High frequency oscillations (HFO, ripples 80-250 Hz, fast ripples 250-500 Hz) are biomarkers of epileptic tissue. They are most commonly observed over areas generating seizures and increase in occurrence during the ictal compared to the interictal period. It has been hypothesized that their rate correlates with the severity of epilepsy and seizure in affected individuals. In the present study it was aimed to investigate whether HFO count mirrors the observed behavioral seizure severity using a kainate rat model for temporal lobe epilepsy. Seizures were selected during the chronic epilepsy phase of this model and classified by behavioral severity according to the Racine scale. Seizures with Racine scale 5&6 were considered generalized and severe. HFO were marked in 24 seizures during a preictal, ictal and postictal EEG segment. Duration covered by HFO during these different segments was analyzed and compared between mild and severe seizures. HFO were significantly increased during ictal periods (p<0.001) and significantly decreased during postictal periods (p< 0.03) compared to the ictal segment. Ictal ripples (p=0.04) as well as fast ripples (p=0.02) were significantly higher in severe seizures compared to mild seizures. The present study demonstrates that ictal HFO occurrence mirrors seizure severity in a chronic focal epilepsy model in rats. This is similar to recent observations in patients with refractory mesio-temporal lobe epilepsy. Moreover, postictal HFO decrease might reflect postictal inhibition of epileptic activity. Overall results provide additional evidence that HFO can be used as biomarkers for measuring seizure severity in epilepsy.

中文翻译：

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在颞叶癫痫大鼠模型中，高频振荡的局部出现与癫痫发作的严重程度相关

高频振荡（HFO，80-250 Hz的波纹，250-500 Hz的快速波纹）是癫痫组织的生物标志。与发作间期相比，在发作期间癫痫发作和发作次数增加的地区最常见。据推测，它们的发生率与患病者的癫痫和癫痫发作的严重程度有关。在本研究中，其目的是研究使用海藻酸盐大鼠模型进行颞叶癫痫的HFO计数是否反映了观察到的行为性癫痫发作的严重程度。在该模型的慢性癫痫期中选择癫痫发作，并根据Racine量表按行为严重程度对其进行分类。Racine等级5和6的癫痫发作被认为是普遍性和严重性。HFO在发作前，发作后和发作后脑电图段发作中有24次发作。分析并比较了轻度和重度癫痫发作在这些不同阶段中由HFO覆盖的持续时间。与发作期相比，发作期HFO显着升高（p <0.001），发作后期HFO显着降低（p <0.03）。与轻度癫痫发作相比，重度癫痫发作的发作期波纹（p = 0.04）和快速脉动（p = 0.02）明显更高。本研究表明，在慢性局灶性癫痫模型中，短暂的HFO发生反映了癫痫发作的严重程度。这与近期难治性中颞叶癫痫患者的观察结果相似。此外，邮政HFO的降低可能反映了邮政对癫痫活动的抑制。总体结果提供了其他证据，表明HFO可用作测量癫痫发作严重程度的生物标志物。