High frequency oscillations and high frequency functional network characteristics in the intraoperative electrocorticogram in epilepsy.

OBJECTIVE: High frequency oscillations (HFOs; > 80 Hz), especially fast ripples (FRs, 250-500 Hz), are novel biomarkers for epileptogenic tissue. The pathophysiology suggests enhanced functional connectivity within FR generating tissue. Our aim was to determine the relation between brain areas showing FRs and 'baseline' functional connectivity within EEG networks, especially in the high frequency bands. METHODS: We marked FRs, ripples (80-250 Hz) and spikes in the electrocorticogram of 14 patients with refractory temporal lobe epilepsy. We assessed 'baseline' functional connectivity in epochs free of epileptiform events within these recordings, using the phase lag index. We computed the Eigenvector Centrality (EC) per channel in the FR and gamma band network. We compared EC between channels that did or did not show events at other moments in time. RESULTS: FR-band EC was higher in channels with than without spikes. Gamma-band EC was lower in channels with ripples and FRs. CONCLUSIONS: We confirmed previous findings of functional isolation in the gamma-band and found a first proof of functional integration in the FR-band network of channels covering presumed epileptogenic tissue. SIGNIFICANCE: 'Baseline' high-frequency network parameters might help intra-operative recognition of epileptogenic tissue without the need for waiting for events. These findings can increase our understanding of the 'architecture' of epileptogenic networks and help unravel the pathophysiology of HFOs.

[Fracture of the femoral neck in bed caused by an epileptic seizure]. / Collumfractuur in bed door een epileptische aanval.

An 82-year-old man was brought into the emergency department after an epileptic seizure. Although the seizure took place in his bed and was not followed by a fall, his right hip was broken. No underlying bone abnormalities were found. The patient received a femoral head & neck prosthesis and recovered fully. Fractures are more common in patients with epilepsy than in the general population, due to both seizure-related trauma and a relatively high prevalence of osteoporosis, which is due partly to the use of anti-epileptic drugs. However, even after a seizure without trauma in a patient without underlying abnormalities of bone structure, a fracture may arise as a result of the force of the muscle contractions during the seizure.