Pterygoideus proprius muscle: stuck between the greater wing and lateral pterygoid plate

The muscles of mastication are derived from a common embryological source, and the presence of accessory muscles in the infratemporal fossa (ITF) is uncommon. Here, we present findings from postmortem dissection of the ITF revealing a unilaterally present muscle extending from the greater wing of the sphenoid to blend inferiorly with the medial and lateral pterygoid muscles before attaching to the lateral pterygoid plate. This muscle is most consistent with the pterygoideus proprius muscle initially described in 1858. Although the exact embryological origin and function of this muscle remain speculative, these topics are nonetheless worth investigating because it may provide insight regarding the ontogeny of muscles descending from the first pharyngeal arch. Additionally, presence of the pterygoideus proprius muscle may have clinical implications and impact surrounding structures such as the mandibular division of the trigeminal nerve, maxillary artery, pterygoid venous plexus, masticatory muscles, and temporomandibular joint (TMJ).