Variation and distribution in temporalis muscle innervation: A systematic review and meta-analysis of anatomical...

Despite extensive discourse on the utilisation of the temporal muscle for facial reanimation, anatomical description regarding the innervation of its motor nerve branches is incomplete and varied. This systematic review aimed to consolidate the existing evidence concerning the distribution and variation in the pattern of temporalis innervation.

A PRISMA-compliant systematic literature search was conducted in November 2023 and included studies offering anatomical insights into the distribution and variation of temporalis innervation patterns. Multiple category prevalence and proportional meta-analysis were conducted.

The initial search yielded 978 results, from which 13 studies were selected for inclusion. The inferior anterior temporalis muscle region was found to receive innervation from the buccal nerve's superior branch and inferior posterior region from the masseteric nerve. In the superior part, comprising anterior, middle and posterior regions, innervation is provided by the branches of the deep temporal nerve (DTN) arising from various branches of the mandibular or masseteric nerves. Analysis revealed that the most common variation of DTN was the presence of two branches (46%, 95% CI: 46%-63%, I²=94%), followed by three branches (26%, 95% CI: 24%-39%). Subgroup analyses of 86 patients indicated high prevalence rates of innervation by the temporal branches of the buccal nerve (85%, 95% CI: 76%-92%, I²=98%) and temporal branches of the masseteric nerve (72%, 95% CI: 63%-81%, I²=90%).

In conclusion, this systematic review and meta-analysis highlight the evolving understanding and complexities of temporalis innervation, revealing the variations in nerve branches and emphasising the need for further research.