Leukoencephalopathies in Mitochondrial Disorders: Clinical and MRI Findings

Diffuse posterior leukoencephalopathy in MELAS without stroke-like episodes: A case report

RATIONALE

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is the most common subtype of mitochondrial encephalopathy. In the past, it was believed that most hereditary white matter lesions were lysosome storage disorders or peroxisome diseases. However, in recent years, white matter lesions have been increasingly regarded as a common feature of patients with mitochondrial diseases. In addition to stroke-like lesions, about half of the patients with MELAS reported white matter lesions in the brain.

PATIENT CONCERNS

Herein, we provide a case of A 48-year-old female who presented with episodic loss of consciousness with twitching of extremities. Previous medical history revealed 10 years of history of epilepsy, 10 years of history of diabetes, a history of hearing loss, and unknown etiology. Ancillary findings included brain magnetic fluid-attenuated inversion recovery showed symmetrical lesions in the bilateral parietal lobe with high signal intensity at the edge, and high signal intensity in the bilateral occipital lobe, paraventricular white matter, corona radiata, and the center of semiovale.

DIAGNOSES

Mitochondrial deoxyribonucleic acid gene sequencing returned A3243G point mutation and it supports the diagnosis of intracranial hypertension.

INTERVENTIONS

Considered the diagnosis of symptomatic epilepsy, the patient was treated with mechanical ventilation, midazolam, and levetiracetam, and the limb twitching symptoms were controlled. The patient was comatose, chronically bedridden, with gastrointestinal dysfunction, and was treated prophylactically with antibiotics against infection, parenteral nutrition, and other supportive measures. B vitamins, vitamin C, vitamin E, coenzyme Q10, and idebenone were given, and mechanical ventilation and midazolam were stopped after 8 days. He was discharged from the hospital on 30 days and continued symptomatic treatment with B-vitamins, vitamin C, vitamin E, coenzyme Q10, and idebenone, and antiepileptic treatment with levetiracetam, with outpatient follow-up.

OUTCOMES

No further seizures were recorded and the patient recovered well.

LESSONS

MELAS syndrome without stroke-like episodes of diffuse posterior cerebral white matter lesions is rare in clinical practice, and the possibility of MELAS syndrome should be considered in symmetric posterior cerebral white matter lesions.

Adult Onset Vanishing White Matter Disease: A Rare Case Report

Vanishing white matter disease (VWMD) is the most common childhood-onset inheritable progressive leukodystrophy disorder, which exclusively affects the white matter of the brain. It shows mutations in one of the five eukaryotic translation initiation factor 2B1-5 genes following an autosomal recessive pattern, of which eIF2B5 mutation is the most frequent. These genes play a vital role in the translation and regulation of protein synthesis and mutation in them leads to a dysregulation of the cellular stress response, which in particular disrupts myelination and affects oligodendrocytes and astrocytes while sparing the neurons. Stressful situations, for example, head trauma, sudden fright, acute psychological stress, or infection, provoke severe and rapid neurological deterioration. Although it is more common in childhood, we report a case of an adult presenting with signs and symptoms of VWMD, such as abusive behavior, emotional liability, and motor incoordination. To our knowledge, this is the first case of adult-onset VWMD in Maharashtra, India, confirmed by magnetic resonance imaging (MRI) of the brain.

Towards Central Nervous System Involvement in Adults with Hereditary Myopathies

There is increasing evidence of central nervous system involvement in numerous neuromuscular disorders primarily considered diseases of skeletal muscle. Our knowledge on cerebral affection in myopathies is expanding continuously due to a better understanding of the genetic background and underlying pathophysiological mechanisms. Intriguingly, there is a remarkable overlap of brain pathology in muscular diseases with pathomechanisms involved in neurodegenerative or neurodevelopmental disorders. A rapid progress in advanced neuroimaging techniques results in further detailed insight into structural and functional cerebral abnormalities. The spectrum of clinical manifestations is broad and includes movement disorders, neurovascular complications, paroxysmal neurological symptoms like migraine and epileptic seizures, but also behavioural abnormalities and cognitive dysfunction. Cerebral involvement implies a high socio-economic and personal burden in adult patients sometimes exceeding the everyday challenges associated with muscle weakness. It is especially important to clarify the nature and natural history of brain affection against the background of upcoming specific treatment regimen in hereditary myopathies that should address the brain as a secondary target. This review aims to highlight the character and extent of central nervous system involvement in patients with hereditary myopathies manifesting in adulthood, however also includes some childhood-onset diseases with brain abnormalities that transfer into adult neurological care.

The disappearance of white matter in an adult-onset disease: a case report

BACKGROUND

Vanishing white matter disease (VWMD) is one of the most prevalent hereditary white matter diseases in childhood, but it is increasingly recognised in adulthood with high phenotypic variation and severity.

CASE PRESENTATION

We report a case of an adult female presenting with emotional lability and cognitive impairment, in addition to progressive dystonia, ataxia, postural instability and recurrent falls. Magnetic resonance imaging (MRI) of the brain and genetic testing confirmed the diagnosis of VWMD.

CONCLUSIONS

VWMD has a broad clinical presentation in adulthood, and the age at onset of symptoms is one of its most important prognostic factors. It is crucial to recognize the pathognomonic MRI patterns and consider VWMD as a differential diagnosis when assessing patients presenting with psychiatric, cognitive and non-specific neurological symptoms.

Cystic Leucoencephalopathy in NDUFV1 Mutation

Complex I deficiency is one of the most common mitochondrial respiratory chain defect. This deficiency of oxidative phosphorylation results from mutation in nuclear and mitochondrial DNA. Mutations in NDUFV1 (Flavin binding subunit of Respiratory complex 1) results in neurological manifestations including Leigh syndrome and leucoencephalopathy. The authors report a one-year-old boy with history of regression of motor milestones following a trivial fall from the bed. His magnetic resonance imaging revealed diffuse, cystic leucoencephalopathy involving corpus callosum and periventricular white matter. Clinical features and radiological findings may resemble those of vanishing white matter disease. Next generation sequencing revealed likely compound heterozygous missense pathogenic variant in exon 8 of NDUFV1 gene [c.1156C > C/T (p.Arg386Cys)] and possibly novel splice site variation in intron 2 of NDUFV1 gene (c.155 + 1G > G/A). NDUFV1 related leucoencephalopathy must be considered among those presenting with sudden onset of motor regression with neuroimaging correlate of diffuse cystic leucodystrophy.

POLG-Associated Ataxia Presenting as a Fragile X Tremor/Ataxia Phenocopy Syndrome

Hyperintensities in the middle cerebellar peduncles (MCP), known as the MCP sign, and progressive late-onset ataxia constitute major characteristics of the fragile X tremor/ataxia syndrome (FXTAS). Here, we describe a 60-year-old male affected by ataxia due to biallelic mutations in the mitochondrial polymerase gamma (POLG) gene in which hyperintensities of the middle cerebellar peduncles (MCP) were found. The initial suspicion of FXTAS was however ruled out by a normal CGG expansion size in the FMR1 gene. We discuss the features of late-onset POLG-A as a phenocopy of FXTAS.

Mutation of the iron-sulfur cluster assembly gene IBA57 causes fatal infantile leukodystrophy

Leukodystrophies are a heterogeneous group of severe genetic neurodegenerative disorders. A multiple mitochondrial dysfunctions syndrome was found in an infant presenting with a progressive leukoencephalopathy. Homozygosity mapping, whole exome sequencing, and functional studies were used to define the underlying molecular defect. Respiratory chain studies in skeletal muscle isolated from the proband revealed a combined deficiency of complexes I and II. In addition, western blotting indicated lack of protein lipoylation. The combination of these findings was suggestive for a defect in the iron-sulfur (Fe/S) protein assembly pathway. SNP array identified loss of heterozygosity in large chromosomal regions, covering the NFU1 and BOLA3, and the IBA57 and ABCB10 candidate genes, in 2p15-p11.2 and 1q31.1-q42.13, respectively. A homozygous c.436C > T (p.Arg146Trp) variant was detected in IBA57 using whole exome sequencing. Complementation studies in a HeLa cell line depleted for IBA57 showed that the mutant protein with the semi-conservative amino acid exchange was unable to restore the biochemical phenotype indicating a loss-of-function mutation of IBA57. In conclusion, defects in the Fe/S protein assembly gene IBA57 can cause autosomal recessive neurodegeneration associated with progressive leukodystrophy and fatal outcome at young age. In the affected patient, the biochemical phenotype was characterized by a defect in the respiratory chain complexes I and II and a decrease in mitochondrial protein lipoylation, both resulting from impaired assembly of Fe/S clusters.

The role of brain MRI in mitochondrial neurogastrointestinal encephalomyopathy

Leukoencephalopathy is a hallmark of mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) a devastating disorder characterized by ptosis, ophthalmoparesis, gastrointestinal dysfunction and polyneuropathy. To characterize MNGIE-associated leukoencephalopathy and to correlate it with clinical, biochemical and molecular data, four MNGIE patients with heterogeneous clinical phenotypes (enteropathic arthritis, exercise intolerance, CIDP-like phenotype and typical presentation) were studied by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). Diffusion weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps were also obtained. In two patients we also investigated the role of brain MRI in monitoring the evolution of leukoencephalopathy by performing follow-up imaging studies at an interval of one and two years. The extension and distribution of leukoencephalopathy were not clearly linked with age, phenotype or disease severity, and did not seem to be related to TYMP mutations, enzyme activity or pyrimidine levels. In the studied patients MRS revealed reduced N-acetyl-aspartate and increased choline signals. Although DWI appeared normal in all patients but one, ADC maps always showed moderate increased diffusivity. Leukoencephalopathy worsened over a two-year period in two patients, regardless of the clinical course, indicating a lack of correlation between clinical phenotype, size and progression of white matter abnormalities during this period. Brain MRI should be considered a very useful tool to diagnose both classical and atypical MNGIE. Serial MRIs in untreated and treated MNGIE patients will help to establish whether the leukoencephalopathy is a reversible condition or not.

[Cavitary lesions in multiple sclerosis: multicenter study on twenty patients]

INTRODUCTION

Cavitary white matter changes are mainly described in leukodystrophies and especially in vanishing white matter disease. Large cavitary lesions are not typical for multiple sclerosis (MS).

METHODS

We studied MS patients with large cavitary brain lesions. Patient characteristics, disease onset/duration/subtype, expanded disability status scale (EDSS), mini mental state (MMS), vanishing white matter disease genetic analysis, and MRI characteristics of the cavitary lesions were analyzed.

RESULTS

Twenty patients were analyzed (6 men and 14 women). Mean age at disease onset was 37.6 (range 17-58). Mean disease duration was 10 years (range 2-20). Five patients had initial relapsing-remitting MS and nine patients had primary-progressive MS. Mean EDSS was 5.5 (range 2-8). Mean MMS was 20/30. Vanishing white matter disease genetic analysis was performed and negative in seven patients. Inferior corpus callosum lesions were seen in all patients with available sagittal FLAIR sequences. Cavitary lesions were strictly supratentorial, and located inside the diffuse leukoencephalopathy, with often a posterior predominance.

CONCLUSION

MS patients with large cavitary lesions seem to represent a MS subgroup, predominantly women, with relatively late disease onset, predominantly primary-progressive type, relatively high EDSS scores, and severe cognitive dysfunction.

Different stages of white matter changes in the original HDLS family revealed by advanced MRI techniques

BACKGROUND

The temporal evolution of white matter (WM) changes on MR examinations in hereditary diffuse leukoencephalopathy with spheroids (HDLS) is largely unknown. Our purpose was to investigate the evolution of these WM changes with diffusion weighted/tensor imaging (DWI/DTI) and MR Spectroscopy (MRS).

METHODS

A newly diagnosed patient with HDLS from the original Swedish family was followed prospectively with 5 MRI as well as DWI/DTI and MRS examinations during 16 months.

RESULTS

The DTI eigenvalues demonstrated changes that suggested early myelin and axonal disturbances in the normal appearing WM (NAWM). DWI/DTI showed a rim of decreased diffusion progressively expanding through the WM from the initial frontal periventricular zones, and indicated complete destruction of axons and myelin in the area behind the front. MRS findings were suggestive of axonal destruction in the NAWM.

CONCLUSION

We describe HDLS changes in three temporal stages of development corresponding to lesions outside, in the vicinity of, and behind a characteristic rim centrifugally progressing from the ventricular horns. The axonal disturbances indicated by MRS changes in the NAWM support a primary axonal degeneration, as proposed in the original HDLS report, rather than axonal degeneration secondary to demyelination. These findings could help in differential diagnosis of HDLS.

Adult-onset leukodystrophies from respiratory chain disorders: do they exist?

Respiratory chain disorders (RCDs) have been included in the differential diagnosis of adult-onset leukodystrophies. Here, we first report a 32-year-old female with an atypical, adult-onset, non-syndromic RCD due to a mitochondrial DNA deletion and manifesting as complicated ataxia. A 'leukodystrophic' pattern was found on brain MRI, but it was neither isolated nor predominant because of the presence of overt basal ganglia and infratentorial lesions, which led us to the proper diagnosis. Subsequently, we evaluated our series of patients with RCDs in order to verify whether a 'leukodystrophic' pattern with little or no involvement of deep grey structures and brainstem may be found in adult-onset RCDs, as reported in children. Among 52 patients with adult-onset RCDs, no case with a 'leukodystrophic' pattern was found, apart from three cases with a classical phenotype of mitochondrial neurogastrointestinal encephalopathy. In addition, no case of RCDs was found among six cases of adult-onset leukodystrophy of unknown origin and at least one feature suggestive of mitochondrial disease. The review of the literature was in agreement with these findings. Thus, we provide evidence that, unlike in children, RCDs should not be included in the differential diagnosis of adult-onset leukodystrophies, except when there are additional MRI findings or clinical features which unequivocally point towards a mitochondrial disorder.