A case presenting with retro-orbital pain during endoscopic burr-hole surgery for organized chronic subdural hematoma.

Background: Retro-orbital pain occurring during burr-hole irrigation surgery for chronic subdural hematoma (CSDH) is extremely rare. Case Description: A 65-year-old man had undergone burr-hole irrigation surgery for organized CSDH 2 months previously. The patient was referred to our hospital for thick residual hematoma and persistent motor weakness after surgery. Endoscopic removal of the hematoma and the inner membrane was performed under local anesthesia. After half of the inner membrane had been resected, the patient complained of pulsatile pain behind his left eyeball. As the removal of the inner membrane progressed, the patient became agitated reporting the pain to be excruciating. He was sedated in an attempt to resume the surgery; however, this was impossible because the brain had expanded to just beneath the dura mater. Postoperative studies revealed subarachnoid and intracerebral hemorrhages in addition to good brain expansion, while the left internal cerebral artery was dilated compared to preoperative studies. The patient recovered and was able to walk but remained disoriented. Conclusion: Surgery for organized CSDH with long-term brain compression requires inner membranectomy. However, rapid decompression by aggressive membranectomy increases the risk of intracranial hemorrhage and mortality, and it is often difficult to determine how much of the membrane should be excised. In the present case, the abrupt increase in cerebral blood flow (CBF) may have resulted in hemorrhage, and this could have been avoided if the surgery had been performed in two stages. Retro-orbital pain suggests excessive CBF increase and could be a warning sign to stop surgery immediately.