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Module Title
Management of severe chronic painModule Author
Dr Debra Galvin & Professor Connail McCroryCPD points
2Module Type
Tutorial1. Trigeminal neuralgia
Trigeminal neuralgia (TGN) is a chronic neuropathic pain condition that affects the trigeminal nerve branches, namely the ophthalmic branch (V1), the maxillary branch (V2) and the mandibular branch (V3). It is the most common facial pain syndrome. Typically, TGN presents in the 40-70-year-old age group with females affected twice as frequently as males. It is most often unilateral but may be bilateral in 3% of cases. The mandibular branch is the most commonly affected branch with the ophthalmic branch being least commonly involved. 40% of cases involve both V2 and V3 branches. The incidence ranges from 4/100,000 in under 50s to 12/100,000 in over 70s.1
Diagnosis
A diagnosis of trigeminal neuralgia can be made on history alone. Typically the patient is a middle-aged female who presents with unilateral facial pain in the distribution of the trigeminal nerve (V1/V2/V2 territories). The pain is described as short, episodic, stabbing-like episodes of pains lasting from a fraction of a second up to three seconds. These episodes may occur up to 200 times per day. Pain may be either triggered or spontaneous. Common triggers causing onset of pain include chewing on affected side, cold wind, inability to brush teeth or wear dentures, inability to brush hair or rub affected side of face. Usually patients are pain-free between pain paroxysms but at times, a dull, continuous pain may be present.
The International Headache Society criteria for diagnosis is based on history alone. The criteria are as follows:
- Paroxysmal attacks of pain lasting from a fraction of a second to 2 minutes, affecting one or more divisions of the trigeminal nerve.
- Pain has at least one of the following characteristics: intense, sharp, superficial or stabbing.
- Precipitated from trigger areas or by trigger factors.
- Attacks are stereotyped in the individual patient.
- There is no clinically evident neurological deficit.
- Not attributed to another disorder.
Although a diagnosis can be made on history alone; MR brain and MR angiography are mandatory to exclude multiple sclerosis, a space occupying lesion, or vascular loop. These diagnoses change management. The vascular loop may be the superior cerebellar artery as it exits the skull at the cerebellar pontine angle.2
Treatment
First-line medical therapy consists of carbamazepine and oxcarbazepine which reduce pain in approximately 90% of patients.3
Second line therapy consists of lamotrigine and baclofen. In cases where medical therapy fails, a referral to Pain Medicine should be made.
Referral to Pain Medicine
Consideration for interventional treatments should usually be reserved for patients with pain refractory to an adequate trial of medication starting with carbamazepine or oxcarbazepine at a sufficient dosage. However, it is recognized that in severe cases a more rapid referral to the pain clinic may need to be made.
After a diagnostic block with local anaesthetic to confirm diagnosis trigeminal ganglion radiofrequency ablation (RFA) may be considered if symptoms recur. This is a destructive technique. 90% of patients report pain relief following this procedure. After 1 year, 68–85% of patients are still pain free, after 3 years this is reduced to 54–64% and after 5 years 50% of patients are still pain free following RFA. The most common side effects are sensory loss (50%) which may be debilitating in itself, dysesthesias (6%), anaesthesia dolorosa (4%) and loss of corneal reflex with risk of keratitis (4%).4 Therefore significant complications may arise from trigeminal radiofrequency ablation. This has led to a trend in pulsing the trigeminal ganglion as opposed to RFA as the incidence of complications is lower. Pulsing the trigeminal ganglion also offers the advantage of sensing the nerve and confirming diagnosis at the same time as the pulsing thereby reducing visits to theatre. However pulsing the trigeminal does not give the same longevity of analgesia as RFA but it is associated with far fewer complications.
Surgical options include microvascular decompression (MVD) in the presence of a vascular loop or Gamma Knife surgery. MVD is a neurosurgical procedure consisting of placement of a sponge material between the compressing vessel and the trigeminal nerve root. MVD provides greater long-term pain relief however it is associated with more severe complications. Gamma knife surgery is use of radiation targeting the trigeminal nerve root as it enters the brain. It provides less analgesia and may take longer to produce analgesia but is associated with less complications post procedure than MVD.
Radicular Neck Pain
Radicular neck pain is pain originating in the neck which radiates to the shoulder, scapula and arm, in a dermatomal/sensory pattern. Pain occurs due to compression of a spinal nerve root either within the spinal canal or as it exits the intervertebral foramen. The patient may also complain of numbness or weakness.
Between a half and two-thirds of people will experience neck pain at some time. 90% of these patients will be asymptomatic or very mildly symptomatic after 4 years.5 Prevalence is highest between 50-55-year olds, with women being affected more than men.6 The prevalence of neck pain reported varies, however, the average point prevalence is 8% (range 6%–39%), annual prevalence of 15% to 50%, with an average lifetime prevalence of 49% (range 14%–71%).
The most common causes include nerve compression from a herniated disc or osteoarthritic osteophytes. The commonest nerve roots affected are C7 (C6/7-disc herniation) followed by the C6 nerve root and the C8 nerve roots.7
Patients with nerve root compression of the upper roots (C2 and C3), may complain of occipital headaches which radiate to the eyes and behind the ears with associated blurring of vision, dizziness and nausea (occipital neuralgia). These symptoms may be worse when lying down. The patient may also complain of tension and “knots” in the neck and shoulder muscles with swelling and stiffness of fingers.
C4 nerve root compression is a rare cause of neck pain. It may present as non-radicular type pain along the base of the neck. It may radiate to the superior aspect of the shoulder and posteriorly to the scapula. Additionally, a sensory deficit around the shoulder area may be present. The diaphragm is supplied by the C4 nerve root (phrenic nerve originates mainly from C4 nerve root) with injury at this level potentially producing dyspnoea clinically and a raised hemidiaphragm radiologically).
C5 nerve root compression presents as pain in neck, shoulder and the lateral part of upper arm over the deltoid.
C6 and C7 symptoms can frequently overlap. Typically, symptoms of C6 nerve root compression are pain in neck, lateral forearm and thumb with C7 symptoms appearing in similar areas as well as pain in palm and middle finger.
C8 symptoms typically include pain radiating into the 4thand 5th digits in addition to neck and forearm pain.
Diagnosis
History
A thorough history must exclude the presence of red flag signs. In patients with neck pain, red flags include age over 55 or under 20, constitutional symptoms such as fever/malaise/nausea/weight loss, severe headache, history of trauma, immunosuppression or cancer, severe stiffness and numbness and/or tingling and/or weakness elsewhere.
Examination
Typically, a patient will present with unilateral neck and arm pain. It is important to determine the dermatomal distribution of the pain. In addition, the presence and distribution of paraesthesia, sensory deficits and motor deficits must be determined to exclude the presence of myelopathy.
Examination should include inspection and palpation of the neck, active and restricted movements of neck (flexion-extension, lateral rotation, side-bending) and application of special tests. Upper limb reflexes must be checked also. Compression of C5 nerve root will result in loss of biceps reflex. Affected C6 nerve root will result in reduction of brachioradialis reflex and affected C7 nerve root will cause reduction in triceps reflex. An increase in upper limb reflexes is consistent with a myelopathy presentation.
Special Tests
Spurling’s test, upper limb tension test and shoulder abduction test. Use of these special tests has a sensitivity and specificity between 60-85% respectfully. 8
Investigations
It is mandatory to organise an urgent MR C spine in the presence of a neurological deficit and/or red flags and arrange an urgent surgical opinion. The patient should be advised that if there is any deterioration in their complaint they should go to ED immediately.
A diagnosis of radicular neck pain can be made on history alone. However, further diagnostic evaluation should be considered if the pain is present for three months or
• X-ray — allows for diagnosis of spondylosis or osteoarthritis/osteophytes
• MRI cervical spine — allows for soft tissue evaluation and provides an excellent view of the spinal canal and intervertebral foramina. It facilitates identification of nerve root compression by a herniated disc or osteophytes. It also allows identification of spinal cord anatomy and any cord compression, syringomyelia or the presence of plaques. MR will also identify the uncommon causes of compression such as tumour or abscess.
• Neurophysiology — nerve conduction studies may be useful when attempting to localise a lesion or affected nerve root or when determining if a large fibre neuropathy (somatosensory evoked potentials) or small fibre neuropathy (quantitative sensory testing) is the cause.
Treatment
Acute
Acute treatment consists of anti-inflammatories, simple analgesics and physical therapy. Up to 90% of acute radicular neck pain will improve spontaneously with conservative management alone. The remaining 10% will continue to report pain up to 3 months post initial presentation.
Subacute
Subacute pain is pain persisting for greater than 6 weeks but less than 3 months. Combination therapy in the form of exercise, analgesics and physiotherapy is the most appropriate management strategies for this group also.
Chronic pain
Pain persisting for more than three months is defined as chronic pain. Interventional epidural steroid injection has shown benefit in the treatment of chronic cervical radiculopathy. Up to 60% of patients who fail to improve with conservative strategies will report an improvement in pain with interventional procedures such as epidural steroid or nerve root intervention, however, complications are associated with this procedure e.g. accidental subarachnoid injection, epidural haematoma, paralysis, vascular injury.9,10
Pulsed radiofrequency (PRF) performed adjacent to the cervical dorsal root ganglion is the recommended interventional pain management technique. In a randomised controlled trial 3 months post PRF procedure, significantly better outcomes were reported with regard to the global perceived effect (>50% improvement) and visual analogue scale.11
Level 2 evidence supports repeating interventional procedures for recurrent radicular symptoms. Repeating interventional procedures is also reasonable in patients either awaiting or those who wish to avoid surgery.12
3. Coccydynia
Coccydynia is a painful disorder of the tailbone, localised just above the rectum. Females are more affected by this disorder with a ratio of 5:1.13 Similarly, an association between increased BMI and coccydynia is noted in females with BMI >27.4 and males with BMI >29.4.14
Causes
Trauma is commonest cause of coccydynia with the idiopathic form causative in approximately 1% of cases. Most commonly, a fall into the sitting position is the cause in most traumatic cases. Repetitive microtrauma may occur if poor sitting posture is adopted or from seated activities such as cycling or motorbiking.
Pregnancy and labour are common causes also with the coccygeal joints involved in 70% of traumatic childbirth cases.15
The following five causes are involved in both traumatic and idiopathic causes of coccydynia: hypermobile coccyx, immobile coccyx, arthritis, epidermal cysts and non-organic causes.
Diagnosis
History
Typically, patients present with tailbone pain worse when sitting, on a background of trauma. These patients may be of increased BMI also. Cycling or prolonged sitting is very difficult for these patients.
Examination
BMI should be measured. Examination should include manual examination of the coccygeal bone. Pain during movement of the coccyx suggests nociceptive pain due to muscles and ligaments attaching to the coccyx compared to absence of pain on movement of coccyx. Absence of pain suggests referred pain from the pelvic region. Performance of the Valsalva manoeuvre will cause pain in disorders of neural structures compared to no pain present if pain is due to primary coccyx involvement.15
Additional testing
Lateral images of coccyx are indicated. Dynamic X-rays should be requested also with comparison of coccygeal mobility measured between sitting and standing. Mobility between 2 – 25 degrees is considered normal (Maigne method measurement).15
MR imaging should be considered in idiopathic cases to rule out malignancy, infection or cysts.
Treatment
Conservative treatment remains the gold standard of treatment for coccydynia. NSAIDs and stool softeners should be considered acutely. Physical activity should be encouraged with regular pelvic floor exercises and stretches. Ergonomic adaptations should be considered also e.g. doughnut cushions or wedge-shaped cushions.16
Interventions that may be offered include Ganglion Impar (GOI) block with steroid. A case series showed that performance of a GOI block resulted in 75% reduction in pain which was replicated with repeat injections.17 In addition to a block alone (after a successful diagnostic block), application of pulsed radiofrequency to the Ganglion Impar produced more than an 80% improvement in pain in 75% of patients at both 6- and 12-month follow-up.18
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