Focal-onset seizures and encephalopathy are prominent Background: features of a stroke-like episode, which is a severe neurological manifestation associated with subtypes of mitochondrial disease. Despite more than 30 years of research, the acute treatment of stroke-like episodes remains controversial.We used the modified Delphi process to harness the clinical Methods: expertise of a group of mitochondrial disease specialists from five European countries to produce consensus guidance for the acute management of stroke-like episodes and commonly associated complications.Consensus on a new definition of mitochondrial stroke-like Results: episodes was achieved and enabled the group to develop diagnostic criteria based on clinical features, neuroimaging and/or

IMPORTANCE Extrapyramidal movement disorders associated with mitochondrial disease are difficult to treat and can lead to considerable disability. Moreover, potential new treatment trials on the horizon highlight the importance of genotype-phenotype associations and deep phenotyping of the movement disorders related to mitochondrial disease. OBJECTIVE To describe the phenotype, genetic etiology, and investigation of extrapyramidal movement disorders in a large and well-defined mitochondrial disease cohort. DESIGN, SETTING, AND PARTICIPANTS An observational cohort study at a single national referral center. Among 678 patients (87% adults) followed up at the Newcastle mitochondrial disease specialized referral center between January 1, 2000, and January 31, 2015, 42 patients (12 pediatric, 30 adult) with genetic or biochemical evidence of mitochondrial disease and with 1 or more predefined extrapyramidal movement disorders (parkinsonism, dystonia, tremor, chorea, and restless legs syndrome) were included. MAIN OUTCOMES AND MEASURES We investigated the prevalence and genetic causes of dystonia and parkinsonism as well as radiological findings in the context of movement disorders in mitochondrial disease. All patients were interviewed and examined. All available medical notes and clinical, radiological, and genetic investigations were reviewed. RESULTS Forty-two patients (mean [SD] age, 37 [25] years; 38% female) with mitochondrial disease (12 pediatric [age range, 4-14 years], 30 adult [age range, 20-81 years]) with extrapyramidal movement disorders were identified. Dystonia manifested in 11 pediatric patients (92%), often in the context of Leigh syndrome; parkinsonism predominated in 13 adult patients (43%), among whom 5 (38%) harbored either dominant (n = 1) or recessive (n = 4) mutations in POLG. Eleven adult patients (37%) manifested with either generalized or multifocal dystonia related to mutations in mitochondrial DNA, among which the most common were the m.11778G>A mutation and mutations in MT-ATP6 (3 of 11 patients [27%] each). Bilateral basal ganglia lesions were the most common finding in brain magnetic resonance imaging, usually associated with generalized dystonia or Leigh syndrome. CONCLUSIONS AND RELEVANCE Dystonia, often associated with Leigh syndrome, was the most common extrapyramidal movement disorder among pediatric patients with mitochondrial disease. Parkinsonism was the most prevalent extrapyramidal movement disorder in adults and was commonly associated with POLG mutations; dystonia was predominantly associated with mitochondrial DNA mutations. These findings may help direct genetic screening in a busy neurology outpatient setting.

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD) patients with motor fluctuations and dyskinesias. The key DBS efficacy studies were performed in PD patients with unknown genotypes; however, given the estimated monogenic mutation prevalence of approximately 5-10%, most commonly LRRK2, PRKN, PINK1 and SNCA, and risk-increasing genetic factors such as GBA, proper characterization is becoming increasingly relevant. We performed a systematic review of 46 studies that reported DBS effects in 221 genetic PD patients. The results suggest that monogenic PD patients have variable DBS benefit depending on the mutated gene. Outcome appears excellent in patients with the most common LRRK2 mutation, p.G2019S, and good in patients with PRKN mutations but poor in patients with the more rare LRRK2 p.R1441G mutation. The overall benefit of DBS in SNCA, GBA and LRRK2 p.T2031S mutations may be compromised due to rapid progression of cognitive and neuropsychiatric symptoms. In the presence of other mutations, the motor changes in DBS-treated monogenic PD patients appear comparable to those of the general PD population.

Objective:To describe the clinical features and brain imaging findings of autosomal dominant Parkinson disease (PD) associated with a recently reported mutation in SNCA.Methods:A Finnish family with PD in 3 successive generations, in accordance with an autosomal dominant inheritance pattern, was identified. We examined 2 available members of the family, the female proband and her daughter (both with early-onset PD), clinically and using dopamine transporter imaging ([123I]FP-CIT SPECT). A possible causative genetic defect was investigated by molecular genetic analyses.Results:A heterozygous c.158C>A (p.A53E) point mutation in SNCA was revealed in both patients. The patients presented with PD clinically characterized by severe bradykinesia but with very little tremor and early onset of levodopa-induced dyskinesia. No cognitive decline or dysautonomic features have emerged during more than 5 years of follow-up. Both patients presented with a severe striatal binding defect in dopamine transporter SPECT imaging.Conclusions:The results of this observational study add evidence to the suggestion that the p.A53E mutation in SNCA is indeed pathogenic and results in autosomal dominant PD. Bradykinesia and early onset of levodopa-induced dyskinesia are the characteristic clinical features associated with the A53E mutation, but the patients did not exhibit dementia or dysautonomia. The [123I]FP-CIT SPECT findings indicated a profound, symmetric dopaminergic defect, in contrast to those observed in patients with idiopathic PD.

Epilepsy is a common manifestation of mitochondrial disease associated with mutations of the mitochondrial polymerase ␥ (POLG). Prognosis of mitochondrial epilepsy is often poor and there are few reports of successful treatment of POLG-related epilepsy. We describe a 26-year-old woman who experienced severe headache during a three-day period, followed by symptoms of visual flashing, speech difficulty, and generalised seizures. EEG recording showed non-convulsive status epilepticus (left occipital area) and brain MRI revealed parieto-occipital T2-hyperintensities. Visual aura and aphasia persisted despite antiepileptic medication with phenytoin, oxcarbazepine, and levetiracetam. Mitochondrial disorder was clinically suspected and a homozygous c.2243G>C mutation (p.Trp748Ser) was discovered in the POLG1 gene. The patient was then set on a low glycaemic index treatment (LGIT) variant of the ketogenic diet, after which the headaches, aphasia, and visual aura progressively improved and disappeared. She returned home two weeks after onset of symptoms and has not had further seizures. She continues to receive levetiracetam monotherapy and LGIT. We conclude that, at least for this patient, the combination of three antiepileptic drugs and LGIT is effective and well tolerated as treatment for severe episodes of POLG-related mitochondrial epilepsy.

Defects in the respiratory chain or mitochondrial ATP synthase (complex V) result in mitochondrial dysfunction that is an important cause of inherited neurological disease. Two of the subunits of complex V are encoded by MT-ATP6 and MT-ATP8 in the mitochondrial genome. Pathogenic mutations in MT-ATP6 are associated with the Leigh syndrome, the syndrome of neuropathy, ataxia, and retinitis pigmentosa (NARP), as well as with non-classical phenotypes, while MT-ATP8 is less frequently mutated in patients with mitochondrial disease. We investigated two adult siblings presenting with features of cerebellar ataxia, peripheral neuropathy, diabetes mellitus, sensorineural hearing impairment, and hypergonadotropic hypogonadism. As the phenotype was suggestive of mitochondrial disease, mitochondrial DNA was sequenced and a novel heteroplasmic mutation m.8561C>G in the overlapping region of the MT-ATP6 and MT-ATP8 was found. The mutation changed amino acids in both subunits. Mutation heteroplasmy correlated with the disease phenotype in five family members. An additional assembly intermediate of complex V and increased amount of subcomplex F were observed in myoblasts of the two patients, but the total amount of complex V was unaffected. Furthermore, intracellular ATP concentration was lower in patient myoblasts indicating defective energy production. We suggest that the m.8561C>G mutation in MT-ATP6/8 is pathogenic, leads biochemically to impaired assembly and decreased ATP production of complex V, and results clinically in a phenotype with the core features of cerebellar ataxia, peripheral neuropathy, diabetes mellitus, and hypergonadotropic hypogonadism.

Distinct clinical syndromes have been associated with pathogenic MT‐ATP6 variants. In this cohort study, we identified 125 individuals (60 families) including 88 clinically affected individuals and 37 asymptomatic carriers. Thirty‐one individuals presented with Leigh syndrome and 7 with neuropathy ataxia retinitis pigmentosa. The remaining 50 patients presented with variable nonsyndromic features including ataxia, neuropathy, and learning disability. We confirmed maternal inheritance in 39 families and demonstrated that tissue segregation patterns and phenotypic threshold are variant dependent. Our findings suggest that MT‐ATP6–related mitochondrial DNA disease is best conceptualized as a mitochondrial disease spectrum disorder and should be routinely included in genetic ataxia and neuropathy gene panels. ANN NEUROL 2019;86:310–315

No abstract