[Autoimmune encephalitis, clinical, radiological and immunological data]

Encephalitis is an inflammatory or infectious disease with an acute or subacute presentation. Immunological abnormalities in serum can be found but may be underdiagnosed. In several cases, a paraneoplastic origin with anti-neuron antibodies is noted. In all cases, other auto-antibodies can be found with or without any neoplastic mechanism.

The aim of our study was to describe a clinical, radiological and immunological cohort of patients with autoimmune encephalitis and suggest a diagnostic and therapeutic algorithm.

We performed a retrospective study in an immunological unit of neurology. All patients with autoimmune encephalitis between March 2000 and October 2009 were included. The clinical, imaging and immunological evaluations were recorded for each patient.

Our cohort included 16 patients (eight men and eight women), mean age 45.3±10years. All patients had acute or subacute neuropsychological or neuropsychiatric impairment and all patients but one had temporal lobe dysfunction confirmed by cerebral MRI, PET or SPECT. Epilepsy was observed in 56% of cases, extra-temporal lobe impairment in 50%, including sleep disturbances. A cancer was found in only 25% (two small-cell lung cancers, one testis seminoma, one non-small-cell lung cancer with Merckel cells cancer). Anti-neuron antibodies were noted in 56% of cases (two with anti-voltage gate potassium channel complex antibodies (ab), two with anti-NMDA-R ab, two with anti-glutamate acid decarboxylase ab, one with anti-Ma2, two with anti-Hu ab and two remained uncharacterized). Systemic antibodies were found in 50% (one anti-gangliosides, one anti-SSA and one anti-DNA and four antinuclear ab uncharacterized, two anti-TPO and two anti-phospholipids). All patients received immunomodulatory treatments, including intravenous immunoglobulins (IgIV) and cancer was treated. Five patients achieved complete recovery, partial improvement was observed in 10 patients and two patients died.

Despite clinical homogeneity at presentation, clinical outcome seems to be different between patients with antibodies against neuronal surface antigens and those with antibodies against intracellular antigens, which are more likely refractory to immunotherapy and paraneoplastic. The frequency of extra-temporal lobe impairment suggests that the term of limbic encephalitis should be changed to autoimmune encephalitis.