Margaret Kaminska

Proportion of life lived with dystonia inversely correlates with response to pallidal deep brain stimulation in both primary and secondary childhood dystonia

The aim of this study was to examine the impact of dystonia aetiology and duration, contracture, and age at deep brain stimulation (DBS) surgery on outcome in a cohort of children with medically refractory, disabling primary, secondary‐static, or secondary‐progressive dystonias, including neurodegeneration with brain iron accumulation (NBIA).

The impact and prognosis for dystonia in childhood including dystonic cerebral palsy: a clinical and demographic tertiary cohort study

Introduction and methods The impact of dystonia in childhood is poorly understood. We report our experience of referrals between 2005 and 2012. Results Of 294/315 assessable children, 15/294 had pure spasticity, leaving 279/294 with dystonia classified as primary (30/279: 10.7%); primary-plus (19/279: 6.8%) and secondary (230/279: 82.4%) dystonia, including heredodegenerative dystonia (29/279: 10.3%); 150/279 (53.7%) with cerebral palsy and 51/279 (18.2%) acquired brain injury. Definitive diagnoses were available in 222/294 (79.6%), but lower in primary/primary-plus compared with secondary groups (11/49 vs 211/230: Fishers exact test p<0.0001). Spasticity comorbidity was present in 79/230 (34.3%) children. Median age (interquartile years) at referral was 9.75 (6.58–13), not significantly differing by aetiology (Kruskal–Wallis test p>0.05); dystonia-onset age was 3 (0.5–7.0) for primary/primary-plus and 0.25 (0.08–0.8) in the secondary/CP groups. Dystonia duration at referral was 4.75 years (3.0–10.33) for primary/primary-plus groups and 7.83 (5.4–11) in the secondary group. The mean (interquartile range) proportion of life lived with dystonia, derived as dystonia duration normalised to age was 0.68 (0.31–0.96); 0.59 (0.35–0.8); 0.75 (0.62–0.95)and 0.9 (0.92–0.99) for primary, primary-plus, heredodegenerative and secondary-static dystonias respectively. Only 91/279 (32.6%) experienced a period of normal motor development. Carers perceived dystonia deterioration in 168/279 (60.2%), stabilisation in 88/279 (31.5%) and improvement in 23/279 (8.2%). Dystonia occurred in 26/225 (11.6%) siblings: 14/26 secondary and 5/26 heredodegenerative dystonia. Comorbidities were identified in 176/279 (63.1%) cases. Gross Motor Function Classification System (GMFCS) levels I–III were commoner in primary/primary-plus (37/49: 75%) compared with secondary/CP (29/230: 13%) cases, χ2 p<0.0001). Discussion In this selective cohort, childhood dystonia is severe, presenting early before worsening without remission. Secondary dystonias spend a higher proportion of life living with dystonia and lower functional capacity. Despite referral bias, services offering neurosurgical interventions and health service planning agencies should understand the context and predicament of life with childhood dystonia.

Interventional studies in childhood dystonia do not address the concerns of children and their carers

AIMS This study aimed to determine the main concerns/priorities of the parents and carers of children with dystonia referred to our service and whether medical interventional studies addressed these concerns. METHODS Records of children assessed by our service from June 2005-December 2012 were reviewed and expressed parental/carer concerns at initial assessment categorized using the International Classification of Functioning (ICF) Framework. Medline, CINAHL and Embase databases were searched for outcome measures of medical and surgical interventional studies in childhood dystonia. RESULTS Data was collected from 273 children and young people with dystonia. The most commonly expressed concerns were: pain (104/273, 38.1%); difficulties in delivering activities of daily-living (66/273, 24.2%), difficulties with hand-use (59/273, 21.6%) and seating (41/273, 15.0%). Literature review identified 70 interventional studies, 46 neurosurgical and 24 pharmacological. The majority of neurosurgical studies (34/46) used impairment scales to measure change, with pharmacological studies typically reporting more subjective changes in motor symptoms. Only a minority of studies used assessments or scales capable of objectively addressing the concerns reported by our cohort. INTERPRETATIONS Existing interventional studies in childhood dystonia poorly address the main concerns of children with dystonia and their carers, limiting the conclusions which may be drawn as to true impact of these interventions in childhood.

Mutations in the histone methyltransferase gene KMT2B cause complex early-onset dystonia

Histone lysine methylation, mediated by mixed-lineage leukemia (MLL) proteins, is now known to be critical in the regulation of gene expression, genomic stability, cell cycle and nuclear architecture. Despite MLL proteins being postulated as essential for normal development, little is known about the specific functions of the different MLL lysine methyltransferases. Here we report heterozygous variants in the gene KMT2B (also known as MLL4) in 27 unrelated individuals with a complex progressive childhood-onset dystonia, often associated with a typical facial appearance and characteristic brain magnetic resonance imaging findings. Over time, the majority of affected individuals developed prominent cervical, cranial and laryngeal dystonia. Marked clinical benefit, including the restoration of independent ambulation in some cases, was observed following deep brain stimulation (DBS). These findings highlight a clinically recognizable and potentially treatable form of genetic dystonia, demonstrating the crucial role of KMT2B in the physiological control of voluntary movement.

Medication use in childhood dystonia

BACKGROUND Data around current prescription practices in childhood dystonia is limited. Medication use may be limited by side effects, the incidence of which is uncertain. For a large cohort assessed by our supra-regional service we aimed to: i) Review medications used at the point of referral. ii) Determine the prevalence of adverse drug responses (ADR) resulting in discontinuation of drug use. iii) Identify clinical risk factors for ADR. METHODS Case note review of 278 children with dystonia referred to our service. Data collected on medications, ADR, dystonia aetiology, Gross Motor Function Classification System (GMFCS) level and motor phenotype (pure dystonia/mixed dystonia-spasticity). Logistic regression analysis was used to identify risk factors for ADR. RESULTS At referral 82/278 (29.4%) children were taking no anti-dystonic medication. In the remainder the median number of anti-dystonic medications was 2 (range 1-5). Medications use increased with worsening GMFCS level. The commonest drugs used were baclofen (118/278: 42.4%), trihexyphenidyl (98/278: 35.2%), l-Dopa (57/278: 20.5%) and diazepam (53/278: 19%). Choice of medication appeared to be influenced by dystonia aetiology. ADR had been experienced by 171/278 (61.5%) of children. The commonest drugs responsible for ADR were trihexyphenidyl (90/171: 52.3%), baclofen (43/171: 25.1%) and l-Dopa (26/171: 15.2%). Binary logistic regression demonstrated no clinical risk factors for ADR. CONCLUSIONS ADR is commonly experienced by children with dystonia, regardless of dystonia severity or aetiology. A wide variation in drug management of dystonia was identified. Collectively these findings highlight the need for a rational approach to the pharmacological management of dystonia in childhood.

Rechargeable deep brain stimulators in the management of paediatric dystonia: well tolerated with a low complication rate.

Background: Deep brain stimulation (DBS) is a recognised method of treatment for primary and secondary dystonia. The size of non-rechargeable batteries has limited their use in small children. Our severe dystonia patients have required battery replacement every 20–24 months. Objectives: To evaluate reliability, care burden, patients’ satisfaction and complications related to the rechargeable neurostimulator Activa® RC (launched by Medtronic in Europe in autumn 2008). Methods: Complications were recorded prospectively, and a questionnaire on neurostimulator maintenance, care burden and parental satisfaction was applied to all patients with at least 3 months of follow-up. Results: 30 Activa RCs were implanted between December 2008 and June 2010, 25 with a follow-up of 3–17 months (mean 10); the mean patient’s age at surgery was 11.1 years; 22/25 questionnaires were completed. All families achieved good standards of recharging. Caregivers were responsible for recharging in 82% of cases. With higher parameters of stimulation, recharging time was longer than initially recommended by the manufacturer. All but one family would recommend Activa RC to other patients. Transient recharging problems were the most common complication (36% of cases). Infection/skin erosion occurred in 8% of cases, self-resolving early seroma in 20%. Conclusions: Activa was found to offer reliable stimulation with a low rate of significant complications and a suitable treatment option for children with dystonia.

Progression to musculoskeletal deformity in childhood dystonia

AIM Dystonia is a movement disorder characterized by involuntary muscle contractions, resulting in abnormalities of posture and movement. Children with dystonia are at risk of developing fixed musculoskeletal deformities (FMDs). FMDs cause pain, limit function and participation and interfere with care. We aimed to explore factors relating to the development of FMD in a large cohort of children with dystonia. METHOD The case notes of all children referred to our Complex Motor Disorder service between July 2005 and December 2011 were reviewed. Data from 279 children (median age 9 years 10 months, Standard Deviation 4 years 2 months) with motor disorders including a prominent dystonic element were analyzed. Parametric accelerated failure time regression was used to identify the factors related to development of contractures. RESULTS FMDs were present at referral in more than half (n = 163, 58%) of cases. Three quarters (n = 120, 74%) of children with FMD had deformities around the hip, and 42% had spinal deformity (n = 68). Compared to pure primary dystonia, FMD onset was earlier with a diagnosis of secondary or heredodegenerative dystonia, and a mixed spastic-dystonic phenotype (all p < 0.001). FMD onset was also earlier with increasing Gross Motor Function Classification System (GMFCS) level (p < 0.001). The effect of aetiological classification was lost when controlling for GMFCS level and motor phenotype. INTERPRETATION Children with secondary or heredodegenerative dystonia are at greater risk of progression to FMD compared to primary dystonia, likely due to more severe dystonia within these groups. Children with additional spasticity are at particular risk, requiring close monitoring.

Intrathecal baclofen trials: complications and positive yield in a pediatric cohort

OBJECT Intrathecal baclofen (ITB) is an effective management option for childhood hypertonia. Given the potential complications of implanted ITB pumps, trials of ITB are usually performed as part of the workup for ITB pumps. Two methods are used for ITB trials, lumbar puncture (LP) and catheter insertion into the intrathecal space. Little has been written to date on the number of positive trials and complications in trials. This study aimed to report the outcomes and complications in ITB trials for childhood hypertonia (dystonia, spastic, or mixed). METHODS A retrospective case notes review was conducted of all patients who underwent ITB trials at the Evelina London Childrens Hospital between 2005 and 2012 (inclusive). Positive trials were defined as a reduction in Modified Ashworth Scale by a minimum of 1 point in at least 2 muscle groups and improvement reported by the caregivers in the areas of goals agreed upon between professionals and the families. RESULTS Our patient group comprised children with dystonia (n = 7), mixed spasticity/dystonia (n = 29), spasticity (n = 4), and pain (n = 1). A total of 47 trials were attempted in 41 children. Forty trials were successfully completed, with 39 being positive. Thirty-three were catheter trials, and 14 were LPs. The overall complication rate in the 47 attempted trials was 53%: 61% in catheter trials, and 36% in LP trials. This difference was not statistically significant. The most common complications were vomiting (n = 9) and CSF leak (n = 4). The most serious complication was meningitis (n = 1) in a catheter trial. No patients experienced a permanent injury. CONCLUSIONS There is a high risk of minor self-limiting complications with ITB trials, which needs to be factored into the decision process of progression to trials. The rate of positive trials in this study was 98%, of which 21% did not progress to pump implantation. While the authors would still advocate for ITB trials prior to ITB pump insertion to aid parental decision-making, this figure suggests that with good patient selection, ITB pumps could be placed without a preceding trial.

Bilateral subthalamic nucleus deep brain stimulation for refractory total body dystonia secondary to metabolic autopallidotomy in a 4-year-old boy with infantile methylmalonic acidemia

The methylmalonic acidemias (MMAs) are a group of inborn errors of metabolism resulting in the accumulation of methylmalonic acid in body tissues and fluids. A recognized complication of MMA is bilateral liquefaction of the globus pallidi, resulting in a fulminant total body dystonia of childhood often refractory to medical treatment. This case of total body dystonia due to MMA in a 4-year-old boy had been medically refractory for 15 months. Complete metabolic destructive liquefaction of the pallidi, that is, autopallidotomy, necessitated an alternative, bilateral subthalamic nucleus (STN) target for deep brain stimulation (DBS) with a marked improvement in dystonia and reduction in pain. The case illustrates the efficacy of STN DBS in this condition and the technical challenges in targeting the STN in a small child.

Shielded Battery Syndrome: A New Hardware Complication of Deep Brain Stimulation

Background: Deep brain stimulation hardware is constantly advancing. The last few years have seen the introduction of rechargeable cell technology into the implanted pulse generator design, allowing for longer battery life and fewer replacement operations. The Medtronic® system requires an additional pocket adaptor when revising a non-rechargeable battery such as their Kinetra® to their rechargeable Activa® RC. This additional hardware item can, if it migrates superficially, become an impediment to the recharging of the battery and negate the intended technological advance. Aim: To report the emergence of the ‘shielded battery syndrome’, which has not been previously described. Methods: We reviewed our deep brain stimulation database to identify cases of recharging difficulties reported by patients with Activa RC implanted pulse generators. Results: Two cases of shielded battery syndrome were identified. The first required surgery to reposition the adaptor to the deep aspect of the subcutaneous pocket. In the second case, it was possible to perform external manual manipulation to restore the adaptor to its original position deep to the battery. Conclusions: We describe strategies to minimise the occurrence of the shielded battery syndrome and advise vigilance in all patients who experience difficulty with recharging after replacement surgery of this type for the implanted pulse generator.