Non-vasculitic Autoimmune Inflammatory Meningoencephalitis (NAIM)

Clinical features:

Progressive encephalopathy, cognitive impairment. Ataxia, seizures, tremors and visual hallucinations can occur.

Findings on investigations:

ESR may be raised
SS-A or SS-B: may be positive
CSF analysis:

  • Often raised WCC and protein
  • Immunoglobulin (Ig)G index and synthesis rate

EEG: mild-moderate diffuse slowing
MRI: normal
Cerebral angiography: normal

Pathology, brain biopsy:

Leptomeningeal perivascular lymphocytic inflammation, mild without evidence of vasculitis.

  • Vessel walls are intact
  • Immunohistochemistry: CD3+ T-cell and B-cell infiltration
Salivary gland biopsy:

Lymphocytic infiltration, Immunohistochemistry: CD3+ T-cell and B-cell infiltration


Steroid therapy with methylprednisone or prednisone

Associated conditions:

  • Sjogren’s syndrome
  • Hypereosinophilic syndrome
  • Hashimoto’s disease
  • Systemic lupus erythematosus

Related articles:


  1. Caselli RJ, Boeve BF, Scheithauer BW, O’Duffy JD, Hunder GG. Nonvasculitic autoimmune inflammatory meningoencephalitis (NAIM): a reversible form of encephalopathy. Neurology. 1999 Oct 22;53(7):1579-81.
  2. Josephs KA, Rubino FA, Dickson DW. Nonvasculitic autoimmune inflammatory meningoencephalitis. Neuropathology. 2004 Jun;24(2):149-52.