Characteristics of internalization of NMDA-type GluRs with antibodies to GluN1 and GluN2B

Case report: Evolution of catatonic mutism and psychotic symptoms in an adolescent with Down syndrome: transition from Down syndrome disintegrative disorder to anti-N-methyl-D-aspartate receptor encephalitis

During her first year of junior high school, a 12-year-old Japanese girl with Down syndrome experienced dizziness, gait disruption, paroxysmal weakness in her hands, and sluggish speaking. Regular blood tests and a brain MRI revealed no abnormalities, and she was tentatively diagnosed with adjustment disorder. Nine months later, the patient experienced a subacute sickness of chest pain, nausea, sleep problem with night terrors, and delusion of observation. Rapid deterioration then developed with simultaneous fever, akinetic mutism, loss of facial expression, and urine incontinence. These catatonic symptoms improved after a few weeks after admission and treatment with lorazepam, escitalopram, and aripiprazole. After discharge, nonetheless, daytime slumber, empty eyes, paradoxical laughter, and declined verbal communication persisted. Upon confirmation of the cerebrospinal N-methyl-D-aspartate (NMDA) receptor autoantibody, methylprednisolone pulse therapy was tried, but it had little effect. Visual hallucinations and cenesthopathy, as well as suicidal thoughts and delusions of death, have predominated in the following years. Cerebrospinal IL-1ra, IL-5, IL-15, CCL5, G-CSF, PDGFbb, and VFGF were raised in the early stage of initial medical attention with nonspecific complaints, but were less prominent in the later stages of catatonic mutism and psychotic symptoms. We suggest a disease concept of progression from Down syndrome disintegrative disorder to NMDA receptor encephalitis, based on this experience.

Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures. The mechanism of epilepsy remains unclear and previous studies suggest that N-methyl-D-aspartate receptors (NMDARs) play an important role in abnormal discharges, nerve conduction, neuron injury and inflammation, thereby they may participate in epileptogenesis. NMDARs belong to a family of ionotropic glutamate receptors that play essential roles in excitatory neurotransmission and synaptic plasticity in the mammalian CNS. Despite numerous studies focusing on the role of NMDAR in epilepsy, the relationship appeared to be elusive. In this article, we reviewed the regulation of NMDAR and possible mechanisms of NMDAR in epilepsy and in respect of onset, development, and treatment, trying to provide more evidence for future studies.

[A case of meningoencephalitis that developed during nivolumab use]

A 72-year-old woman developed a fever and consciousness disturbance after completing 8 courses of nivolumab for lung adenocarcinoma. A cerebrospinal fluid test showed an increased cell count, but bacterial culture, herpes simplex virus-polymerase chain reaction, acid-fast staining, and cytology were negative; serum paraneoplastic syndrome-related antibody was also negative. Serum and cerebrospinal fluid specimens were positive for anti-glutamate receptor (GluR) antibody, and fluid-attenuated inversion recovery images on head magnetic resonance imaging showed a high signal intensity at the right parietal lobe. The condition was determined to be immune-mediated encephalitis, and pulse steroid therapy was performed. The symptoms promptly improved after treatment. The patient in the present case was anti-GluR antibody-positive but was determined to have nivolumab-related encephalitis based on the clinical course. The use of immune checkpoint inhibitors has become widespread in recent years, although it can occasionally lead to encephalitis. We herein report our experience with immune checkpoint inhibitor-related encephalitis, which is seldom reported in Japan.