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

Abstract

Objectives:

Evaluate the risk of pre- and postoperative trigeminal nerve (V) impairment in large ANs. Determine predictive risk factors on pre- and postoperative MRIs.

Methods:

Retrospective study (1994-2009) including patients with stage 4 or 5 AN (classification of Zini-Magnan). All underwent surgical resection (chiefly translabyrinthine approach). Pre- and postoperative trigeminal symptoms were sought. Pre- and 3-month-postoperative MRIs were obtained.

Results:

Fifty-four patients (30 females, mean 51 years) were operated. Preoperatively, 3 patients (5.5%) had trigeminal neuralgia, 29 (54%) had trigeminal hypoesthesia (V1 < V2 = V3), and 16 (30%) had no corneal reflex (V1 branch). Postoperatively, 2 patients (4%) had trigeminal neuralgia, 1 (2%) had trigeminal anesthesia, 25 (46%) had trigeminal hypoesthesia (V1 = V2 = V3), 26 (48%) had no corneal reflex, and most also had House-Brackmann ≥ grade IV facial paralysis. 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/compressive ANs has to be sought particularly to avoid corneal complications. If the frequency of trigeminal hypoesthesia slightly diminishes after tumor removal, there is worsening of preoperative function of V1 and increased frequency of absent corneal reflex, also worsened by facial paralysis. We were able to correlate trigeminal involvement with pre- and postoperative MRI findings.