Abnormal sensory-motor integration in a patient with anti-NMDA-receptor encephalitis

Seroprevalence survey of selective anti-neuronal autoantibodies in patients with first-episode schizophrenia and chronic schizophrenia

Autoimmune encephalopathy caused by autoantibodies against neuronal cell-surface proteins in the brain is a newly discovered disease category associated with psychiatric disorders. Correct diagnosis of this condition relies on the detection of specific autoantibodies in the blood or cerebral spinal fluid in addition to the clinical presentations. The study aimed to understand the seroprevalence of selective anti-neuronal autoantibodies in our patients with schizophrenia. First, we screened for six anti-neuronal autoantibodies in an archived blood sample collected from patients with the first-episode schizophrenia. The six autoantibodies including antibodies against N-methyl-d-aspartate (NMDA) receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors 1 and 2, γ-butyric acid receptor type B1 (GABARB1), leucine-rich glioma inactivated-1 (LGI1) protein, and contactin-associated protein-like 2 (CASPR2) protein. A total of 78 plasma samples (46 males and 32 females) were investigated; however, no positive case was identified. In this second study, we screened anti-NMDA receptor autoantibodies in a blood sample of 234 patients with chronic schizophrenia (133 females and 101 males) including 48 patients defined as treatment resistance. None of this sample was detected as positive. The negative findings in this study suggest that the seroprevalence of autoantibodies against neuronal surface proteins might be low in patients diagnosed with schizophrenia.

Altered paired associative stimulation-induced plasticity in NMDAR encephalitis

OBJECTIVE

To determine whether neurophysiological mechanisms indicating cortical excitability, long-term potentiation (LTP)-like plasticity, GABAergic and glutamatergic function are altered in patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis and whether they can be helpful as markers of diagnostic assessment, disease progression, and potentially therapy response.

METHODS

Neurophysiological characterizations of patients with NMDAR encephalitis (n = 34, mean age: 28 ± 11 years; 30 females) and age/gender-matched healthy controls (n = 27, 28.5 ± 10 years; 25 females) were performed using transcranial magnetic stimulation-derived protocols including resting motor threshold, recruitment curve, intracortical facilitation, short intracortical inhibition, and cortical silent period. Paired associative stimulation (PAS) was applied to assess LTP-like mechanisms which are mediated through NMDAR. Moreover, resting state functional connectivity was determined using functional magnetic resonance imaging.

RESULTS

PAS-induced plasticity differed significantly between groups (P = 0.0056). Cortical excitability, as assessed via motor-evoked potentials after PAS, decreased in patients, whereas it increased in controls indicating malfunctioning of NMDAR in encephalitis patients. Lower PAS-induced plasticity significantly correlated with the modified Rankin Scale (mRS) (r = -0.41; P = 0.0031) and was correlated with lower functional connectivity within the motor network in NMDAR encephalitis patients (P < 0.001, uncorrected). Other neurophysiological parameters were not significantly different between groups. Follow-up assessments were available in six patients and demonstrated parallel improvement of PAS-induced plasticity and mRS.

INTERPRETATION

Assessment of PAS-induced plasticity may help to determine NMDAR dysfunction and disease severity in NMDAR encephalitis, and might even aid as a sensitive, noninvasive, and well-tolerated "electrophysiological biomarker" to monitor therapy response in the future.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: Identifier: NCT01865578.