Intraoperative electrophysiological balloon test occlusion (BTO): A novel Solution to an inconclusive conventional BTO.

Parent Artery Occlusion (PAO) is a valid treatment choice in giant internal carotid artery (ICA) aneurysms of the cavernous segment when the preoperative balloon test occlusion (BTO) demonstrates an adequate cross circulation from the contralateral side. A high flow arterial bypass is, however, mandatory if the result suggests otherwise or is indeterminate. We present here a case of a 72-year lady where the BTO results were inconclusive. Rather than proceeding for the ICA ligation and a high flow bypass straight away, we replicated the BTO in the operation theatre, using intraoperative electrophysiologic neuromonitoring under the general anaesthesia. A temporary clip was applied on the ICA followed by gradual reduction of the blood pressure up to 30% from the baseline and sustained for 30 min. The motor evoked potential (MEP) and somatosensory evoked potential (SSEP) monitoring did not show ipsilateral hemispheric ischemia. Assured by this electrophysiologic evidence, we proceeded with ligation of the cervical ICA. The patient recovered from surgery without any neurological deficits and remains functionally intact at 4-years follow-up. Based on this case, this novel method can be considered a further refinement of the conventional BTO, allowing clarification of the inconclusive results that may sometimes be encountered.