Devastating effects of peripheral neuropathy

If you have ever slept on an arm and awakened with a ‘dead’ hand, or sat too long with your legs crossed and had your foot fall asleep, you have some inkling of what many people with peripheral neuropathy experience day in and day out, often with no relief in sight.
And numbness and tingling are hardly the worst symptoms of this highly variable condition, which involves damage to one or more of the myriad nerves outside the brain and spinal cord. Effects may include disabling pain, stinging, swelling, burning, itching, muscle weakness, twitching, loss of sensation, hypersensitivity to touch, lack of coordination, difficulty breathing, digestive disorders, dizziness, impotence, incontinence, and even paralysis and death.
I realise now that I had a mild, reversible bout of peripheral neuropathy several decades ago when a misplaced shot of morphine damaged a sensory nerve in my thigh. It took three years for the nerve to recover, and for much of that time I could not tolerate anything brushing against my leg.

One of my sons, too, was afflicted when a nerve behind his knee was injured during a basketball game. He had no feeling or mobility in his foot for nine months, but after several years the nerve healed and he regained full use of his foot.

And a good friend was nearly paralysed, also temporarily, following a flu shot, by a far more serious form of peripheral neuropathy — an autoimmune affliction called Guillain-Barre syndrome, in which one’s own antibodies attack the myelin sheath that protects nerves throughout the body.

There are hundreds of forms of peripheral neuropathy. A medical guide describing them, compiled by a team of neurologists at the behest of the Neuropathy Association, fills a booklet the size of a two-year wall calendar.

The association, which sponsors research and provides education and support for patients and families dealing with peripheral neuropathy, estimates that the disorder afflicts more than 20 million Americans at any given time. If the cause can be corrected, peripheral nerves can regenerate slowly and patients can recover, although not always completely.
But many people never recover. They must learn to live with the disorder, with the help of treatments and devices that can ease their discomfort and disability. With such a wide array of symptoms and causes, getting a correct diagnosis is often a challenge. Worse, frustrated patients are sometimes told, “It’s all in your head.”

Causes behind ailment
There are three types of peripheral nerves: sensory nerves, which transmit sensations like pain, touch, heat and cold; motor nerves, which control the action of muscles throughout the body; and autonomic nerves, which regulate functions that are not under conscious control, like blood pressure, digestion and heart rate. Symptoms of neuropathy depend on what nerves are involved.

Someone with damaged sensory nerves might not feel heat, for example, and could be scalded by an overly hot bath. Neuropathy of the motor nerves can result in weakness, lack of coordination or paralysis; neuropathy of the autonomic nerves can lead to high blood pressure, irregular heart rate, diarrhea or constipation, impotence and incontinence.
The list of possible causes of neuropathy is far too long for this column. They include inherited conditions like Charcot-Marie-Tooth disease; infections or inflammatory disorders like hepatitis, Lyme disease, AIDS, rheumatoid arthritis and lupus; organ diseases like diabetes, hypothyroidism and kidney disease; exposure to toxic substances like industrial solvents, heavy metals, sniffed glue and some cancer drugs; trauma to or pressure on a nerve from an injury, cast, crutches, abnormal body position, repetitive motion, tumour or abnormal bone growth; alcoholism; and deficiency of vitamin B12.

The most common cause, accounting for nearly a third of neuropathy cases, is diabetes, especially among those whose blood sugar levels are poorly controlled. Half of all people with diabetes eventually begin to lose sensation and develop pain and sometimes weakness in their feet and hands. In people with diabetes, even minor injuries to the feet, if not quickly and properly treated, can result in gangrene and amputations.
In nearly a third of cases, no cause is ever found, leaving patients with no other recourse than treatment of their symptoms.

Suspected cases are best referred to a neurologist, who should begin by taking a complete personal and family medical history and performing a physical and neurological examination, checking on reflexes, muscle strength and tone, sensations, balance and coordination.
A complete workup is likely to include blood tests, urinalysis, a nerve conduction study and electronic measurements of muscle activity. Imaging studies, like a CT scan or an MRI, may reveal a tumour, vertebral damage or abnormal bone growth. In some cases, a nerve or muscle biopsy may be done.

Relief and restoration
If the underlying cause cannot be corrected, the goals of treatment are relief of symptoms and restoration of lost functions. Pain control is paramount. Effective relief may come from over-the-counter remedies or a lidocaine patch but sometimes requires prescribed opiates.
Many with neuropathic pain have benefited from drugs licensed for other uses, including antiseizure medications like gabapentin, topiramate (Topamax) and pregabalin (Lyrica) and antidepressants like the tricyclic amitriptyline and the selective serotonin and norepinephrine reuptake inhibitor duloxetine (Cymbalta). Vitamin B12 deficiency can be treated with supplements and fortified cereals or by judicious consumption of meats, poultry, fish, eggs and dairy products.

And since alcohol and tobacco are particularly risky for people with neuropathy, or a health problem that predisposes them to it, they have every reason to quit smoking and to drink only in moderation.
Many patients are helped by physical therapy, occupational therapy and devices like braces, splints and wheelchairs. Railings on stairways and in the bathroom, elimination of tripping hazards like scatter rugs, and improved lighting (including night-lights) can reduce the risk of falls. For those insensitive to heat, a thermometer should be used to test water in a tub, shower or sink. Orthopedic shoes are invaluable to patients with lost sensitivity in their feet or impaired balance.

A variety of mechanical aids can make it easier to live with peripheral neuropathy, among them kitchen tools made by Oxo. Those with digestive problems might try eating small frequent meals and sleeping with their heads elevated.
Other helpful sources include the book ‘Peripheral Neuropathy: When the Numbness, Weakness and Pain Won’t Stop’ (‘Demos Health’, 2006), by Dr Norman Latov. The association maintains a list of support groups and of centres that specialise in diagnosing and treating neuropathy.
The New York Times