Genetic heterogeneity in patients with pantothenate kinase-associated neurodegeneration and classic magnetic resonance imaging eye-of-the-tiger pattern.

We performed a detailed molecular study in two unrelated families with pantothenate kinase-associated neurodegeneration (PKAN) and the specific magnetic resonance imaging (MRI) eye-of-the-tiger pattern. In the first family with classic PKAN, linkage analysis using polymorphic markers from the PANK2 region ruled out linkage with this locus, and no mutation of the PANK2 gene was found. In the second family with atypical PKAN, we identified a novel homozygous C-to-T transition at nucleotide 1069 of the PANK2 gene, which resulted in an arginine to tryptophane substitution at codon 357. As far as we are aware, this is the first case of classic PKAN with the specific MRI eye-of-the-tiger pattern not carrying a PANK2 mutation. Therefore, the present observation reinforces the notion of the phenotypic and genetic heterogeneity in PKAN.     

Clinical heterogeneity of neurodegeneration with brain iron accumulation (Hallervorden-Spatz syndrome) and pantothenate kinase-associated neurodegeneration.

Hallervorden Spatz syndrome (HSS), also referred to as neurodegeneration with brain iron accumulation (NBIA), is a rare inherited neurodegenerative disorder with childhood, adolescent, or adult onset. Patients with HSS/NBIA have a combination of motor symptoms in the form of dystonia, parkinsonism, choreoathetosis, corticospinal tract involvement, optic atrophy, pigmentary retinopathy, and cognitive impairment. After the recent identification of mutations in the PANK2 gene on chromosome 20p12.3-p13 in some patients with the HSS/NBIA phenotype, the term pantothenate kinase-associated neurodegeneration (PKAN) has been proposed for this group of disorders. To characterize clinically and genetically HSS/NBIA, we reviewed 34 affected individuals from 10 different families, who satisfied the inclusion criteria for NBIA. Relatives of patients who had clinical, magnetic resonance imaging (MRI), or pathological findings of NBIA were included in the study. Four patients were found to have mutations in the pantothenate kinase 2 (PANK2) gene. We compared the clinical features and MRI findings of those with and without PANK2 mutations. The presence of mutation in the PANK2 gene is associated with younger age at onset and a higher frequency of dystonia, dysarthria, intellectual impairment, and gait disturbance. Parkinsonism is seen predominantly in adult-onset patients whereas dystonia seems more frequent in the earlier-onset cases. The phenotypic heterogeneity observed in our patients supports the notion of genetic heterogeneity in the HSS/NBIA syndrome.     

Battery lifetime in pallidal deep brain stimulation for dystonia

Background and Purpose: The aim of the study was to analyse the lifetime of Soletra implantable pulse generators (IPG) in deep brain stimulation (DBS) of the globus pallidus internus (GPi) for dystonia, depending on stimulation parameters and the total electrical energy delivered (TEED) by the IPG. Methods: In a prospective series of 20 patients with GPi DBS for dystonia, we recorded IPG longevity and stimulation parameters over time. An evaluation of the TEED was performed using the previously suggested equation [(voltage² × pulse width × frequency)/impedance] × 1 s. Results: During median follow‐up of 57 months (range 23–79 months), 64 IPGs were replaced because of battery depletion or end of life signal. We found a mean IPG longevity of 25.1 ± 10.1 (range 16–60) months, which was inversely correlated with the TEED (r = −0.72; P < 0.001). IPG longevity was not different between bipolar and monopolar stimulation (24.9 ± 10.8 vs. 25.4 ± 9.0 months, P = 0.76). Incongruously, the mean TEED applied throughout the lifetime cycle was significantly higher in patients with bipolar compared with monopolar stimulation (584 ± 213 vs. 387 ± 121 Joule; P < 0.01). Conclusions: Battery lifetime in GPi DBS for dystonia is substantially shorter compared with that reported in DBS for Parkinson’s disease, caused by a considerably higher voltage and greater pulse width and therefore a higher TEED applied during the battery lifetime cycle. The commonly used equation to calculate TEED, however, seems to be correct only for monopolar, but not bipolar stimulation.     

Partial deficit of pantothenate kinase 2 catalytic activity in a case of tremor-predominant neurodegeneration with brain iron accumulation.

We describe an atypical case of pantothenate kinase-associated neurodegeneration (PKAN) in which slowly progressive arm tremor was the predominant symptom beginning at the age of 25, with late-onset dystonia and dysarthria developing at the age of 50. Compound heterozygous mutations resulting in missense amino acid substitutions G521R and I529V were identified in the pantothenate kinase (PANK2) gene. We demonstrate that while the G521R mutation results in an unstable and inactive protein, the previously unreported I529V substitution has no apparent effect on the stability or catalytic activity of PanK2. The phenotype that results from this combination of mutations suggests that atypical presentations of PKAN may arise from partial deficits in PanK2 catalytic activity.     

The effects of frequency in pallidal deep brain stimulation for primary dystonia

Abstract. The effect of stimulation frequency for pallidal deep brain stimulation in five patients with either generalized or segmental dystonia was evaluated three to twelve months postoperatively via a randomized, double-blind paradigm. The quality of life and the severity of dystonic symptoms improved by approximately 60% and 43% respectively using a frequency of 130 Hz. Compared with 130 Hz a significant further clinical improvement was observed at frequencies of 180 and 250 Hz, which contrasted with a significant deterioration at lower frequencies (5, 50 Hz) compared to 130 Hz.     

Lower stimulation frequency can enhance tolerability and efficacy of pallidal deep brain stimulation for dystonia.

We report the case of a patient with medically refractory primary dystonia who was treated with bilateral pallidal deep brain stimulation. Stimulation at 130 Hz or higher, by means of the more ventral contacts generated capsular side effects, which made their use impractical. Consequently, the patient was treated for 9 months at 130 to 185 Hz, by means of the more dorsal contacts, achieving modest results. By reducing the stimulation frequency to 80 Hz, we were able to activate the ventral contacts without inducing side effects. Within days, the patient experienced a dramatic improvement in function that has persisted for 1 year. A further reduction in stimulation frequency to 60 Hz resulted in a worsening of his symptoms. We conclude that chronic stimulation at frequencies of <100 Hz may be efficacious in dystonia and may enhance the tolerability of stimulation by means of contacts that are positioned posteroventrally within the internal globus pallidus, nearer the internal capsule.     

Meige syndrome and pallidal deep brain stimulation.

The cause of primary Meige syndrome is unknown, and although gender and age predilections are different from idiopathic torsion dystonia, most investigators consider Meige syndrome a variant of that disorder. Interest in the use of stereotactic brain surgery for refractory forms of dystonia is thus increasing. There is little experience with the use of deep brain stimulation (DBS) in focal dystonias, and reports of its use in Meige syndrome are very rare. We report on a case of Meige syndrome successfully treated with bilateral pallidal DBS.     

Acquired stuttering after pallidal deep brain stimulation for dystonia

We report two patients, in whom stuttering evolved as an adverse effect of pallidal deep brain stimulation for treating dystonia. Speech dysfluency was observed under conditions that optimally suppressed dystonic symptoms without inducing other extrinsic stimulation effects. This emphasizes a role of the sensorimotor part of the internal globus pallidus in regulating speech fluency. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Globus pallidus deep brain stimulation in dystonia.

Globus pallidus deep brain stimulation (GPi-DBS) is a useful alternative in the treatment of dystonia. Patients selected for GPi-DBS were prospectively rated with the Unified Dystonia Rating Scale (UDRS). Also, "blinded" videotape assessments were performed. Eleven patients were identified. Compared with pre-DBS scores, there were improvements in mean total UDRS score (15.3%) and in the following subscores: neck (18.18%), trunk (32.9%), arm (17.9%), and leg (19.9%). One patient developed a skin infection and erosion requiring surgical debridement. GPi-DBS is a safe and effective treatment for generalized dystonia in patients who remained impaired, despite optimal medical therapy.     

Factors predicting improvement in primary generalized dystonia treated by pallidal deep brain stimulation

Despite the beneficial effects of Globus Pallidus internus (GPi) deep brain stimulation (DBS) in patients with primary generalized dystonia (PGD), the degree of improvement varies from one patient to another. The objective of this study was to examine the effects of clinical, anatomical (volume of the GPi), and electrical variables on the postoperative Burke‐Fahn‐Marsden Dystonia rating scale (BFMDRS) motor score to identify which factors may be predictive of the degree of improvement. We reviewed retrospectively the clinical records of 40 steady‐state patients with PGD who had been treated by bilateral GPi lead implantation. The follow‐up period was 2 to 8 years. The correlation between the electrical parameters (voltage, impedance, and current) and the clinical outcome was studied. An analysis of covariance was performed to identify factors predictive of the magnitude of improvement. The most influential factors according to the model are as follows: the preoperative BFMDRS score (P < 0.0001); age at surgery (P < 0.0001); the right GPi volume (P = 0.002); the left stimulated GPi volume (P = 0.005). No significant correlation was found between the electrical parameters used and the mean motor scores in steady state. © 2009 Movement Disorder Society     

Staged bilateral stereotactic pallidothalamotomy for life-threatening dystonia in a child with Hallervorden-Spatz disease.

Hallervorden-Spatz disease (HSD) is a rare disorder characterized by progressive motor dysfunction and dementia. Dystonia is the most prominent and disabling symptom, responding only to a modest extent to pharmacological therapy. At the moment, only a few cases have been reported to improve dystonia and even fewer to resolve status dystonicus for a longer period in children. The authors present the case of a 10-year-old boy who had progressive generalized dystonia, resulting in spontaneous femur fracture and life-threatening swallowing and respiratory disability. As a rescue solution, staged bilateral pallidothalamotomy was performed. Postoperatively, Burke-Fahn-Marsden Dystonia Rating Scale and Dystonia Disability Rating Scale improved (from 116 and 30 points to 41 and 18 points, respectively) and painful dystonia was resolved, which was still continuous 4 years later (47 and 20 points). Stereotactic staged bilateral pallidothalamotomy should be considered as a potential treatment in the management of life-threatening generalized dystonia related to HSD.     

Reversal of hypertonic co-contraction after bilateral pallidal stimulation in generalised dystonia: a clinical and electromyogram case study.

In a patient of generalised dystonia treated with bilateral pallidal stimulation, serial surface EMGs recorded from the neck muscles during alternating head movements revealed progressive reduction in hypertonic activity and reversal of co-contraction to reciprocal contraction, which preceded clinical improvement.     

Novel compound heterozygous mutations in the PANK2 gene in a Chinese patient with atypical pantothenate kinase-associated neurodegeneration.

We investigated the presence of mutations in the pantothenate kinase (PANK2) gene in a 27-year-old male Chinese patient with atypical pantothenate kinase-associated neurodegeneration (PKAN), formerly Hallervorden-Spatz syndrome. Automated DNA sequence analyses revealed compound heterozygous mutations in the exon 3 and 5. This patient had a 10-year history of PKAN characterized by a slight tremor of the right hand when writing at onset and a slow progressive rigidity of the neck and the right arm and resting tremor in upper extremities. Dysarthria, dysphagia, and dystonic-athetoid movements of the face and right fingers were marked. Magnetic resonance showed the typical "eye-of-the-tiger" sign.     

A practical guide to troubleshooting pallidal deep brain stimulation issues in patients with dystonia

High frequency deep brain stimulation (DBS) of the internal portion of the globus pallidus has, in the last two decades, become a mainstream therapy for the management of medically-refractory dystonia syndromes. Such increasing uptake places an onus on movement disorder physicians to become familiar with this treatment modality, in particular optimal patient selection for the procedure and how to troubleshoot problems relating to sub-optimal efficacy and therapy-related side effects.Deep brain stimulation for dystonic conditions presents some unique challenges. For example, the frequent lack of immediate change in clinical status following stimulation alterations means that programming often relies on personal experience and local practice rather than real-time indicators of efficacy. Further, dystonia is a highly heterogeneous disorder, making the development of unifying guidelines and programming algorithms for DBS in this population difficult. Consequently, physicians may feel less confident in managing DBS for dystonia as compared to other indications e.g. Parkinson's disease.In this review, we integrate our years of personal experience of the programming of DBS systems for dystonia with a critical appraisal of the literature to produce a practical guide for troubleshooting common issues encountered in patients with dystonia treated with DBS, in the hope of improving the care for these patients.     

丘脑底核电刺激治疗继发性肌张力障碍

目的 探讨丘脑底核（STN）的脑深部电剌激（DBS）治疗继发性肌张力障碍的可行性、适应证和并发症。方法 5例行双侧STN—DBS，1例行单侧STN—DBS。结果 术中利用微电极记录的电信号获得STN的准确靶点定位，电刺激后患者肌张力有不同程度下降，但扭转改善不明显。随访半年至3年，6例患者中，药物引起的迟发性肌张力障碍及外伤性肌张力障碍的患者疗效理想，BFMDRS评分改善均在90％以上，且随着随访时间的延长，效果持续不断改善；其余4例患者疗效不佳，4例均肌张力略有改善，其中1例扭转略改善，1例语言及步态略有改善。手术后患者均无明显合并症，但1例术后16个月发现左侧电极折断，后取出。结论 DBS治疗迟发性和外伤性继发性肌张力障碍效果理想，而对于缺氧或脑基底节区弥漫性损害的继发性肌张力障碍效果不佳；STN可以成为治疗本病的理想靶点；术中应根据电生理记录结果和肌张力的轻度改善作为靶点定位的指标；手术无明显合并症。     

Focal childhood‐onset,action induced primary hip dystonia treated with pallidal deep brain stimulation

Focal proximal lower limb dystonias are rare. Unlike the adult form, focal lower limb dystonias in children usually become generalized. The condition is often unrecognized and the patient often receives orthopedic or psychiatric treatment for years before the diagnosis eventually made. Previously reported cases of isolated lower limb dystonias have been managed nonsurgically. We present a case of a childhood‐onset action‐induced primary hip dystonia that has remained focal even in adulthood and which responded successfully to pallidal deep brain stimulation. Additionally, our results suggest that neurons representing the leg lie within the most ventral aspect of the globus pallidus interna. © 2008 Movement Disorder Society     

Pantothenate kinase-associated neurodegeneration in Korea: recurrent R440P mutation in PANK2 and outcome of deep brain stimulation

Background and Purpose: The purpose of this study was to evaluate the mutation status of PANK2 among Korean patients with pantothenate kinase‐associated neurodegeneration (PKAN) and to document the outcome of pallidal deep brain stimulation (DBS). Methods: Direct sequencing and deletion/duplication analysis of PANK2 were conducted in 12 patients (11 unrelated) with PKAN, diagnosed on the basis of extrapyramidal dysfunction and the ‘eye‐of‐the‐tiger sign’ on brain magnetic resonance imaging (MRI). Pallidal DBS was conducted in four patients, and the outcomes were measured using the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS). Results: A PANK2 mutation was identified in both alleles in all patients. The most prevalent mutation was c.1319G>C (p.R440P) in 8/22 mutated alleles (36%). An intragenic deletion ranging from exons 2 to 4 was found in one allele (1/22, 4.5%) using deletion/duplication analysis. The outcome of pallidal DBS was favorable in two patients with atypical PKAN and moderate severity of dystonia. However, two patients with typical PKAN and relatively severe symptoms showed variable responses. Conclusions: The c.1319G>C (p.R440P) mutation appears to be a founder genotype among Korean patients with PKAN. Furthermore, this study provides additional data for the recent international effort to evaluate the efficacy of pallidal DBS in the treatment of patients with PKAN.     

Dualistic effect of pallidal deep brain stimulation on motor speech disorders in dystonia

Background

Although pallidal deep brain stimulation (GPi-DBS) is an effective treatment for dystonia, it may cause important stimulation-induced side-effects such as hypokinetic dysarthria or stuttering. However, the reasons behind the occurrence of these side-effects remain unknown.