Leigh syndrome and partial deficit of cytochrome c oxidase associated with epilepsia partialis continua

The molecular and cellular basis of copper dysregulation and its relationship with human pathologies

Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu⁺ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.

Epilepsy in Leigh Syndrome With Mitochondrial DNA Mutations

Background: Leigh syndrome is a mitochondrial cytopathy that presents as a neurodegenerative disease with apparent manifestation in the central nervous system. The aim of the present study was to describe its dominant neurological clinical features and analyze data related to epilepsy in Leigh syndrome accompanied by a mitochondrial DNA mutation.

Methods: Whole mitochondrial sequencing was performed on 125 patients clinically suspected of Leigh syndrome. Among them, 25 patients were identified to have mitochondrial DNA associated Leigh syndrome. Electroencephalography (EEG) findings, semiology, brain imaging findings, and biochemical results, were evaluated. We also compared brain magnetic resonance imaging findings and biochemical features in patients with Leigh syndrome based on the presence of epilepsy.

Results: Clinical seizures were observed in 14 out of 25 enrolled patients (56%), with focal seizures being the most common type (6/14, 42.8%). All patients were found to have slow and disorganized background neural activity while eight exhibited epileptic discharges on EEG. Mutations at base pairs 10,191 and 8,993 were revealed in a relatively larger number of patients of Leigh syndrome with epilepsy. The presence of gastrointestinal symptoms was significantly more frequent in the epilepsy group (P = 0.042). Diffuse cerebral atrophy was significantly increased (P = 0.042) and cortex signal abnormalities were also increased (P = 0.033) in the epilepsy group.

Conclusions: Patients with Leigh syndrome and mitochondrial DNA mutations had a high proportion of central nervous system comorbidities, though the prevalence of epilepsy in this population was not particularly high. Various types of seizure and EEG findings are common in those with Leigh syndrome. Future imaging studies involving more patients and proper mitochondrial DNA mutation analyses are needed to further evaluate the natural course of Leigh syndrome with epilepsy.

Mitochondrial epilepsy in pediatric and adult patients

Few data are available about the difference between epilepsy in pediatric mitochondrial disorders (MIDs) and adult MIDs. This review focuses on the differences between pediatric and adult mitochondrial epilepsy with regard to seizure type, seizure frequency, and underlying MID. A literature search via Pubmed using the keywords 'mitochondrial', 'epilepsy', 'seizures', 'adult', 'pediatric', and all MID acronyms, was carried out. Frequency of mitochondrial epilepsy strongly depends on the type of MID included and is higher in pediatric compared to adult patients. In pediatric patients, mitochondrial epilepsy is more frequent due to mutations in nDNA-located than mtDNA-located genes and vice versa in adults. In pediatric patients, mitochondrial epilepsy is associated with a syndromic phenotype in half of the patients and in adults more frequently with a non-syndromic phenotype. In pediatric patients, focal seizures are more frequent than generalized seizures and vice versa in adults. Electro-clinical syndromes are more frequent in pediatric MIDs compared to adult MIDs. Differences between pediatric and adult mitochondrial epilepsy concern the onset of epilepsy, frequency of epilepsy, seizure type, type of electro-clinical syndrome, frequency of syndromic versus non-syndromic MIDs, and the outcome. To optimize management of mitochondrial epilepsy, it is essential to differentiate between early and late-onset forms.

The neurologic manifestations of mitochondrial disease

The nervous system contains some of the body's most metabolically demanding cells that are highly dependent on ATP produced via mitochondrial oxidative phosphorylation. Thus, the neurological system is consistently involved in patients with mitochondrial disease. Symptoms differ depending on the part of the nervous system affected. Although almost any neurological symptom can be due to mitochondrial disease, there are select symptoms that are more suggestive of a mitochondrial problem. Certain symptoms that have become sine qua non with underlying mitochondrial cytopathies can serve as diagnostic "red-flags." Here, the typical and atypical presentations of mitochondrial disease in the nervous system are reviewed, focusing on "red flag" neurological symptoms as well as associated symptoms that can occur in, but are not specific to, mitochondrial disease. The multitudes of mitochondrial syndromes are not reviewed in-depth, though a select few are discussed in some detail.

The uncommon causes of status epilepticus: a systematic review

This paper reports the first systematic review of uncommon causes of status epilepticus reported in the literature between 1990 and 2008. Uncommon causes are defined as those not listed in the main epidemiological studies of status epilepticus. 181 causes were identified. These were easily categorised into 5 specific aetiological categories: immunological disorders, mitochondrial disorders, infectious diseases, genetic disorders and drugs/toxins. A sixth category of 'other causes' has also been included. Knowledge of these causes is important for clinical management and treatment, and also for a better understanding of the pathophysiology of status epilepticus.

POLG DNA testing as an emerging standard of care before instituting valproic acid therapy for pediatric seizure disorders

PURPOSE

To review our clinical experience and determine if there are appropriate signs and symptoms to consider POLG sequencing prior to valproic acid (VPA) dosing in patients with seizures.

METHODS

Four patients who developed VPA-induced hepatotoxicity were examined for POLG sequence variations. A subsequent chart review was used to describe clinical course prior to and after VPA dosing.

RESULTS

Four patients of multiple different ethnicities, age 3-18 years, developed VPA-induced hepatotoxicity. All were given VPA due to intractable partial seizures. Three of the patients had developed epilepsia partialis continua. The time from VPA exposure to liver failure was between 2 and 3 months. Liver failure was reversible in one patient. Molecular studies revealed homozygous p.R597W or p.A467T mutations in two patients. The other two patients showed compound heterozygous mutations, p.A467T/p.Q68X and p.L83P/p.G888S. Clinical findings and POLG mutations were diagnostic of Alpers-Huttenlocher syndrome.

CONCLUSION

Our cases underscore several important findings: POLG mutations have been observed in every ethnic group studied to date; early predominance of epileptiform discharges over the occipital region is common in POLG-induced epilepsy; the EEG and MRI findings varying between patients and stages of the disease; and VPA dosing at any stage of Alpers-Huttenlocher syndrome can precipitate liver failure. Our data support an emerging proposal that POLG gene testing should be considered in any child or adolescent who presents or develops intractable seizures with or without status epilepticus or epilepsia partialis continua, particularly when there is a history of psychomotor regression.

Epilepsia partialis continua associated with widespread gliomatosis cerebri

We report an uncommon association of intractable epilepsia partialis continua that was the main presentation of widespread gliomatosis cerebri in two females. Both children had a preceding prolonged secondary generalized seizure 2-4 months before the evolution of epilepsia partialis continua, including recurrent clusters of left-sided myoclonic twitching and sensory impairment. During these events, the children remained fully alert. These seizures were corroborated by prolonged focal epileptic spike/wave discharges evident on the electroencephalograms. Cerebral magnetic resonance imaging in the first patient demonstrated a wide area of increasing signals over the right frontocentral regions, along with diffuse cortical-subcortical infiltration impinging on the left hemisphere. In the second patient a cortical lesion was suspected. Evaluation for Rasmussen's encephalitis, focal cortical dysplasia, or a gliomatous process was conducted; the patients underwent a stereotactic brain biopsy in which the histologic findings were compatible with gliomatosis cerebri with diffuse widespread infiltration of glioma cells with no constitution of a circumscribed tumor mass. The first patient was treated with cranial radiation, chemotherapy, steroids, and combined antiepileptic therapy. The focal seizures gradually but markedly decreased in frequency, and sensory impairment abated within 18 months after establishment of the diagnosis and ensuing therapy. Cognition remains intact. The second female died 2 years after presentation despite massive chemotherapy and antiepileptic medications. Although rare, gliomatosis cerebri should be taken into account in the differential diagnosis of epilepsia partialis continua in children to facilitate a rapid diagnosis and initiation of prompt treatment of this rare disorder that may respond to a concurrent effective combination of cranial radiation, chemotherapy, and antiepileptic medications.

Leigh disease: clinical, neuroradiologic, and biochemical study of three new cases with cytochrome c oxidase deficiency

Three cases of Leigh disease are described. In all three, symptoms began in the first months of life, with muscle hypotonia, lactic acidosis, and psychomotor delay. The diagnosis was made on the basis of the clinical characteristics, biochemical abnormalities, and typical brain magnetic resonance imaging with symmetric lesions suggesting bilateral necrosis at the level of the basal ganglia and of the midbrain. Cytochrome c oxidase (complex IV of the mitochondrial respiratory chain) deficiency was demonstrated in muscle tissue in all patients and confirmed in skin fibroblasts in patient 3. A genetic heterogeneity was present in these patients since only one had a SURF-1 gene mutation. The clinical, biochemical, and neuroradiologic aspects are discussed. Finally, the finding of facial dysmorphisms in the cytochrome c oxidase deficiency observed in one of the described cases is of extreme interest; to our knowledge, this association has never been reported in the literature.

Creutzfeldt-Jakob syndrome presenting as epilepsia partialis continua

Creutzfeldt-Jakob disease (CJD) is an uncommon rapidly progressive neurological disorder which can have protean clinical presentations. We report an autopsy-proven case of CJD presenting initially as epilepsia partialis continua but then developing the typical clinical features of CJD over several weeks. CJD should be considered in the differential diagnosis of new onset epilepsia partialis continua in adults.

Epilepsia partialis continua (Koshevnikov): a preliminary case report

We report on the preliminary clinical and electrophysiological aspects of an in-patient possibly presenting epilepsia partialis continua (Koshevnikov). We discuss the different etiologies and emphasize on the possible idiopathic form in this case.

Evidence that Alpers-Huttenlocher syndrome could be a mitochondrial disease

We report an 11-year-old boy with a slight developmental delay and epilepsy. After he was placed on valproate, he developed hepatic failure and increasing neurologic symptoms, including epilepsia partialis continua, and died. Autopsy findings in liver and cerebrum were consistent with progressive neuronal degeneration of childhood with liver disease, also called Alpers-Huttenlocher syndrome. Ragged red fibers and cytochrome c oxidase negative fibers were present in muscle. These results suggest that Alpers-Huttenlocher syndrome, at least in some patients, is a mitochondrial disease.

Epilepsia partialis continua associated with a homoplasmic mitochondrial tRNA(Ser(UCN)) mutation

Epilepsia partialis continua (EPC) is a rare epileptic syndrome characterized by continuous focal seizures. We report on a 16-year-old girl who died of prolonged pharmacoresistant EPC in whom we identified a 7472insC mutation within the mitochondrial transfer ribonucleic acid (tRNA)(ser(UCN)). Additional symptoms included ataxia, lactic acidosis, myopathy, sensorineural hearing loss, severe headaches, and mental retardation. Quantification revealed 100% mutant mitochondrial DNA (mtDNA) in the patient, 4% in her mother, and none in her half-sister. This highly skewed mtDNA distribution is most improbable (approximately 3 x 10(-30)) if only explained by random genetic drift. Clustering of dysfunctional mitochondria and replicatory advantage of mutant mtDNA may play a role in the rapid segregation towards homoplasmy within one generation.

The role of clinical neurophysiology in the management of epilepsy

Clinical neurophysiologic studies have an important role in the diagnosis and management of the patient with epilepsy. Epilepsy is a clinical diagnosis and the EEG is an important adjunct used to differentiate epileptic seizures from nonepileptic events, refine the diagnosis of epilepsy into specific seizure types and epileptic syndromes, and provide a measure of brain function. The value of the EEG is highly dependent on the clinical context in which it is being applied. In some epilepsies the interictal EEG may be diagnostic whereas in others an ictal recording may be necessary to obtain a specific diagnosis. Both the interictal and ictal EEG characteristics vary with specific seizure types and epilepsies and are described in detail in this review. The usefulness of the EEG in the management of epilepsy and in aiding in the decision to discontinue antiepileptic therapy is also discussed.

Leigh syndrome, cytochrome C oxidase deficiency and hypsarrhythmia with infantile spasms

A rare patient with infantile spasms, hypsarrhythmia, cytochrome c oxidase deficiency and Leigh syndrome is reported. Although rare, infantile spasms and Leigh syndrome may occur simultaneously. Leigh syndrome should be included in the differential diagnosis of infantile spasms.