Anti-NMDA receptor encephalitis in Japan: long-term outcome without tumor removal

Autoantibodies and neurodegeneration in multiple sclerosis

Neurodegeneration develops in association with inflammation and demyelination in multiple sclerosis. Available data suggest that the progressive neuroaxonal loss begins in the earliest stages of the disease and underlies the accumulation of clinical disability. The loss of neurons and their processes is driven by a complex molecular mechanism involving cellular and humoral immune histotoxicity, demyelination, reduced neurotrophic support, metabolic impairment, and altered intracellular processes. Here we survey available data concerning the role of autoreactive immunoglobulins in neurotoxicity. A better understanding of molecular pathways leading to immune-mediated neurodegeneration may have key importance in the successful treatment of the disease.

Paraneoplastic syndromes of the CNS

Major advances in the management of paraneoplastic neurologic disorders (PND) include the detection of new antineuronal antibodies, the improved characterisation of known syndromes, the discovery of new syndromes, and the use of CT and PET to reveal the associated tumours at an early stage. In addition, the definition of useful clinical criteria has facilitated the early recognition and treatment of these disorders. In this article, we review some classic concepts about PND and recent clinical and immunological developments, focusing on paraneoplastic cerebellar degeneration, opsoclonus-myoclonus, and encephalitides affecting the limbic system.

Neurological response to early removal of ovarian teratoma in anti-NMDAR encephalitis

We report an 18-year-old woman with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, who developed psychiatric symptoms, progressive unresponsiveness, dyskinesias, hypoventilation, hypersalivation and seizures. Early removal of an ovarian teratoma followed by plasma exchange and corticosteroids resulted in a prompt neurological response and eventual full recovery. Serial analysis of antibodies to NR1/NR2B heteromers of the NMDAR showed an early decrease of serum titres, although the cerebrospinal fluid titres correlated better with clinical outcome. The patients' antibodies reacted with areas of the tumour that contained NMDAR-expressing tissue. Search for and removal of a teratoma should be promptly considered after the diagnosis of anti-NMDAR encephalitis.

[Rasmussen encephalitis and non-herpetic acute limbic encephalitis]

Rasmussen syndrome (RS) and non-herpetic acute limbic encephalitis (NHALE) have pathophysiological background related with autoimmunity to glutamate receptors (GluRs) after infections. RS and NHALE were reviewed, depending mainly on our recent studies. RS is the prototype of autoimmune-mediated epilepsy. In patients with RS, several kinds of autoantibodies against neuronal molecules, for example, GluR3, GluRepsilon2 (NMDA-R2B), etc., are reported. These autoantibodies are not specific for RS. About autoantibodies against GluR3, significance and stimulating effects to GluR3 are controversial. Autoantibodies against GluRepsilon2 were detected in all patients within six months from epilepsy onset, and in some patients at chronic stage. These data suggest that autoantibodies against GluRepsilon2 may be involved in the pathological mechanisms in the early stage, but we could not confirm the effect of the autoantibodies from RS patients on excitatory postsynaptic NMDA current using patch clump methods. However, anti-double-stranded DNA antibodies in patients with SLE are reported to cross-react with n-terminal of GluRepsilon2, and cause neuronal apoptosis in rat hippocampus, ensuing memory impairment, and emotional behavior impairment in mice. Therefore, autoantibodies against GluRepsilon2 may contribute to the cognitive and behavioral changes in RS. Concerning about cellular immunity in RS, lymphocytes stimulating tests revealed peripheral lymphocytes sensitized by antigens containing GluRepsilon2. Cytotoxic T cells (CTLs) excreting Granzyme B were reported in resected brain tissue, and we confirmed the elevated levels of Granzyme B, not in sera, but in CSF. These data suggest that CTLs activated by infection invade into CNS, and recognize neural antigens, and excrete Granzyme B. The incidence of NHALE is 4.1/1 million/year in Japanese adults. Our study in 91 adult patients with NHALE revealed the following characteristics. Mean onset age was 35.2 +/- 16.9 years old, and preceding infections existed in 68.7% of patients, and predominant symptoms at the onset were psychiatric symptoms (33.3%) and convulsions (25.0%). CSF showed slightly elevated cell counts (55.5 +/- 139.9), protein levels (48.1 +/- 36.0 mg/dl), and IgG levels (4.5 +/- 3.9 mg/dl). MRI lesions with high intensity were found in 40.8% (DWI) and 54.2% (FLAIR) of patients in various stages after onsets. Autoantibodies against GluRepsilon2 in sera were detected in approximately 60% of NHALE patients from acute to chronic stages, and the autoantibodies in CSF were detected in 51.8% (acute stage), 41.4% (recovery stage), 28.6% (chronic stage) of patients and included epitopes to n-terminal of GluRepsilon2 (NT1). These data suggest that autoantibodies against GluRepsilon2 produced in sera after infection infiltrate into CNS through damaged BBB in acute stages, and affect n-terminal of GluRepsilon2. In chronic stage, recovery of function of BBB reduces levels of the autoantibodies in CSF. Because BBB in hippocampi and amygdala are vulnerable, autoantibodies against GluRepsilon2 including epitopes to n-terminal may contribute to the limbic symptoms around onset. Among several autoantibodies related with NHALE, autoantibodies against GluRepsilon2 were found in patients around 15-34 years old, autoantibodies against VGKC were around 50.4 years old, autoantibodies against NAE were around 59 years old, autoantibodies against Hu were around 61.5 years old. These data suggest that autoantibodies related with NHALE have age-dependent heterogeneity.

Neuropathological studies of patients with possible non-herpetic acute limbic encephalitis and so-called acute juvenile female non-herpetic encephalitis

OBJECTIVE

This study was to clarify the neuropathological findings of non-herpetic acute limbic encephalitis (NHALE) and so-called acute juvenile female non-herpetic encephalitis (AJFNHE).

METHODS

We examined three rare autopsied cases consisting of probable one NHALE and two AJFNHLE. For comparison, we also studied 10 autopsied cases of hippocampal sclerosis mainly caused by anoxia.

RESULTS

In NHALE, neuronal loss with gliosis and microglia/macrophage infiltrations were mainly seen in the CA1 areas in the hippocampus. However, there were no apparent anoxic neuronal changes in the remaining neurons in the CA1, and astrocyte proliferations and microglia/macrophage infiltrations were also observed in the claustrum, while these were mildly present in the basal ganglia. In AJFNHE, pathological findings differed from those of NHALE with regard of the absence of limited pathology in the limbic system, microglia/macrophages widely infiltrated the brain including the hippocampal areas and mild lymphocytic infiltrations were observed in the subarachnoid spaces as well as in the parenchyma.

CONCLUSIONS

The pathomechanism of NHALE and AJFNHE is obscure and autoimmune theory is proposed, however we must collect and examine many autopsied cases in order to clarify the pathomechanism.