Influence of contact size on the detection of HFOs in human intracerebral EEG recordings.

OBJECTIVE: High frequency oscillations (HFOs) are brief electroencephalographic events associated with epileptic activity, and likely representing biological markers of the epileptogenic zone. HFOs are usually detected with intracranial EEG and detection is influenced by contact size. The size of commercially available intracerebral electrodes varies widely. This study assesses HFO detection rates from adjacent electrode contacts in human intracerebral recordings.
METHODS: Intracerebral recordings were collected from 11 patients undergoing stereoelectroencephalographic investigation using hybrid depth electrodes containing adjacent large (0.8 or 5 mm(2)) and small (0.2 or 0.3 mm(2)) contacts. HFOs were marked manually during 5-min tracings in 131 pairs of adjacent large and small contacts. HFO rates per minute and mean event durations were compared between adjacent contacts.
RESULTS: A minimal but statistically significant advantage in ripple detection was found in a subgroup of large contacts. Otherwise, HFO rates and mean event durations were not statistically different between groups.
CONCLUSION: The size of clinical contacts within the studied range did not influence HFO detection in a clinically relevant manner. Larger contacts provide a minimal advantage for ripple detection. SIGNIFICANCE: Our findings suggest that commercially available intracerebral electrodes with contacts between 0.2 and 5 mm(2) likely possess similar HFO detection abilities.