A cause of entrapment of the lingual nerve : ossified pterygospinous ligament – a case report

The pterygospinous ligament extends from the pterygospinous process of the lateral lamina of the pterygoid process of the sphenoid bone, coursing inferior level of the oval foramen, to the spine of sphenoid bone in the infratemporal fossa. The ossification of ligament forms the pterygospinous bony bridge and pterygospinous foramen (Figure 1). In existence of this case, branches of the mandibular nerve innervating the temporal, masseter and lateral pterygoid muscles run through the pterygospinous foramen [1–5]. The lingual nerve is a branch of the mandibular nerve, itself a branch of the trigeminal nerve. The lingual nerve supplies sensory innervation to the mucous membrane of the anterior two-thirds of the tongue. It also carries nerve fibers that do not originate from the trigeminal nerve, including taste sensation to the anterior part of the tongue as well as parasympathetic and sympathetic fibers. It runs between the tensor veli palatini and lateral pterygoid muscles, where the chorda tympani joins it. Normally, the soft muscular tissue that covers the lingual nerve protects it against compression and tension. In existence of a pterygospinous bony bridge, the nerve can be entrapped between the bone and the pterygoid muscle during contraction. The entrapment of the lingual nerve causes numbness on its area of distribution and pain during talking. The ossified pterygospinous ligament is a major cause of the entrapment of the lingual nerve or a branch of the mandibular nerve. The ossified pterygospinous ligament or a wide lateral lamina may cause mandibular neuralgia [4–6]. Moreover, ossified pterygospinous ligament can constitute an obstacle for the mandibular nerve block that is a preferred method for pain relief especially for the fractures of mandible or cancer patients [1,2,7].