CLINICAL ARTICLE J Neurosurg Spine 33:658–666, 2020 Unilateral pallidotomy as a potential rescue therapy for cervical dystonia after unsatisfactory selective peripheral denervation *Yijie Lai, MD,1 Peng Huang, MD,1 Chencheng Zhang, MD, PhD,1 Liangyun Hu, ME,1 Zhengdao Deng, MD,1,2 Dianyou Li, MD, PhD,1 Bomin Sun, MD, PhD,1 Wei Liu, MD, PhD,1 and Shikun Zhan, MD, PhD1 1Department of Functional Neurosurgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; and 2Research Group of Experimental Neurosurgery and Neuroanatomy, KU Leuven, Leuven, Belgium OBJECTIVE Selective peripheral denervation (SPD) is a widely accepted surgery for medically refractory cervical dys- tonia (CD), but when SPD has failed, the available approaches are limited. The authors investigated the results from a cohort of CD patients treated with unilateral pallidotomy after unsatisfactory SPD. METHODS The authors retrospectively analyzed patients with primary CD who underwent unilateral pallidotomy after SPD between April 2007 and August 2019. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) was used to evaluate symptom severity before surgery, 7 days postsurgery, 3 months postsurgery, and at the last follow-up. TWSTRS subscores for disability and pain and the 24-item Craniocervical Dystonia Questionnaire (CDQ-24) were used to assess quality of life. RESULTS At a mean final follow-up of 5 years, TWSTRS severity subscores and total scores were significantly im- proved (n = 12, mean improvement 57.3% and 62.3%, respectively, p = 0.0022 and p = 0.0022), and 8 of 12 patients (66.7%) were characterized as responders (improvement ≥ 25%). Patients with rotation symptoms before pallidotomy showed greater improvement in TWSTRS severity subscores than those who did not (p = 0.049). The most common adverse event was mild upper-limb weakness (n = 3). Patients’ quality of life was also improved. CONCLUSIONS Unilateral pallidotomy seems to offer an effective and safe option for patients with CD who have other- wise experienced limited benefits from SPD. https://thejns.org/doi/abs/10.3171/2020.4.SPINE191523 KEYWORDS pallidotomy; selective peripheral denervation; cervical dystonia; functional neurosurgery ERVICAL dystonia (CD), also known as spasmodic Botulinum toxin (BT) is the first-line therapy for CD.4 torticollis, is the most common form of dystonia.1 However, BT therapy sometimes loses its initial efficacy It has been estimated to affect 28–183 cases per due to immunoresistance, and its prolonged use carries in- millionC people worldwide, with the incidence ranging cremental risks of side effects, such as dysphagia.4 In an from 8 to 12 cases/million person-years.2 CD is charac- international survey of 1071 patients with CD in 38 coun- terized by involuntary contraction of the neck muscles, tries, only 56% of those treated with BT were satisfied which leads to jerky head movements (turning, tilting, or with their clinical outcome.5 Selective peripheral dener- shifting) or awkward head positions. Patients experience vation (SPD) is an alternative treatment for patients who decreased quality of life and impaired socio-occupational have not responded adequately to BT therapy. The thera- functioning due not only to motor impairment, but also to peutic improvement in patients who underwent SPD has pain and social stigma.3 been reported to range from 22% to 59%, as measured by ABBREVIATIONS AC-PC = anterior commissure–posterior commissure; BT = botulinum toxin; CD = cervical dystonia; CDQ-24 = 24-item Craniocervical Dystonia Ques- tionnaire; DBS = deep brain stimulation; GPi = globus pallidum internus; SPD = selective peripheral denervation; TWSTRS = Toronto Western Spasmodic Torticollis Rating Scale. SUBMITTED December 19, 2019. ACCEPTED April 8, 2020. INCLUDE WHEN CITING Published online June 26, 2020; DOI: 10.3171/2020.4.SPINE191523. * Y.L. and P.H. contributed equally to this work and share first authorship. 658 J Neurosurg Spine Volume 33 • November 2020 ©AANS 2020, except where prohibited by US copyright law Unauthenticated | Downloaded 09/29/21 02:21 AM UTC Lai et al. the Toronto Western Spasmodic Torticollis Rating Scale brain atrophy (detected by MRI or CT); and relevant or- (TWSTRS).6 However, despite careful intraoperative ganic brain diseases, e.g., tumor, cerebrovascular disease, searching for small nerve branches and variations of in- or other neurological or psychiatric comorbidities (Fig. 1). nervation, clinically relevant symptoms of major concern occurred after about 29% of SPD procedures, due to either Surgical Procedure reinnervation of the denervated muscles or disease pro- The main criterion for choosing pallidotomy rather gression to muscles in the neck that were not previously 6,7 than a repeat SPD or muscle resection was electromyo- denervated. Moreover, complications may occur after gram results showing widespread activity involving neck SPD, including dysesthesia, dysphagia, and weakness of 6–9 muscles available for denervation. Stereotactic pallidoto- the corresponding muscles. my was performed contralateral to the contracting spleni- The globus pallidus is a known brain target for vari- 17 10,11 us-complexus group using the Leksell G frame under lo- ous kinds of dystonia, including CD. For patients who cal anesthesia. CT scans and 1.5-T MRI were performed, have not benefited from BT and SPD treatment, globus and the scans were fused using the Leksell SurgiPlan sys- pallidum internus (GPi) deep brain stimulation (DBS) or 12,13 tem (Electra). GPi was located 2–4 mm anterior to the ablation (pallidotomy) may serve as a rescue therapy. anterior commissure–posterior commissure (AC-PC) line While GPi DBS is a preferential treatment for refractory midpoint, 18–22 mm lateral to the AC-PC line, and 2–4 dystonia, it is more expensive than pallidotomy, and the mm below the AC-PC line. A radiofrequency electrode hardware implantations make it unacceptable for many 10,13,14 (Radionics) with a 2-mm-diameter radiofrequency probe patients. Choosing an appropriate pallidal approach and a 2-mm exposed tip was used for impedance mea- for patients in whom medical or surgical peripheral de- surement, followed by a stimulation test and creation of a nervation has failed is a crucial clinical question. How- lesion. Test stimulation was conducted through the elec- ever, evidence for the efficacy of pallidotomy for CD after 13 trode, with administration of 2 Hz and 100 Hz, respec- SPD failure is limited to 1 case report published in 2016. tively, for motor and sensory responses while the patient Moreover, although neuroablation, including pallidotomy, was awake. Corticospinal tract activation was evaluated has been used as an approach for dystonia, its effective- 11 by the patient’s subjective symptoms and objective signs ness has seldom been assessed with validated scales. of muscle contractions. A contraction response from the Also, most reports of the effectiveness of pallidotomy in corticospinal tract to > 1 V or patient symptoms of par- CD have included either too few cases or only cases with 11,15 esthesia were considered to indicate a safe level of activa- relatively short follow-ups. tion. A coagulation test was then carried out through the In this article, we report the results of a series of patients electrode at 50°C for 60 seconds to check symptoms and with CD who were treated with unilateral pallidotomy and signs. The tip of the electrode was then heated to 70°C– whose therapeutic improvement was assessed with stan- 80°C for 60 seconds. The length of the lesion was about dardized TWSTRS scoring. Also, we propose factors that 5 mm. MRI or CT was performed within 48 hours after may be predictive for the effectiveness of this method for surgery to visualize the localization of the lesion and to treating CD. identify possible complications (Fig. 2). The volumes of the lesions were calculated as the hyperintense ring seen Methods on early T1-weighted scans using the Leksell GammaPlan Patients system (Electra).18 Distances from the center of the lesion This retrospective observational study was approved by lateral to the midline, inferior to the AC-PC line, and an- the ethics committee of the Ruijin Hospital Shanghai Jiao terior to the midcommissural point were also measured. Tong University School of Medicine. Written informed The patient’s preoperative medication regimen remained consent was obtained from each patient. Between April unchanged after the surgery and until the patient achieved 2007 and August 2019, 15 patients who had complaints a satisfactory response. about unsatisfactory outcomes of SPD were treated with unilateral pallidotomy at our center. Of these patients, 2 Assessment of CD Severity and Quality of Life (13%) were lost during follow-up and 1 patient (7%) lacked Evaluations were performed regularly before surgery data records of TWSTRS severity scores before pallidot- and at 7 days and 3 months following surgery. All in- omy. The inclusion criteria for participation in this study cluded patients were contacted for long-term follow-up. were as follows: diagnosed with idiopathic CD by an ex- CD severity was assessed with the TWSTRS, which is a perienced neurologist; < 25% improvement in TWSTRS reliable and validated instrument that is widely used in severity score after SPD; data recorded by an experi- CD clinical trials.12,19,20 The TWSTRS includes both pa- enced neurologist for TWSTRS assessment total scores tient- and clinician-rated scores, with a minimum score and subscores for severity, disability, and pain at baseline of 0 and a maximum of 75. TWSTRS scores were divided (before SPD and before pallidotomy), 7 days postsurgery, into subscores for severity (range 0–35), disability (range and short-term (3 months postsurgery) and long-term (≥ 0–20), and pain (range 0–20).46,47 Patients were classified 1 year postsurgery) follow-ups; unsatisfactory response to as responders if they showed ≥ 25% improvement in the 3 sessions of BT treatment and to oral medications be- TWSTRS severity score.16 The 24-item Craniocervical fore SPD;16 normal neurological functioning other than Dystonia Questionnaire (CDQ-24) was administered be- the dystonia; and normal MRI of the brain.