Koos grade IV vestibular schwannomas: considerations on a consecutive series of 60 cases—searching for the balance between preservation of function and maximal tumor removal

Abstract

PurposeKoos Grade IV vestibular schwannomas (VS) (maximum diameter >3cm) compress the brainstem and displace the fourth ventricle. Microsurgical resection with attention to the right balance between preservation of function and maximal tumour removal is the treatment of choice. MethodsOur series consists of 60 consecutive patients with unilateral VS, operated on from December 2010 to July 2019. All patients underwent microsurgical removal via the retrosigmoid approach. The adherence of VS' capsule to surrounding nervous structures and the excessive tendency of tumor to bleed during debulking, because of a redundant vascular architecture, was evaluated by reviewing video records.Microsurgical removal of tumor was classi ed as total (T), near-total (NT: residue<5%), subtotal (ST: residue 5-10%) or partial (P: residue>10%). ResultsMaximal mean tumor diameter was 3,97cm (SD±1,13; range 3,1-5,8cm). Preoperative severely impaired hearing or deafness (AAO-HNS Classes C-D) was present in 52 cases (86,7%). Total or NT resection was accomplished in 46 cases (76,7%), 65,8% in cases with and 95,4% without tight adhesion of capsule to nervous structures (p<0,001). Endoscopic-assisted microsurgical removal of VS in the IAC was performed in 23 patients: in these cases a T resection was obtained in 78,3% versus 45,9% of microsurgery only (p<0,001).The capsule of VS was tightly adherent to nervous structures in 63,3% of patients, whereas hypervascular high-bleeding tumors represented 56,7%. Hearing preservation was possible in 2 out of 8 patients with preoperative class B hearing. At last follow-up, 34 patients (56,7%) had a normal postoperative FN outcome (HBI), 9 (15,0%) were HBII, 8 (13,3%) HBIII, and 9 (15,0%) HBIV. Total-NT resection of solid and low-bleeding VS, without tight capsule adhesion was associated with better FN outcome. Mortality was zero; permanent complications were observed in 2 cases (diplopia, hydrocephalus), transient in 9. ConclusionsMicrosurgery of Koos Grade IV VS seems to be associated with more than acceptable functional results, with high rate of T and NT removal of tumor. Long-term FN results seem to be worse in patients with cystic Koos Grade IV VS, in cases with tight capsule adherences to nervous structures and in highbleeding tumors.

Stereotactic radiosurgery for Koos grade IV vestibular schwannoma: a multi-institutional study

“…Hearing and facial nerve function preservation were noted in 25% and 90% of the cases, respectively. 17 To improve functional outcomes, subtotal resection followed by SRS has become increasingly popular. 3 Also, at some centers, there has been a trend for planned subtotal resection followed by SRS for larger VSs.…”

Development and Validation of a Deep Learning Predictive Model Combining Clinical and Radiomic Features for Short-Term Postoperative Facial Nerve Function in Acoustic Neuroma Patients

“…Another possible reason for the excellent performance of our model is that we have contained intratumor heterogeneity, such as adhesion between the tumor capsule and facial nerve. The degree of adhesion is a universally acknowledged critical risk factor of poor FN function [30] . Nonetheless, there are two problems with determining the adhesive degree: 1) identification criterion is so objective and different as it mainly depends on observation by the neurosurgeon with naked eyes during surgery [31] and 2) the FN is almost integrated anatomically with the mass as a wholly enhanced lesion on MRI, leaving unrecognizable intraoperative dissection plane [32] .…”