The Natural History of Facial Schwannomas: A Meta-analysis of Case Series

Background Facial nerve schwannomas generate a clinical dilemma because the morbidity of intervention can be comparable to its natural course. The factors leading to morbidities associated with this neoplasm are poorly understood.

Objective To establish predictors of facial paralysis and auditory morbidity secondary to facial nerve schwannomas by assimilating patient-level patient data from the literature.

Methods A systematic review of the English literature was conducted for studies regarding facial schwannomas. Studies were included only if they presented patient-level data and reported House-Brackmann scores. Odds ratios were estimated using generalized linear mixed models with case series as a random effect.

Results Data from 505 patients were collected from 32 studies. The mean age was 42.8 years (SD = 16.0, N = 387), 46.7% were males (N = 351), and 50.6% were left-sided (N = 89) in studies where those factors were recorded. The most common presenting symptom was facial palsy for intratemporal tumors and hearing loss for intradural tumors. Patient age, sex, and tumor size were not associated with facial nerve or hearing function. The odds of higher grades of facial weakness were greater for left-sided tumors (OR = 3.05, p = 0.01), intratemporal involvement (OR = 5.52, p < 0.001), and a greater number of facial nerve segments involved (OR = 1.31, p < 0.001). Intradural (OR = 0.60, p = 0.01) and extracranial (OR = 0.53, p < 0.001) involvement was associated with lower odds of facial weakness. Positive predictors of hearing loss were intradural involvement (OR = 2.97, p < 0.001) and number of facial nerve segments involved (OR = 1.37, p = 0.02). Extracranial involvement was a negative predictor of hearing loss (OR = 0.28, p = 0.02), and intratemporal involvement had a protective effect (OR = 0.44, p < 0.05).

Discussion The most important factors associated with facial weakness and hearing loss are tumor location and the number of facial nerve segments involved. Facial weakness is associated with intratemporal location and hearing loss is associated with tumors more proximal to the brainstem. An understanding of the factors that contribute most heavily to the natural morbidity can help guide the appropriate timing and type of intervention in future cases.