Peripheral Silent Period In Cervical and Generalized Dystonia

Dicle Tıp Dergisi / Dicle Med J (2021) 48 (1) : 205-211 Original Article / Özgün Araştırma Peripheral Silent Period In Cervical and Generalized Dystonia Melih Tutuncu 1, Hikmat Abbaszade 1, Aysegul Gunduz 1, Meral E. Kiziltan 1 1 Department of Neurology, Cerrahpasa Medical Faculty, Istanbul University-Cerrahpasa, Istanbul, Turkey Received: 14.02.2021; Revised: 01.03.2021; Accepted: 01.03.2021 Abstract Objective: Dystonia is a movement disorder described by continuous or alternating muscle contractions causing unusual postures or insistent motions. Abnormal sensorimotor integration and abnormalities in inhibitory pathways are thought to have a role in pathogenesis. This paper aims to research the state of inhibitory pathways in the spinal cord in dystonia through documenting a silent period (SP) through cutaneous stimulation (CuSP) or mixed nerve stimulation (MnSP). Methods: 23 patients with dystonia were included in the study. Also, 19 healthy subjects were included in the study as a control group. Ages were similar between two groups. (p=0.092). CuSP and MnSP are recorded through abductor pollicis brevis and median nerve at the wrist respectively. Results: Onset latency, time, and suppression index of CuSP were equivalent between two groups. Moreover, the initiation and terminate latencies of MnSP, also duration, were similar between these two groups. I2 suppression index was lower in generalized dystonia patients compared to patients with cervical dystonia (100.0 vs 86.7±21.4%; F=4.252, 0.035). Conclusions: The most striking result to emerge from the data is that there was lower suppression during CuSP in generalized dystonia patients. Our results suggest that spinal inhibitory circuits are less active if only there is clinical involvement of the relevant segment. Keyword: Dystonia, Cutaneous silent period, mixed nerve silent period DOI: 10.5798/dicletip.888781 Correspondence / Yazışma Adresi: Melih Tutuncu, Department of Neurology, Cerrahpasa Medical Faculty, Istanbul University-Cerrahpasa, Istanbul, Turke e-mail: 205 Tutuncu M., Abbaszade H., Gundu A., KiziltaM.E. Servikal ve Jeneralize Distonide Periferik Sessiz Periyot Öz Amaç: Distoni, sürekli veya aralıklı kas kasılmalarının anormal duruşlara veya tekrarlayan hareketlere neden olduğu istemsiz bir hareket bozukluğudur. Distoni sadece bir motor sistem hastalığı değildir. Patofizyolojisinde, anormal sensorimotor entegrasyon yaygın olarak kabul edilmektedir. Diğer bir patofizyolojik açıklama, inhibitör yolaklardaki anormalliklerdir. Bu çalışmanın amacı, kutanöz stimülasyonu (CuSP) veya miks sinir stimülasyonunu (MnSP) takiben sessiz period (SP) kaydederek distonide, omurilikteki inhibitör yolakların durumunu araştırmaktır. Yöntemler: Çalışmaya 23 distonili hasta dahil edildi. Ayrıca kontrol grubu olarak 19 sağlıklı denek mevcuttu. Yaş gruplar arasında benzerdi. (p = 0.092). CuSP ve MnSP, sırasıyla abdüktör pollicis brevis ve median sinir aracılığıyla kaydedildi. Bulgular: CuSP'nin başlangıç latansı, süresi ve supresyon indeksi ile ilgili olarak, distoni hastaları ile sağlıklı bireyler arasında fark yoktu. MnSP'nin başlangıç ve bitiş latansları ayrıca süreleri, hastalar ve sağlıklı bireyler arasında farklı değildi. Segmental ve jeneralize distonili hastaların karşılaştırılması, jeneralize distoni hastalarında I2 supresyon indeksinin düşük olduğunu gösterdi (100.0'a karşı 86.7 ± 21.4%; F = 4.252, 0.035). Tartışma: Jeneralize distonili hastalarda CuSP sırasında daha az supresyon görülürken, servikal distonili hastalarda sağlıklı deneklere benzerdi. Sonuçlarımız, spinal inhibitör devrelerin, sadece ilgili segmentin klinik tutulumu varsa daha az aktif olduğunu. Anahtar kelimeler: Distoni, kutanöz sessiz dönem, Mikst sinir sessiz dönemi. INTRODUCTION Dystonia is a condition that is resistant to most medical treatments, which may affect almost all body parts due to various etiologies. It is a hyperkinetic movement disorder described by continuous or alternating muscle contractions causing unusual posture1. The contractions have similar features: abnormal twisting or repetitive movements. An involuntary movement that involves muscle often triggers dystonia. Also, contractions may develop in the muscles that should not participate in the activity during voluntary movement (overflow phenomenon)2. The cutaneous silent phase (CuSP) is a powerful inhibition of EMG activity, due to exposure of the cutaneous nerve fibers in the fingers to relatively great intensity, painful electrical stimuli3. The electromyographic silent period generated by electrical stimulation of larger fibers is a mixed nerve silent period (MNSP). The electrophysiological principles and adaptive function of the CuSP, which is thought to be a spinal reflex consisting of afferent arc Adelta fibers, and efferent arc consisting of alpha motor neurons, have not been clarified yet. The CuSP is thought to represent the inhibitory part of the complex defensive reflex. It works with excitatory cutaneous withdrawal reflexes, which are used to pull the extremity from the painful stimulus4. Various movement disorders such as dystonia and tremor have been studied in spinal cord injuries such as syringomyelia and 5,6 intramedullary masses . To date, various electrophysiological studies have been conducted in dystonia. Blink reflex (BR), BR recovery cycle; startle reflexes showed the hyperexcitability of the relevant circuits. The transcranial magnetic stimulation study showed that intracortical facilitation decreased during sensory manipulation. Dystonia is not just a motor system disease. Although the nociceptive pathways are normal, the activity of the somatosensory pathways has also been shown to increase. Besides, it was observed that the activity increased during the movement dystonia. This paper aims to evaluate the condition of nociceptive pathways in dystonia through MNSP and CuSP7,8. 206 Dicle Tıp Dergisi / Dicle Med J (2021) 48 (1) : 205-211 SUBJECTS AND METHOD Subjects 23 patients (12 female, 11 male); 10 patients with cervical dystonia, and 13 patients with generalized dystonia were included in the study. Also, 19 healthy subjects (11 female, 8 male; p=0.711) were included in the study as a control group. There were no similarities in terms of age. (41.4±12.1 vs 36.2±5.2 years, p=0.092). We excluded all patients with diseases that prevent electrophysiological examinations or create contraindications for examinations and had any other neurological disease that may affect electrophysiological examinations. The study was approved by İstanbul UniversityCerrahpaşa ethical committee at 21 May 2021 with decision number A-06 and the patients signed informed consent. METHOD Electrophysiological recordings were done using Neuropack Sigma MEB-5500 (Nihon Kohden, Tokyo, Japan) EMG device and silversilver chloride surface electrodes. Individuals were in a comfortable chair, which support the arm. The elbow joint was maintained at a 90⁰ angle (...truncated)