Headaches that accompany disease of ligaments, muscles, and apophysial joints in the upper part of the cervical spine are referred to the occiput and nape of the neck on the same side and sometimes to the temple and forehead. These headaches have been reproduced by the injection of hypertonic saline solution into the affected ligaments, muscles, and facet joints and are comparable to the regions of sclerotogenous referred pain that is discussed in Chap. 7. Such pains are especially frequent in late life because of the prevalence of degenerative changes in the cervical spine and tend also to occur after whiplash injuries or other forms of sudden flexion, extension, or torsion of the head on the neck. If the pain is arthritic in origin, the first movements after the individual has been still for some hours are stiff and painful. The pain of fibromyalgia, a controversial entity, is characterized by tender areas near the cranial insertion of cervical and other muscles. There are no pathologic data as to the nature of these vaguely palpable and tender regions, and it is uncertain whether the pain actually arises in them. They may represent only the deep tenderness felt in the region of referred pain or the involuntary secondary protective spasm of muscles. Massage of muscles, heat, and injection of the tender spots with local anesthetic has unpredictable effects but relieves the pain in some cases. Unilateral occipital headache is often misinterpreted as occipital neuralgia (see further on).
The headache of meningeal irritation (usually due to infection or hemorrhage) is typically acute in onset, usually severe, generalized, deep seated, constant, and associated with stiffness of the neck, particularly on forward bending of the neck. It has been ascribed to increased intracranial pressure; indeed, the withdrawal of CSF may afford some relief. However, dilatation and inflammation of meningeal vessels and the chemical irritation of pain receptors in the large vessels and meninges by endogenous chemical agents, particularly serotonin and plasma kinins, are probably more important factors in the production of pain and spasm of the neck extensors. In the chemically induced meningitis from rupture of an epidermoid cyst, for example, the spinal fluid pressure is usually normal, but the headache is severe. Meningeal irritation or inflammation may also be chronic and have as its main feature a concurrently ongoing headache.
A distinctive type of headache is produced by aneurysmal subarachnoid hemorrhage; it is very intense and very sudden in onset and is usually associated with vomiting and neck stiffness. Other causes of an identical syndrome discussed further on, of what has been called “thunderclap headache,” simulate this disease (see Chap. 33). Among them are a type of diffuse cerebrovascular spasm, spontaneous or the result of sympathomimetic drugs, extracranial vascular dissection of the carotid or vertebral arteries, and cerebral venous thrombosis. There are also varieties of exertional headaches, noted below, that cause the thunderclap pattern.