Presentation of opsoclonus myoclonus ataxia syndrome with glutamic acid decarboxylase antibodies

Autoimmune meningoencephalitis associated with anti‐glutamic acid decarboxylase antibody following COVID‐19 infection: A case report

Anti‐glutamic acid decarboxylase (Anti‐GAD) are associated with various neurologic condition; but no meningitis has been reported with it, so far. Evidence demonstrates the associated of autoimmune meningoencephalitis with COVID‐19 infection. Here, we report a 44‐year‐old female with progressive loss of consciousness with anti‐GAD65 meningoencephalitis 1 month after COVID‐19 infection.

Enoxaparin-induced Wunderlich syndrome in a young patient with anti-GAD 65-associated opsoclonus and limbic encephalitis: a rare complication in a rare disease

Wunderlich syndrome is a rare condition characterised by acute spontaneous non-traumatic renal haemorrhage into the subcapsular and perirenal spaces. Our case of anti-GAD65-associated autoimmune encephalitis (AE), aged 30 years, developed this complication following use of enoxaparin and was managed by selective glue embolisation of subsegmental branches of right renal cortical arteries. Our case had opsoclonus as one of the clinical manifestations, which has till now been described in only two patients of this AE. This patient received all forms of induction therapies (steroids, plasmapheresis, intravenous immunoglobulin and rituximab) following which she had good improvement in her clinical condition. The good response to immunotherapy is also a point of discussion as this has been rarely associated with anti-GAD65 AE.

GABA-A receptor impairment in cerebellar ataxia with anti-glutamic acid decarboxylase antibodies

Antibodies against glutamic acid decarboxylase (GAD-Abs) are associated with cerebellar ataxia, which is refractory to treatment with GABAergic drugs. To investigate the GABAergic neuronal system in vivo, we performed a combined positron emission tomography (PET) study with [(11)C]-flumazenil and [(18)F]-fluorodeoxyglucose (FDG) in three patients with cerebellar ataxia with GAD-Abs. The GABA-A receptor function was investigated using flumazenil, which is a selective GABA-A receptor ligand, while FDG-PET using a three-dimensional stereotactic surface projection analysis was performed to estimate the metabolic rates of glucose (MRGlc) in the patients. GABAergic drugs showed no efficacy for the cerebellar ataxia in all three patients, and all three displayed a significant decrease in flumazenil binding in the cerebellum. No MRGlc decrease in the cerebellum was found in the two patients who presented with amelioration of cerebellar ataxia following intravenous immunoglobulin (IVIG) therapy, whereas a significant MRGlc decrease in the cerebellar hemisphere was observed in another patient who showed severe cerebellar atrophy on magnetic resonance images and no response to the IVIG therapy. The decreased flumazenil binding in the present patients indicated cerebellar GABA-A receptor impairment, which may be due to either neuronal cell loss, as demonstrated by the decreased MRGlc, or a dysfunction in GABAergic neuronal inhibition. Although GAD-Abs have been postulated to prevent the synthesis of GABA, resulting in decreased GABAergic transmission, the GABA-A receptor impairment may play another pathogenic role in cerebellar ataxia associated with GAD-Abs resulting in a condition refractory to GABAergic drug therapy.