|13||CRANIAL NEURALGIAS AND CENTRAL CAUSES OF FACIAL PAIN||G44.847, G.44.848 or G44.85|
Pain in the head and neck is mediated by afferent fibres in the trigeminal nerve, nervus intermedius, glossopharyngeal and vagus nerves and the upper cervical roots via the occipital nerves. Stimulation of these nerves by compression, distortion, exposure to cold or other forms of irritation or by a lesion in central pathways may give rise to stabbing or constant pain felt in the area innervated.
The cause may be clear, such as infection by herpes zoster or a structural abnormality demonstrated by imaging, but in some cases there may be no cause apparent for neuralgic pain.
Trigeminal and glossopharyngeal neuralgias present a problem of terminology. When pain is found to result from compression of the nerve by a vascular loop at operation, the neuralgia should strictly be regarded as secondary. Since many patients do not come to operation, it remains uncertain as to whether they have primary or secondary neuralgias. For this reason the term classical rather than primary has been applied to those patients with a typical history even though a vascular source of compression may be discovered during its course. The term secondary can then be reserved for those patients in whom a neuroma or similar lesion is demonstrated.
Another difficulty arises with the condition that used to be known as atypical facial pain (an inappropriate term since many cases conform to a pattern). The fact that some cases follow surgery or injury to the face, teeth or gums suggests the possibility of an infectious or traumatic cause. Until more is known of the condition, persistent idiopathic facial pain seems a preferable non-committal title.