Use of Magnetic Resonance Imaging to Visualize Leptomeningeal Inflammation in Patients With Multiple Sclerosis: A Review.

IMPORTANCE: Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system traditionally characterized by an initial relapsing-remitting clinical course and focal inflammatory lesions that have a predilection for the periventricular white matter. Recently, however, histopathologic and imaging studies have illustrated a more complex pathologic substrate involving cortical demyelination, gray matter atrophy, and meningeal inflammation. Neuroimaging advances have facilitated improved detection of cortical pathology, but our understanding of the pathogenesis of cortical disease remains incomplete. The purpose of this review is to evaluate the current status and future prospects regarding the emerging role of magnetic resonance imaging to visualize leptomeningeal enhancement in patients with MS and place these findings in the proper pathobiologic and clinical context. OBSERVATIONS: Cortical atrophy and demyelination along the subpial surface appear early in the disease course in patients with MS but accelerate in progressive stages. Histopathologic studies of patients have shown the presence of inflammatory infiltrates, in some cases with features of B cell-rich tertiary lymph follicles, along the cortical meningeal surface. Recent magnetic resonance imaging data demonstrate the ability to detect such inflammation using high-resolution gadolinium-enhanced contrast scans by the presence of leptomeningeal enhancement. Clinical and magnetic resonance imaging correlation studies indicate that leptomeningeal enhancement is most common in patients with progressive forms of MS and shows a relationship to subpial cortical lesions and cortical atrophy. CONCLUSIONS AND RELEVANCE: A growing body of evidence suggests that gray matter demyelination, cortical atrophy, and leptomeningeal inflammation may be important components of progressive MS pathology and provide a new therapeutic target. Leptomeningeal enhancement may prove a useful surrogate marker for such pathology, perhaps improving our understanding of the natural history of progressive MS, although its ultimate effect on therapeutic development and clinical care requires further study.