gms | German Medical Science

Objective: The nervus intermedius (NI) is the parasympathetic and sensory part of the facial nerve. It can be affected by vestibular schwannoma (VS) surgery. NI dysfunctions are however poorly reported. In this study, we are analyzing NI dysfunctions before and after VS surgery, and we are proposing a grading system for of NI deficits.

Methods: We prospectively examined 40 patients with VS who were operated between April 2014 and February 2017 in our institution. The taste functions were examined using taste strips. Basal lacrimation was examined using Schirmer I test. The patients were asked to report about subjective changes in salivation and nasal secretion. These tests were performed before surgery and repeated two weeks and six months after surgery. We tested the correlation between NI dysfunctions and the grade of facial nerve palsy.

Results: The taste sensation was lost on the side of surgery in 3 patients and decreased in 6 patients. The disturbance of taste sensation was not statistically correlated to the motor facial nerve dysfunction. In 30 patients, the basal lacrimation was lower on the operated side, and it was significantly correlated to the motor facial nerve outcome. After six months, basal lacrimation improved in correlation to the improvement of the motor facial nerve dysfunction. The taste impairment recovered in 5 patients. Three patients suffered from the permanent loss of the taste sensation on the operated side. None of the patients reported about change in salivation or nasal secretion. A grading system could be established based on the grade of the deficit and the reversibility of the symptoms.

Conclusion: NI dysfunctions can occur after VS resection and can affect the patients’ quality of life. The disturbance of the basal lacrimal secretion was correlated to the motor facial nerve dysfunction. However, disturbance of the taste sensation was not correlated with the grade of facial nerve palsy. Dysfunctions of nervus intermedius should be evaluated and separately reported when reporting on facial nerve outcome after VS surgery.