Headaches that accompany diseases of the upper cervical spine are well recognized, but their mechanism is obscure and their frequency possibly overestimated. Recent writings have focused on a wide range of causative lesions, such as apophyseal (facet) arthropathy, C2 dorsal root entrapment, calcified ligamentum flavum, hypertrophied posterior longitudinal ligament, and rheumatoid arthritis of the atlantoaxial region. As summarized by Bogduk and Govind, the most credible evidence for this group of disorders comes from systematic injection of anesthetics into cervical structures and effecting complete relief of headache. Even this is not uniformly successful in patients whose cranial pain has been attributed to a cervicogenic mechanism. CT and MRI have divulged a number of these abnormalities. One special variety is discussed further below, under “‘Third Occipital Nerve’ Headache,” and further in Chap. 10.
OTHER CRANIOFACIAL PAINS (SEE CHAP. 44)
This is a common disorder of middle age and later life, consisting of paroxysms of intense, stabbing pain in the distribution of the mandibular and maxillary divisions (rarely the ophthalmic division) of the fifth cranial nerve. The pain seldom lasts more than a few seconds or rarely a minute or two, but it is often so intense that the patient winces involuntarily; hence the term tic. It is uncertain whether the tic is reflexive or quasivoluntary. The paroxysms recur frequently, both day and night, for several weeks or months at a time. Another characteristic feature is the initiation of a jab or a series of jabs of pain by stimulation of certain areas of the face, lips, or gums, as in shaving or brushing the teeth, or by movement of these parts in chewing, talking, or yawning, or even by a breeze—the so-called trigger factors. Sensory or motor loss in the distribution of the fifth nerve cannot be demonstrated, though there are minor exceptions to this rule. In addition to the paroxysmal pain, some patients complain of a more or less continuous discomfort, itching, or sensitivity of restricted areas of the face, features regarded as atypical even though not infrequent.
In studying the relationship between stimuli applied to the trigger zones and the paroxysms of pain, touch and possibly tickle are more likely to be precipitants rather than painful or thermal stimulus. Usually a spatial and temporal summation of impulses is necessary to trigger a paroxysm of pain, which is followed by a refractory period of up to 2 or 3 min.
The diagnosis of tic douloureux rests on the strict clinical criteria enumerated above, so that the condition can be distinguished from other forms of facial and cephalic neuralgia and pain arising from diseases of the jaw, teeth, or sinuses. Most cases of trigeminal neuralgia have no obvious cause (idiopathic), in contrast to symptomatic trigeminal neuralgia, in which paroxysmal facial pain is because of involvement of the fifth nerve by some other disease: multiple sclerosis (may be bilateral), aneurysm of the basilar artery, or tumor (acoustic or trigeminal schwannoma, meningioma, epidermoid) in the cerebellopontine angle. Each of the forms of symptomatic trigeminal neuralgia may give rise only to pain in the distribution of the trigeminal nerve, or it may produce a loss of sensation as well.
Vascular Loop as a Cause of Trigeminal Neuralgia