Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is one of the most common autoimmune encephalitis that presents with a wide variety of movement disorders. The purpose of our study is to review the manifestations and duration of movement disorders in different ages with NMDAR encephalitis.A retrospective cohort of 28 patients (20 females and 8 males) with positive cerebrospinal fluid (CSF) anti-NMDAR antibody in a 5-year period from major hospitals in Taiwan was enrolled. They were categorized into 3 age groups: 7 patients were ≤10 years, 14 patients were 10 to 18 years, and 7 patients were >18 years.Total 28 patients (20 females and 8 males) with age ranging from 8 months to 38 years were enrolled. Nearly all patients (n = 27/28, 96%) presented with at least 2 types of disorders, including orofacial–lingual dyskinesia (OFLD; n = 20), catatonia (n = 19), tremor (n = 11), bradykinesia (n = 11), dystonia (n = 11), choreoathethosis (n = 9), and ballism (n = 3). Only 1 patient below 10 years presented with isolated periodic choreoathethosis without other movement disorders. OFLD was common in all age groups. Choreoathetosis was most common in patients aged ≤10 years, while catatonia was most common in patients aged >10 years (P = 0.001 and 0.020, respectively). Bradykinesia was also more common in patients aged >10 years (P = 0.020). The clinical presentations of movement disorders were not significantly different in the age of 10 to 18 years and those >18 years. Neither patient ≤10 years old nor male patients had associated tumors. All patients’ movement disorders were improved after treatment, while female patients with tumors had worse short-term outcome (P = 0.014). Compared with other disorders, choreoathetosis persisted significantly longer in patients ≤10 years (P = 0.038), while OFLD and catatonia last longer in patients >10 years (P = 0.047 and 0.002, respectively).Our study shows that hyperkinetic movements such as choreoathetosis are more common and last longer in younger age groups, whereas hypokinetic movements such as catatonia and bradykinesia are more common and last longer in older age groups. Female patients with ovarian tumors had worse short-term outcome.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is most commonly caused by the A3243G mutation of mitochondrial DNA. The capacity to utilize fatty acid or glucose as a fuel source and how such dynamic switches of metabolic fuel preferences and transcriptional modulation of adaptive mechanism in response to energy deficiency in MELAS syndrome have not been fully elucidated. The fibroblasts from patients with MELAS syndrome demonstrated a remarkable deficiency of electron transport chain complexes I and IV, an impaired cellular biogenesis under glucose deprivation, and a decreased ATP synthesis. In situ analysis of the bioenergetic properties of MELAS cells demonstrated an attenuated fatty acid oxidation that concomitantly occurred with impaired mitochondrial respiration, while energy production was mostly dependent on glycolysis. Furthermore, the transcriptional modulation was mediated by the AMP-activated protein kinase (AMPK) signaling pathway, which activated its downstream modulators leading to a subsequent increase in glycolytic flux through activation of pyruvate dehydrogenase. In contrast, the activities of carnitine palmitoyltransferase for fatty acid oxidation and acetyl-CoA carboxylase-1 for fatty acid synthesis were reduced and transcriptional regulation factors for biogenesis were not altered. These results provide novel information that MELAS cells lack the adaptive mechanism to switch fuel source from glucose to fatty acid, as glycolysis rates increase in response to energy deficiency. The aberrant secondary cellular responses to disrupted metabolic homeostasis mediated by AMPK signaling pathway may contribute to the development of the clinical phenotype.

Summary Objective Variants in human PRRT2 cause paroxysmal kinesigenic dyskinesia (PKD) and other neurological disorders. Most reported variants resulting in truncating proteins failed to localize to cytoplasmic membrane. The present study identifies novel PRRT2 variants in PKD and epilepsy patients and evaluates the functional consequences of PRRT2 missense variations. Methods We investigated two families with PKD and epilepsies using Sanger sequencing and a multiple gene panel. Subcellular localization of mutant proteins was investigated using confocal microscopy and cell surface biotinylation assay in Prrt2‐transfected cells. Results Two novel PRRT2 variants, p.His232Glnfs*10 and p.Leu298Pro, were identified, and functional study revealed impaired localization of both mutant proteins to the plasma membrane. Further investigation of other reported missense variants revealed decreased protein targeting to the plasma membrane in eight of the 13 missense variants examined (p.Trp281Arg, p.Ala287Thr, p.Ala291Val, p.Arg295Gln, p.Leu298Pro, p.Ala306Asp, p.Gly324Glu, and p.Gly324Arg). In contrast, all benign variants we tested exhibited predominant localization to the plasma membrane similar to wild‐type Prrt2. Most likely pathogenic variants were located at conserved amino acid residues near the C‐terminus, whereas truncating variants spread throughout the gene. Significance PRRT2 missense variants clustering at the C‐terminus often lead to protein mislocalization. Failure in protein targeting to the plasma membrane by PRRT2 variants may be a key mechanism in causing PKD and related neurological disorders.