Electrocerebral activity and epileptic attacks at various blood sugar levels; with a case report

An insulinoma with clinical and electroencephalographic features resembling complex partial seizures

We described a female patient with insulinoma who experienced recurrent episodes of automatism, confusion and convulsion. Furthermore, her electroencephalography (EEG) findings resembled the pattern in complex partial seizures with secondary generalization. The interictal EEG showed spikes and sharp waves, as well as focal slowing over the left temporal lobe, and the ictal EEG revealed generalized spikes and sharp waves associated with diffused slowing. She was initially misdiagnosed as pharmacoresistant epilepsy. After the insulinoma was found and surgically removed, her EEG turned normal and she was seizure-free during the 4-year follow-up. This report highlights the need for careful reassessment of all seizures refractory to medication, even for the patients associated with epileptiform discharges on EEG.

Seizure and acute osmotic change: clinical and neurophysiological aspects

There are a number of clinical situations where overhydration may occur. If the reduction in plasma osmolality is acute, passive water influx swells brain cells, shrinking the extracellular space around them. It is during this time that susceptibility to generalized tonic-clonic seizure dramatically increases. Common clinical examples include hastened rehydration therapy, the dialysis disequilibrium syndrome, compulsive polydipsia, the syndrome of inappropriate ADH secretion (SIADH) and post-TURP syndrome. Treatments that tend to restore normal cellular volume (dehydration, mannitol infusion) help protect against this form of seizure. Support for a correlation between plasma osmolality and seizure susceptibility is scattered amongst the literature of several medical disciplines and spans almost 70 years. However a cellular basis to explain how overhydration might promote epileptiform activity has been examined only recently. The neocortical and hippocampal brain slice preparations permit an examination of how acute osmotic change alters cortical excitability independent of vascular damage, brain compression or other factors secondary to brain swelling. Electrophysiological evidence indicates that hyposmolality promotes epileptiform activity by strengthening both excitatory synaptic communication in neocortex and field effects among the entire cortical population. Moreover there is little evidence that associated hyponatremia in itself leads to increased CNS excitability. Such findings help in understanding how rapid lowering of plasma osmolality in clinical situations can promote the hyperexcitability associated with generalized tonic-clonic seizure.