Trigeminal Nerve Deficit in Large and Compressive Acoustic Neuromas (ANs) and Its Correlation with MRI Findings

Objectives: To evaluate the risk of pre- and postoperative trigeminal nerve (V) impairment in large ANs, and to determine predictive risk factors on pre- and postoperative MRIs.

Design: Retrospective study (1994–2009).

Patients and Methods: Patients included had stage 4 or stage 5 AN, using classification of Zini and Magnan. All underwent surgical resection (chiefly using the translabyrinthine approach). Pre- and postoperative trigeminal symptoms were sought. Pre- and 3-month-postoperative MRIs were obtained.

Results: Fifty-four patients (30 females; mean age, 51 years) were operated on. Preoperatively, 3 patients (5.5%) had trigeminal neuralgia, 1 (2%) trigeminal anesthesia, 28 (52%) facial hypoesthesia, and 16 (30%) had no corneal reflex (V1 branch). Postoperatively, 2 patients (4%) had trigeminal neuralgia, 1 (2%) had trigeminal anesthesia, 24 (44%) had facial hypoesthesia, and 26 (48%) had no corneal reflex. Keratitis occurred in 42% of patients with absent corneal reflex postoperatively. After analyzing preoperative MRI, there was only one predictive factor of preoperative trigeminal impairment: impaction of the tumor on cerebellar peduncles (P < 0.05). Postoperative trigeminal deficit was correlated with one finding on postoperative MRI: nonvisibility of V on MRI (P < 0.05). Postoperative trigeminal deficit was correlated with one finding on preoperative MRI: impaction of the tumor on cerebellar peduncles (P < 0.05).

Conclusions: Trigeminal impairment in large and compressive ANs has to be sought to avoid corneal complications in particular. If trigeminal hypoesthesia remains relatively stable (≈50%) after tumor removal, there appears to be a worsening of preoperative function of V1. We were able to correlate trigeminal involvement with pre- and postoperative MRI findings.