Anatomical injury of the facial nerve during removal of large and giant vestibular schwannomas

The removal of large and giant vestibular schwannomas remains one of the most challenging tasks in neurosurgery. The probability of anatomical injury to the facial nerve during the removal of these neoplasms is 10.3–17%. Objective of the article was to analyze the frequency and risk factors for anatomical injury of the facial nerve during the removal of large and giant vestibular schwannomas.

Materials and methods. A total of 93 patients were examined. To determine risk factors, linear and angular parameters of the posterior cranial fossa, magnetic resonance characteristics of the tumor, as well as clinical and intraoperative data were investigated. Statistical analysis was performed using the Statistica software package (version 10.0) for Windows (StatSoft, USA). Statistical significance was assessed using the Mann – Whitney U test, Pearson’s χ2 test, or Fisher’s exact test for categorical data.

Results. Anatomical injury to the facial nerve during tumor removal was recorded in 8 patients, accounting for 8.6%. The length of the posterior cranial fossa was statistically significantly smaller than in the comparison group: 73.3 mm and 78.8 mm, respectively (U = 491.0, p = 0.039). The width of the posterior cranial fossa was also smaller but without statistical significance: 108.8 mm and 113.3 mm, respectively (U = 433.0, p = 0.205). According to MRI results, patients in the main group more frequently exhibited peritumoral edema (p = 0.345), hydrocephalus and periventricular edema (p = 0.204), and absence of a cerebrospinal fluid (CSF) cleft (p = 0.426). According to CT perfusion data, a higher CBF (cerebral blood flow) index was noted in the tumor tissue (p = 0.800). The identified differences were not statistically significant. Among intraoperative risk factors, the radicality of tumor removal should be noted. In the main group, all tumors were removed radically, while in the comparison group, the percentage of radically resected schwannomas was only 62.3% (p = 0.047).

Conclusion. In addition to well-known factors leading to an increased risk of intraoperative nerve injury, we also identified the influence of anatomical features of the posterior cranial fossa structure. This complication occurs more often in patients with a narrow and short fossa. The probability of anatomical injury to the facial nerve during radical removal of large and giant vestibular schwannomas is statistically significantly higher compared to subtotal removal.

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