Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery

Mild hypothermia is assumed to protect against secondary brain injury. Howe ver, the accuracy of brain temperature estimation remains debatable if dire ct measurement in the target area is to be avoided or is impossible. Furthe rmore, intracerebral temperature:gradients exist, especially under intraope rative conditions. We aimed to establish how brain surface temperatures (T- Brain) relate to temperatures taken at standard sites in posterior fossa su rgery. Ten patients undergoing cerebellopontine angle tumor removal were mo nitored for T-Brain, esophageal temperature (T-Eso), bladder temperature (T -Blad), ipsi- and contralateral tympanic membrane (TTymp-I, TTymp-C), and s calp temperatures; (T-Scalp). During monitoring, T-Eso increased from 35.3 +/- 0.2 degrees C to 36.0 +/- 0.3 degrees C. After dura opening, T-Brain wa s -0.14 +/- 0.1 degrees C below T-Eso. At the end of tumor removal, this di fference increased to -0.43 +/- 0.31 degrees C (P < 0.05). TTymp-C was -0.2 9 +/- 0.18 degrees C below T-Brain at dura opening. TTymp-C reflected the b ehavior of T-Eso adequately (r = 0.938), however, with a mean difference of -0.39 +/- 0.04 degrees C. In contrast, TTymp-I readings closely,followed t emperature changes in the area of surgery. T-Blad reflected T-Eso except in periods of rapid temperature changes. Tn posterior fossa (PF) surgery, loc al T-Brain is most accurately reflected by T-Eso. Far clinical use T-Blad a nd TTymp-C are also sufficient to assess brain surface temperature in the P F. Intraoperative surface cooling of the brainstem is:less than the previou sly described cooling rate of exposed cerebral cortex.