Anatomical Variations of the Temporalis Muscle: A Magnetic Resonance Imaging-Based Study

Area of Science:

• Anatomy
• Radiology
• Human Physiology

Background:

• The temporalis muscle, crucial for mastication and jaw movement, possesses complex superficial and deep layers.
• Anatomical variations in the temporalis muscle can impact chewing efficiency and are linked to temporomandibular joint disorders (TMDs) and bruxism.

Purpose of the Study:

• To investigate and classify anatomical variations of the temporalis muscle, focusing on superficial and deep layer integrity and hypoplasia.
• To enhance understanding of temporalis muscle morphology for improved clinical diagnostics and treatment strategies.

Main Methods:

• Magnetic Resonance Imaging (MRI) was employed to examine the temporalis muscle anatomy in 58 participants (34 female, 24 male).
• Assessment included the presence of superficial and deep muscle layers, a longitudinal muscle core, and hypoplasia in the superficial layer's posterior portion.
• Participants were categorized based on observed anatomical variations, with descriptive statistics and nonparametric tests used for analysis.

Main Results:

• Significant anatomical variability was observed in the temporalis muscle.
• Hypoplasia of the superficial layer's posterior portion was noted in 26 cases and was significantly more prevalent in males (p=0.02168).
• The temporalis muscle was classified into three groups: intact layers (72.4%), hypoplastic superficial posterior layer (22.4%), and only deep layer present (5.2%).

Conclusions:

• This study highlights significant anatomical variability in the temporalis muscle, including layer presence and hypoplasia.
• Findings underscore the importance of recognizing these variations for accurate radiological diagnosis of temporomandibular joint disorders (TMDs).
• Understanding temporalis muscle anatomy variations can lead to more effective, personalized treatment strategies for related conditions.