Characteristics of Prolonged Afterdischarges in Children With Malformations of Cortical Development

Abstract

We investigated aberrant cortical excitability in malformations of cortical development From subdural electrodes, we recorded afterdischarges lasting > or = 6 seconds in 12 of 13 patients with malformations of cortical development and 6 of 10 pediatric patients with nonmalformations of cortical development and reviewed amperage thresholds, distribution of afterdischarges, and motor responses. In patients with malformation of cortical development, motor response thresholds were high; afterdischarge and motor response thresholds, which essentially overlapped, inversely correlated with age (P < .01); afterdischarge thresholds declined with age; and 8 patients showed afterdischarges in remote sites. In nonmalformation of cortical development, afterdischarge thresholds did not significantly correlate with age; motor response thresholds tended to decline with age; and 2 patients had remote afterdischarges. Adolescent patients with malformations of cortical development had lower afterdischarge thresholds than adolescents with nonmalformation of cortical development (P < .05). From their high afterdischarge (and motor response) thresholds, we concluded that preadolescent patients with malformation of cortical development have less excitable, immature cortices, whereas adolescent patients with malformation of cortical development with low afterdischarge thresholds have hyperexcitable cortices. Remote afterdischarges over focal dysplastic cortex suggest aberrant cortical excitability and neural circuits.

Clinical, functional, and neurophysiologic assessment of dysplastic cortical networks: Implications for cortical functioning and surgical management

“…Postnatal maturation influences the expression of dysplastic hyperexcitability, as afterdischarge thresholds show a steep decline with age (Jayakar et al., 1992; Chitoku et al., 2003). Younger patients evidence remote afterdischarges distant to the stimulation site (Chitoku et al., 2003).…”

Characterizing magnetic spike sources by using magnetoencephalography-guided neuronavigation in epilepsy surgery in pediatric patients

“…We defined an epileptic zone as the place where synchronized spike discharges were seen at three or more ECoG electrodes. 7,29 Patients with lesions or interictal zones around the central sulcus underwent intraoperative median nerve electrical stimulation to identify the SSEP N20 component.…”

A randomized clinical trial of repetitive transcranial magnetic stimulation in patients with refractory epilepsy

“…In fact, it has been shown that prolonged after-discharges occur more frequently in patients with neuronal migration disorders than in patients with other epileptic disorders. 41 Therefore, a decrease in the local excitability in the area with cortical dysplasia may result in a decrease of the abnormal excitatory input to the normal, healthy surrounding cortex that ultimately results in an increase of the inhibitory drive to the dysplastic cells. Because rTMS may disrupt this pathological excitatory network, the reestablishment of the normal activity is possible.…”