Department of Neurosciences, Biomedicine and Movement Sciences, Section of Neurosurgery, University Hospital, Piazzale Stefani 1, 37124, Verona, Italy.
Intraoperative Neurophysiology Unit, Division of Neurology, University Hospital, Verona, Italy.
Childs Nerv Syst. 2021 May;37(5):1505-1514. doi: 10.1007/s00381-021-05126-7. Epub 2021 Apr 9.
Cerebellar mutism can occur in a third of children undergoing cerebellar resections. Recent evidence proposes it may arise from uni- or bilateral damage of cerebellar efferents to the cortex along the cerebello-dento-thalamo-cortical pathway. At present, no neurophysiological procedure is available to monitor this pathway intraoperatively. Here, we specifically aimed at filling this gap.
We assessed 10 patients undergoing posterior fossa surgery using a conditioning-test stimulus paradigm. Electrical conditioning stimuli (cStim) were delivered to the exposed cerebellar cortex at interstimulus intervals (ISIs) of 8-24 ms prior to transcranial electric stimulation of the motor cortex, which served as test stimulus (tStim). The variation of motor-evoked potentials (MEP) to cStim + tStim compared with tStim alone was taken as a measure of cerebello-cortical connectivity.
cStim alone did not produce any MEP. cStim preceding tStim produced a significant inhibition at 8 ms (p < 0.0001) compared with other ISIs when applied to the lobules IV-V-VI in the anterior cerebellum and the lobule VIIB in the posterior cerebellum. Mixed effects of decrease and increase in MEP amplitude were observed in these areas for longer ISIs.
The inhibition exerted by cStim at 8 ms on the motor cortex excitability is likely to be the product of activity along the cerebello-dento-thalamo-cortical pathway. We show that monitoring efferent cerebellar pathways to the motor cortex is feasible in intraoperative settings. This study has promising implications for pediatric posterior fossa surgery with the aim to preserve the cerebello-cortical pathways and thus prevent cerebellar mutism.
小脑性缄默症可发生于三分之一接受小脑切除术的儿童。最近的证据表明，它可能是由于小脑传出纤维沿小脑齿状核丘脑皮质通路单侧或双侧损伤引起的。目前，没有神经生理程序可用于术中监测此通路。在此，我们旨在填补这一空白。
我们使用条件-测试刺激范式评估了 10 例接受后颅窝手术的患者。在经颅电刺激运动皮质之前，将电刺激条件刺激（cStim）施加到暴露的小脑皮质，刺激间隔（ISIs）为 8-24ms，作为测试刺激（tStim）。与单独施加 tStim 相比，cStim+tStim 引起的运动诱发电位（MEP）的变化被用作小脑皮质连接的测量。
单独施加 cStim 不会产生任何 MEP。当将刺激施加到前小脑的 IV-V-VI 叶和后小脑的 VIIB 叶时，与其他 ISIs 相比，8ms 时 cStim 单独产生了显著的抑制（p<0.0001）。对于较长的 ISIs，在这些区域观察到 MEP 幅度的减少和增加的混合效应。
cStim 在 8ms 时对运动皮质兴奋性的抑制作用可能是沿着小脑齿状核丘脑皮质通路的活动产物。我们表明，在术中环境中监测到运动皮质的传出小脑通路是可行的。本研究对小儿后颅窝手术具有重要意义，旨在保护小脑皮质通路，从而预防小脑性缄默症。
