17 Headaches
Introduction
Headaches can be due to a variety of causes but are generally categorised into primary and secondary headaches (Box 17.1). The primary headaches, the main focus of this chapter, are headaches that are not caused by another disease or condition, unlike secondary headaches. The International Headache Society (IHS) maintains a list of conditions that can produce headache symptoms secondary to the disorder (International Headache Society 2004). This list is extensive and the clinician managing the headache patient needs to be familiar with these conditions and include or exclude them as appropriate. Such causes may include intracranial mass, vascular lesions, systemic disorders or infection. In particular, the clinician needs to be aware of the following danger signs that may indicate the need for aggressive investigation.
• Sudden onset of headache, severe in nature, that peaks quickly (minutes to a few hours) or that gets progressively worse. For example, subarachnoid haemorrhage may be of sudden onset, or headache due to infection such as abscess or meningitis may worsen over hours to days.
• Any patient that presents with the ‘worst headache of my life’.
• Focal neurological signs, particularly on the first occurrence of the headache, including changes in personality, mental status, and level of consciousness.
• Headache precipitated or made worse by bending, sneezing, coughing, or exertion. This may indicate raised intracranial pressure. Vomiting with headache may also be associated with raised intracranial pressure.
• Changes in the headache pattern of an existing headache sufferer.
• Association of headache with fever, rash, nucal rigidity, lymphadenopathy, and particularly if for the first time, photophobia.
• New headaches in patients under 5 or over 50 years of age.
Box 17.1
The primary and secondary headaches
Primary headaches | Secondary headaches (attributed to:) |
---|---|
Adapted from IHS 2004, with permission.
Migraine
Migraine is a common disabling condition that is ranked nineteenth by the World Health Organization amongst worldwide diseases causing disability (IHS 2004). Approximately 15–20% of the general population suffers from migraine headaches (Bolay et al. 2002). It has considerable social and economic impact; hence effective treatment strategies have the ability to make significant improvements in the quality of life of the sufferer, and have positive social benefit as well. In this chapter we will discuss the two most common forms of migraine, migraine with aura and migraine without aura, along with the childhood syndromes that are often the precursor of migraine.
Migraine without aura (MWOA)
Migraine without aura was previously known as common migraine.
The International Headache Society (2004) describes MWOA as: ‘Recurrent headache disorder manifesting in attacks lasting 4–72 hours. Typical characteristics of the headache are unilateral location, pulsating quality, moderate or severe intensity, aggravation by routine physical activity and association with nausea and/or photophobia and phonophobia’.
To be diagnosed with MWOA the individual must have had at least five attacks lasting 4–72 hours with at least two of the following characteristics: unilateral pain location, pulsating quality, moderate to severe pain intensity and/or aggravated by routine activity. It must also be accompanied by either nausea and/or vomiting or phono- and photophobia (Box 17.2) (IHS 2004).
Box 17.2
Diagnostic criteria for migraine without aura
Diagnostic criteria
A. At least five attacks fulfilling criteria B–D
B. Headache attacks lasting 4–72 hours (untreated or unsuccessfully treated)
C. Headache has at least two of the following characteristics:
D. During headache at least one of the following:
From IHS 2004, with permission.
Peripheral sensitisation in migraine
Migraine is a complex phenomenon that likely has multiple causes. However, current thought on the pathophysiology of migraine is that an initial activation of meningeal nociceptors causes a release of substance P and salcitonin gene related peptide (CRGP) from the nociceptive nerve endings, which in turn causes vasodilation and protein extravasation (Dalkara et al. 2006). This process is known as neurogenic inflammation and/or peripheral sensitisation. In peripheral sensitisation the increased sensitivity of the nociceptors to activation may develop to a degree that, in combination with central sensitisation, they are susceptible to activation by the arterial pulse and head movements (Dalkara et al. 2006). In this way, normal physiological activities may become sources of pain. The causes of the initial activation are still not fully described but several possible mechanisms are discussed below.
Central sensitisation
Accompanying peripheral sensitisation is the phenomenon of central sensitisation. Activation of trigeminovascular nociceptors leads to an increase in activity in the second-order neurons in the trigeminocervical nucleus (Bolay et al. 2002). Furthermore, activation in the trigeminocervical nucleus occurs with stimulation of both meningeal afferents and those from the greater occipital nerve (a branch of the C2 dorsal root), and that stimulation for just 5 minutes can lead to an increase in response in the nucleus for over an hour to other nociceptive stimuli, including if that stimulation is received from the C2 innervation (Goadsby 2005). This is particularly relevant for manual therapy practitioners with their focus on removal of pain generators from the cervical spine. It is likely that this sensitisation involves the activation of NMDA receptors in the nucleus as in vitro application of sumatriptan, an antimigraine drug, is effective in blocking NMDA receptor activation (Buzzi & Moskowitz 2005).
The cutaneous allodynia is often associated with migraine and is thought to be another symptom of this central sensitisation of the trigeminocervical nucleus. The allodynia usually occurs on the ipsilateral forehead to the headache, but has been documented to occur over the ipsi- and contralateral hands as well (Dalkara, Zervas et al. 2006).
Brainstem dysfunction and disinhibition
Brainstem dysfunction has also been implicated in migraine, both as a primary migraine generator, and through failure of brainstem pain inhibition mechanisms. Goadsby (2005) reports activation of the locus ceruleus and periaqueductal grey (PAG) in migraine without aura, and that these correspond to areas that have generated migraine-like symptoms in patients when stimulated electrically. Similarly, Goadsby reports excess iron has been found in the PAG of episodic and chronic migraineurs, and lesions in this area have been known to cause migraine. The notion of brainstem dysfunction is further supported by the presence of measured balance deficits, vestibular changes (Akdal et al. 2007; Akdal et al. 2009; Asai et al. 2009), and subclinical cerebellar deficits in migraineurs (Sandor et al. 2001).
The PAG is involved in descending pain control mechanisms, along with the locus ceruleus and raphae nuclei. In 2001, Knight and Goadsby (2001) published research that suggests that it is dysfunction in the PAG that leads to disinhibition of the trigeminocervical nucleus and hence pain.
Mechanisms leading to initial trigeminovascular activation
The brain of the migraineur displays different neurophysiological behaviours to that of the normal individual. Evoked potential and transcranial magnetic stimulation (TMS) studies have shown that the cerebral cortex of the migraine sufferer shows an impaired ability to habituate to sensory stimulation across all sensory modalities (Schoenen 2006; Brighina et al. 2009). This is thought to be due to impaired functioning of inhibitory networks in the cortex, and it has been suggested that this dysfunction occurs in a manner similar to the GABA circuit down-regulation that occurs in sensory deafferentation (Brighina et al. 2009). Interestingly, Brighina et al. (2009) report that repeated trains of TMS have been shown to improve the functioning of the inhibitory networks that could have long-term effects. This is consistent with the functional neurology paradigm that it is possible to improve neuronal functioning by repeated stimulation within the tolerance of fatigue, thereby promoting gene expression, protein synthesis, and thus building plasticity.
It is logical to assume that this inability to habituate to sensory stimulation could predispose the cortex to excitotoxic events, and evidence suggests that this is the case (Dalkara et al. 2006). This is further supported by evidence that there is impaired energy metabolism in migraineurs (Lodi et al. 2006), which will predispose to anaerobic metabolism. Anaerobic metabolism is toxic to neurons and the metabolic by-products associated with it such as lactic acid are able to activate nociceptive fibres. Functional neurological interventions to promote aerobic metabolism and to protect from anaerobic metabolism should be considered by the clinician. Interventions that may be considered include:
• Supplementation with co-enzyme Q10 due to its antioxidant capabilities and involvement in oxidative phosphorylation (Lodi et al. 2006);
• Supplementation with other antioxidants;
• Supplementation with magnesium to reduce the likelihood of activation of NMDA receptors on nociceptive fibres (Lodi et al. 2006);
• Reduction of circulating adrenaline levels as adrenaline reduces the threshold to activation of C fibres via the alpha 1 receptors. Examples may be stress reduction or the reduction of caffeine intake;
• Ensuring good respiratory mechanisms through preservation of the lumbar lordosis and normal rib mechanics;
• Management of autonomic function to ensure optimum vascular supply to the brain; and
• Lifestyle advice to ensure the patient only stimulates their nervous system within the tolerance of fatigue.
It is also thought that the migraineurs have immunological changes that predispose them to the activation of the inflammatory cascade, which in turn leads to the migraine attack. These triggers may be infections, foods, or other environmental factors (Longoni & Ferrarese 2006). Any management plan for the migraineur should include the identification and, as far as possible, the removal of the triggers. Headache diaries including diet and environmental exposures can be useful for identifying the triggers.
Migraine with aura (MWA)
Migraine with aura was previously known as classic migraine.
The International Headache Society (2004) describes MWA as: ‘Recurrent disorder manifesting in attacks of reversible focal neurological symptoms that usually develop gradually over 5–20 minutes and last for less than 60 minutes. Headache with the features of migraine without aura usually follows the aura symptoms. Less commonly, headache lacks migrainous features or is completely absent’ (Box 17.3).
Box 17.3
Diagnostic criteria for migraine with aura
Diagnostic criteria
A. At least 2 attacks fulfilling criterion B
B. Migraine aura fulfilling criteria 1 and 2 for one of the subforms: