Peripheral Neuropathy

Treating peripheral neuropathy can be one of the toughest problems facing a clinician. Peripheral neuropathy simply means disease affecting the peripheral nerves.

There are a great many cause of peripheral neuropathy. This is just a partial list to give you an idea of the things that a clinician has to think about before starting treatment:

1. Metabolic illnesses: Diabetes mellitus; porphyria; chronic renal failure; amyloidosis and disturbances in circulating proteins
2. Vitamin deficiencies: Vitamins, B1, B3, B6 and B12
3. Drugs and chemicals: Alcohol; Heavy metals like arsenic, lead and mercury; organic pesticides; several drugs used in cancer chemotherapy; isoniazid; nitrofurantoin
4. Infections: Lyme disease; Herpes zoster (shingles); Diphtheria; Brucellosis; Leprosy; Tetanus; Botulism
5. Malignant illnesses
6. Inflammatory and autoimmune illnesses: Rheumatoid arthritis; Systemic lupus erythematosus; Polyarteritis nodosa; Sarcoidosis; Guillain-Barre syndrome; Celiac disease
   
7. Physical injury: Trauma, stretching and compression of nerves, which can include things like carpal tunnel syndrome.
8. Congenital illnesses

Many causes of peripheral neuropathy, particularly diabetes, may also damage the autonomic nervous system that controls the heart, blood pressure, swallowing, intestinal and bladder function.

Neuropathic symptoms typically start in the feet, because the nerves running down there are longer and more vulnerable than the ones going to the hands.
The most common symptoms are:

1. Numbness
2. Tingling
3. Abnormal sensations called dysesthesias
4. A characteristic form of pain, called neuropathic pain or neuralgia: people usually describe it as “pins and needles,” a steady burning sensation or “electric shocks.” These pains can be difficult to describe: typically pains, like stubbing your toe or stepping on something sharp, are transmitted through pain fibers. Neuropathy also involves other neurological pathways, so that the brain receives impressions that it cannot process.

There has been a revolution in out understanding of neuropathic pain in recent years. It is now considered to be a disease rather than a symptom. Normal pain is designed to protect you: you put your foot on a hot plate and you pull it away immediately. Neuropathic pain is different: it is non-protective and it persists and therefore behaves like a disease.

Multiple different classes of medications have been shown to be effective in some people with neuropathic pain, though most are not approved for use by the Food and Drug Administration:

1. Lidocaine patches and creams
2. Capsaicin creams
3. Opioid analgesics
4. Tricyclic antidepressants
5. Serotonin-norepinephrine reuptake inhibitors (SNRIs)
6. Anticonvulsants: Carbamazepine; gabapentin; pregabalin

Earlier this week, data presented at the European Federation of IASP (International Association for the Study of Pain) Chapters (EFIC) indicated that an innovative combination of painkillers might hold the key to unlocking the severe and relatively untreatable pain of peripheral neuropathy.

Dr Magdi Hanna, Director of Pain Clinical Research Hub at King’s College Hospital in London, has been studying the combination of the strong opioid oxycodone (OxyContin) with gabapentin (neurontin) in over 300 patients with severe diabetic neuropathy. This combination demonstrated a significant 33% improvement on top of the best pain relief achievable using the maximum tolerated dose of gabapentin as monotherapy. The study was part funded by one of the medicine manufacturers.

This study is good news, but even in this study there were a great many people who were not helped. In another blog item, I’m going to talk about some of the unorthodox approaches that have helped some people.