Perfusion Imaging in Autoimmune Encephalitis

Abstract

Encephalitis is characterized by inflammation of brain tissue and has various infectious and noninfectious causes. CSF analysis and MRI usually reveal inflammatory changes although sometimes brain imaging may be normal. Autoimmune encephalitis is caused by antibodies against neuronal synaptic receptors, surface proteins, or intracellular proteins. In this case report, we present a 65-year-old female who presented with a fall and altered mental status. Workup for infectious etiologies was negative and MRI of the brain displayed focal restricted diffusion with corresponding T2-FLAIR hyperintensity involving gray matter structures, making the diagnosis unclear. CT perfusion of the brain demonstrated increased cerebral blood volume and cerebral blood flow in the left parietooccipital gray matter, with corresponding normal mean transit time. Following treatment failure with acyclovir, antibiotics, and steroids, the patient was found to be positive for GAD65 antibodies and diagnosed with autoimmune encephalitis. Symptoms markedly improved with plasmapheresis. Autoimmune encephalitis rarely causes restricted diffusion and this is the first case report to describe corresponding hyperperfusion on CT perfusion study.

Imaging in Encephalitis

“…Encephalitis refers to inflammation of the brain and can present with an array of clinical symptoms including altered level of consciousness, memory loss, psychiatric changes, sleep disturbances, seizures, and weakness. 1 While there are numerous causes, etiologies can be classified into two broad categories: autoimmune and infectious. Autoimmune encephalitis is a result of the generation of immune responses against components of the host's central nervous system (CNS).…”

“…In contrast, infectious encephalitis is often a result of viral or bacterial infections, and thus may additionally manifest with fever and other systemic infectious symptoms and signs. 1,2 As many clinical manifestations are shared between autoimmune and infectious encephalitis, various diagnostic modalities are employed to help discern the specific etiology. While electroencephalography (EEG) and cerebrospinal fluid (CSF) analysis are used in attempting to confirm the diagnosis of encephalitis and determining the specific cause, neuroimaging plays an increasingly important role.…”

Stroke Mimics in the Acute Setting: Role of Multimodal CT Protocol

“…Perfusion findings have also been anecdotally described in case reports such as in Wernicke encephalopathy, 27 Hashimoto encephalopathy, 28 and viral infections. 29,30 In addition, we did not encounter, in our cohort, luxury perfusion conditions, which may pose a challenge in a differential diagnosis between a postreperfusion iCVE and a stroke mimic. Luxury perfusion represents, in fact, the recovery of CBF to normal or increased levels in regions of infarcted brain when re-vascularization is established after a stroke, sometimes spontaneously.…”

Seronegative limbic encephalitis manifesting as subacute amnestic syndrome: a case report and review of the literature

“…Perfusion studies can also demonstrate abnormalities even before the lesions are identifiable on conventional MRI sequences. The main findings are increased rCBF and cerebral blood volume (CBV), probably due to loss of cerebral vascular autoregulation [ 16 ].…”