Monitoring of Brain Function by Means of Evoked Potentials in Cerebral Aneurysm Surgery

  • A. Ducati
  • A. Landi
  • M. Cenzato
  • E. Fava
  • P. Rampini
  • M. Giovanelli
  • R. Villani
Part of the Acta Neurochirurgica Supplementum 42 book series (NEUROCHIRURGICA, volume 42)


Deliberate arterial hypotension is currently used to operate upon cerebral aneurysms. However, it is not ascertained whether this practice is really safe for all patients, especially those presenting with preoperative vasospasm. 50 patients, requiring surgical treatment for cerebral aneurysm, have been submitted, during surgery, to the recording of Somatosensory Evoked Potentials (SEPs) on median nerve stimulation. This technique allows the functional evaluation of neural pathways mediating the somatosensory stimuli and of primary somatosensory cortex; it is known that a decrease of cerebral perfusion may affect the SEP waveforms in terms of reduced subcortical conduction velocity (i.e., increased central conduction time, CCT) and of reduced cortical response amplitude. These changes may be apparent before a permanent neurological damage is produced. Preoperative SEP recording demonstrated a prolonged CCT, possibly related to vasospasm, in 9 patients, a normal clinical evaluation notwithstanding (grade I and II).

During intraoperative deliberate hypotension, a SEP change has always been produced. No postoperative damage has been observed, however, as long as the CCT did not exceed 9 msec for 10 minutes (maximum normal CCT value is 6.7 msec) and as the cortical response had been visible throughout the whole surgical procedure. The critical value of CCT has been reached at a mean arterial pressure (MAP) lower than 60 Torr in patients with a normal preoperative SEP recording; at the opposite, in patients presenting with a prolonged preoperative CCT, the value of 9 msec was arrived at with a MAP value that is generally accepted as safe for all patients (75 Torr).

In conclusion, SEP monitoring has proved to be a useful technique to identify the minimum safe MAP value for the individual patient undergoing surgery for cerebral aneurysm.


Mean Arterial Pressure Cerebral Aneurysm Evoke Potential Somatosensory Evoke Potential Primary Somatosensory Cortex 
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Copyright information

© Springer-Verlag/Wien 1988

Authors and Affiliations

  • A. Ducati
    • 1
  • A. Landi
    • 1
  • M. Cenzato
    • 1
  • E. Fava
    • 2
  • P. Rampini
    • 1
  • M. Giovanelli
    • 1
  • R. Villani
    • 1
  1. 1.Institute of NeurosurgeryUniversity of MilanoMilanoItaly
  2. 2.CNR Centre for Muscle PhysiologyMilanoItaly

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