Chronic progressive external ophthalmoplegia: MR spectroscopy and MR diffusion studies in the brain

Early-onset ophthalmoplegia, cervical dyskinesia, and lower extremity weakness due to partial deletion of chromosome 16: A case report

BACKGROUND

We explored the genotype-phenotype correlation of the novel deletion 16p13.2p12.3 in an 8-year-old child with progressive total ophthalmoplegia, cervical dyskinesia, and lower limb weakness by comparing the patient’s clinical features with previously reported data on adjacent copy number variation (CNV) regions.

CASE SUMMARY

Specifically, we first performed whole-exome sequencing, CNV-sequencing, and mitochondrial genome sequencing on the patient and his parents, then applied “MitoExome” (the entire mitochondrial genome and exons of nuclear genes encoding the mitochondrial proteome) analysis to screen for genetic mitochondrial diseases. We identified a de novo 7.23 Mb deletion, covering 16p13.2p12.3, by both whole-exome sequencing and CNV sequencing. We also detected 16p13.11 in the deleted region, which is the recurrent distinct region associated with neurodevelopmental disorder. However, the patient only displayed features of progressive total ophthalmoplegia, cervical dyskinesia, and weakness in his lower limbs without neurodevelopmental disorder. The “MitoExome” sequencing was negative. Brain magnetic resonance imaging revealed non-specific sporadic changes in the occipital parietal lobe and basal ganglia.

CONCLUSION

Taken together, these results indicated that 16p13.2p12.3 deletion causes a syndrome with the phenotype of early-onset total ophthalmoplegia. The “MitoExome” analysis is powerful for the differential diagnosis of mitochondrial diseases. We report a novel copy number variant in this case, but further confirmation is required.

Ophthalmoplegia in Mitochondrial Disease

PURPOSE

To evaluate the classification, diagnosis, and natural course of ophthalmoplegia associated with mitochondrial disease.

MATERIALS AND METHODS

Among 372 patients with mitochondrial disease who visited our hospital between January 2006 and January 2016, 21 patients with ophthalmoplegia were retrospectively identified. Inclusion criteria included onset before 20 years of age, pigmentary retinopathy, and cardiac involvement. The 16 patients who were finally included in the study were divided into three groups according to disease type: Kearns-Sayre syndrome (KSS), KSS-like, and chronic progressive external ophthalmoplegia (CPEO).

RESULTS

The prevalences of clinical findings were as follows: ptosis and retinopathy, both over 80%; myopathy, including extraocular muscles, 75%; lactic acidosis, 71%; and elevated levels of serum creatine kinase, 47%. Half of the patients had normal magnetic resonance imaging findings. A biochemical enzyme assay revealed mitochondrial respiratory chain complex I defect as the most common (50%). The prevalence of abnormal muscle findings in light or electron microscopic examinations was 50% each, while that of large-scale mitochondrial DNA (mtDNA) deletions in a gene study was 25%. We compared the KSS and KSS-like groups with the CPEO patient group, which showed pigmentary retinopathy (p<0.001), cardiac conduction disease (p=0.013), and large-scale mtDNA deletions (p=0.038). KSS and KSS-like groups also had gastrointestinal tract disorders such as abnormal gastrointestinal motility (p=0.013) unlike the CPEO group.

CONCLUSION

Patients with KSS had gastrointestinal symptoms, which may indicate another aspect of systemic involvement. The presence of large-scale mtDNA deletions was an objective diagnostic factor for KSS and a gene study may be helpful for evaluating patients with KSS.

Mitochondrial mutations in 12S rRNA and 16S rRNA presenting as chronic progressive external ophthalmoplegia (CPEO) plus: A case report

RATIONALE

Chronic progressive external ophthalmoplegia (CPEO) is a classical mitochondrial ocular disorder characterized by bilateral progressive ptosis and ophthalmoplegia. Kearns -Sayre syndrome (KSS) is a multisystem disorder with PEO, cardiac conduction block, and pigmentary retinopathy. A few individuals with CPEO have other manifestations of KSS, but do not meet all the clinical diagnosis criteria, and this is called "CPEO plus."

PATIENT CONCERNS

We report a 48-year-old woman exhibiting limb weakness, ptosis, ophthalmoparesis, and cerebellar dysfunctions.

DIAGNOSES

The patient was diagnosed as exhibiting CPEO plus syndrome.

INTERVENTIONS

The patient underwent clinical, genetic, histological, and histochemical analysis. She was treated orally with CoQ10, vitamin Bs, L-carnitine, and vitamin E.

OUTCOMES

The patient's serum creatine kinase levels, electrocardiography, and nerve conduction study results were normal; an electromyogram revealed myopathic findings. Magnetic resonance imaging showed global brain atrophy, particularly in the brainstem and cerebellum areas. A muscle biopsy showed the presence of abundant ragged red fibers. Sequencing of the mitochondrial DNA from the skeletal muscle biopsy revealed C960del mutation in 12S rRNA and homozygous mutation C2835T in 16S rRNA. She took medicines on schedule, the clinical features were similar as 2 years ago.

LESSONS

This is the first report of 2 rRNA mutations in a patient with MRI findings showing global brain atrophy, particularly in brainstem and cerebellum areas. Early recognition and appropriate treatment is crucial. This case highlights the cerebellar ataxia can occur in CPEO plus.

Cerebral Manifestations of Mitochondrial Disorders

This review aims at summarizing and discussing previous and recent findings concerning the cerebral manifestations of mitochondrial disorders (MIDs). MIDs frequently present as mitochondrial multiorgan disorder syndrome (MIMODS) either already at onset or later in the course. After the muscle, the brain is the organ second most frequently affected in MIMODS. Cerebral manifestations of MIDs are variable and may present with or without a lesion on imaging or functional studies, but there can be imaging/functional lesions without clinical manifestations. The most well-known cerebral manifestations of MIDs include stroke-like episodes, epilepsy, headache, ataxia, movement disorders, hypopituitarism, muscle weakness, psychiatric abnormalities, nystagmus, white and gray matter lesions, atrophy, basal ganglia calcification, and hypometabolism on 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron-emission tomography. For most MIDs, only symptomatic therapy is currently available. Symptomatic treatment should be supplemented by vitamins, cofactors, and antioxidants. In conclusion, cerebral manifestations of MIDs need to be recognized and appropriately managed because they strongly determine the outcome of MID patients.

Lactate and its many faces

BACKGROUND

Lactate is traditionally seen as a marker of ischemia and a waste product of anaerobic glycolysis. In the last thirty years a more beneficial side of lactate as an alternative 'glucose sparing' fuel has been demonstrated. However, the translation of these growing insights to clinical practice seems to appear with great delay.

METHODS

A review of the literature was performed, focusing on glucose and lactate in relation to cerebral energy metabolism, in the context of four typical clinical situations, namely (transient states of) low glucose availability for the brain due to hypoglycemia, combined with high blood lactate concentrations; permanent neuroglycopenia; lactic acidosis in mitochondrial disorders; and ischemic as well as traumatic brain injury.

RESULTS

Lactate is thought to be an alternative fuel in the brain of patients with glucose transporter type 1 deficiency syndrome and glycogen storage disease, and it has been demonstrated that lactate might have a protective role in ischemic and traumatic brain injury.

CONCLUSION

Lactate has an apparently largely ignored, but potential beneficial role in the clinical management of several neurologic disorders.

In Vivo NMR Studies of the Brain with Hereditary or Acquired Metabolic Disorders

Metabolic disorders, whether hereditary or acquired, affect the brain, and abnormalities of the brain are related to cellular integrity; particularly in regard to neurons and astrocytes as well as interactions between them. Metabolic disturbances lead to alterations in cellular function as well as microscopic and macroscopic structural changes in the brain with diabetes, the most typical example of metabolic disorders, and a number of hereditary metabolic disorders. Alternatively, cellular dysfunction and degeneration of the brain lead to metabolic disturbances in hereditary neurological disorders with neurodegeneration. Nuclear magnetic resonance (NMR) techniques allow us to assess a range of pathophysiological changes of the brain in vivo. For example, magnetic resonance spectroscopy detects alterations in brain metabolism and energetics. Physiological magnetic resonance imaging (MRI) detects accompanying changes in cerebral blood flow related to neurovascular coupling. Diffusion and T1/T2-weighted MRI detect microscopic and macroscopic changes of the brain structure. This review summarizes current NMR findings of functional, physiological and biochemical alterations within a number of hereditary and acquired metabolic disorders in both animal models and humans. The global view of the impact of these metabolic disorders on the brain may be useful in identifying the unique and/or general patterns of abnormalities in the living brain related to the pathophysiology of the diseases, and identifying future fields of inquiry.

Aberrant synthesis of ATP synthase resulting from a novel deletion in mitochondrial DNA in an African patient with progressive external ophthalmoplegia

A young, adult, African male patient presented with progressive proximal muscle weakness, external ophthalmoplegia and ptosis, as well as cardiac conduction abnormalities resembling Kearns-Sayre syndrome (KSS). Magnetic resonance imaging (MRI) of the brain revealed normal basal ganglia but bilateral well-circumscribed lesions in the cerebellar peduncles. Enzyme deficiencies in oxidative phosphorylation (OXPHOS) complexes I, IV and V was measured in muscle tissue. Blue native polyacrylamide gel electrophoresis (BN-PAGE) confirmed decreased protein content and activity of these complexes and revealed the presence of two catalytically active complex V sub-complexes. Upon investigation by molecular genetics, the mitochondrial DNA (mtDNA) copy number was found to be elevated and a novel deletion of 3431 bp was found in 80% of muscle mtDNA between positions 7115 and 10546, flanked by a 5 bp direct repeat sequence. In addition, it could also be concluded that the absence of mtDNA-encoded ATPase6 and ATPase8 genes in this patient clearly resulted in aberrant synthesis of ATP synthase.

The neuro-ophthalmology of mitochondrial disease

Mitochondrial diseases frequently manifest neuro-ophthalmologic symptoms and signs. Because of the predilection of mitochondrial disorders to involve the optic nerves, extraocular muscles, retina, and even the retrochiasmal visual pathways, the ophthalmologist is often the first physician to be consulted. Disorders caused by mitochondrial dysfunction can result from abnormalities in either the mitochondrial DNA or in nuclear genes which encode mitochondrial proteins. Inheritance of these mutations will follow patterns specific to their somatic or mitochondrial genetics. Genotype-phenotype correlations are inconstant, and considerable overlap may occur among these syndromes. The diagnostic approach to the patient with suspected mitochondrial disease entails a detailed personal and family history, careful ophthalmic, neurologic, and systemic examination, directed investigations, and attention to potentially life-threatening sequelae. Although curative treatments for mitochondrial disorders are currently lacking, exciting research advances are being made, particularly in the area of gene therapy. Leber hereditary optic neuropathy, with its window of opportunity for timely intervention and its accessibility to directed therapy, offers a unique model to study future therapeutic interventions. Most patients and their relatives benefit from informed genetic counseling.

MR spectroscopy of the brain in Leigh syndrome

Brain magnetic resonance spectroscopy in two patients with Leigh syndrome revealed the presence of lactate in gray and white matter brain tissue and relatively high choline levels in the white matter. The latter observation, most probably related to an ongoing demyelination process, underlines specific involvement of white matter metabolism in Leigh syndrome even in cases without involvement of the white matter as visualized on MRI. Magnetic resonance spectroscopy might thus be of help in differentiating Leigh syndrome from a range of other mitochondrial diseases, such as ophthalmoplegia and Kearns-Sayre syndrome, showing lack of lactate in brain tissues appearing normal on MRI.