The styloid diaphragm: An underrecognized anatomical landmark for transcervical styloidectomy

The styloid diaphragm (SD) is a band-like anatomical structure located deep to the parotid gland and composed of the styloid process (SP), the styloglossus, stylopharyngeus, and stylohyoid muscles, the stylomandibular and stylohyoid ligaments, and the posterior belly of the digastric muscle. Although the SD may serve as an important anatomical landmark during transcervical styloidectomy, its surgical significance has not been specifically emphasized. We present the surgical anatomy of the SD using schematic illustrations and operative video obtained during transcervical styloidectomy. Through a transcervical approach, the SP was accessed through the prestyloid space without exposing critical retrostyloid neurovascular structures. The SD was identified as a distinct anatomical boundary separating the prestyloid and retrostyloid compartments. Circumferential dissection of the SD allowed complete mobilization and resection of the SP while avoiding unnecessary manipulation of the internal carotid artery, internal jugular vein, vagus nerve, hypoglossal nerve, and other lower cranial nerves located within the retrostyloid space. Recognition of the SD provides a practical anatomical framework for orientation during surgery and facilitates a prestyloid surgical corridor to the SP. Understanding the SD may contribute to safer and more efficient transcervical styloidectomy.