ABSTRACT
PURPOSE OF REVIEW: Tremor is an important phenotypic feature of dystonia with wide variability in the reported prevalence ranging from 14 to 86.67%. This variability may be due to the types of dystonia patients reported in different studies. This article reviews research articles reporting tremor in primary monogenic dystonia. RECENT FINDINGS: We searched the MDS gene data and selected all research articles reporting tremor in primary monogenic dystonia. Tremor was reported in nine dystonia genes, namely DYT-HPCA, DYT-ANO3, DYT-KCTD17, DYT-THAP1, DYT-PRKRA, DYT-GNAL, DYT-TOR1A, DYT-KMT2B, and DYT-SGCE in the descending order of its frequency. HPCA gene mutation is rare, but all reported patients had tremor. Similarly, tremor was reported in eight genes associated with dystonia parkinsonism, namely DYT-SLC6A3, DYT-TH, DYT-SPR, DYT-PTS, DYT-GCH1, DYT-TAF1, DYT-QDPR, and DYT-SCL30A10 in the descending order of its prevalence. DYT-HPCA and DYT-ANO3 gene showed the highest prevalence of tremor in isolated dystonia, and DYT-SLC6A3 has the highest prevalence of tremor in combined dystonia.
Subject(s)
Dystonia , Dystonic Disorders , Anoctamins , Apoptosis Regulatory Proteins/genetics , DNA-Binding Proteins/genetics , Dopamine Plasma Membrane Transport Proteins , Dystonia/epidemiology , Dystonia/genetics , Dystonic Disorders/epidemiology , Dystonic Disorders/genetics , Humans , Molecular Chaperones , Mutation/genetics , Tremor/epidemiology , Tremor/geneticsABSTRACT
In a recent consensus statement on tremor, the task force of the International Parkinson and Movement Disorder Society proposed a new term, 'essential tremor-plus (ET-plus)' which includes patients with the characteristics of essential tremor (ET) and additional soft neurological signs of uncertain significance such as questionable dystonic posturing. The clinical interpretation of questionable dystonia has been left to the investigator. The consensus statement also stated that the ET-plus syndrome does not include other clearly defined syndromes like dystonic tremor. However, the boundary between questionable dystonia and definite dystonia is not distinct leading to diagnostic uncertainty in a clinical setting. A similar case may be classified as ET-plus by one observer and dystonic tremor by another. Following the new definition, many studies have reclassified their ET cohort, and they have highlighted the problem of defining questionable dystonia in the diagnosis of ET plus. ET-plus is likely to be a mixture of patients that actually have dystonia and those that don't, and clinically all we can do is to be suspicious that there might be dystonia. For example, it is not clear whether we should consider spooning and index finger pointing as a sign of questionable or definite dystonia. There are major research and possible therapeutic implications of questionable dystonia in the diagnosis of ET-plus. The concept of ET-plus is extremely difficult to implement without definite guidelines. The resolution will need a biomarker such as physiology or imaging.
