Autoantibodies against Glutamate Receptor ε2-Subunit Detected in a Subgroup of Patients with Reversible Autoimmune Limbic Encephalitis

Autoimmune Encephalitis in a Patient with a Solitary Intracranial Plasmacytoma

A 65-year-old woman presented with fever and abnormal behavior. Magnetic resonance imaging showed swelling of the left medial temporal lobe and an intracranial extra-axial occipital tumor. While her neurological symptoms improved after the administration of corticosteroid therapy under the suspicion of autoimmune encephalitis, the occipital tumor unexpectedly shrank, and the diagnosis of a solitary plasmacytoma was confirmed by biopsy. Additional examinations revealed elevated anti-glutamate receptor antibodies in the cerebrospinal fluid. The patient was diagnosed with autoimmune encephalitis concurrent with an intracranial solitary plasmacytoma. Central nervous system involvement can be considered a neurological complication in patients with a solitary plasmacytoma.

Successful Treatment of Syndrome of Inappropriate Antidiuretic Hormone Secretion Associated with Neuro-Sweet Disease in Myelodysplastic Syndrome

Sweet disease may occur in several organs, and central nervous system involvement, known as Neuro-Sweet disease (NSD), is rare. The clinical features of NSD include recurrent encephalomeningitis accompanied by fever and erythematous plaques; systemic corticosteroid therapy is highly effective. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is an important electrolyte abnormality because it can be life-threatening. We describe the first case of SIADH and NSD associated with low-risk myelodysplastic syndrome that was successfully treated with corticosteroids and cyclosporine. The patient has remained stable for 1 year without any recurrence.

Glutamate receptor antibodies directed against AMPA receptors subunit 3 peptide B (GluR3B) associate with some cognitive/psychiatric/behavioral abnormalities in epilepsy patients

Antibodies (Ab's) to glutamate receptors, directed specifically against AMPA receptors subunit 3 peptide B (i.e. GluR3 amino acids 372-395), named GluR3B Ab's, can by themselves activate GluR3-containing glutamate/AMPA receptors, evoke ion currents via the receptor's ion channel, kill neurons and damage the brain. Herein we first tested 14 consecutive epilepsy patients and 10 healthy controls, and found that 7 (50%) patients had GluR3B Ab's. Second, in 71 other consecutive epilepsy patients (20 generalized epilepsy, 51 partial epilepsy) and 49 controls, we found that 17 (24%) patients had GluR3B Ab's, of which 8 had generalized and 9 partial epilepsy. We then studied 41 epilepsy patients: 21 patients with GluR3B Ab's and 20 without such Ab's (pooled of both tests without biased selection), for possible association of GluR3B Ab's with disease severity and/or neurobehavioral/cognitive comorbidities. Of the 21 patients with GluR3B Ab's, 6 had symptomatic, 7 cryptogenic, and 8 idiopathic epilepsy. Of the 20 patients without GluR3B Ab's, 16 had idiopathic etiology, and 4 nonidiopathic epilepsy. We found that among the 21 patients with GluR3B Ab's, 19 patients (90%) had learning problems, 16 (76%) attention problems, and 15 (71%) psychiatric problems. In contrast, among the 20 patients without GluR3B Ab's, only 6 (30%) had learning problems (p<0.0001), 5 (25%) attention problems (p=0.0017), and 2 (10%) psychiatric problems (p<0.0001). These findings suggest either that neurobehavioral abnormalities occur more frequently in epilepsy patients already having GluR3B Ab's, and may be due to them, or that GluR3B Ab's are more frequent in patients already having neurobehavioral abnormalities.

Focal encephalopathy with recurrent episodes of epileptic status and cluster mimicking hemiconvulsion-hemiplegia-epilepsy syndrome

Hemiconvulsion-hemiplegia-epilepsy syndrome is characterized by unilateral convulsions during fever, transient hemiplegia, and subsequent partial epilepsy with atrophy in the cerebrum. A 9-year-old boy with a history of West syndrome and hypoglycemic attacks had three episodes of epileptic status and clusters mimicking HHE syndrome over a 2-year period. Magnetic resonance imaging revealed the involvement of the right and left cerebrums. Because no abnormalities were detected in an endocrine examination, screening tests for metabolic errors, or magnetic resonance spectroscopy, a diagnosis of metabolic errors was not supported. Immunohistochemistry using the patient's sera showed binding of the serum immunoglobulin with neurons in the temporal and occipital cerebral cortices, indicating the possible involvement of autoimmune mechanisms in this case. Focal encephalopathy should be considered in children showing convulsions, psychiatric disorders, and/or involuntary movements for several months in a row. In such cases, immunohistochemistry using the patient's sera may be useful for the investigation of the pathogenesis of the illness.

Autoimmune focal encephalitis shows marked hypermetabolism on positron emission tomography

A 22-month-old toddler presented with involuntary movements, hemiparesis, and behavioral changes. Magnetic resonance imaging showed no abnormality, but positron emission tomography (PET) showed focal hypermetabolism. By immunohistochemical technique with the patient's sera in control brain sections, autoantibodies recognizing the same areas as found by PET scanning were identified and disappeared after intravenous immunoglobulin therapy. PET scanning may be useful in the diagnosis of autoimmune encephalitis.

Acute encephalitis with refractory, repetitive partial seizures

Acute encephalitis with refractory, repetitive partial seizures (AERRPS) represents a peculiar form of encephalitis mainly affecting children. They usually present abruptly with seizure or impaired consciousness as well as high-grade fever following antecedent infection. Seizures in AERRPS are almost exclusively of localized origin, whose semiology includes eye deviation, hemifacial twitching, hemiclonic convulsion, and autonomic manifestations. Partial seizures are brief, but repeat with increasing frequency and develop status epilepticus at nadir. They are extremely pharmaco-resistant and are only suppressed by intravenous administration of high-dose barbiturates. Although acute seizures are hardly controlled, patients gradually recover with decreasing seizure frequency and continuously evolve into post-encephalitic epilepsy without latent period. Residual cognitive impairment is common. Electroencephalograms in active stage demonstrate electrical seizure activities and interictal periodic discharges. Magnetic resonance imaging reveals late cerebral atrophy with limited signal abnormality. Persistent fever during active stage, cerebrospinal fluid (CSF) pleocytosis, and up-regulation of neopterin raise the hypothesis that inflammatory process is involved in this condition. Furthermore, early production of autoantibody against NMDA receptor 2B in serum and CSF, although its disease specificity is still in controversy, is suggestive of autoimmune etiology. Exploration for definite clinical marker is currently in progress.

Diagnostic and pathogenic significance of glutamate receptor autoantibodies

Autoantibodies against glutamate receptors, first reported in Rasmussen encephalitis, have been observed in other focal epilepsies, central nervous system ischemic infarcts, transient ischemic attacks, sporadic olivopontocerebellar atrophy, systemic lupus erythematosus, and paraneoplastic encephalopathies. The detection of glutamate receptor autoantibodies is not useful in the evaluation of Rasmussen encephalitis but may be a biomarker for brain ischemia, and it is helpful in diagnosing certain paraneoplastic encephalopathies. Passive transfer of glutamate receptor autoantibodies from patients with systemic lupus erythematosus or paraneoplastic encephalopathy suggests that glutamate receptor autoantibodies can actively contribute to neurologic dysfunction.