Remote Ischemic Preconditioning in Vestibular Schwannoma Surgery

Remote Ischemic Preconditioning in Vestibular Schwannoma Surgery and Its Neuroprotective Effect on the Cochlear and Facial Nerve Function

Vestibular schwannomas are primarily benign (WHO grade I) tumors originating from the Schwann cells of the vestibular nerve and are among the most common tumors of the skull base. Common treatment options are surgical tumor resection or targeted radiation therapy. The special challenge of surgical treatment is the functional preservation of the cranial nerves, especially the cochlear and facial nerves. Perioperative ischemia of the cochlea and cochlear nerve is postulated as the underlying mechanism of postoperative hearing loss. Ischemic preconditioning is a non-invasive procedure that triggers the release of vasoactive cytokines and mediators by repeated short-term induction of limb ischemia. Improved perfusion of critically perfused end organs as well as a reduction of cerebral infarct volumes has already been shown in other pathologies. In the planned study, possible neuroprotective effects of remote ischemic preconditioning on postoperative hearing as well as facial nerve function in patients with vestibular schwannomas will be examined.

Purpose: Does remote ischemic preconditioning improve hearing and/or facial nerve palsy after resection of vestibular schwannomas?

Study Design: Prospective, randomized, double-blind, single-center.

Case number: The study should include 120 patients (60 treatment arm, 60 control arm). Case number calculation (mean effect sizes, chi-square test, alpha error = 0.05, beta error = 20%) results in a necessary total patient number of 100 with 50 patients per group. Including the expected dropout rate (approx. 20%), the required total number of study participants is set at 120 patients. With approximately 55 patients/year in whom anatomic preservation of the cochlear nerve is possible intraoperatively, the total study duration is estimated to be approximately 2-2.5 years.

Study procedure: Day 1

• Preoperative pure tone audiometry including speech discrimination and preoperative AEP measurement
• preoperative assessment of facial nerve function according to House and Brackmann and photo documentation
• Preoperative blood sample (Hg, WBC, platelet count, creatinine, sodium, potassium, CRP, PCT, IL-6, INR, Quick, aPTT, d-dimer)
• Evaluation of inclusion and exclusion criteria, informed consent

Day 2

• Randomization

• At skin incision RIC procedure or sham control.

  • RIC arm: 5 minutes inflation of a blood pressure cuff to 200mmHg on the right arm, then 5 minutes rest, the procedure will be performed 4 times in total.
  • Control arm: 5 minutes inflation of a blood pressure cuff to 0mmHg on the right arm, then 5 minutes rest, the procedure will be performed 4 times in total.

• Performance of tumor resection under electrophysiological monitoring.

• blood sample (Hg, WBC, platelet count, creatinine, sodium, potassium, CRP, PCT, IL-6, INR, Quick, aPTT, d-dimer)

Day 3

• blood sample (Hg, WBC, platelet count, creatinine, sodium, potassium, CRP, PCT, IL-6, INR, Quick, aPTT, d-dimer)
• Clinical assessment of facial nerve function
• Evaluation of complications

Before discharge

• Clinical assessment of facial nerve function and photo documentation
• Evaluation of complications occurring in the course of the procedure
• Postoperative AEP measurement and pure tone audiometry incl. speech discrimination

Outpatient follow-up after 3 months

• Evaluation of postoperative pure tone audiometry incl. speech discrimination
• Clinical assessment of facial nerve function and photo documentation

Objective:

Primary outcome: patients undergoing RIC will show better hearing 3 months postoperatively than the sham control group.

Secondary outcome hypothesis: patients undergoing RIC will show better postoperative facial nerve function than the sham control group before discharge and 3 months postoperatively.

Inclusion Criteria:

• Age ≥ 18 years
• total or gross-total resection of a vestibular schwannoma is planned
• Functional hearing is still present on the affected side preoperatively (AEP evocable and Gardner-Robertson grade I, II, or III).
• Preoperatively, facial function is unimpaired or mildly impaired (House and Brackmann grade I or II).

Exclusion Criteria:

• Symptomatic peripheral artery disease.
• Active or previous thrombosis in the extremity where the RIC procedure is to be performed.
• Neurofibromatosis type 2
• Only planned decompression of the internal auditory canal without relevant tumor resection
• Pregnant or breastfeeding females
• Previous radiotherapy of the vestibular schwannoma that will be resected