Biopsychosocial approaches to posttraumatic headaches
Headache patients want to be understood by their clinician. In order to help, it’s important for the therapist to fully grasp the facets of this complicated condition and to formulate a mutual understanding of it, together with the patient.
All sensory experiences, and pain most of all, shape the neural processing and organisation of thoughts and emotions, whilst also driving behaviours. In order to modulate a person’s headache condition, therapy needs to target all the involved processes, including the vicious cycles that may have been formed.
The challenge for the therapist is to combine science-based recommendations with creative therapy skills to engage the doubtful or worried patient. Quite frequently, one has to think “outside the box.”
The following sections introduce ideas concerning the nature of persisting headaches associated with mild brain trauma. Examples of how such ideas can be shared with patients are described one by one. Certain models are more suitable for some patients than for others. As the dialogue with patients and professional colleagues unfolds, these stand-alone models can gradually be woven together into the biopsychosocial approach. The sections that follow set the scene for the holistic assessment and therapy guide presented later in the book.
Pain processing models
The absence of pain is a fundamental need for the well-being of humans and, indeed, for a vast range of species. Understanding pain has been the core theme of healing and medical science since the early days of mankind.
Pain processing models attempt to describe the links between an injury and the perception of pain. The assumption is that pain signals travel along dedicated pathways and reach higher-level structures, where they might be processed. Classical pain theories simplify the illustration of pain. Through the sharing of such theories, headaches can be demystified for patients, thus enabling them to let go of their sense of helplessness, failure to cope or even guilt.
Pain Gate Theory
Acute pain has an important function in signalling tissue damage to bodily systems responsible for the initiation of healing and repair. The injured area becomes hypersensitive, especially when in contact with external stimulation. This has a protective function so that further injury, or the interruption of the healing process, can be avoided.
The Gate Control Theory of Pain was introduced by Melzack and Wall. It can be an ideal starting point for patients who prefer a practical, down-to-earth explanation. The theory proposes neurophysiological mechanisms in the dorsal horns of the spinal cord that act like a gate, which increases or decreases the flow of nerve impulses from the periphery of the body to the central nervous system. If the Pain Gate opens the pathways, then the pain messages can be received by the brain and, following processing, the person perceives pain. In the case of a closed Pain Gate, the brain is less able to receive and interpret the messages and, as a result, the pain experience is modulated (Figure 1.5). The pain receptors in the body, called nociceptors, encode the mechanical, chemical, metabolic or thermal sensations and convert them into pain signals.
Afferent fibres carry the nociceptive message to the corresponding area of the central nervous system. The fast-acting and thinly myelinated A8 fibres rapidly conduct impulses that are modulated by the slower-acting, unmyelinated C fibres.
The dorsal horn, part of the spinal cord, contains both types of pain fibres. The Pain Gate represents a junction in the pain transmission, which is essentially a neuro-chemical process. The incoming stimuli lead to neuro-transmitter release, which, depending on the type and persistence of the stimulation, results in enhanced synaptic plasticity and, hence, pain signal transmission.
Ascending neurons project from the dorsal horn through the spine to the thalamus, mesencephalic formation and several other midbrain regions. This is the so-called “spino-thalamic tract.” The reticular formation is a set of neural networks in the brain stem, which is responsible for core physical systems, body rhythms and cortical arousal. The reticular formation is critical for the development of a pain experience. It integrates motor, autonomic and sensory functions and mediates affective and motivation components of pain via pathways to the thalamus and limbic system.
Figure 1.5 Pain pathways.
The thalamus has a central role in relaying sensory information, including pain sensation, to the cortex. The subcortical limbic system - consisting of a number of components and, most importantly, the amygdala and hippocampus - processes motivational elements of the pain and related pain behaviour (avoidance, escape, etc.). The cerebral cortex benefits from the pain information, pre-processed by the anterior cingulate cortex. This part of the brain plays a vital role in detecting and evaluating sensations and stimuli that do not fit with expectations or that pose a cortical dissonance. Somatosensory areas of the anterior insular are also receivers of pain stimulation.
Descending pathways modulate and inhibit all kinds of sensory experiences, including pain. Interactive cortical networks participate in the generation of action patterns, which influence immediate and future pain responses. These are referred to as Action Systems. Descending pain messages can undergo such cortical modulation and inhibition when passing through higher-level cortical areas, the thalamus, the grey matter of the midbrain, the brain stem, the dorsal horns in the medulla and spinal cord. Neurotransmitter activity within these structures can suppress or enhance nociception at the central brain level. The final modulation of descending nociceptive messages takes place in the spinal cord. Concentrated neurotransmitters within the dorsal horn are known for their inhibitory properties in the transmission of nociceptive messages.