Long-Term Outcomes of Deep Brain Stimulation in Pantothenate Kinase-Associated Neurodegeneration-Related Dystonia

Objective

To investigate the long-term clinical outcomes of pallidal deep brain stimulation (GPi-DBS) in patients with pantothenate kinase-associated neurodegeneration (PKAN).

Methods

We reviewed the records of patients with genetically confirmed PKAN who received bilateral GPi-DBS for refractory dystonia and were clinically followed up for at least 2 years postoperatively at two centers in Korea. Pre- and postoperative Burke- Fahn-Marsden Dystonia Rating Scale motor subscale (BFMDRS-M) scores, disability subscale (BFMDRS-D) scores, and qualitative clinical information were prospectively collected. Descriptive analysis was performed for BFMDRS-M scores, BFMDRSD scores, and the orofacial, axial, and limb subscores of the BFMDRS-M at 6-12, 24-36, and 60-72 months postoperatively.

Results

Five classic-type, four atypical-type, and one unknown-type PKAN cases were identified. The mean preoperative BFMDRS-M score was 92.1 for the classic type and 38.5 for the atypical or unknown type, with a mean BFMDRS follow-up of 50.7 months and a clinical follow-up of 69.0 months. The mean improvements in BFMDRS-M score were 11.3%, 41.3%, and 30.5% at 6-12, 24-36, and 60-72 months, respectively. In four patients with full regular evaluations until 60-72 months, improvements in the orofacial, axial, and limb subscores persisted, but the disability scores worsened from 24-36 months post-operation compared to the baseline, mainly owing to the aggravation of eating and feeding disabilities.

Conclusion

The benefits of GPi-DBS on dystonia may persist for more than 5 years in PKAN. The effects on patients' subjective disability may have a shorter duration despite improvements in dystonia owing to the complex manifestations of PKAN.

Two cases with mitochondrial membrane protein-associated neurodegeneration: genetic features and long-term clinical follow-up

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a rare neurological disease with childhood or adult onset. It is a subtype of clinically and genetically heterogeneous group of disorders, collectively known as neurodegeneration with brain iron accumulation . MPAN is generally associated with biallelic pathogenic variants in C19orf12. Herein, we describe genetic and clinical findings of two MPAN cases from Turkey. In the first case, we have identified the relatively common pathogenic variant of C19orf12 in the homozygous state, which causes late-onset MPAN. The second case was homozygous for an essential splice-site variation.

MR imaging for the quantitative assessment of brain iron in aceruloplasminemia: A postmortem validation study

AIMS

Non-invasive measures of brain iron content would be of great benefit in neurodegeneration with brain iron accumulation (NBIA) to serve as a biomarker for disease progression and evaluation of iron chelation therapy. Although magnetic resonance imaging (MRI) provides several quantitative measures of brain iron content, none of these have been validated for patients with a severely increased cerebral iron burden. We aimed to validate R₂* as a quantitative measure of brain iron content in aceruloplasminemia, the most severely iron-loaded NBIA phenotype.

METHODS

Tissue samples from 50 gray- and white matter regions of a postmortem aceruloplasminemia brain and control subject were scanned at 1.5 T to obtain R₂^*, and biochemically analyzed with inductively coupled plasma mass spectrometry. For gray matter samples of the aceruloplasminemia brain, sample R₂* values were compared with postmortem in situ MRI data that had been obtained from the same subject at 3 T - in situ R₂*. Relationships between R₂* and tissue iron concentration were determined by linear regression analyses.

RESULTS

Median iron concentrations throughout the whole aceruloplasminemia brain were 10 to 15 times higher than in the control subject, and R₂* was linearly associated with iron concentration. For gray matter samples of the aceruloplasminemia subject with an iron concentration up to 1000 mg/kg, 91% of variation in R₂* could be explained by iron, and in situ R₂* at 3 T and sample R₂* at 1.5 T were highly correlated. For white matter regions of the aceruloplasminemia brain, 85% of variation in R₂* could be explained by iron.

CONCLUSIONS

R₂* is highly sensitive to variations in iron concentration in the severely iron-loaded brain, and might be used as a non-invasive measure of brain iron content in aceruloplasminemia and potentially other NBIA disorders.

Neurodegeneration with Brain Iron Accumulation and a Brief Report of the Disease in Iran

Neurodegeneration with brain iron accumulation (NBIA) is a term used for a group of hereditary neurological disorders with abnormal accumulation of iron in basal ganglia. It is clinically and genetically heterogeneous with symptoms such as dystonia, dysarthria, Parkinsonism, intellectual disability, and spasticity. The age at onset and rate of progression are variable among individuals. Current therapies are exclusively symptomatic and unable to hinder the disease progression. Approximately 16 genes have been identified and affiliated to such condition with different functions such as iron metabolism (only two genes: Ferritin Light Chain (FTL) Ceruloplasmin (CP)), lipid metabolism, lysosomal functions, and autophagy process, but some functions have remained unknown so far. Subgroups of NBIA are categorized based on the mutant genes. Although in the last 10 years, the development of whole-exome sequencing (WES) technology has promoted the identification of disease-causing genes, there seem to be some unknown genes and our knowledge about the molecular aspects and pathogenesis of NBIA is not complete yet. There is currently no comprehensive study about the NBIA in Iran; however, one of the latest discovered NBIA genes, GTP-binding protein 2 (GTPBP2), has been identified in an Iranian family, and there are some patients who have genetically remained unknown.

Is there heart disease in cases of neurodegeneration associated with mutations in C19orf12?

INTRODUCTION

In mitochondrial membrane protein-associated neurodegeneration (MPAN), a subtype of neurodegeneration with brain iron accumulation (NBIA), patients suffer from optic nerve atrophy and dementia, which are also typical for another group of diseases, the mitochondrial diseases (MD). Around 30% of patients with MD have heart disease, commonly cardiomyopathy and arrhythmias, and 10% experience a major adverse cardiovascular event. The aim of this study was to assess cardiac involvement in MPAN.

METHODS

Thirteen patients with MPAN were evaluated after written informed consent. All patients had echocardiography and 12 patients had 24-h Holter electrocardiogram (ECG) monitoring using 3-channel digital recorders.

RESULTS

Echocardiography revealed normal values for the dimensions of all heart chambers. The systolic function of the left ventricle was normal in all cases. Right ventricle systolic impairment was found in three patients. 24-hour Holter ECG revealed predominant resting tachycardia during daytime with no physiological slowing of heart rate during sleep in seven cases. No significant arrhythmias were found. In nine patients, selected heart rate variability (HRV) parameters were lower than reference values.

CONCLUSION

Cardiomyopathy, typical of MD, was not found in patients with MPAN. There were no significant arrhythmias, but disturbances in the circadian rhythm of the heart rate were observed in most cases. The decrease in HRV may reflect an early sign of autonomic dysfunction. A standard cardiac work-up is recommended for patients with MPAN to assess if additional treatment is needed.

PLA2G6-associated neurodegeneration: New insights into brain abnormalities and disease progression

INTRODUCTION

PLA2G6-associated neurodegeneration (PLAN) comprises a continuum of three phenotypes with overlapping clinical and radiologic features.

METHODS

Observational clinical study in a cohort of infantile and childhood onset PLAN patients and genetic analysis of the PLA2G6 gene. We analysed chronological evolution in terms of age at onset and disease course through a 66-item questionnaire. We performed qualitative and quantitative assessment of MRI abnormalities and searched for clinical and radiological phenotype and genotype correlations.

RESULTS

Sixteen PLAN patients (mean age: 10.2 years, range 3-33) were evaluated, with a median onset (years) of signs/symptoms as follows: neurological regression (1.5), oculomotor abnormalities (1.5), hypotonia (1.8), gait loss (2.2), pyramidal signs (3.0), axonal neuropathy (3.0), dysphagia (4.0), optic atrophy (4.0), psychiatric symptoms (4.0), seizures (5.9), joint contractures (6.0), dystonia (8.0), bladder dysfunction (13.0) and parkinsonism (15.0). MRI assessment identified cerebellar atrophy (19/19), brain iron deposition (10/19), clava hypertrophy (8/19) and T2/FLAIR hyperintensity of the cerebellar cortex (6/19). The mid-sagittal vermis relative diameter (MVRD) correlated with age at onset of clinical variants, meaning that the earlier the onset, the more severe the cerebellar atrophy. All patients harboured missense, nonsense and frameshift mutations in PLA2G6, including four novel variants.

CONCLUSIONS

Cerebellar atrophy was a universal radiological sign in infantile and childhood onset PLAN, and correlated with the severity of the phenotype. Iron accumulation within the globus pallidum and substantia nigra was also a common and strikingly uniform feature regardless of the phenotype.

Botulinum Toxin-A Injection in the Treatment of Spasticity in a Infantile-Onset Neurodegeneration With Brain Iron Accumulation: A Case Report

Pantothenate kinase-associated neurodegeneration (PKAN) is a neurodegenerative disorder characterized by iron accumulation in the globus pallidus (GP) of the brain (neurodegeneration with brain iron accumulation [NBIA]), which is characterized by dystonia and spasticity resulting in postural difficulties. A 33-month-old boy was admitted with a pronounced gait disturbance. Marked hypertonicity in the patient's both calf muscles was noted, resulting in waddling with repeated slip-falls. NBIA was suspected by high T2 intensity in the GP on brain MRI, then it was confirmed by detecting PANK2 mutation. Botulinum toxin-A injection was administered to both calf muscles. After 2 weeks, a decrease in spasticity and an increase in range of motion were observed, and consequently, an increase in the patient's gait stability with both heels touching the ground, enabling him to walk straight independently. A definitive treatment for NBIA has not been established, and a symptomatic therapy is currently the mainstay of treatment in this case. This is the first case report of botulinum toxin injection for treatment of gait disturbance caused by spasticity in an infantile-onset PKAN.

Transcranial Sonography in Mitochondrial Membrane Protein-Associated Neurodegeneration

Introduction

Although the nature of basal ganglia hyperechogenicity in transcranial sonography (TCS) examinations remains unclear, many studies have shown associations between hyperechogenicity and iron accumulation. The role of iron in basal ganglia hyperechogenicity raises interest in the use of TCS in forms of neurodegeneration with brain iron accumulation (NBIA). Here we analyzed TCS and magnetic resonance imaging (MRI) findings among patients affected by one type of NBIA, mitochondrial membrane protein-associated neurodegeneration (MPAN).

Methods

Investigations using MRI and TCS were performed on 13 patients exhibiting a C19orf12 gene mutation.

Results

The use of T2/T2* MRI revealed hypointense lesions restricted to the globus pallidus and substantia nigra. Using TCS examination, 12 patients exhibited bilateral hyperechogenicity of the lenticular nucleus, while no patients showed substantia nigra hyperechogenicity.

Conclusion

Investigations with TCS revealed a distinctive hyperechogenicity pattern of the basal ganglia in MPAN patients, which might be useful for differential diagnostics. The variable TCS imaging findings in NBIA patients may result from the presence of different iron content, iron binding partners, such as ferritin and neuromelanin, as well as structural changes, such as gliosis.

A Novel Deletion Mutation of Exon 2 of the C19orf12 Gene in an Omani Family with Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN)

Mutations in the C19orf12 gene are known to cause mitochondrial membrane protein-associated neurodegeneration (MPAN), which is a neurodegeneration with brain iron accumulation (NBIA) type 4 disorder. To the best of our knowledge, this is the first report of a genetically confirmed case of MPAN from Oman. A novel homozygous deletion of exon 2 of the C19orf12 gene was confirmed on the proband, a seven-year-old girl, who presented with gait instability. Brain magnetic resonance imaging showed iron deposition on the basal ganglia. This report highlights the importance of genetic testing of such a clinically and genetically heterogeneous condition among a population with a high consanguinity rate. To overcome the diagnostic difficulty, implementation of a cost-effective approach to perform cascade screening of carriers at risk is needed as well as programs to address risky consanguineous marriages.

Identification of Novel Compound Mutations in PLA2G6-Associated Neurodegeneration Patient with Characteristic MRI Imaging

Neurodegeneration with brain iron accumulation comprises a heterogeneous group of disorders characterized clinically by progressive motor dysfunction. Accurate identification of de novo and rare inherited mutations is important for determining causative genes of undiagnosed neurological diseases. In the present study, we report a unique case with cerebellar ataxia symptoms and social communication difficulties in an intermarriage family. MRI showed a marked cerebellar atrophy and the "eye-of-the-tiger"-like sign in the medial globus pallidus. Potential genetic defects were screened by whole-exome sequencing (WES) for the patient and four additional family members. A previously undescribed de novo missense mutation (c.1634A>G, p.K545R) in the exon 12 of the PLA2G6 gene was identified. A second rare variant c.1077G>A at the end of exon 7 was also identified, which was inherited from the mother, and resulted in a frame-shift mutation (c.1074_1077del.GTCG) due to an alternative splicing. In conclusion, the identification of the "eye-of-the-tiger"-like sign in the globus pallidus of the patient expands the phenotypic spectrum of PLA2G6-associated disorders and reveals its value in differential diagnosis of PLA2G6-associated disorders.

Behr syndrome with homozygous C19ORF12 mutation

OBJECTIVE

Behr syndrome, first described in 1909 by the ophthalmologist Carl Behr, is a clinical entity characterised by a progressive optic atrophy, ataxia, pyramidal signs and mental retardation. Some reported cases have been found to carry mutations in the OPA1, OPA3 or C12ORF65 genes which are known causes of pure optic atrophy or optic atrophy complicated by movement disorder.

METHODS

We present the long-term observation of two Turkish sisters with Behr syndrome. We performed neurophysiological, imaging and molecular genetic studies to identify the underlying genetic cause in our patients.

RESULTS

Magnetic resonance imaging of the brain showed bilateral hypointense signals in the basal ganglia which prompted us to consider neurodegeneration with brain iron accumulation (NBIA) as a differential diagnosis. Molecular genetic studies revealed a homozygous mutation in the C19ORF12 gene which has been previously reported in patients with a subtype of NBIA, mitochondrial membrane protein-associated neurodegeneration (MPAN).

CONCLUSION

We expand the spectrum of genetic causes of Behr syndrome. Genetic testing of patients presenting with Behr syndrome should include C19ORF12 mutation screening.

Mitochondrial protein associated neurodegeneration - case report

Neurodegeneration with brain iron accumulation (NBIA) is a group of genetic disorders with a progressive extrapyramidal syndrome and excessive iron deposition in the brain, particularly in the globus pallidus and substantia nigra. We present the case of a 31-year-old woman with mitochondrial protein associated neurodegeneration (MPAN). MPAN is a new identified subtype of NBIA, caused by mutations in C19orf12 gene. The typical features are speech and gait disturbances, dystonia, parkinsonism and pyramidal signs. Common are psychiatric symptoms such as impulsive or compulsive behavior, depression and emotional lability. In almost all cases, the optic atrophy has been noted and about 50% of cases have had a motor axonal neuropathy. In the MRI on T2- and T2*-weighted images, there are hypointense lesions in the globus palidus and substantia nigra corresponding to iron accumulation.

Aceruloplasminemia: an update

Aceruloplasminemia is an inherited neurodegenerative disorder involving "neurodegeneration with brain iron accumulation," which is caused by genetic defects in the ceruloplasmin gene. Ceruloplasmin is a multicopper oxidase with ferroxidase activity that oxidizes ferrous iron following its transfer to extracellular transferrin. In the central nervous system, a glycosylphosphatidylinositol-linked ceruloplasmin bound to the cell membranes was found to be the major isoform of this protein. Aceruloplasminemia is characterized by diabetes, retinal degeneration, and progressive neurological symptoms, including extrapyramidal symptoms, ataxia, and dementia. Clinical and pathological studies and investigations of cell culture and murine models revealed that there is an iron-mediated cellular radical injury caused by a marked accumulation of iron in the affected parenchymal tissues. The aim of this chapter is to provide an overview of not only the clinical features, genetic and molecular pathogenesis, and treatment of aceruloplasminemia but also the biological and physiological features of iron metabolism.

Pantothenate kinase-associated neurodegeneration (PKAN) and PLA2G6-associated neurodegeneration (PLAN): review of two major neurodegeneration with brain iron accumulation (NBIA) phenotypes

Neurodegeneration with brain iron accumulation (NBIA) comprises a heterogeneous group of disorders characterized by the presence of radiologically discernible high brain iron, particularly within the basal ganglia. A number of childhood NBIA syndromes are described, of which two of the major subtypes are pantothenate kinase-associated neurodegeneration (PKAN) and PLA2G6-associated neurodegeneration (PLAN). PKAN and PLAN are autosomal recessive NBIA disorders due to mutations in PANK2 and PLA2G6, respectively. Presentation is usually in childhood, with features of neurological regression and motor dysfunction. In both PKAN and PLAN, a number of classical and atypical phenotypes are reported. In this chapter, we describe the clinical, radiological, and genetic features of these two disorders and also discuss the pathophysiological mechanisms postulated to play a role in disease pathogenesis.