Sudden Death in Epilepsy: Can Any Lessons be Learned From Convulsive Therapy?

Postictal generalized electroencephalographic suppression is associated with generalized seizures

Postictal generalized electroencephalographic suppression (PGES) may be involved in sudden unexpected death in epilepsy (SUDEP). We examined whether the occurrence of PGES depends on seizure type and whether PGES occurs more frequently in people with epilepsy who died suddenly. EEG recordings of people with pharmacoresistant focal epilepsies who died from SUDEP after presurgical video/EEG telemetry were compared with recordings of living controls. To test if PGES depends on seizure type, EEG recordings of people with temporal lobe epilepsy who had complex partial seizures (CPS) and secondarily generalized tonic-clonic seizures (GTCS) were reviewed. A total of 122 seizures in 57 individuals have been included. PGES was observed in 15% of all seizures in 26% of all individuals. Secondarily GTCS were significantly associated with PGES. Neither presence nor duration of PGES differed between the SUDEP and control groups. In conclusion, PGES is facilitated by secondarily GTCS, but does not seem to be an independent risk factor for SUDEP.

Bilateral fronto-occipital polymicrogyria and epilepsy

We present a clinico-pathological case report in which both cortical dysplasia and epilepsy coexisted: a 30 year old male who was dead on arrival at hospital. One and a half hours earlier he had developed complex partial status with peri-oral cyanosis. At post mortem examination his brain showed bilateral occipital frontal polymicrogyria with unlayered neuronal migration disorder; in other parts there were fourth layer migration disorders. The white matter exhibited multicystic encephalopathy. In the heart there was chronic interstitial and perivascular fibrosis, although he died of a cardiac arrest. Bilateral frontal-occipital polymicrogyria is highly epileptogenic. This was a sporadic case and we cannot define a clear aetiology. There was a pathological cardiac condition without previous vascular risk factors which might be related to repetition of seizures and possibly to his sudden death during status epilepticus.

Excitatory but not inhibitory synaptic transmission is reduced in lethargic (Cacnb4(lh)) and tottering (Cacna1atg) mouse thalami

Excitatory but not inhibitory synaptic transmission is reduced in lethargic (Cacnb4(lh)) and tottering (Cacna1atg) mouse thalami. Recent studies of the homozygous tottering (Cacna1atg) and lethargic mouse (Cacnb4(lh)) models of absence seizures have identified mutations in the genes encoding the alpha1A and beta4 subunits, respectively, of voltage-gated Ca2+ channels (VGCCs). beta subunits normally regulate Ca2+ currents via a direct interaction with alpha1 (pore-forming) subunits of VGCCs, and VGCCs are known to play a significant role in controlling the release of transmitter from presynaptic nerve terminals in the CNS. Because the gene mutation in Cacnb4(lh) homozygotes results in loss of the beta4 subunit's binding site for alpha1 subunits, we hypothesized that synaptic transmission would be altered in the CNS of Cacnb4(lh) homozygotes. We tested this hypothesis by using whole cell recordings of single cells in an in vitro slice preparation to investigate synaptic transmission in one of the critical neuronal populations that generate seizure activity in this strain, the somatosensory thalamus. The primary finding reported here is the observation of a significant decrease in glutamatergic synaptic transmission mediated by both N-methyl-D-aspartate (NMDA) and non-NMDA receptors in somatosensory thalamic neurons of Cacnb4(lh) homozygotes compared with matched, nonepileptic mice. In contrast, there was no significant decrease in GABAergic transmission in Cacnb4(lh) homozygotes nor was there any difference in effects mediated by presynaptic GABAB receptors. We found a similar decrease in glutamatergic but not GABAergic responses in Cacna1atg homozygotes, suggesting that the independent mutations in the two strains each affected P/Q channel function by causing defective neurotransmitter release specific to glutamatergic synapses in the somatosensory thalamus. This may be an important factor underlying the generation of seizures in these models.