Peripheral Neuropathy

Peripheral neuropathy is damage to the nerves that run between the spinal cord and the rest of the body. Three kinds of fibre can be affected and they produce different complaints: the sensory fibres that carry touch, temperature and position, the motor fibres that drive muscle, and the automatic fibres that govern blood pressure, sweating, digestion and the bladder.

The commonest pattern affects the longest nerves first, so it begins in the toes and creeps up the feet over months, with the fingers joining later once the damage in the legs has reached about knee height. Because it advances so slowly, most people cannot say when it started.

Diabetes is the commonest cause in India and worldwide. The other frequent ones are heavy alcohol use, deficiency of vitamin B12 and related vitamins, an underactive thyroid, kidney disease, some infections, several medicines including some used in chemotherapy and in the treatment of tuberculosis, and inherited conditions that run in families. In a real proportion of people no cause is found even after full testing. Identifying the cause matters more than anything else, because treating it is what stops the damage going further.

Your doctor takes the history first and it carries most of the weight: where the symptoms began, how far they have spread, how quickly, whether they are symmetrical, and what you have been exposed to, including alcohol, every medicine you take and whether anyone in the family has had the same thing with high arches or difficulty walking.

The examination is where the answer usually comes from. Your doctor tests light touch, pinprick, temperature, vibration with a tuning fork, and your sense of where your toes are when they are moved with your eyes shut. They test power in the feet, ankles and hands, and tap the reflexes, which at the ankles are typically reduced or absent. They then look at the feet themselves for dry skin, clawing of the toes, calluses over pressure points and any ulcer you have not felt, feel the pulses, and check your blood pressure lying and then standing.

What that builds is a pattern, and the pattern directs everything after it. Damage that is symmetrical in both feet points one way; a single nerve or a single limb points somewhere quite different, and so does weakness that arrived over days instead of years. Blood tests look for the treatable causes. Testing of the nerves themselves is arranged where the picture is unusual, asymmetrical, or moving quickly.

Nerves repair slowly when they repair at all, at roughly a millimetre a day, so improvement is measured in months and often over a year or more. The first goal is to stop the damage advancing. Where a cause is found and corrected, that usually happens within a few months, even though the sensation you have already lost lags a long way behind.

Where a vitamin deficiency is responsible, replacement often improves things over three to twelve months, and damage that has been present for years may not come back at all. Where diabetes is responsible, keeping blood sugars steady slows progression, and steady matters more than low: sugars that swing widely are harder on nerves than sugars that sit a little high and stay there.

Treating the burning and shooting pain is a separate job from repairing the nerve. The medicines used for it are started low and built up over several weeks, and each deserves about a month at a proper dose before it is judged. A realistic aim is pain that is manageable and sleep that is undisturbed. Once sensation is reduced, foot care becomes a daily habit for good: looking at both feet every evening, well-fitting shoes, and never walking barefoot indoors or out.