Imaging CNS autoimmune and inflammatory disease
This is the second lecture in a case based review of imaging of the brain and spine for autoimmune and inflammatory conditions. We will cover the MRI findings of some of the common conditions and some potential pitfalls and mimics.
This second lecture covers causes of encephalitis, including inflammatory and autoimmune etiology. This section also covers infectious encephalitis, which is the most common mimic.
Limbic encephalitis is an immune mediated encephalitis often associated with neoplasm and a variety of circulating antibodies. It most commonly is manifested as bilateral (asymmetric or symmetric) temporal lobe FLAIR/T2 abnormalities. Enhancement is variable but less common than seen in herpes encephalitis.
Chronic limbic encephalitis
Over time, chronic limbic encephalitis can result in temporal lobe sclerosis and atrophy. Volumetric analysis of the brain and temporal lobes may be useful in highlighting the differences over time.
Lupus is a systemic autoimmune condition which can be associated with intracranial findings, including encephalitis, vasculitis, and posterior reversible encephalopathy syndrome (PRES). Vessel imaging may be normal, as it tends to affect the small vessels of the brain.
Viral encephalitis has a nonspecific imaging appearance with patchy white matter FLAIR/T2 abnormalities, often involving the temporal lobes. There are a number of causes of viral encephalitis, including herpes, west nile virus, St. Louis encephalitis, and others.
Herpes encephalitis is the most dreaded of the encephalitis causes because it has high morbidity and mortality. Compared to nonspecific viral and inflammatory encephalitis, it tends to have more enhancement and more DWI abnormality. Patients suspected of having herpes encephalitis should be started empirically on treatment immediately to improve the prognosis.
Summary and Conclusion
The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties, such as neurology, who have an interest in neuroradiology or may see patients with CNS demyelinating or inflammatory conditions.