Occult Temporal Bone Facial Nerve Involvement by Parotid Malignancies with Perineural Spread

To characterize disease presentation and outcomes following surgical treatment of parotid malignancies with occult temporal bone facial nerve (FN) involvement.

Case series with chart review.

Tertiary academic referral center.

Thirty consecutive patients (mean age 58 years; 77% men) who underwent surgery for parotid malignancies with occult perineural involvement of the intratemporal FN were included. Primary outcome measures included margin status and recurrence.

The mean duration of clinical follow-up was 49 months, and the most common presenting symptom was FN paresis (n = 23; 77%) followed by pain (n = 15; 50%). To obtain a proximal FN margin, 27 patients (90%) underwent mastoidectomy, and 3 patients (10%) had lateral temporal bone resection. The intratemporal FN margin was cleared in 26 patients (87%), most commonly in the mastoid segment (60%). Adjuvant therapy was given in 25 patients (83%). Ten patients (33%) experienced locoregional (4; 13%) and/or distant (8; 27%) recurrence at a median of 19 months (mean 26, 2-54 months) following surgery. Locoregional failure was significantly more common in cases with a positive intratemporal FN margin (66% vs 8%; P = .045). Overall 1-, 3-, and 5-year disease-specific survival rates were 83%, 79%, and 72%, respectively.

Perineural invasion of the intratemporal FN by parotid malignancy is uncommon. Normal preoperative FN function does not preclude histopathologic involvement. Temporal bone FN exploration should be considered when a positive margin is encountered at the stylomastoid foramen, as failure to do so is associated with an increased rate of locoregional recurrence.