Neuropathic pain is a common complication of cancer and may be due to:
- vertebral metastases from prostate, lung, bowel and breast cancer causing root or cord compression
- breast cancer brachial plexopathy
Other causes of neuropathic pain include:
- neurological illnesses such as Multiple Sclerosis
- treatment e.g. chemotherapy-induced peripheral neuropathy
- other co-morbid conditions e.g. post-herpetic neuralgia or diabetic neuropathy
Red flags
Always consider spinal cord compression in patients with neuropathic pain.
Key symptoms of cord compression include:
- new intractable, progressive pain, especially thoracic or legs.
- New spinal nerve root pain may radiate down the leg (like sciatica), or the arm, or more like a band around the chest or abdomen
- Coughing, straining or weight bearing may aggravate pain
- New difficulty walking or climbing stairs; reduced power and heavy legs
Late signs include:
- Sensory impairment at an abdominal or thoracic level plus altered limb sensation
- Bowel or bladder disturbance; loss of sphincter control
Clinical features
- Patients often describe neuropathic pain as burning, shooting, tingling or stabbing in nature
- Altered sensation is also a symptom. Sensitivity to light touch may be reduced or increased (allodynia)
- Pain may follow a dermatomal distribution
When examining always compare both sides of the body.
An initial approach to treatment
- Tricyclic antidepressants e.g. Amitriptyline 10mgs at night and titrate to 25mg
- Anticonvulsant e.g. Pregabalin or Gabapentin. Pregabalin is a BD dosage and easier to titrate than Gabapentin. Remember that Pregabalin and Gabapentin are sedative in combination with opioids
- Duloxetine is another alternative and may help mood as well as pain
- A combination of neuropathic agent, Paracetamol and opioid analgesics may be needed
- Bloods to exclude a metabolic cause e.g. B12 deficiency
Specialist care
If the above approaches are not working and sleep in disturbed, then specialist advice is recommended. Options include:
- Dexamethasone 6mg for 6 days (or 40mg Prednisolone) with PPI cover for urgent control of neuropathic pain. This takes the pressure off the nerve
- Other anticonvulsants may be tried e.g. Oxcarbazepine 150mg BD
- Urgent MRI to inform whether further intervention is needed e.g. radiotherapy, surgery or nerve block