1
|
Wang R, Li Y, Lin J, Sun C, Chen N, Xu W, Hu B, Liu X, Geng D, Yang L. Altered spontaneous brain activity at attack and remission stages in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS): Beyond stroke-like lesions. Mitochondrion 2020; 54:49-56. [DOI: 10.1016/j.mito.2020.07.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 05/29/2020] [Accepted: 07/08/2020] [Indexed: 12/24/2022]
|
2
|
Finsterer J. Mitochondrial metabolic stroke: Phenotype and genetics of stroke-like episodes. J Neurol Sci 2019; 400:135-141. [PMID: 30946993 DOI: 10.1016/j.jns.2019.03.021] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 03/21/2019] [Accepted: 03/22/2019] [Indexed: 02/07/2023]
Abstract
Stroke-like episodes (SLEs) are the hallmark of mitochondrial encephalopathy with lactic acidosis and stroke-like episode (MELAS) syndrome but rarely occur also in other specific or nonspecific mitochondrial disorders. Pathophysiologically, SLLs are most likely due to a regional disruption of the blood-brain barrier triggered by the underlying metabolic defect, epileptic activity, drugs, or other factors. SLEs manifest clinically with a plethora of cerebral manifestations, which not only include features typically seen in ischemic stroke, but also headache, epilepsy, ataxia, visual impairment, vomiting, and psychiatric abnormalities. The morphological correlate of a SLE is the stroke-like lesion (SLL), best visualised on multimodal MRI. In the acute stages, a SLL presents as vasogenic edema but may be mixed up with cytotoxic components. Additionally, SLLs are characterized by hyperperfusion on perfusion studies. In the chronic stage, SLLs present with a colorful picture before they completely disappear, or end up as white matter lesion, cyst, laminar cortical necrosis, focal atrophy, or as toenail sign. Treatment of SLLs is symptomatic and relies on recommendations by experts. Beneficial effects have been reported with nitric-oxide precursors, antiepileptic drugs, antioxidants, the ketogenic diet, and steroids. Lot of research is still needed to uncover the enigma SLE/SLL.
Collapse
Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Vienna, Austria.
| |
Collapse
|
3
|
Abstract
OBJECTIVES Because the central nervous system (CNS) is the second most frequently affected organ in mitochondrial disorders (MIDs) and since paediatric MIDs are increasingly recognised, it is important to know about the morphological CNS abnormalities on imaging in these patients. This review aims at summarising and discussing current knowledge and recent advances concerning CNS imaging abnormalities in paediatric MIDs. METHODS A systematic literature review was conducted. RESULTS The most relevant CNS abnormalities in paediatric MIDs on imaging include white and grey matter lesions, stroke-like lesions as the morphological equivalent of stroke-like episodes, cerebral atrophy, calcifications, optic atrophy, and lactacidosis. Because these CNS lesions may be seen with or without clinical manifestations, it is important to screen all MID patients for cerebral involvement. Some of these lesions may remain unchanged for years whereas others may be dynamic, either in the sense of progression or regression. Typical dynamic lesions are stroke-like lesions and grey matter lesions. Clinically relevant imaging techniques for visualisation of CNS abnormalities in paediatric MIDs are computed tomography, magnetic resonance (MR) imaging, MR spectroscopy, single-photon emission computed tomography, positron-emission tomography, and angiography. CONCLUSIONS CNS imaging in paediatric MIDs is important for diagnosing and monitoring CNS involvement. It also contributes to the understanding of the underlying pathomechanisms that lead to CNS involvement in MIDs.
Collapse
Affiliation(s)
| | - Sinda Zarrouk-Mahjoub
- University of Tunis, El Manar and Genomics Platform, Pasteur Institute of Tunis, Tunisia
| |
Collapse
|
4
|
Finsterer J, Zarrouk-Mahjoub S. MELAS can be psychiatric and neurological. eNeurologicalSci 2018; 11:3-4. [PMID: 29928708 PMCID: PMC6007055 DOI: 10.1016/j.ensci.2018.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 04/10/2018] [Indexed: 11/18/2022] Open
Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria
- Corresponding author at: Postfach 20, 1180 Vienna, Austria.
| | - Sinda Zarrouk-Mahjoub
- University of Tunis El Manar and Genomics Platform, Pasteur Institute of Tunis, Tunisia
| |
Collapse
|
5
|
Youssef AA, Speiser U, Schaefer J, Reichmann H, Richter N, Strasser RH, Quick S. Thinking beyond borders. Infective myocarditis on top of MELAS-cardiomyopathy first case description. Int J Cardiol 2016; 203:1020-1. [PMID: 26630629 DOI: 10.1016/j.ijcard.2015.10.054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 10/04/2015] [Indexed: 10/22/2022]
Affiliation(s)
- Akram A Youssef
- Technische Universität Dresden, Heart Center, University Hospital, Clinic of Internal Medicine and Cardiology, Germany
| | - Uwe Speiser
- Technische Universität Dresden, Heart Center, University Hospital, Clinic of Internal Medicine and Cardiology, Germany
| | - Jochen Schaefer
- Technische Universität Dresden, University Hospital, Department of Neurology, Germany
| | - Heinz Reichmann
- Technische Universität Dresden, University Hospital, Department of Neurology, Germany
| | - Nicole Richter
- Technische Universität Dresden, University Hospital, Department of Neurology, Germany
| | - Ruth H Strasser
- Technische Universität Dresden, Heart Center, University Hospital, Clinic of Internal Medicine and Cardiology, Germany
| | - Silvio Quick
- Technische Universität Dresden, Heart Center, University Hospital, Clinic of Internal Medicine and Cardiology, Germany.
| |
Collapse
|
6
|
Abstract
Imaging of central-nervous-system (CNS) abnormalities is important in patients with mitochondrial disorders (MCDs) since the CNS is the organ second most frequently affected in MCDs and some of them are potentially treatable. Clinically relevant imaging techniques for visualization of CNS abnormalities in MCDs are computed tomography, magnetic resonance imaging, and MR-spectroscopy. The CNS abnormalities in MCDs visualized by imaging techniques include stroke-like lesions with cytotoxic or vasogenic edema, laminar cortical necrosis, basal ganglia necrosis, focal or diffuse white matter lesions, focal or diffuse atrophy, intra-cerebral calcifications, cysts, lacunas, hypometabolisation, lactacidosis, hemorrhages, cerebral hypo- or hyperperfusion, intra-cerebral artery stenoses, or moyamoya syndrome. The CNS lesions may proceed with or without clinical manifestations, why neuroimaging should be routinely carried out in all MCDs to assess the degree of CNS involvement. Some of these lesions may remain unchanged for years, some may show contiguous spread and progression, but some may even disappear, spontaneously or in response to medication. Dynamics of Stroke-like lesions may be positively influenced by L-arginine, dichloracetate, steroids, edavarone, or antiepileptics. Symptomatic treatment of CNS abnormalities in MCD patients may positively influence their outcome.
Collapse
|
7
|
Joo JC, Seol MD, Yoon JW, Lee YS, Kim DK, Choi YH, Ahn HS, Cho WH. A Case of Myopathy, Encephalopathy, Lactic Acidosis and Stroke-Like Episodes (MELAS) Syndrome with Intracardiac Thrombus [corrected]. Korean Circ J 2013; 43:204-6. [PMID: 23613701 PMCID: PMC3629250 DOI: 10.4070/kcj.2013.43.3.204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/02/2012] [Accepted: 07/06/2012] [Indexed: 11/16/2022] Open
Abstract
Myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a multisystem clinical syndrome manifested by mitochondrial myopathy, encephalopathy, lactic acidosis and recurrent stroke-like episodes. A 27-year-old female with MELAS syndrome presented with cerebral infarction. Echocardiography revealed a thrombus attached to the apex of the hypertrophied left ventricle, with decreased systolic function. The embolism of the intracardiac thrombus might have been the cause of stroke. There should be more consideration given to the increased possibility of intracardiac thrombus formation when a MELAS patient with cardiac involvement is encountered.
Collapse
Affiliation(s)
- Jung-Chul Joo
- Sahmyook Medical Center Seoul Hospital, Seoul, Korea
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Tzoulis C, Bindoff LA. Acute mitochondrial encephalopathy reflects neuronal energy failure irrespective of which genome the genetic defect affects. Brain 2012; 135:3627-34. [PMID: 23065482 DOI: 10.1093/brain/aws223] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial dysfunction and disease may arise as a result of mutations in either the mitochondrial genome itself or nuclear encoded genes involved in mitochondrial homeostasis and function. Irrespective of which genome is affected, mitochondrial encephalopathies share clinical and biochemical features suggesting common pathophysiological pathways. Two common paradigms of mitochondrial encephalopathy are mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes caused by maternally transmitted mutations of mitochondrial DNA and mitochondrial spinocerebellar ataxia and epilepsy caused by recessively inherited mutations of the nuclear-encoded DNA polymerase gamma, which replicates and repairs the mitochondrial genome. We studied and compared the disease mechanisms involved in these two syndromes. Despite having different genetic origins, their pathophysiological pathways converge on one critical event, damage to the respiratory chain leading to insufficient energy to maintain cellular homeostasis. In the central nervous system, this appears to cause selective neuronal damage leading to the development of lesions that mimic ischaemic damage, but which lack evidence of decreased tissue perfusion. Although these stroke-like lesions may expand or regress dynamically, the critical factor that dictates prognosis is the presence of epilepsy. Epileptic seizures increase the energy requirements of the metabolically already compromised neurons establishing a vicious cycle resulting in worsening energy failure and neuronal death. We believe that it is this cycle of events that determines outcome and which provides us with a mechanistic structure to understand the pathophysiology of acute mitochondrial encephalopathies and plan future treatments.
Collapse
Affiliation(s)
- Charalampos Tzoulis
- Department of Neurology, Haukeland University Hospital, 5021 Bergen, Norway.
| | | |
Collapse
|
9
|
Lee SK, Kim J, Kim HD, Lee JS, Lee YM. Initial experiences with proton MR spectroscopy in treatment monitoring of mitochondrial encephalopathy. Yonsei Med J 2010; 51:672-5. [PMID: 20635440 PMCID: PMC2908880 DOI: 10.3349/ymj.2010.51.5.672] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE Mitochondrial encephalopathy (ME) is a rare disorder of energy metabolism. The disease course can roughly be evaluated by clinical findings. The purpose of this study was to evaluate metabolic spectral changes using proton MR spectroscopy (MRS), and to establish a way to monitor ME by neuroimaging. MATERIALS AND METHODS Proton MRS data were retrospectively reviewed in 12 patients with muscle biopsy-confirmed ME (M : F = 7 : 5, Mean age = 4.8 years). All received 1H-MRS initially and also after a ketogenic diet and mitochondrial disease treatment cocktail (follow up average was 10.2 months). Changes of N-acetylaspartate/ creatine (NAA/Cr) ratio, choline/creatine (Cho/Cr) ratio, and lactate peak in basal ganglia at 1.2 ppm were evaluated before and after treatment. Findings on conventional T2 weighted MR images were also evaluated. RESULTS On conventional MRI, increased basal ganglia T2 signal intensity was the most common finding with ME (n = 9, 75%), followed by diffuse cerebral atrophy (n = 8, 67%), T2 hyperintense lesions at pons and midbrain (n = 4, 33%), and brain atrophy (n = 2, 17%). Lactate peak was found in 4 patients; 2 had disappearance of the peak on follow up MRS. Quantitative analysis showed relative decrease of Cho/Cr ratio on follow up MRS (p = 0.0058, paired t-test, two-tailed). There was no significant change in NAA/Cr ratio. CONCLUSION MRS is a useful tool for monitoring disease progression or improvement in ME, and decrease or disappearance of lactate peak and reduction of Cho/Cr fraction were correlated well with improvement of clinical symptoms.
Collapse
Affiliation(s)
- Seung-Koo Lee
- Department of Radiology, Yonsei University College of Medicine, 250 Seongsan-ro, Seodaemun-gu, Seoul 120-752, Korea.
| | | | | | | | | |
Collapse
|
10
|
Tarnacka B, Szeszkowski W, Golebiowski M, Czlonkowska A. MR spectroscopy in monitoring the treatment of Wilson's disease patients. Mov Disord 2008; 23:1560-6. [DOI: 10.1002/mds.22163] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
|
11
|
Karkare K, Sinha S, Ravishankar S, Gayathri N, Yasha TC, Goyal MK, Vijayan J, Vanniarajan A, Thangaraj K, Taly AB. Epilepsia partialis continua in mitochondrial dysfunction: Interesting phenotypic and MRI observations. Ann Indian Acad Neurol 2008; 11:193-6. [PMID: 19893669 PMCID: PMC2771970 DOI: 10.4103/0972-2327.42942] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2008] [Revised: 06/23/2008] [Accepted: 06/24/2008] [Indexed: 11/07/2022] Open
Abstract
An 11-year-old girl manifested with photophobia, ptosis, external ophthalmoplegia, hypotonia, weakness of proximal limb muscles, hyporeflexia, and generalized seizures (six months). Her elder sister had had uncontrolled seizures and photophobia and died at seven years of age. In the patient, serum lactate was high (55 mg/dl). Muscle biopsy revealed characteristic ragged red and ragged blue fibers, diagnostic of mitochondrial cytopathy. Sequencing of the complete mitochondrial genome of the DNA obtained from the muscle biopsy of the patient did not show any characteristic mutation. Four months later, the girl was admitted with a one-week history of epilepsia partialis continua (EPC). EEG revealed Periodic Lateralized Epileptiform Discharges (PLEDs), once in 2-4 seconds, over the right temporo-occipital leads. MRI revealed signal change of right motor cortex, which had restricted diffusion. MR spectroscopy (MRS) from this region revealed lactate peak. EPC remained refractory to multiple anti-epileptic drugs, immuno-modulators, coenzyme-Q, and carnitine. This thought provoking report expands the spectrum of mitochondrial cytopathies.
Collapse
|
12
|
Saneto RP, Friedman SD, Shaw DWW. Neuroimaging of mitochondrial disease. Mitochondrion 2008; 8:396-413. [PMID: 18590986 DOI: 10.1016/j.mito.2008.05.003] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 05/11/2008] [Accepted: 05/14/2008] [Indexed: 10/22/2022]
Abstract
Mitochondrial disease represents a heterogeneous group of genetic disorders that require a variety of diagnostic tests for proper determination. Neuroimaging may play a significant role in diagnosis. The various modalities of nuclear magnetic resonance imaging (MRI) allow for multiple independent detection procedures that can give important anatomical and metabolic clues for diagnosis. The non-invasive nature of neuroimaging also allows for longitudinal studies. To date, no pathonmonic correlation between specific genetic defect and neuroimaging findings have been described. However, certain neuroimaging results can give important clues that a patient may have a mitochondrial disease. Conventional MRI may show deep gray structural abnormalities or stroke-like lesions that do not respect vascular territories. Chemical techniques such as proton magnetic resonance spectroscopy (MRS) may demonstrate high levels of lactate or succinate. When found, these results are suggestive of a mitochondrial disease. MRI and MRS studies may also show non-specific findings such as delayed myelination or non-specific leukodystrophy picture. However, in the context of other biochemical, structural, and clinical findings, even non-specific findings may support further diagnostic testing for potential mitochondrial disease. Once a diagnosis has been established, these non-invasive tools can also aid in following disease progression and evaluate the effects of therapeutic interventions.
Collapse
Affiliation(s)
- Russell P Saneto
- Division of Pediatric Neurology, Children's Hospital and Regional Medical Center/University of Washington, 4800 Sand Point Way NE, Seattle, WA 98105, USA.
| | | | | |
Collapse
|
13
|
Abstract
The central nervous system (CNS) is, after the peripheral nervous system, the second most frequently affected organ in mitochondrial disorders (MCDs). CNS involvement in MCDs is clinically heterogeneous, manifesting as epilepsy, stroke-like episodes, migraine, ataxia, spasticity, extrapyramidal abnormalities, bulbar dysfunction, psychiatric abnormalities, neuropsychological deficits, or hypophysial abnormalities. CNS involvement is found in syndromic and non-syndromic MCDs. Syndromic MCDs with CNS involvement include mitochondrial encephalomyopathy, lactacidosis, stroke-like episodes syndrome, myoclonic epilepsy and ragged red fibers syndrome, mitochondrial neuro-gastrointestinal encephalomyopathy syndrome, neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome, mitochondrial depletion syndrome, Kearns-Sayre syndrome, and Leigh syndrome, Leber's hereditary optic neuropathy, Friedreich's ataxia, and multiple systemic lipomatosis. As CNS involvement is often subclinical, the CNS including the spinal cord should be investigated even in the absence of overt clinical CNS manifestations. CNS investigations comprise the history, clinical neurological examination, neuropsychological tests, electroencephalogram, cerebral computed tomography scan, and magnetic resonance imaging. A spinal tap is indicated if there is episodic or permanent impaired consciousness or in case of cognitive decline. More sophisticated methods are required if the CNS is solely affected. Treatment of CNS manifestations in MCDs is symptomatic and focused on epilepsy, headache, lactacidosis, impaired consciousness, confusion, spasticity, extrapyramidal abnormalities, or depression. Valproate, carbamazepine, corticosteroids, acetyl salicylic acid, local and volatile anesthetics should be applied with caution. Avoiding certain drugs is often more beneficial than application of established, apparently indicated drugs.
Collapse
Affiliation(s)
- J Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria.
| |
Collapse
|
14
|
Abstract
The application of MR spectroscopy (MRS) in pediatric brain disorders yields valued information on pathologic processes, such as ischemia, demyelination, gliosis, and neurodegeneration. Because these processes manifest in inborn errors of metabolism, the purposes of this article are to (1) describe the spectral changes that are associated with the relatively common metabolic disorders, with summaries of known spectroscopic features of these disorders; (2) offer suggestions for recognition and distinction of disorders; and (3) provide general guidelines for MRS implementation. Although many conditions have a similar presentation, MRS offers valuable information for the individual patient in diagnosis and therapy when integrated fully into the clinical setting.
Collapse
Affiliation(s)
- Kim M Cecil
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
| |
Collapse
|
15
|
Möller HE, Kurlemann G, Pützler M, Wiedermann D, Hilbich T, Fiedler B. Magnetic resonance spectroscopy in patients with MELAS. J Neurol Sci 2004; 229-230:131-9. [PMID: 15760631 DOI: 10.1016/j.jns.2004.11.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Localized magnetic resonance spectroscopy (MRS) yields sensitive metabolic markers to provide insight into the pathophysiology of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) in vivo. Findings in full MELAS syndrome at 1H MRS of the brain typically include severely elevated lactate and reduced N-acetylaspartate, glutamate, myo-inositol, and total creatine concentrations in stroke-like lesions. Similar but less extreme alterations are also common in gray matter (GM) regions that appear normal at magnetic resonance imaging. Phosphorus spectroscopy of peripheral muscle permits investigation of the bioenergetic status. A decline of the phosphorylation potential indicates a low energy reserve at rest. Phosphocreatine resynthesis during post-exercise recovery is delayed pointing to reduced mitochondrial capacity. As MRS is inherently non-invasive, follow-up studies can be performed to assess treatment response quantitatively.
Collapse
Affiliation(s)
- Harald E Möller
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstrasse 1A, 04103 Leipzig, Germany.
| | | | | | | | | | | |
Collapse
|
16
|
Ulmer S, Flemming K, Hahn A, Stephani U, Jansen O. Detection of acute cytotoxic changes in progressive neuronal degeneration of childhood with liver disease (Alpers-Huttenlocher syndrome) using diffusion-weighted MRI and MR spectroscopy. J Comput Assist Tomogr 2002; 26:641-6. [PMID: 12218835 DOI: 10.1097/00004728-200207000-00030] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Alpers-Huttenlocher syndrome (AHS) is a rare mitochondrial disorder of childhood onset that is characterized by progressive encephalopathy and hepatopathy. MRI studies are rare and have not added substantial information to the pathogenesis of the encephalopathy. Diffusion-weighted MRI (DWI) and MR spectroscopy (MRS) were used in a patient with AHS during acute clinical deterioration and after improvement. DWI detected signal hyperintensity in several brain areas not restricted to any vascular territory. MRS revealed an unequivocal lactate peak and a reduced N-acetyl-aspartate-creatinine (NAA/Crea) ratio. DWI signal hyperintensity was correlated with neurologic symptoms and decreased after clinical improvement. Potentially reversible neuronal cytotoxic edema resulting from acute impairment of mitochondrial function is strongly suggested to be an important pathogenetic mechanism in AHS encephalopathy.
Collapse
Affiliation(s)
- Stephan Ulmer
- Section of Neuroradiology, Deparment of Neurosurgery, University Hospital, Kiel, Germany.
| | | | | | | | | |
Collapse
|
17
|
Abstract
There is an expanding understanding of primary genetic oxidative-phosphorylation disorders and the recognition of new multi-system clinical phenotypes in the energy metabolism diseases. Although initially recognized in association with mitochondrial DNA mutations, there is progress in the more laborious identification of nuclear DNA encoded genes relevant to mitochondrial structure and function. More pathogenic mitochondrial DNA and nuclear DNA mutations have been identified. Diagnosis of these disorders is often difficult and relies on a concurrence of findings, including recognition of a variety of clinical signs and symptoms, biochemical marker screening, electron transport chain enzyme measurements, and mitochondrial DNA or nuclear DNA mutation assay of genes relevant to mitochondrial structure, function or adenosine triphosphate metabolic pathways. Clinical diagnostic assessment now can be augmented by physiologic imaging techniques, including nuclear magnetic resonance spectroscopy and positron emission tomography. These capabilities should be increasingly helpful for studies of clinical progression and therapeutic intervention. Biologic studies, in families and patients, are beginning to address the factors of mitochondrial replication and segregation that underlie cellular/tissue heteroplasmy and clinical variability. Most epigenetic factors affecting organ-specific and phenotypic variability, however, remain to be elaborated.
Collapse
Affiliation(s)
- Katherine Sims
- Department of Neurology, Massachusetts General Hospital, Boston, 02129, USA
| | | |
Collapse
|