[Monitoring of Somatosensory Evoked Potentials during Foramen Magnum Decompression of Chiari Malformation Type I Complicated with Syringomyelia: A Report of Two Cases].

: Few reports exist on anesthetic management for foramen magnum decompression (FMD) of Chiari malformation type I (CM I) complicated with syringomyelia. In two such cases we monitored somatosensory evoked potentials (SEP). Case 1 : A 40-year-old woman presented with occipital headache and nuchal pain for 2 months; numbness and muscular weakness of bilateral upper limbs for a month. Magnetic resonance imaging (MRI) scan showed CM I complicated with syringomyelia. Case 2 : A 32-year-old man presented with numbness and muscular weakness of bilateral upper limbs for 5 months; numbness and muscular weakness of lower limbs for 2 months. MRI scan showed CM I complicated with syringomyelia. They underwent FMD. In both cases, general anesthesia was induced with remifentanil, propofol and rocuronium, and was maintained with oxygen, air, remifentanil and propofol. Moreover, we monitored SEP. Their operative courses were uneventful. In case 1, SEP latency became shorter after FMD. Her preoperative neurologic symptoms disappeared on first postoperative day. In contrast there was no change of SEP latency after FMD in case 2. His preoperative neurologic symptoms showed no change on fifth postoperative day. SEP monitoring may be a useful index for prediction of early recovery of neurologic symptoms after FMD.