Diagnostic and Therapeutic Approach to Autoimmune Neurologic Disorders

A. Sebastian López-Chiriboga, MD; Eoin P. Flanagan, MD

Disclosures

Semin Neurol. 2018;38(3):392-402. 

In This Article

Neuroimaging

Magnetic Resonance Imaging

MRI can be helpful to support the diagnosis of several autoimmune neurologic disorders, particularly autoimmune encephalitis, autoimmune epilepsy, and neuromyelitis optica spectrum disorders (NMOSD). MRI with and without contrast of the brain (or neuroaxis, depending on focality) is the initial test of choice. The MRI in the acute phase in antibody-mediated autoimmune encephalitis usually shows temporal lobe and limbic dysfunction abnormalities (Figure 1E), but may be normal.[16] Different characteristic features associated with specific antibodies have been reported:

Figure 1.

(A) Tissue immunofluorescence with prominent hippocampal and granular layer staining, typical of NMDA-R antibody. (B) Positive cell-based assay for NMDA-R. (C) Left temporal lobe hypermetabolism in a patient with LGI-1 encephalitis. (D) Bilateral temporal lobe hypermetabolism in a critically ill patient with AMPA encephalitis. (E). Bilateral T2 flair hyperintense signal in the hippocampus and mild left hippocampal enlargement in a patient with GABA-B encephalitis (arrows). (F) Bilateral optic nerve gadolinium enhancement in a patient with AQP4 + NMOSD. (G) Cervicothoracic longitudinally extensive spinal cord lesion with contrast enhancement in the same (F) patient. (H1) Thermoregulatory sweat-test pre and post. (H.2) 12 weeks of immunotherapy (IVIG) in a patient with an autoimmune autonomic neuropathy accompanied by ganglionic acetylcholine receptor (α3-AChR) antibody.

  • In NMDA-R antibody encephalitis, MRI is abnormal in 25 to 50% of patients; multiple findings have been described including T2 hyperintensities in the frontal lobe, mesiotemporal, thalamic, basal ganglia, and cerebellum.[17] Recently, the use of structural and resting-state functional MRI revealed significant alterations of functional connectivity[18] and decreased occipital lobe metabolism by fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT).[19]

  • Patients with LGI-1 autoantibody encephalitis can also have a normal MRI, but abnormalities include uni- or bilateral T2/FLAIR hyperintensities of mesiotemporal lobes in most patients;[17] basal ganglia T1 or T2 hyperintense lesions may be seen in those with faciobrachial dystonic seizures;[20] and follow-up imaging may reveal pronounced hippocampal atrophy.[21,22]

  • Bilateral mesial temporal lobe T2 hyperintensities are frequently found in GABAB antibody encephalitis, but cerebellar MRI abnormalities have also been reported.[23]

  • The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R) antibodies frequently have abnormal MRI findings characterized by mesiotemporal T2/FLAIR hyperintensities, although cases with normal MRIs have been encountered.[24]

  • Extensive multifocal bilateral cortical and subcortical T2 FLAIR hyperintensities have been reported in patients with GABAA antibodies.[25]

  • Perivascular periventricular radial enhancement is a characteristic feature of an autoimmune meningoencephalomyelitis associated with CSF autoantibodies to GFAP.[26]

  • Collapsin response mediator protein 5 (CRMP-5)-IgG with chorea can be accompanied by bilateral basal ganglia T2-hyperintensities.[27]

  • Diencephalic and hypothalamic lesions can be seen in anti-Ma2[28] or Aquaporin 4 (AQP4)-IgG encephalitis.[29]

  • MRI is typically normal in patients with metabotropic glutamate receptor type 1 autoimmunity,[30] dipeptidyl-peptidase-like protein-6 antibodies (DPPX),[31] or glycine receptor antibodies–associated syndromes.[32]

  • Hippocampal atrophy or frontotemporal atrophy has been reported for multiple antibodies on follow-up imaging.[17]

  • Optic nerve enhancement, sometimes bilateral involvement (Figure 1F), in combination with T2 hyperintense often longitudinally extensive spinal cord lesions (Figure 1G) is typical imaging features of patients with AQP-4 and MOG antibodies and different patterns of brain involvement can help differentiate between these antibody-associated syndromes.[33]

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