Other noninfectious inflammatory disorders.

Idiopathic inflammatory-demyelinating diseases (IIDDs) represent a broad spectrum of central nervous system (CNS) disorders, including monophasic, multiphasic, and progressive disorders that range from highly localized forms to multifocal or diffuse variants. In addition to the classic multiple sclerosis (MS) phenotypes, several MS variants have been described, which can be differentiated on the basis of severity, clinical course, and lesion distribution. Other forms of IIDD are now recognized as distinct entities and not MS variants, such as acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. The CNS can also be affected by a variety of inflammatory diseases. These include primary angiitis of the CNS (PACNS), a rare disorder specifically targeting the CNS vasculature, and various systemic conditions which, among other organs and systems, can also affect the CNS, such as systemic vasculitis and sarcoidosis. The diagnosis of PACNS is difficult, as this condition may be confused with reversible cerebral vasoconstriction syndrome (RCVS), a term comprising a group of conditions characterized by prolonged but reversible vasoconstriction of the cerebral arteries. Magnetic resonance imaging of the brain and spine is the radiologic technique of choice for diagnosing these disorders, and, together with the clinical and laboratory findings, enables a prompt and accurate diagnosis.