GABAA receptor antibody encephalitis

Last revised by Rohit Sharma on 18 Nov 2021

GABAA receptor antibody (anti-GABAAR) encephalitis is an autoimmune encephalitis characterized by a severe seizure disorder and distinctive radiographic features.

Given the rarity of the condition, epidemiological data pertaining to anti-GABAAR encephalitis is not well established. Based on existing case series-level data, the condition can be seen in both adult and pediatric populations 1.

There may be an association with an underlying tumor or malignancy in approximately 40% of cases, most commonly thymomas are implicated 1. The condition has also been described following viral encephalitis 1.

The clinical presentation can be varied, but the most common presentation is with treatment-refractory seizures, including status epilepticus and epilepsia partialis continua 1-3. Less commonly, patients may have cognitive impairment, behavioral disturbances, or a decreased level of consciousness 1.

Gamma-aminobutyric acid (GABA) is an important inhibitory central nervous system neurotransmitter. GABA has two receptor classes, namely the GABAA receptor (GABAAR) and the GABAB receptor (GABABR), the former of which is implicated in anti-GABAAR encephalitis. Given the general inhibitory role of GABAAR, antibodies directed to this receptor result in increased neuronal excitability and thus the most common clinical phenotype of seizures 1-3.

The key marker is the IgG GABAAR antibody (anti-GABAAR), specifically reactive with the α1β3 subunit, which can be detected in specimens from either the CSF or serum 1-3. Additionally, CSF will often have an inflammatory phenotype, with high protein and a pleocytosis 1.

MRI brain in patients with anti-GABAAR encephalitis is usually abnormal 1-3.

  • T2/FLAIR: multifocal cortical and subcortical hyperintensities, most commonly affecting the temporal and frontal lobes, and most commonly bilateral
  • DWI: generally normal
  • T1 C+ (Gd): generally lesions are non-enhancing

Management does not differ from other causes of autoimmune encephalitis, namely with immunotherapy and symptomatic management 1-3.

The identification of anti-GABAAR as a cause for cases of autoimmune encephalitis was made in 2014 by Mar Petit-Pedrol and international colleagues 2.

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