MR-IMAGING OF THE MENINGES .1. NORMAL ANATOMIC FEATURES AND NONNEOPLASTIC DISEASE

The structural organization of the dura and leptomeninges is reflected in its magnetic resonance (MR) imaging appearance in normal and disea se states. Two distinct enhancement patterns are characterized: dura-a rachnoid enhancement and pia-subarachnoid space enhancement. The dura- arachnoid pattern consists of curvilinear enhancement overlying the br ain and immediately deep to the inner table of the calvaria, as well a s along the fair and tentorium. Pial enhancement closely follows the b rain surface into sulci and outlines the basal cisterns. Recognition o f these enhancement patterns and other MR imaging characteristics may enhance the role of MR imaging in the detection, diagnosis, and follow up of neoplastic and nonneoplastic disorders affecting the meninges. T he focus of this article (Part I) is the MR appearance of the normal m eninges and nonneoplastic causes of meningeal disease. Part II of this series will discuss neoplastic conditions affecting the coverings of the brain and spinal cord with an emphasis on pathways of disease spre ad.