The pterygospinous ligament (Latin: ligamentum pterygospinosum) is a short, fibrous band located in the posterior cranial base. It extends from the lateral pterygoid plate of the sphenoid bone to the spine of the same bone, situated just posterolateral to the foramen ovale. The ligament lies deep to the temporalis muscle and is part of the complex of connective tissue structures that demarcate the infratemporal and pterygopalatine fossae.
Anatomical description
- Origin and insertion: The ligament originates from the posterior edge of the lateral pterygoid plate (also called the pterygoid process) and inserts onto the spine of the sphenoid bone.
- Relations: Anteriorly it is adjacent to the mandibular division (V₃) of the trigeminal nerve as the nerve passes through the foramen ovale. Posteriorly it is close to the otic capsule and the middle meningeal artery.
- Variability: In a minority of individuals the pterygospinous ligament undergoes ossification, forming a bony bridge that creates the pterygospinous foramen (also termed the foramen of Civin). This anatomical variant is reported in roughly 0.5–5 % of skulls examined in anatomical studies.
Clinical significance
- Neurovascular compression: When ossified, the resulting bony arch may encroach upon the mandibular nerve (V₃) or its branches, potentially leading to neuralgia or altered sensation in the distribution of V₃.
- Surgical considerations: Knowledge of a pterygospinous ossification is important in neurosurgical and maxillofacial procedures that involve the infratemporal fossa, foramen ovale, or the mandibular nerve, as the additional bony barrier may complicate access or increase the risk of iatrogenic injury.
- Radiological identification: Ossified pterygospinous ligaments can be visualized on computed tomography (CT) scans of the skull base and are occasionally noted in radiology reports as an incidental finding.
Embryology
The pterygospinous ligament, like other cranial base ligaments, develops from mesenchymal condensation associated with the sphenoid bone during early fetal life. Its potential to ossify is thought to result from metaplastic transformation of fibrocartilaginous tissue, a process similar to that observed in other cranial base ligaments (e.g., the pterygomaxillary ligament).
History and terminology
The term “pterygospinous” combines the Greek pterygo (wing) referring to the pterygoid processes of the sphenoid, and spinosus (spine) referring to the bony spine of the sphenoid. Early anatomical literature from the 19th century described the ligament as a variable structure, and modern anatomical texts retain the nomenclature while noting its clinical relevance when ossified.
References
- Standring, S. (Ed.). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd ed. Elsevier, 2020.
- Tubbs, R. S., et al. “Variations of the Pterygospinous Ligament and Their Clinical Significance.” Journal of Neurosurgery, vol. 127, no. 5, 2017, pp. 1305‑1312.
- Hisham, A., & Goh, Y. “Incidence of Ossified Pterygospinous Ligament in a Malaysian Population.” Anatomy & Cell Biology, vol. 54, no. 4, 2022, pp. 299‑304.
The information presented reflects current anatomical and clinical knowledge as of 2024.