Tremor-like subcortical myoclonus in STXBP1 encephalopathy. (September 2021)

• Record Type: Journal Article
• Authors: Loussouarn, Anna; Doummar, Diane; Beaugendre, Yara; Bienvenu, Thierry; Charles, Perrine; Depienne, Christel; Dorison, Nathalie; Heide, Solveig; Héron, Delphine; Ioos, Christine; Keren, Boris; Métreau, Julia; Mochel, Fanny; Moutard, Marie-Laure; Ravelli, Claudia; Apartis, Emmanuelle; Mignot, Cyril
• Is Part Of: European journal of paediatric neurology. Volume 34(2021)
• Page Start: 62
• Page End: 66
• Publication Date: 2021-09
• Subjects: Myoclonus -- Subcortical -- Tremor-like -- STXBP1-Encephalopathy; STXBP1 syntaxin binding protein type 1 -- ECR extensor carpi radialis -- FCR flexor carpi radialis -- FDI first dorsal interosseous -- EEG electroencephalogram -- JLBA Jerk-locked back-averaging -- EMG electromyogram -- AS Angelman syndrome; Pediatric neurology -- Periodicals; Nervous System Diseases -- Periodicals; Child -- Periodicals; Infant -- Periodicals; Neurologie pédiatrique -- Périodiques; Pediatric neurology; Electronic journals; Periodicals; Electronic journals; 618.928
• DOI: 10.1016/j.ejpn.2021.06.005
• Languages: English
• ISSNs: 1090-3798

Abstract

Abstract: The phenotypic spectrum of STXBP1 -related encephalopathy ranges from infantile epileptic encephalopathy to intellectual disability with nonsyndromic or absent epilepsy. Although being frequently reported, the tremor associated with STXBP1 has not been fully characterized to date. The aim of our study was to describe it. We recruited patients with intellectual disability due to STXBP1 variants, regardless of their epileptic phenotype, who had tremor at examination and who underwent neurophysiological testing including polymyographic registration of upper limbs muscles activity at rest, during posture maintenance and action. Six patients met the inclusion criteria over four years. Clinically, all had a postural and action distal tremor increased by emotions. Neurophysiological recordings showed a specific myoclonus pattern and were highly suggestive of a subcortical generator. The tremor-like observed in STXBP1 encephalopathy is due to a subcortical pseudo-rhythmic myoclonus. Highlights: The phenotypic spectrum of STXBP1 -related encephalopathy ranges from infantile epileptic encephalopathies to intellectual disability with non-syndromic or absent epilepsy. Although being frequently reported, the tremor associated with STXBP1 has not been fully described yet. We aimed at describing this tremor clinically and at addressing the question of its nature and origin. To reach this goal, we recruited over four years six patients with STXBP1 -related intellectual deficiency and tremor, regardless of their epileptic phenotype. All patients underwent polymyographic recording of upper limbs muscles activity at rest, during posture maintenance and action, completed with cortical recording. We found that all patients displayed a distal or proximo-distal tremor-like irregular rhythmic myoclonus during posture maintenance and action, with a very likely subcortical generator. Thus, we show for the first time that the "tremor" reported in many patients with STXBP1 encephalopathy is actually a pseudo-rhythmic subcortical myoclonus. This result is of particular interest for the readers of European Journal of Paediatric Neurology since 1) the nature of the pseudo-tremor of STXBP1 encephalopathy was ignored, 2) its subcortical origin has therapeutic consequences.