No association between Parkinson disease and autoantibodies against NMDA-type glutamate receptors

Background:IgG-class autoantibodies to N-Methyl-D-Aspartate(NMDA)-type glutamate receptors define a novel entity of autoimmune encephalitis.Studies examining the prevalence of NMDA IgA/IgM antibodies in patients with Parkinson disease with/without dementia produced conflicting results.We measured NMDA antibodies in a large,well phenotyped sample of Parkinson patients without and with cognitive impairment(n=296)and controls(n=295)free of neuropsychiatric disease.Detailed phenotyping and large numbers allowed statistically meaningful correlation of antibody status with diagnostic subgroups as well as quantitative indicators of disease severity and cognitive impairment.Methods:NMDA antibodies were analysed in the serum of patients and controls using well established validated assays.We used anti-NMDA antibody positivity as the main independent variable and correlated it with disease status and phenotypic characteristics.Results:The frequency of NMDA IgA/IgM antibodies was lower in Parkinson patients(13%)than in controls(22%)and higher than in previous studies in both groups.NMDA IgA/IgM antibodies were neither significantly associated with diagnostic subclasses of Parkinson disease according to cognitive impairment,nor with quantitative indicators of disease severity and cognitive impairment.A positive NMDA antibody status was positively correlated with age in controls but not in Parkinson patients.Conclusion:It is unlikely albeit not impossible that NMDA antibodies play a significant role in the pathogenesis or progression of Parkinson disease e.g.to Parkinson disease with dementia,while NMDA IgG antibodies define a separate disease of its own.

Rest tremor revisited:Parkinson’s disease and other disorders

Tremor is the most common movement disorder characterized by a rhythmical,involuntary oscillatory movement of a body part.Since distinct diseases can cause similar tremor manifestations and vice-versa,it is challenging tomake an accurate diagnosis.This applies particularly for tremor at rest.This entity was only rarely studied in the past,although a multitude of clinical studies on prevalence and clinical features of tremor in Parkinson’s disease(PD),essential tremor and dystonia,have been carried out.Monosymptomatic rest tremor has been further separated from tremor-dominated PD.Rest tremor is also found in dystonic tremor,essential tremor with a rest component,Holmes tremor and a few even rarer conditions.Dopamine transporter imaging and several electrophysiological methods provide additional clues for tremor differential diagnosis.New evidence from neuroimaging and electrophysiological studies has broadened our knowledge on the pathophysiology of Parkinsonian and non-Parkinsonian tremor.Large cohort studies are warranted in future to explore the nature course and biological basis of tremor in common tremor related disorders.