Table 8

Frequent neuroimaging patterns in autoimmune-induced encephalopathy

Acute disseminated encephalomyelitis
 CTUsually normal
  • ▸ T2 and FLAIR hyperintensities in multiple brain regions, mostly in the deep and subcortical white matter, and up to 1/3 have hyperintense lesions in the spinal cord especially acutely, with contrast enhancement

  • ▸ DWI shows variable abnormalities depending on the stage of the disease. In the first week (ie, acute phase) DWI reveals a restricted diffusion, and later (ie, subacute phase) diffusion increases

  • ▸ Brainstem and spinal cord abnormalities on MRI are common

  • ▸ Haemorrhagic demyelinating lesions are mostly seen in the hyperacute ADEM variants

  • ▸ Reduction of N-acetyl-aspartate in regions corresponding to the areas of high T2 signal intensity in the subacute phase in MRS

Autoimmune and paraneoplastic limbic encephalitis
 CTUsually normal
  • ▸ Contrast enhancing mesial temporal T2 and FLAIR hyperintensities in >50%

  • ▸ Subcortical regions, the cerebellum or brainstem may be involved

  • ▸ In NMDAR-antibody-mediated limbic encephalitis MRI is often normal. Sometimes, however, FLAIR and T2 hyperintensity signal changes typically involve temporal regions, and sometimes extratemporal areas

  • ▸ In SREAT, white matter changes are atypical, however, MRI findings can resemble acute demyelinating encephalomyelitis. Hippocampal hyperintensities and multifocal hyperintensities on T2, FLAIR and DWI with corresponding hypointensities on T1 may appear

  • ▸ In SREAT, decreased N-acetyl-aspartate, myoinositol peaks, elevations in lipid, lactate, glutamate/glutamine and choline peaks on MRS support inflammation

  • ▸ Some cases show imaging regression after high doses of corticosteroids

 SPECTIn SREAT, decreased tracer uptake in the striatum and global hypoperfusion of the whole cerebral cortex
  • ADEM, acute disseminated encephalomyelitis; DWI, diffusion-weighted imaging; FLAIR, fluid-attenuated inversion recovery; MRS, MR spectroscopy; NMDAR, N-methyl-d-aspartate receptor; SPECT, single-photon emission CT; SREAT, steroid-responsive encephalitis with autoimmune thyroiditis.