Seizure Semiology, EEG, and Imaging Findings in Epilepsy Secondary to Mitochondrial Disease

A practical approach to in-hospital management of new-onset refractory status epilepticus/febrile infection related epilepsy syndrome

New-onset refractory status epilepticus (NORSE) is "a clinical presentation, not a specific diagnosis, in a patient without active epilepsy or other preexisting relevant neurological disorder, with new onset of refractory status epilepticus without a clear acute or active structural, toxic, or metabolic cause." Febrile infection related epilepsy syndrome (FIRES) is "a subcategory of NORSE that requires a prior febrile infection, with fever starting between 2 weeks and 24 h before the onset of refractory status epilepticus, with or without fever at the onset of status epilepticus." These apply to all ages. Extensive testing of blood and CSF for infectious, rheumatologic, and metabolic conditions, neuroimaging, EEG, autoimmune/paraneoplastic antibody evaluations, malignancy screen, genetic testing, and CSF metagenomics may reveal the etiology in some patients, while a significant proportion of patients' disease remains unexplained, known as NORSE of unknown etiology or cryptogenic NORSE. Seizures are refractory and usually super-refractory (i.e., persist despite 24 h of anesthesia), requiring a prolonged intensive care unit stay, often (but not always) with fair to poor outcomes. Management of seizures in the initial 24-48 h should be like any case of refractory status epilepticus. However, based on the published consensus recommendations, the first-line immunotherapy should begin within 72 h using steroids, intravenous immunoglobulins, or plasmapheresis. If there is no improvement, the ketogenic diet and second-line immunotherapy should start within seven days. Rituximab is recommended as the second-line treatment if there is a strong suggestion or proof of an antibody-mediated disease, while anakinra or tocilizumab are recommended for cryptogenic cases. Intensive motor and cognitive rehab are usually necessary after a prolonged hospital stay. Many patients will have pharmacoresistant epilepsy at discharge, and some may need continued immunologic treatments and an epilepsy surgery evaluation. Extensive research is in progress now via multinational consortia relating to the specific type(s) of inflammation involved, whether age and prior febrile illness affect this, and whether measuring and following serum and/or CSF cytokines can help determine the best treatment.

Stroke-like episodes in adult mitochondrial disease

Stroke-like episode is a paroxysmal neurological manifestation which affects a specific group of patients with mitochondrial disease. Focal-onset seizures, encephalopathy, and visual disturbances are prominent findings associated with stroke-like episodes, with a predilection for the posterior cerebral cortex. The most common cause of stroke-like episodes is the m.3243A>G variant in MT-TL1 gene followed by recessive POLG variants. This chapter aims to review the definition of stroke-like episode and delineate the clinical phenomenology, neuroimaging and EEG findings typically seen in patients. In addition, several lines of evidence supporting neuronal hyper-excitability as the key mechanism of stroke-like episodes are discussed. The management of stroke-like episodes should focus on aggressive seizure management and treatment for concomitant complications such as intestinal pseudo-obstruction. There is no robust evidence to prove the efficacy of l-arginine for both acute and prophylactic settings. Progressive brain atrophy and dementia are the sequalae of recurrent stroke-like episode, and the underlying genotype in part predicts prognosis.

Mitochondrial Epilepsy, a Challenge for Neurologists

Primary mitochondrial diseases are relatively common inborn errors of energy metabolism, with a combined prevalence of 1 in 4300. These disorders typically affect tissues with high energy requirements, including the brain. Epilepsy affects >1% of the worldwide population, making it one of the most common neurological illnesses; it may be the presenting feature of a mitochondrial disease, but is often part of a multisystem clinical presentation. The major genetic causes of mitochondrial epilepsy are mutations in mitochondrial DNA and in the nuclear-encoded gene POLG. Treatment of mitochondrial epilepsy may be challenging, often representing a poor prognostic feature. This narrative review will cover the most recent advances in the field of mitochondrial epilepsy, from pathophysiology and genetic etiologies to phenotype and treatment options.

Seizure Semiology, EEG, and Imaging Findings in Epilepsy Secondary to Mitochondrial Disease

Background: Identification of an underlying mitochondrial disorder can be challenging due to the significant phenotypic variability between and within specific disorders. Epilepsy can be a presenting symptom with several mitochondrial disorders. In this study, we evaluated clinical, electrophysiologic, and imaging features in patients with epilepsy and mitochondrial disorders to identify common features, which could aid in earlier identification of a mitochondrial etiology. Methods: This is a retrospective case series from January 2011 to December 2019 at a tertiary referral center of patients with epilepsy and a genetically confirmed diagnosis of a mitochondrial disorder. A total of 164 patients were reviewed with 20 patients fulfilling inclusion criteria. Results: A total of 20 patients (14 females, 6 males) aged 0.5-61 years with epilepsy and genetically confirmed mitochondrial disorders were identified. Status epilepticus occurred in 15 patients, with focal status epilepticus in 13 patients, including 9 patients with visual features. Abnormalities over the posterior cerebral regions were seen in 66% of ictal recordings and 44% of imaging studies. All the patients were on nutraceutical supplementation with no significant change in disease progression seen. At last follow-up, eight patients were deceased and the remainder had moderate-to-severe disability. Discussion: In this series of patients with epilepsy and mitochondrial disorders, we found increased propensity for seizures arising from the posterior cerebral regions. Over time, electroencephalogram (EEG) and imaging abnormalities increasingly occurred over the posterior cerebral regions. Focal seizures and focal status epilepticus with visual symptoms were common. Additional study is needed on nutraceutical supplementation in mitochondrial disorders.