13 Pain
Pain is a totally subjective phenomenon. It is the product of a noxious stimulus, which evokes a response in the patient. That response is predicated by the patient’s pain tolerance and psychological state at the time of stimulation. What represents debilitating pain for one patient may be largely ignored by another.
More recently, there has emerged the concept of ‘neuropathic pain’ with an inherent grading system that allows cross-referencing for research as well as clinical purposes.1 The working definition of neuropathic pain is pain provoked by a lesion or disease affecting the somatosensory system. The problem with such a definition is that it could, for all practical purposes, encapsulate all pain syndromes thereby making it less than specific.
Some authors have tried to differentiate chronic pain from neuropathic pain, citing prevalence rates of 20–30% for the former and 5–7% for the latter.2 Others just divide pain into acute and chronic with claim of distinctive characteristics for each, and different approaches to management (see Table 13.1).
TABLE 13.1 Differentiating acute and chronic pain
| Characteristic | Acute pain | Chronic pain |
|---|---|---|
| Duration | ≤ 2 weeks | > 3 months |
| Associated features | Tachypnoea Tachycardia Sympathetic autonomic release (fright/flight) |
No sympathetic features Local reaction (e.g. swelling, skin changes) |
| Effects on quality of life | Little to none | Significant |
| Altered behaviour | Little to none | Significant |
| Management | Primarily pharmacological | Multidisciplinary team approach (beyond pharmacological) |
This chapter will examine the approach to pain management and provide useful tips to help the general practitioner cope with the patient in pain. As with so many areas of medicine, and neurology in particular, there has been a concerted effort to classify various conditions to enhance international collaboration and consensus. This is equally true for pain3 but application of these classifications contributes little to coalface general practice and will not be further reviewed in this chapter.
History
The fact that pain may provide the presenting complaint for psychological problems does not negate the fact that the pain is still felt. Pain is a very subjective phenomenon and may follow very specific patterns that go hand-in-glove with specific complaints. The symptom constellation will provide the diagnosis (see Table 13.2).
| Diagnosis | Classical symptoms |
|---|---|
| Trigeminal neuralgia (tic douloureux) | Sharp stabbing pain in the face (jabs of pain) Pain triggered by chewing, cleaning teeth, cold air Pain within the distribution of maxillary branch of CNV shooting from the jaw upwards |
| Glossopharyngeal neuralgia | Stabbing pain similar to trigeminal neuralgia Pain usually shoots into back of tongue Pain may shoot into ipsilateral ear |
| Temporomandibular (TM) joint dysfunction | Pain localised in face Pain may be in TM joint Pain provoked by chewing Aware of clicking in TM joint |
| Atypical facial pain | Pain in the face that does not fit other diagnoses of unilateral face pain |
| Post-herpetic neuralgia | History of herpes zoster infection Pain follows distribution of a cranial nerve or nerve root |
| Radicular pain | Pain corresponding to the distribution of a nerve root |
As with all neurology, there are certain questions that need to be asked: When did the pain start? Was there a provocative incident that caused the pain? Where is the pain? Are there precipitating or relieving factors? What is the nature of the pain? Are there associated features with the pain? What is the frequency and duration of the pain? A perfect example of how these questions provide diagnostic answers is found in Chapter 6 on headache. It is these questions that differentiate tension-type headache from migraine.
Certain conditions, such as diabetes with peripheral neuropathy and diabetic amyotrophy, may provoke very severe pain symptoms. Pain is a particular feature of small fibre diabetic sensorimotor neuropathy. From the neurological perspective, pain in the head, neck, back and limbs may be of primary neurological origin. Pain in the thorax or abdomen is almost always a feature of a visceral disorder rather than primary neurological complaint, for instance, spinal or radicular pathology, thus dictating an alternative investigational paradigm to the diagnosis of thoraco or abdominal pain. There are some exceptions, such as herpes zoster infection with shingles (and post-herpetic pain) and diabetic radiculopathy, already identified.
Pain evokes its own set of jargon and possible confounding language, which may lead to confusion. Thankfully much of this jargon has not yet found its way into common daily language and so is largely ignored by patients (see Table 13.3).
TABLE 13.3 Glossary of pain jargon
| Term | Meaning |
|---|---|
| Allodynia | Pain perceived following non-noxious, innocuous stimulus (e.g. light touch causes burning pain) |
| Antalgia (antalgic) | Pain perception (noun), pain provoked action (adjective) (e.g. antalgic gait—altered gait due to the influence of pain) |
| Dysaesthesia | An altered perception of sensation with abnormal (often unpleasant) feeling associated with stimulation, such as touching over the affected area causes ‘strange feeling’ |
| Hypaesthesia / hypoaesthesia | Reduced perception of stimulus (both words are interchangeable) |
| Decreased sensation | |
| Hyperalgesia | Increased perception of pain |
| Hyperaesthesia | Increased perception of stimulus (need not be pain) |
| Hyperpathia | Decreased sensation to one or more modalities while concurrently having increased perception of pain (hyperalgia) or pain with innocuous stimulation (allodynia) |
| Hypoalgia | Reduced perception of pain |
| Paraesthesia | Abnormal sensations, such as ‘pins and needles’, tingling, pricking, reduced or even loss of sensation. It implies abnormality anywhere along the sensory pathway from peripheral nerve to sensory cortex—the epitome of ‘neuropathic pain’ |
