Surgical resection of fourth ventricular tumors. Comparison of the efficiency and safety of telovelar and median aperture approaches to the fourth ventricle

The study objective is to compare the efficacy and safety of the fourth ventricle tumor removal using median (through the median aperture) or telovelar approach.

Materials and methods. The analysis included 41 patients with space-occupying lesion of the fourth ventricle operated in the Neurosurgery Clinic of S.M. Kirov Military Medical Academy in 2007–2018. The anatomical characteristics (size and extension) and manifestations of the fourth ventricle tumors, as well as surgical factors (surgical approach to the fourth ventricle) which affect the functional outcome of the treatment were estimated. Complications associated with the approach were assessed clinically using diffusion-weighted magnetic resonance imaging. Logistic regression and ROC analysis were used to analyze the anatomical factors and extent of resection as predictors that affect the worsening of gait disturbance, speech/swallowing deficits in the postoperative period.

Results. The analysis revealed main advantages of the median approach in comparison to the telovelar approach: a lower frequency of C laminectomy; no need for prolonged constant tonsillar retraction; a shorter surgery duration and lower number of ischemic changes in the surgical area, caused by approach. Meanwhile the telovelar approach was used to remove lesions bigger in size. Other factors, such as tumor extension, the need to preliminary insertion of an external ventricular drain, the frequency of postoperative complications, the extent of resection and the functional outcomes did not differ significantly between the approaches. Lesion size ≥37.5 mm is a significant prognostic factor for speech/swallowing deficits after the surgery with sensitivity of 86 % and specificity of 84 %.

Conclusion. Median aperture approach is a reasonable alternative to telovelar or transvermian approaches in the surgery of small fourth ventricle tumors (<30 mm). The median approach allows to reduce the surgical injury rate and the likelihood of postoperative complications. If a lesion has a size ≥37.5 mm, an increase speech/swallowing deficits should be expected.

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