Its posterior border usually presents, towards its upper part, a sharp spine from which the pterygospinous ligament extends backwards and laterally to the spine of sphenoid.
Ossified pterygospinous ligament seems to be a major cause of entrapment of lingual nerve or a branch of mandibular nerve and may cause mandibular neuralgia.
Osseous bars were either complete or incomplete, that is, if bony bridges were extending from lateral pterygoid plate to sphenoid spine apex, it was termed complete, and if pterygospinous ligament failed to make a contact with sphenoid spine, it was considered incomplete.
The pterygospinous ligament, described by Civinini in 1835 (cited by Tebo ), is directed from the spine of sphenoid to the pterygospinous process, when ossified, establishing the pterygospinous foramen, also known as Civinini foramen.
Wood  reported an 8% pterygospinous ligament ossification in Hawaiian skulls.
Complete ossification of pterygospinous ligament was found in 3.6% skulls--1.31% bilaterally as well as 1.31% on the right side and 0.98% on the left side.
 studied 452 adult dry crania in Anatolian population and observed completely ossified pterygospinous ligament in 5.5% skulls.
 were the first to demonstrate the presence of ossified pterygospinous ligament causing compression of lingual nerve between the bony bridge and medial pterygoid muscle, which results in lingual numbness and pain, associated with speech impairment.
In the presence of an ossified pterygospinous ligament, the main trunk of mandibular nerve is redirected laterally and its dividing neural routes (lingual nerve and inf.
Causes of ossification of pterygospinous ligament may not be known but these formations were more often present in males and unilateral presence was more common than bilateral one.
Out of 500 studied skulls, the presence of pterygospinous bars and broad lateral pterygoid plates was reported in 51 (10.2%) skulls--completely ossified pterygospinous ligament in 20 skulls (4%) and incomplete ossification of pterygospinous ligament in 31 skulls (6.2%).
Knowledge of these anatomical variations is important because ossification of pterygospinous ligament can result in formation of a foramen through which mandibular nerve branches may pass in most of the cases which may get compressed, depicting various clinical symptoms, depending upon the dimensions of the pterygospinous foramina and grades of compression.