G62.9/G50.0
DESCRIPTION
Defective functioning of nerves, which may involve both peripheral nerves (peripheral neuropathy) and cranial nerves. Different patterns are noted, i.e. polyneuropathy, mononeuritis multiplex, and mononeuropathy, each of which may be caused by axonal degeneration or demyelination or a combination of the above. Clinical features may be predominantly of a sensory, sensorimotor or motor nature.
Important causes of a predominantly sensory neuropathy include:
- alcohol,
- diabetes,
- HIV infection,
- thiamine deficiency, vitamin B12 deficiency, (although the latter more commonly presents as subacute combined degeneration of the cord),
- medicines (e.g. isoniazid, stavudine, metronidazole, amiodarone)
Important causes of a predominantly motor neuropathy include:
- Acute Inflammatory Demyelinating Polyradiculoneuropathy (AIDP – also known as Guillain-Barrè syndrome),
- Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP),
- acute porphyrias
GENERAL MEASURES
If there is a history of rapid progression, particularly in patients with features suggestive of AIDP, (e.g. rapid progression with stabilisation within 4 weeks) admit the patient and monitor vital capacity carefully with spirometry, as intubation and ventilatory support may be required.
Manage the cause where possible.
Specialised nursing care and dedicated physiotherapy may be indicated. If not managed appropriately, chronic cases may develop contractures, weakness affecting gait, and chronic bedsores, and they may become wheel chair-bound. Encourage activity, with referral to OT and physiotherapy.
Address psychosocial stressors and enhance perceived social support, and refer to social worker as required.
Treat comorbid mental illness (see chapter 15: Mental health conditions).
Assess outcome of treatment with objective measures of function, e.g. Pain, Enjoyment and General Activity (PEG) scale.
http://www.med.umich.edu/1info/FHP/practiceguides/pain/PEG.Scale.12.2016.pdf
MEDICINE TREATMENT
Most cases respond to management of the underlying disease process or removal of the aetiological agent.
In addition to the analgesics for chronic nociceptive pain (see Analgesia for chronic non-cancer pain), anti-neuropathic pain medicines to stabilise affected sensory nerves can be used.
- Amitriptyline, oral, 10 mg, two hours before usual sleep time.
LoEII [9]- Titrate up to 75 mg (to a maximum of 200 mg) at night if needed.
- In the elderly: 10–25 mg daily, increasing gradually up to 50–100 mg daily, if required and tolerated. A single bedtime dose is optimal for most patients.
LoEIII [10] - Use regularly, as takes 2–6 weeks for maximal effect.
LoEIII [11]
Post-herpetic neuralgia
Initiate treatment with adjuvant amitriptyline therapy early.
If no response after 2-4 weeks or amitriptyline is contraindicated:
ADD/REPLACE WITH
- Carbamazepine, oral, 100–200 mg 12 hourly for 2 weeks.
- If response is inadequate, increase the dose every 2 weeks to a maximum dose of 600 mg 12 hourly.
- Monitor for possible drug interactions in patients on ART.
Note: Aciclovir is not beneficial in treating post-herpes zoster neuropathy.
Isoniazid–induced polyneuropathy
- Pyridoxine, oral 75 mg daily for 3 weeks.
- Follow with 25–50 mg daily.
Trigeminal neuralgia (G50.0)
Sudden, usually unilateral, severe, brief, stabbing, recurrent episodes of pain in the distribution of one or more branches of the trigeminal nerve.
- Carbamazepine, oral 100 mg 12 hourly, initial dose.
- Increase dose slowly. Doses of up to 1200 mg daily may be required.
- After exacerbation, reduce to maintenance dose of 400–800 mg daily.
REFERRAL
For neuropathic pain unresponsive to these medicines, refer patient to an experienced pain clinician.