gms | German Medical Science

Objective: Perioperative visual loss (POVL) is a rare but serious complication in surgical disciplines, especially in spine surgery. The exact pathophysiology of POVL still remains unclear but an elevated intraocular pressure (IOP) is known to be part of it. As POVL is rarely described in patients undergoing intracranial or intradural operations the aim of this study was to investigate the effect of IOP during neurosurgical procedures with opening of the Dura mater (DM) and loss of cerebrospinal fluid (CSF).

Methods: In this prospective, controlled trial 64 patients were distributed into 4 groups of 16 patients each. Group A included patients undergoing spine surgery in the prone position, group B patients with intracranial surgeries in the prone position and group C patients were treated for intracranial pathologies in a modified semilateral position with rotated head. In groups A-C the DM was opened during surgery. Group D patients underwent spine surgeries in the prone position with an intact DM. IOP was measured pre- and postoperatively, after the induction of anesthesia, final positioning for surgery, subsequently every 30min and additionally after opening of the DM.

Results: In all groups IOP decreased after the induction of anesthesia and increased time-dependently after final-positioning for the operation. The maximum IOP in group A prior to opening of the DM was 28.6 ± 6.2mmHg and decreased to 23.44 ± 4.9mmHg directly after opening of the DM (p<0.0007). This effect lasted for 30min (23.5 ± 5.6mmHg, p=0.0028), after 60min IOP slowly increased again (24.5 ± 6.3mmHg, p=0.15). In group B, the last measured IOP before CSF loss was 28.1±5.0mmHg and decreased to 23.5±6.1 mmHg (p=0.0039) after opening of the DM. Significant IOP drop in group B lasted 30 (23.6 ± 6.0mmHg, p=0.0039) and 60min (23.7 ± 6.0mmHg, p=0.0189), respectively. In group C only the lower eye showed a decrease of IOP up to 60min after loss of CSF (p=0.00007; 0,0477; 0.0243, resp.) while no statistically significant decrease of IOP was seen in the upper eye. In control group D, the IOP remained stable throughout the operation after reaching prone position.

Conclusion: Our study is the first to demonstrate that opening of the DM with loss of CSF during neurosurgical procedures results in a decrease of the IOP. This might explain why POVL predominantly occurs in spinal procedures but hardly ever in intracranial procedures. This offers new insights into the pathophysiology of POVL and provides the basis for further research and treatment of POVL.