Autoimmune and inflammatory conditions
There are a wide variety of autoimmune conditions that affect the brain and spine. Some, like demyelinating disease, are common, but have a variety of manifestations that can appear differently. Others, such as unusual inflammatory encephalitis, are rare but it is relatively important for radiologists to know about them.
This page covers the most common autoimmune and demyelinating disease that affect the brain and spine. To review all the videos on this topic, check out the entire autoimmune/inflammatory playlist.
CNS demyelinating disease is common, with the most common being multiple sclerosis (or MS), neuromyelitis optica (NMO), and acute disseminated encephalomyelitis (ADEM). These are all demyelinating/autoimmune conditions in which the brain loses its normal myelination. Susac syndrome is a small vessel vasculitis which can mimic demyelinating disease.
MS is the most common demyelinating disease, affecting women more than men, with 2 age distribution peaks in younger and middle age women. MS commonly presents with optic nerve or visual symptoms, affects the brain more commonly than the spine, and can result in short segment spine lesions.
Neuromyelitis optica, or NMO, is an autoimmune disease characterized by predominantly optic nerve and spine lesions. It is often associated with an antibody to aquaporin 4.
ADEM is an acute fulminant demyelinating syndrome characterized by acute onset and often many supratentorial lesions. The majority of patients recover, although some may have residual symptoms and it can even progress to death.
AHEM is a closely related variant of ADEM which is associated with hemorrhage.
Susac syndrome is a small vessel vasculitis with small vessel infarcts, most commonly in the retina, cochlea, and periventricular white matter and corpus callosum. It can frequently mimic demyelinating disease because the distribution of lesions is similar.
For more detailed information, check out the more specific videos about multiple sclerosis and pitfalls of interpretation below.
Interpreting MRI in Multiple sclerosis patients
Encephalitis is a condition in which the brain parenchyma becomes acutely inflamed or irritated. It can occur from infectious, autoimmune, or inflammatory causes. There are imaging features which help us distinguish them, but often it depends on clinical history, CSF results, and other testing.
There are a few CNS inflammatory diseases which have masslike manifestations, so I’ve lumped them in here. This includes orbital inflammatory disease and sarcoidosis. These diseases often have expansile enhancement, nodules, and masses, even though they are not neoplastic processes. If you see nodular or masslike enhancement, particularly at the skull base or in the orbits, think of these diseases.
A few inflammatory or demyelinating diseases affect the spine (in addition to MS, which we won’t really discuss here. These are trasnverse myelitis, which is commonly seen in a viral or post-viral setting, and sarcoidosis. Sarcoid can mimic a number of other conditions, such as tumors and lymphoma, so watch out.
Amyloid deposition disorders can also affect the CNS. There are three main manifestations:
- Cerebral amyloid angiopathy
- Inflammatory amyloid
While related, these disorders have different imaging appearances that can be clues to their presence.
There are inflammatory vascular processes that can also appear in the CNS. These include Moya Moya disease/syndrome, CADASIL, and MELAS, among others. These involve an inflammatory or autoimmune component of the vessels and can both affect the vessels directly or result in a characteristic parenchymal appearance.