal role in their evaluation, providing critical information for accurate diagnosis and effective management. This article serves as a comprehensive guide for radiologists, offering a structured approach to the imaging and differential diagnosis of meningeal diseases. It begins with a review of the normal meningeal anatomy, including recent discoveries about the glymphatic system and the fourth meningeal layer, and proceeds to detail the utility of key imaging modalities, particularly magnetic resonance imaging (MRI) and computed tomography (CT), in assessing meningeal pathology. Emphasis is placed on distinguishing between pachymeningeal and leptomeningeal involvement based on enhancement patterns, as well as identifying hallmark imaging signs such as dural thickening, nodular lesions, and enhancement distribution. Common and rare disease entities including meningitis, meningioma, dural metastases, neurosarcoidosis, and carcinomatous meningitis are explored through detailed imaging features and differential considerations. The article also highlights advanced techniques including contrast-enhanced 3D FLAIR, dynamic contrast-enhanced MRI, and emerging applications of artificial intelligence in meningeal evaluation. Through illustrative case examples and a systematic diagnostic framework based on current evidence, this guide aims to enhance radiologists' diagnostic accuracy and clinical confidence, ultimately contributing to more timely and informed management of patients with meningeal abnormalities.