Headache and vertigo of cervical origin
Headache
Headache is one of the most prevalent pain disorders, affecting 66% of the global population, with a daily prevalence of 4–5%.1 This major health problem, disturbing both quality of life and work, is comparable to back pain in that it affects mostly the active population and thus has socio-economic consequences, generating high costs for therapy as well as for absence from work. It was reported in 1999 that in the US alone, migraine headache cost American employers about $US13 billion per year because of missed workdays and impaired work function.2 Headache is not an easy issue. It occurs in many forms and the causal mechanisms are still not well understood.3 Furthermore, the patient’s description may be so vague that distinction between the common benign forms and more serious syndromes is sometimes difficult. Sensitive structures within the skull can become stimulated by tension, stretching, compression or displacement, all of which can be the consequence of inflammation (e.g. meningitis), increase of pressure (e.g. tumour, haematoma) or decrease in pressure (e.g. lumbar puncture). The same happens when vascular structures dilate or constrict.
Very often the problem lies outside the skull, as in tension-type headache of muscular contraction, trigeminal neuralgia, temporal arteritis and conditions affecting the teeth, the temporomandibular joint, the eyes, the sinuses or other structures in this region. Headache may also be psychogenic.4
The differential diagnosis of headache is challenging and should proceed in an orderly fashion. Crucial elements include a thorough history, supplemented by general medical and neurological examinations, as well as laboratory testing and neuroimaging in selected patients. By using a logical and clinical classification system, the clinician will be able to identify those patients with headache suited to orthopaedic therapy.
The first step is to distinguish primary from secondary headaches. The International Headache Society (IHS) has classified headaches as primary, where there is no other causative factor, or secondary, where the headache occurs in close relationship to another disorder to which it is attributed.5 The former tends to decline with age, while the prevalence of the latter increases.6
Primary headache is usually classified into three main groups. The most common form is tension-type headache, a mild to moderate dull pain, often brought on by stress which has a global prevalence of 83%.7 Migraine has a prevalence of 10%, and cluster headache constitutes for about 3% (Box 1). Except migraine, which can sometimes be treated with techniques described in this book, these primary headache disorders fall outwith the scope of this work and will, therefore, only be discussed briefly.
Secondary headaches are related to other disorders. This can be a local lesion in the head or neck or a generalised lesion (Box 2). Orthopaedic medicine is interested in the secondary headaches in which the cause must be sought in the cervical spine.8
Primary headache
Tension-type headache
Tension-type headaches (TTH) are the most common chronic headaches. Rasmussen and colleagues surveyed 1000 adults from the general population and reported a lifetime prevalence of TTH of 69% in men and 88% in women.9 Jensen reported a lifetime prevalence of 78% in a general adult population.10 Some 30% were affected more than 2 weeks a year and 3% were labelled as chronic. The term describes headaches that have previously been grouped under various ill-defined headings such as ‘tension headache’, ‘stress headache’ and ‘muscle contraction headache’.
TTH is described as a dull, non-pulsatile pain, affecting the entire head, of oppressive and progressive character, moderate or severe intensity, variable duration (up to several days) and lacking the typical features of migraine. In 90% of cases the pain is bilateral, the typical location being in the occipital, parietal, temporal and frontal areas.11,12 Though the duration and intensity of the pain is variable, this headache is not as debilitating as migraine, and sufferers are usually able to continue their daily activities.
Box 3 cites the IHS operational criteria for tension-type headache.13
Although TTH is the most frequent type of primary headache (two-thirds of the population have suffered an episodic TTH), its physiopathology is still the cause of controversy. For many years it has been thought that TTH was directly related to muscular tension. However, more recently it has been postulated that, although muscular tension is usually present in most cases, it is possible that the origin is more central, due to the hyperexcitability of the trigeminal caudal nucleus and of other structures of the central nervous system that register, modulate and interpret head pain. Precipitating factors for tension-type headache are emotional stress, anxiety, depression and myofascial pain.14,15 This pathology type may also be induced, intensified or made chronic by analgesic abuse.16
Treatment
For acute episodes, the most common treatment involves the use of simple analgesics and anti-inflammatory medications. For chronic tension-type headache and for prevention, amitriptyline17,18 is considered the treatment of choice, but also nortriptyline, mirtazapine19 and tizanidine can be used. Amitriptyline (AMT) is a tricyclic antidepressant, possessing an analgesic effect that is independent of its antidepressive effect. The analgesic mechanism is not precisely known. Probably, serotonin (5-HT) and noradrenaline reuptake inhibition of the CNS plays a fundamental role in the control of the pain.20
Migraine headache
Migraine is a neurovascular disorder characterized by neuronal aura symptoms and vascular headache. Since 1988 migraine is defined by the criteria set by the Headache Classification Committee of the International Headache Society (IHS).13 It consists of two subgroups: migraine with aura and migraine without aura. In 20% of cases, the migraine headache is preceded by a visual hallucination/illusion known as an aura. Typically, the aura is a serrated arc of scintillating, shining, crenulated shapes, beginning adjacent to central vision and expanding peripherally over 5–20 min, within one visual field, usually followed by headache. The scintillations are followed temporarily by a blind region, after the same retinotopic progression from central to peripheral visual fields. Sometimes the visual hallucinations are accompanied by unilateral paraesthesia or numbness, hemiparesis and dysphasia. The typical characteristics of migraine headache are unilateral location, pulsating quality, moderate or severe intensity and aggravation by routine physical activity. The pain peaks and then subsides, and usually lasts between 4 and 72 hours in adults and 1 and 48 hours in children. The frequency of attacks is extremely variable, from a few in a lifetime to several times a week, and the average migraineur experiences from one to three headaches a month. The pain is accompanied by other features. Nausea occurs in almost 90% of patients, while vomiting occurs in about one-third of patients. Many patients experience sensory hyperexcitability manifested by photophobia, phonophobia, osmophobia and seek a dark and quiet room. Blurred vision, nasal stuffiness, diarrhoea, polyuria, pallor or sweating may be noted during the headache phase. There may be localized oedema of the scalp or face, scalp tenderness, prominence of a vein or artery in the temple, or stiffness and tenderness of the neck. Impairment of concentration and mood are common. Box 4 presents the diagnostic criteria.21
Many theories have been formulated in the last six decades about the pathogenesis of migraine, but the problem is still not fully clarified.
The first theory, conceived by Wolff in 1948, is build up on a vascular basis, considering three observations: (a) during the migraine attack extra-cranial vessels dilate and are throbbing in many patients; (b) the stimulation of intra-cranial vessels provokes an ipsilateral headache; (c) vasoconstrictor drugs, like ergot derivatives, show a curative effect. On these observations, he hypothesized that an intra-cranial vasoconstriction could be responsible of the migraine aura and of the following hyperaemic reaction with local vasodilatation and activation of the perivascular nociceptive endings, resulting in acute unilateral headache.22
Another possible interpretation of the migraine pain is proposed on the basis of a depression of the cortical electrical activity, the so-called ‘cortical spreading depression theory’. Shortly before migraine headache begins, a spreading depression develops in the cortex of one hemisphere. This cortical spreading depression (CSD) is a relatively short-lasting wave of depolarization that spreads across the surface of the brain, moving from the back (occipital region) of the cerebral cortex toward the front at about 3–5 mm/minute. This phenomenon is frequently referred to in the literature as the ‘spreading depression of Leao’.23 CSD begins with a brief wave of excitation, followed by a prolonged period of neuronal depression, which is associated with disturbances in nerve cell metabolism and regional reductions in blood flow.24 Experimental evidence supports a relationship between CSD as a cause of migraine aura.25 Also during an aura, cerebral blood flow abnormalities are often seen. Support for the CSD theory comes from observations that, in patients who have migraine with aura, a gradual spread of reduced blood flow that mimics the rate of progression of CSD can be measured during the aura phase.26
Current theories however explain migraine as a neurovascular disorder27 in which the trigeminocerebrovascular system plays an unique pivotal role. It is hypothesized that the primary dysfunction in migraine occurs within the central nervous system and that this evokes changes in blood vessels within pain-producing intracranial meningeal structures that give rise to headache pain.28 The brain itself is not provided with pain sensitive endings, while meninges are rich of nociceptors.29 Tracing studies have identified the trigeminal nerve as the major afferent pathway for pain from the vessels and dura mater.30 This trigeminovascular system consists of the neurons that innervate the cerebral vessels and the dura and whose cell bodies are located in the trigeminal ganglion. This ganglion contains bipolar cells. Peripheral fibres innervate blood vessels in the meninges, the extracranial arteries, and those in the circle of Willis. These nerve fibres contain nociceptors that are capable of generating pain impulses, and the endings of these nerve fibres contain peptide neurotransmitters.31 The centrally projecting fibre synapses in the caudal brain stem or high cervical cord. The trigeminal innervation is predominantly to the forebrain but extends posteriorly to the rostral basilar artery, whereas the more caudal vessels are innervated by the C2 and C3 dorsal roots, which also synapse with the central trigeminal neurons.
The neurovascular hypothesis proposes that either migraine triggers or CSD (cortical spreading depression)32 can activate trigeminal nerve axons, which then release neuropeptides (such as substance P, neurokinin A, and CGRP) from axon terminals near the meningeal and other blood vessels.33 Substance P and neurokinin A cause vasodilation and promote the extravasation of plasma proteins and fluid from nearby meningeal blood vessels, where they produce an inflammatory response. This response is termed sterile neurogenic perivascular inflammation. The neuropeptides may also sensitize nerve endings, providing a mechanism for sustaining the headache. When activated, the trigeminal nerve also transmits pain impulses to the trigeminal nucleus caudalis, which relays pain impulses to higher centres of the brain. According to the neurovascular theory, vasodilation is not the cause of migraine headaches but is an accompanying phenomenon attributable to trigeminal nerve activation. Although the cause of this activation is not known, it may be due to ionic and metabolic disturbances in brain function, such as those associated with CSD. It has also been proposed that abnormal activity in brain stem sensory nuclei may cause antidromic activation of trigeminal sensory pathways.34
The integrated hypothesis of migraine pathogenesis is an attempt to consolidate various theories and explain several observations related to migraine pain. According to this theory, triggers such as stress, glare, noise, the patient’s internal clock, the dilation of the internal or external carotid arteries, or other factors may activate specific centres in the brain stem. One such centre, the locus ceruleus, causes changes in epinephrine levels. Another centre, the dorsal raphe nucleus, affects serotonin levels in the brain.35 They cause constriction of cerebral blood vessels and a localized deficiency in blood flow, provoking CSD. This, in turn, stimulates trigeminovascular fibres, eliciting neurogenic inflammation and headache pain. Nerve fibres from the locus ceruleus, the dorsal raphe nucleus, and the trigeminal nerve cause a stimulation of cranial nerves that dilate both cerebral and extracranial blood vessels. The dilation of meningeal vessels contributes to pain generation.36 The locus ceruleus also sends fibres to higher centres of the cerebral cortex, where it influences a person’s state of arousal and awareness, and descending projections interact with the body’s pain control mechanisms. Likewise, the dorsal raphe nucleus sends multiple fibres to blood vessels and upward toward the cerebral cortex. These serotonin-secreting fibres help regulate sleep and neuro-endocrine functions. Other connections are made with lower brain stem areas and with the hypothalamus. A disruption in the normal function of the hypothalamus may be responsible for prodromal signs and symptoms of migraine such as mood changes, food cravings, drowsiness, thirst and yawning.37 These signs and symptoms may occur several hours, or even as long as 1 day, before headache pain begins.
Treatment
The classic therapeutic approach has three major pillars: avoidance of migraine triggers, treatment of the acute attack by medication and regular use of preventive medications.
Acute attacks are treated with simple analgesics and NSAIDS, and more migraine-specific drugs, such as ergot-derivates38 and triptans, which are active at 5-HT1 receptors. However, triptans (sumatriptan and its six licensed successors), because of their better tolerability, have replaced ergotamine in most cases.39 They reduce neuronal activity via these receptors at the trigeminocortical complex and thalamic level. There are still situations where tolerability and contraindications to use are a problem. The main issue for triptans relates to their vasoconstrictor properties and related cardiovascular and cerebrovascular safety concerns. This necessitates that triptans are not used in patients with cerebrovascular or cardiovascular contraindications.40
Prevention
Migraine prevention is an important component of therapy aimed at reducing the attack frequency and severity. Unfortunately, the mechanisms of action of current preventives are not well understood. A potential mechanism is the inhibition of cortical spreading depression but, as noted above, the efficacy against cortical spreading depression does not necessarily predict the efficacy in treating migraine without aura. Substances that have proven beneficial in migraine, with and without aura, broadly comprise compounds from the following classes: beta-blockers (propranolol), antidepressants (amitriptyline), anticonvulsants (valproate and topiramate), calcium channel blockers (flunarizine) and serotonin antagonists (methysergide). According to the pathophysiological concepts discussed above, these drugs most probably target the activity of modulatory circuits as well as the neuronal activity in afferent sensory pathways such as the trigeminal system.41 Although many patients can be effectively managed using the available substances, side effects and contraindications because of co-morbidities can complicate treatment. A particular problem is the prediction of which patients will respond to which substance as treatment is still largely conducted by trial and error.
Migraine and orthopaedic medicine
On empirical grounds Cyriax42 found that manipulation of the cervical spine may have a therapeutic effect. He discovered that the onset of an acute attack could sometimes be aborted by 30 seconds of strong neck traction. Other observations have also demonstrated some relationship between mechanical stimulation of the occipital nerve and induction or abortion of migraine attacks.43 Also nerve blocks of the greater occipital nerves proved to be curative in a high percentage of migraine sufferers.44,45 These results reinforce previous evidence of convergence of cervical afferents on the trigeminal sensory circuit and suggest that, by modifying the central processing of pain signals in migraine in the thalamus, greater occipital nerve blocks shut down several symptom generators.46,47 Therefore, manipulation of the cervical spine can have a preventive effect in some patients, especially the middle-aged or elderly and it is always worthwhile manipulating the cervical spine in migraineurs of over 40 years of age. When the neck movements are painless, one session usually suffices. Manipulation is performed in four directions: both rotations and both lateral flexions. Painful neck movements may require two or three sessions. The techniques are described in Chapter 11.
Cluster headache
Also called ‘Horton’s neuralgia’, this headache is characterized by recurrent short-lasting attacks (15 to 180 minutes) of excruciating unilateral periorbital pain accompanied by ipsilateral autonomic signs (lacrimation, nasal congestion, ptosis, miosis, lid oedema, redness of the eye).48,49 It affects young adults, predominantly males. Prevalence is estimated at 0.5–1.0/1000. Cluster headache (CH) has a circannual and circadian periodicity, attacks being clustered (hence the name) in bouts that can occur during specific months of the year. An attack can be triggered by alcohol, strong odours and napping. During bouts, attacks may happen at precise hours, especially during the night. Cluster headache seems to be associated with trigeminovascular activation and neuroendocrine and vegetative disturbances, though the precise causative mechanisms remain unknown. Involvement of the hypothalamus has been confirmed, explaining, at least in part, the cyclic aspects of CH.50 The disease is familial in about 10% of cases. Genetic factors play a role in the susceptibility, and a causative role has been suggested for the hypocretin receptor gene. Diagnosis is clinical. Differential diagnoses include other primary headache diseases such as migraine. At present, there is no curative treatment. There are efficient treatments to shorten the painful attacks and to reduce the number of daily attacks. Acute treatment is based on subcutaneous or intra-nasal administration of sumatriptan.51 Verapamil, lithium, methysergide, prednisone, greater occipital nerve blocks and topiramate may be used for prophylaxis. In refractory cases, deep-brain stimulation of the hypothalamus and greater occipital nerve stimulators have been tried in experimental settings.52 The disease course over a lifetime is unpredictable. Some patients have only one period of attacks, while in others the disease evolves from episodic to chronic form.
Cervicogenic headache
Cervicogenic headache (CEH) is a syndrome characterized by chronic hemi-cranial pain that is referred to the head from either bony structures or soft tissues of the neck. Sjaastad and colleagues53,54 have, in consecutive publications since 1990, established criteria for the diagnosis of headache of cervical origin (Box 5), since 1983 known as ‘cervicogenic headache’.
The pain is mild, usually has an undulating course and may eventually become chronic. There is a marked female preponderance. The neck seems to be involved, either because there has been a trauma, for example whiplash, or because there is limitation of neck movement. There may be accompanying shoulder and/or arm pain. An attack can be precipitated either as the result of neck movement or of direct pressure, for example on examination.55 In their early publications Sjaastad et al mention the headache as being strictly unilateral. Later they restate this and define unilaterality as follows: the headache dominates on one side; when weak, the pain may be only on that side; when severe, it may also be felt on the contralateral side, but to a lesser extent. It never dominates on the contralateral side.56
The fact that neck structures can give rise to headache is now generally accepted. There seems to be a consensus on the pathophysiology. The neuroanatomical basis for CEH is the ‘trigemino-cervical nucleus’. This is a region of the upper cervical spinal cord where sensory nerve fibres in the descending tract of the trigeminal nerve (trigeminal nucleus caudalis) are believed to interact with sensory fibres from the upper C1–C4 cervical roots. This functional convergence of upper cervical and trigeminal sensory pathways allows the bi-directional referral of painful sensations between the neck and trigeminal sensory receptive fields of the face and head. C1 spinal nerve has some ectopic sensory ganglia and it innervates the short muscles of the suboccipital triangle.57 The C2 spinal nerve gives sensory supply to the median and lateral atlantoaxial joints; to several neck muscles (prevertebral, sternocleidomastoid, trapezius, semispinalis and splenius muscles); to the dura of the posterior cranial fossa and the upper spinal canal. Both the C2 and C3 spinal nerves supply the zygapophyseal joints of the adjacent segments. The atlantoaxial ligaments and the dura mater of the spinal canal are innervated by the sinuvertebral nerves stemming from the C1–C3 spinal nerves. The origin is sympathetic; the nerves contain nociceptive, proprioceptive, vasomotor and vaso-sensory fibres.58
Cervicogenic headache and orthopaedic medicine
There are a number of orthopaedic medical conditions that can give rise to headache and that often can be approached very successfully by the use of local treatment (see p. 122). Lesions of the extracranial soft tissues of the locomotor system, especially the capsulo-ligamentous structures of the occipito-atlantoaxial complex, may give rise to segmental headache. The cervical dura mater is often responsible for the vague, multisegmental occipito-frontal, temporal or retro-orbital pain (see p. 16).
Headache, referred from the cervical dura mater
A disco-dural interaction at any cervical level or any space-occupying lesion in the spinal canal may give rise to pain felt in the head. The pain usually radiates from the mid-neck up to the temple, the forehead and behind one or both eyes but rarely to the bridge of the nose. This ‘multi-segmentally referred pain’ is dural in origin and will disappear when treatment to the neck is accomplished. For further details see p. 16.
Matutinal headache in the elderly
As the result of arthrosis at the upper cervical joints, ligamentous contracture may develop and can result in ‘segmental’ pain felt in the upper cervical dermatomes which cover the head. The patient typically complains of occipito-frontal headache felt especially in the morning. Treatment includes capsulo-ligamentous stretching. For a detailed description see p. 163.
Postconcussional headache
The upper cervical capsules and ligaments can also become sprained during trauma, for example an accident that causes concussion of the brain after which a period of immobilization follows. The subsequent build-up of ligamentous adhesions finally results in ‘segmental’ headache. Several authors recognize the possibility of upper cervical capsuloligamentous conditions causing pain in the head. The adhesions can be broken manipulatively. A full description can be found on p. 168.
Vertigo
