Ictal single photon emission computed tomographic study of myoclonic absence seizures

Research progress on epilepsy with myoclonic absence

Epilepsy with myoclonic absence (EMA) is a rare childhood-onset generalized epilepsy syndrome characterized by myoclonic absence seizures. First discovered by Tassinari et al. in 1969, EMA has been extensively studied by researchers from all over the world. This review synthesizes recent studies on EMA, covering its discovery history, classification, epidemiology, pathophysiology, etiology, clinical manifestations, diagnosis and differential diagnosis, treatment, prognosis and evolution, and especially discusses the etiology and pathophysiology mechanism, to help clinicians understand this relatively rare epilepsy syndrome, reduce the rate of missed diagnosis and misdiagnosis, and effectively guide treatment to alleviate the long-term cognitive impairment in affected individuals.

Periodic electroencephalographic discharges and epileptic spasms involve cortico-striatal-thalamic loops on Arterial Spin Labeling Magnetic Resonance Imaging

Periodic discharges are a rare peculiar electroencephalogram pattern, occasionally associated with motor or other clinical manifestations, usually observed in critically ill patients. Their underlying pathophysiology remains poorly understood. Epileptic spasms in clusters and periodic discharges with motor manifestations share similar electroencephalogram pattern and some aetiologies of unfavourable prognosis such as subacute sclerosing panencephalitis or herpes encephalitis. Arterial spin labelling magnetic resonance imaging identifies localizing ictal and inter-ictal changes in neurovascular coupling, therefore assumed able to reveal concerned cerebral structures. Here, we retrospectively analysed ictal and inter-ictal arterial spin labelling magnetic resonance imaging in patients aged 6 months to 15 years (median 3 years 4 months) with periodic discharges including epileptic spasms, and compared these findings with those of patients with drug-resistant focal epilepsy who never presented periodic discharges nor epileptic spasms as well as to those of age-matched healthy controls. Ictal electroencephalogram was recorded either simultaneously with arterial spin labelling magnetic resonance imaging or during the close time lapse of patients' periodic discharges, whereas inter-ictal examinations were performed during the patients' active epilepsy but without seizures during the arterial spin labelling magnetic resonance imaging. Ictal arterial spin labelling magnetic resonance imaging was acquired in five patients with periodic discharges [subacute sclerosing panencephalitis (1), stroke-like events (3), West syndrome with cortical malformation (1), two of them also had inter-ictal arterial spin labelling magnetic resonance imaging]. Inter-ictal group included patients with drug-resistant epileptic spasms of various aetiologies (14) and structural drug-resistant focal epilepsy (8). Cortex, striatum and thalamus were segmented and divided in six functional subregions: prefrontal, motor (rostral, caudal), parietal, occipital and temporal. Rest cerebral blood flow values, absolute and relative to whole brain, were compared with those of age-matched controls for each subregion. Main findings were diffuse striatal as well as cortical motor cerebral blood flow increase during ictal examinations in generalized periodic discharges with motor manifestations (subacute sclerosing panencephalitis) and focal cerebral blood flow increase in corresponding cortical-striatal-thalamic subdivisions in lateralized periodic discharges with or without motor manifestations (stroke-like events and asymmetrical epileptic spasms) with straight topographical correlation with the electroencephalogram focus. For inter-ictal examinations, patients with epileptic spasms disclosed cerebral blood flow changes in corresponding cortical-striatal-thalamic subdivisions (absolute-cerebral blood flow decrease and relative-cerebral blood flow increase), more frequently when compared with the group of drug-resistant focal epilepsies, and not related to Vigabatrin treatment. Our results suggest that corresponding cortical-striatal-thalamic circuits are involved in periodic discharges with and without motor manifestations, including epileptic spasms, opening new insights in their pathophysiology and new therapeutical perspectives. Based on these findings, we propose a model for the generation of periodic discharges and of epileptic spasms combining existing pathophysiological models of cortical-striatal-thalamic network dynamics.

De novo variants in SETD1B cause intellectual disability, autism spectrum disorder, and epilepsy with myoclonic absences

Epilepsy with myoclonic absences is a specific seizure type characterized by bilateral rhythmic clonic jerks with impairment of consciousness. Here, we report an individual with epilepsy with myoclonic absences, mild intellectual disabilities, language disorder, and autism spectrum disorder. His interictal electroencephalogram revealed a spike-and-slow wave complex dominant in the frontal area. His ictal polygraphic and video-electroencephalogram showed a characteristic diffuse synchronous 3-Hz spike-and-wave burst associated with bilateral upper limb myoclonic jerks with impairment of consciousness. Using whole-exome sequencing, we found a novel de novo variant, c.386T>G, p.(Val129Gly), in SETD1B (SET domain containing 1B). We previously reported that two individuals with a de novo SETD1B variant showed intellectual disability, epilepsy, and autism. Of note, one of those individuals and the present case showed epilepsy with myoclonic absences. Therefore, this report supports the indication that SETD1B may be a causative gene for neurodevelopmental disorders and suggests that epilepsy with myoclonic absences may be a characteristic feature of SETD1B-related disorders.

Myoclonic absence seizures with complex gestural automatisms

Epilepsy with myoclonic absences is a rare generalized epilepsy syndrome with distinctive seizures. Two unrelated children had mild developmental impairment and onset of myoclonic-absences at 3 and 8 years. Seizures were characterized by bilateral 3 Hz myoclonic jerks superimposed on tonic abduction of the upper limbs. Events lasted 10-60 s, and complex gestural automatisms were often observed; in one case, a boy undid his seatbelt and attempted to exit a moving vehicle. Post-ictally, both children immediately regained awareness without recollection of their actions. Ictal EEGs showed 3 Hz generalized spike-wave. Complex automatisms have not been described in myoclonic absence seizures. This generalized seizure type can be confused with focal seizures when these ictal behaviours occur.