Predictors of temporalis muscle atrophy and head asymmetry following frontotemporal craniotomy: A retrospective analysis of clinical factors and volumetric comparison.

Background: Temporalis muscle (TM) atrophy is a commonly encountered cosmesis issue following craniotomies. This retrospective study aims to investigate the correlation of clinical and surgical factors with postoperative TM volume and head symmetry in patients undergoing frontotemporal craniotomy.

Methods: Medical records were retrospectively reviewed for patients undergoing pterional or middle fossa craniotomy. Pre- and post-operative clinical factors, intraoperative factors, and magnetic resonance imaging magnetic resonance imaging scans were obtained. TM volumes (cm³) were measured using volumetric analysis. 3-D reconstructed images of the head were independently reviewed to grade head symmetry on a binary scale. Pairwise correlation matrix, multiple linear regression (MLR), and logistic regression (LR) were used to assess the relationship of clinical and operative factors with TM volume and head symmetry.

Results: A total of 46 patients were included for analysis, including pterional (n = 27) and middle fossa (n = 19) groups. The average TM volume loss was 36.8% (standard deviation [Std]: 17.18%) and 29.5% (Std: 16.72%) for patients receiving pterional and middle fossa craniotomies, respectively, indicating the pterional approach may carry a greater risk of disrupting the TM neurovascular supply ensuing subsequent cosmetic disfigurement. MLR identified age and scalp thickness as predictors of TM volume (P < 0.05). Age and scalp thickness were also the only factors found to be predictors of head asymmetry (P < 0.01).

Conclusion: Pterional and middle fossa craniotomy procedures are both associated with significant TM volume loss and subsequent head asymmetry. Age and preoperative scalp thickness are independent risk factors for the development of TM volume loss and head asymmetry. These findings could contribute to the development of preoperative risk stratification algorithms, enabling neurosurgeons to predict the likelihood of cosmetic disfigurement. This would enhance preoperative counseling for patients undergoing craniotomy procedures, especially for elderly individuals and those with thin scalps. Overall, this study provides valuable insights into prognostic factors that may impact the development of poor cosmesis following frontotemporal craniotomy.