Migrating focal seizures during infancy: a case report and pathologic study

Two Patients With KCNT1-Related Epilepsy Responding to Phenobarbital and Potassium Bromide

KCNT1 encodes a sodium-activated potassium channel highly expressed in the brain, regulating hyperpolarization following repetitive firing. Mutations in KCNT1 were originally implicated in autosomal-dominant nocturnal frontal lobe epilepsy and epilepsy of infancy with migrating focal seizures. It is now known that there is variability in phenotypic expression and incomplete penetrance. We describe 2 patients with KCNT1-related epilepsy, one with epilepsy of infancy with migrating focal seizures and one with multifocal epilepsy. As most patients with KCNT1 variants have treatment-resistant epilepsy, drugs that specifically target the KCNT1 channel have been of great interest. Quinidine, a broad-spectrum potassium channel blocker, has shown promise; however, clinical trial results have been variable. Our patient with epilepsy of infancy with migrating focal seizures did not respond to a trial of quinidine at 6 weeks of age-one of the earliest reported quinidine trials in the literature for KCNT1-related epilepsy. This indicates that timing of treatment and response may not be related. Both patients responded to high-dose phenobarbital. The patient with epilepsy of infancy with migrating focal seizures also had a significant reduction in seizures with potassium bromide (KBr). Our data suggest that alternative therapies to quinidine should be considered as a therapeutic option for patients with KCNT1-related epilepsy. Although improved seizure control led to parent-reported improvements in neurodevelopment, it is unknown if phenobarbital and KBr impact the overall developmental trajectory of patients with KCNT1-related epilepsy. Further multicenter longitudinal studies are required.

KCNT1 epilepsy with migrating focal seizures shows a temporal sequence with poor outcome, high mortality and SUDEP

Data on KCNT1 epilepsy of infancy with migrating focal seizures are heterogeneous and incomplete. Kuchenbuch et al. refine the syndrome phenotype, showing a three-step temporal sequence, poor prognosis with acquired microcephaly, high prevalence of extra-neurological manifestations and early mortality, particularly due to SUDEP. Refining the electro-clinical spectrum should facilitate early diagnosis.

Clinical management of epileptic encephalopathies of childhood and infancy

Epileptic encephalopathies represent a group of devastating epileptic disorders that appear early in life and are characterized by pharmacoresistant generalized or focal seizures, persistent severe EEG abnormalities, and cognitive dysfunction or decline. The ictal and interictal epileptic discharges are age-specific and are either the main cause or contribute to cognitive deterioration in the idiopathic or symptomatic group respectively. Despite choosing the most appropriate anti-seizure drugs for the seizure-type and syndrome the results are often disappointing and polytherapy and/or alternative therapy becomes unavoidable. In those cases, consideration should be given to the quality of life of the child and carers. In this review we will discuss the clinical and EEG characteristics, evolution and management of age-related epileptic encephalopathies, recognized by the International League Against Epilepsy.

Potassium bromide for treatment of malignant migrating partial seizures in infancy

BACKGROUND

The syndrome of malignant migrating partial seizures in infancy is a rare epileptic syndrome with a devastating course characterized by early onset of continuous pharmacoresistent multifocal seizures arising from multiple independent sites of both hemispheres with unknown etiology.

PATIENT

A 2-month-old boy with the characteristic clinical and electroencephalograph pattern of migrating partial seizures in infancy was treated with potassium bromide. His seizures were unresponsive to the conventional and new generation antiepileptic drugs.

RESULTS

The seizure frequency was reduced markedly with potassium bromide.

CONCLUSIONS

Potassium bromide, an old antiepileptic drug, is useful in the treatment of malignant migrating partial seizures in infancy.

Migrating partial seizures of infancy: expansion of the electroclinical, radiological and pathological disease spectrum

Migrating partial seizures of infancy, also known as epilepsy of infancy with migrating focal seizures, is a rare early infantile epileptic encephalopathy with poor prognosis, presenting with focal seizures in the first year of life. A national surveillance study was undertaken in conjunction with the British Paediatric Neurology Surveillance Unit to further define the clinical, pathological and molecular genetic features of this disorder. Fourteen children with migrating partial seizures of infancy were reported during the 2 year study period (estimated prevalence 0.11 per 100,000 children). The study has revealed that migrating partial seizures of infancy is associated with an expanded spectrum of clinical features (including severe gut dysmotility and a movement disorder) and electrographic features including hypsarrhythmia (associated with infantile spasms) and burst suppression. We also report novel brain imaging findings including delayed myelination with white matter hyperintensity on brain magnetic resonance imaging in one-third of the cohort, and decreased N-acetyl aspartate on magnetic resonance spectroscopy. Putaminal atrophy (on both magnetic resonance imaging and at post-mortem) was evident in one patient. Additional neuropathological findings included bilateral hippocampal gliosis and neuronal loss in two patients who had post-mortem examinations. Within this cohort, we identified two patients with mutations in the newly discovered KCNT1 gene. Comparative genomic hybridization array, SCN1A testing and genetic testing for other currently known early infantile epileptic encephalopathy genes (including PLCB1 and SLC25A22) was non-informative for the rest of the cohort.