An Article Written By Shaun Vu
Podiatrist – New Step Podiatry
Diabetes is the most common cause of peripheral neuropathy. But did you know that there are other ways people can get neuropathy with slightly different presentations? This article will provide information about less common causes of neuropathy including alcohol-related, chemotherapy-induced, vitamin B deficiency, age-related changes and nerve entrapment.
If you are uncertain about what peripheral neuropathy is, have a read of ‘Nervous About Neuropathy? Diabetic Foot Neuropathy Explained’ by Cecilia Brennan first.
Alcohol Related Peripheral Neuropathy
How does alcohol cause peripheral neuropathy?
There are two mechanisms:
1. Ethanol and metabolites in alcohol are neurotoxins, which can directly damage the nerves.
2. When people drink chronically, a lot of them get malnourished and lack vitamins including thiamine, folate, and other B vitamins, which are critical for neural function.
How much is too much?
Everyone is different, it is suggested that 100 mL ethyl alcohol (10 standard drinks) per day for 3 years is “too much”. However, the total lifetime amount of alcohol and duration of alcohol consumption are also important.
Does the type of drink matter?
Wine is mostly strongly linked to neuropathy, perhaps due to the higher concentration impurities in alcohol including lead, which can make it more severe.
What are the Australian guidelines to reduce health risk from drinking alcohol?
There are numerous resources by the Australian Government to educate our communities on safe drinking levels. Check them out here
Please note that the alcohol recommendations for adults are for healthy adults. If you are not in a healthy state, speak to your general practitioner about what your safe alcohol consumption is.
Chemotherapy Induced Peripheral Neuropathy
Chemotherapy-induced peripheral neuropathy occurs in 30-40% of chemotherapy patients. This can begin weeks to months after initiating treatments and peaks at, or after the end of treatment.
The factors that demonstrate the extent of nerve damage depends on:
● Chemotherapeutic agent
● Duration of therapy
● Cumulative dose
● Concomitant use of other neurotoxic agent
● Age
● Pre-existing condition that cause nerve damage
The cause is different between the classes of chemotherapeutic agents; It is not fully understood but it is known that the chemotherapeutic agents cause problems with the signaling within the nerves. This causes spontaneous pains and unusual sensations and people can get central sensitisation which means an increased sensitivity to feeling pain and an extreme response to pain.
In some cases, the pain and paraesthesia completely resolve after treatment is stopped, but for most people, the neuropathy is only partly reversible and is permanent.
Vitamin B12 Deficiency
Our bodies do not produce our own vitamin B12 or also known as Cobalamin. They help keep your body’s blood and nerve cells healthy and help make the genetic material in all of your cells meaning your DNA.
Vitamin B12 deficiency has been linked to peripheral neuropathy. A vitamin B12 deficiency can happen if you are taking certain medications, aren’t eating enough vitamin B12 in your diet (common with strict vegetarians), or if your body simply can’t absorb it due to an underlying condition. Low vitamin B12 levels can lead to changes in the myelin sheath that wrap around your nerves. We can compare this to an electrical cord – if the protective outer layer is damaged, the electrical cord still works but the function may be impaired.
How to detect vitamin B12 deficiency?
A blood test called homocysteine can be measured in the plasma of our blood. Therefore, a blood test referral by your General Practitioner can assess your Vitamin B12 levels.
What are good food sources of vitamin B12 and what is the recommended daily intake?
Foods that have vitamin B12 include fish, meat, poultry, eggs, milk and milk products and some cereals.
Over the age of 14: 2.4 micrograms per day of vitamin B12 is recommended.
Age Related Changes
Generally speaking all your nerves deteriorate a bit as people get older, the number of axons decline and myelin sheath (nerve conduction that runs up and down) deteriorates so the speed of the nerves in both the sensory and action potentials to fire the muscles do not act as quickly.
The nerve receptors of touch, pressure and vibration reduce in number and density. There is a significant decline in ability to detect sensations with increasing age – difference more apparent after 75 years of age. 40-50% of people over 75 do not have an Achilles reflex on normal clinical testing and increases in percentage as people get older. This can all impair balance and foot protection.
Proprioception, which is the ability to detect sway and position of body parts, does get compromised due to impairment in skin receptors and small connective tissues called the golgi tendons in older people, which makes them a lot more prone to falls.
Nerve Entrapment
When a patient with symptoms of neuropathy presents to New Step Podiatry our podiatrists will assess if the cause is systemic (global) such as the causes above or a more local cause in the lower limbs or back such as nerve entrapment.
There are multiple ways a nerve can be impinged, however the most common version would be trauma. The other causes include motor vehicle accidents, nerve root compression from lower back pain, osteoarthritis or osteoporosis in the spine, local compression or stretch injury.
Entrapment is a form of compression, the nerve is compressed and restricted by adjacent soft tissue and/or bone, often near a joint. The nerve becomes constricted and narrowed at the entrapment and around areas of swelling. Myelin distortion and demyelination occurs which then shows reduced speed of the nerve conduction. This can lead to loss of pain, temperature sensations and even vibration sense and proprioception. In some cases, people can experience a foot drop, which then the individual would require a functional aid called an ankle-foot orthoses to help maintain mobility and movement.
The most common nerve entrapment we see is called Morton’s neuroma or forefoot neuroma. It is an entrapment and thickening of a plantar common digital nerve, possibly by prolapse of a compressed intermetatarsal bursa. This can be due to:
• Obesity
• Reduced ankle joint range of motion
• Poor fitting footwear, high heels
• Reduced plantar fat pad integrity
• Activities that put more pressure on the ball of the foot (e.g. dancing, running, skipping) • Structural abnormalities such as a short 1st metatarsal (long bone behind the toe) or a long 2nd metatarsal.
• Presence of a bunion or a hammer toe causing imbalances in the foot structure. • Hypermobile joints, especially at the forefoot.
• Prolonged or excessive pronation when walking – this can push the big toe joint up and move more force onto the 2nd toe.
• Prolonged or excessive supination – the foot is unable to absorb force efficiently and more pressure is put on the forefoot.
Fortunately for this type of neuropathy, the symptoms of neuropathy may be resolved with a successful podiatry treatment plan.
There are numerous nerves in the feet that can be compressed and cause symptoms of neuropathy
Other Causes of Neuropathy
Additional less common causes of peripheral neuropathy and other neuropathies.
• Autoimmune diseases: Sjogren’s syndrome, lupus, rheumatoid arthritis, Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy and vasculitis.
• Infections: including Lyme disease, shingles, Epstein-Barr virus, hepatitis B and C, Hansen’s disease (leprosy), diphtheria, and HIV.
• Inherited disorders: such as Charcot-Marie-Tooth disease.
• Heavy metal and chemical exposure: including lead and mercury.
• Other vitamin deficiencies: Vitamin B1, B2, B3/ niacin and E vitamins.
• Tumours: cancerous and noncancerous growths can press on a nerve or grow on a nerve.
• Bone marrow disorders: These include an abnormal protein in the blood (monoclonal gammopathies), a form of bone cancer (myeloma), lymphoma and the rare disease amyloidosis. • Certain medications: extended use of certain prescription medications.
• Physically traumatic episodes: such as a motor vehicle accident, falls, sporting injuries can sever or damage a nerve.
References
Ann Neurol 1977; 2:95-110
CLIN PHARM & THER 2011; 90 (3) 377-87
Harvard Health
MacLennan et al, 1980
mayoclinic.org/diseases-conditions/peripheral-neuropathy/symptoms-causes/syc-2035206
Muscle & Nerve. 2011 March 309-16
Perry, S.,Neuroscience letters, 2006. 392. P62-67 Lord SR and Ward JA Age and Ageing 1994. 23. p452-460
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