Isolated bilateral temporalis hypertrophy: a rare case report and technical insight into botulinum toxin type A injection

Isolated bilateral temporalis muscle hypertrophy (IBTMH) is a rare clinical condition characterized by symmetrical enlargement of the temporalis muscles without masseter involvement. This case report presents a 47-year-old male with progressive bilateral temporal swelling and discomfort during mastication, significantly affecting his quality of life. Clinical examination and magnetic resonance imaging (MRI) confirmed homogenous enlargement of the temporalis muscles with no underlying pathology. The patient was treated with botulinum toxin type A (BTxA) injections in two sessions, following anatomical landmarks and established guidelines to ensure safety and efficacy. Post-treatment follow-ups revealed significant improvement in symptoms and normalization of temporal contours, with MRI confirming muscle volume reduction. This case contributes to the limited literature on IBTMH and supports BTxA as a safe, non-invasive, and effective treatment modality. It also underscores the need for standardized injection techniques to minimize complications in the anatomically complex temporal region. Further case reports and research are essential to improve clinical understanding and guide best practices for diagnosis and management of this rare entity.