Makindo Medical Notes

Related Subjects: |Analgesia and Pain management |Sedation and Analgesia on ITU |Neuropathic Pain Management |Codeine |Dihydrocodeine |Diamorphine |Morphine |Paracetamol (Acetaminophen)

🧠 Neuropathic pain is challenging to treat because of its varied causes, symptoms, and mechanisms. Conventional analgesics (like paracetamol/NSAIDs) are usually ineffective.

📖 About

• Defined by the International Association for the Study of Pain (2011) as: “pain caused by a lesion or disease of the somatosensory nervous system.”
• Unlike nociceptive pain, neuropathic pain arises from dysfunction or injury of the nerves themselves.

🧬 Aetiology

• Peripheral nerve entrapment (e.g., carpal tunnel, thoracic outlet, piriformis syndrome).
• Ischaemic neuropathy or nerve root compression.
• Post-traumatic neuropathy (surgery, trauma, injection injury).
• Post-amputation stump pain & phantom limb pain 🦵.
• Postherpetic neuralgia (after shingles).
• Complex Regional Pain Syndrome (CRPS) 🔥.
• Diabetic neuropathy (long-term hyperglycaemia).
• Cancer-related neuropathies 🎗️ (tumour compression, chemotherapy).

🩺 Clinical Features

• Burning, shooting, stabbing pain ⚡.
• Pain can be spontaneous or evoked, continuous or intermittent.
• Often worse at night 🌙.
• Triggers: hot/cold, light touch, or movement.
• Skin may appear abnormal (atrophic, shiny, cyanosed).
• Characteristic sensory phenomena:
  • Allodynia: pain from a non-painful stimulus (e.g., light touch).
  • Dysaesthesia: unpleasant abnormal sensation.
  • Hyperaesthesia: exaggerated sensitivity to stimuli.
  • Hyperalgesia: heightened response to painful stimuli.

🔎 Investigations

• Imaging (e.g., MRI, CT) to exclude structural causes such as compression or tumour.
• Consider glucose/HbA1c in suspected diabetic neuropathy.

💊 Management

• Specialist referral if: diagnostic uncertainty, severe disability, or deterioration of underlying health condition.
• Address mental health (anxiety, depression) and functional issues; physiotherapy, splints, and graded exercise can improve outcomes.
• Amitriptyline: Start 10 mg at night, increase by 10 mg weekly. Typical range: 25–75 mg nocte. Best taken in evening to avoid daytime drowsiness. Titrate slowly to reduce side effects.
• Gabapentin: Week 1: 300 mg OD → Week 2: 300 mg BD → Week 3: 300 mg TDS. In elderly: start 100 mg, titrate in 100 mg steps. Watch for sedation, oedema, fatigue.
• Combination with Paracetamol may help, but simple analgesics alone are usually ineffective.

📚 References

• The Pathophysiology of Neuropathic Pain
• NHS Pain Management Guidance