Total RNA from CSF was extracted using the miRNeasy Serum/Plasma Kit (QIAGEN, NO. 217184) according to the manufacturer's protocol. Quantitation of total RNA was performed using an Agilent 2100 Bioanalyzer (Agilent Technology, USA) Total RNA was ligated to adapters at each end. Next, the adapter-ligated RNA was reverse-transcribed to cDNA, and PCR amplification was performed. PCR products ranging from 140 to 160 bp were isolated and purified as small RNA libraries. Library quality was assessed with the Agilent Bioanalyzer 2100 system using DNA High Sensitivity Chips. The libraries were finally sequenced using the Illumina HiSeq X Ten platform.