Headache is a common malady experienced by 90% of the US population. Half of the population has suffered from a severe headache, and 25% experience recurrent disabling attacks. Four percent endure chronic daily headaches.
Head pain can be elicited by inflammation or traction of pain-sensitive structures, vasodilation, and muscle contraction (Table 8–1). Nearly all pain-sensitive intracranial structures are innervated by trigeminovascular neurons, mainly of the ophthalmic division. For this reason, most forms of head pain are referred to the eye or temple. Trigeminovascular neurons are bipolar neurons whose cell bodies reside in the trigeminal ganglion. A peripheral branch innervates pain-producing dural blood vessels and the dura itself, and a branch projects centrally into the trigeminal nucleus caudalis. The trigeminal nucleus caudalis also receives afferents from upper cervical pain fibers. The superior salivatory nucleus, a parasympathetic nucleus, ultimately has synaptic connections with the trigeminal nucleus caudalis, probably accounting for the autonomic symptoms of nasal congestion and lacrimation that accompany many headache syndromes.
Table 8–1.Pain sensitivity of structures of the head. ||Download (.pdf) Table 8–1. Pain sensitivity of structures of the head.
|Pain-Sensitive Structures ||Structures Largely Insensitive to Pain |
|Venous sinuses and their tributaries ||Brain parenchyma |
|Dural and meningeal arteries, arteries at the base of the brain ||Ventricular ependyma |
|Portions of the meninges ||Most of the dura |
|Upper cervical nerve roots ||Pia arachnoid |
|Scalp muscles and aponeurosis || |
APPROACH TO THE PATIENT WITH HEADACHE
Clinical descriptions of headache and the neurologic examination usually suffice to diagnose headache types, and further testing is not useful in most cases of primary headache syndromes. Increasing frequency or severity of attacks, subjective dizziness or incoordination, pain increasing by Valsalva maneuver, awakenings with headaches from sleep, new attacks in the elderly, and new attacks in those with cancer or HIV infections increase the chance of detecting a structural abnormality. Magnetic resonance imaging (MRI) scanning is more sensitive than computed tomography (CT) in detecting abnormalities relevant to headache, with the exception of apoplectic headaches, whereas the presence of intracerebral hemorrhage is better detected by CT. Electroencephalography is rarely useful in the evaluation of headache, except in rare patients in whom fleeting focal complaints could be secondary to a seizure disorder. Thermography does not provide additional useful information.
PRIMARY HEADACHE SYNDROMES
ESSENTIALS OF DIAGNOSIS
Migraine Without Aura (80% of patients)
At least five attacks
Headache attacks lasting 4–72 hours (unless successfully treated)
At least two of the following pain characteristics:
During headache at least one of the following:
Migraine With Aura (15–20% of patients)
Same features as migraine without aura
Visual symptoms, including positive features (eg, flickering lights, spots, ...