Tingling sensation in hand could be carpal tunnel syndrome

THE median nerve is sometimes known as the “eye of the hand”.

It is so called because of the work it does in providing sensation to large parts of the hand and fingers as well as powering various muscles, including those that flex the wrist.

It is one of three major nerves that help to deliver all the power and sensation we experience in our hands (the other two being the ulnar and radial nerves) but it is the only nerve to pass through what we call the carpal tunnel.

The carpal tunnel is an anatomical space in the wrist that is bordered on three sides by the carpal bones and on the remaining one (the one on the underside of the wrist near the skin fold) by a fibrous ceiling of tissue and ligament known as the flexor retinaculum.

The median nerve is accompanied though the tunnel by the tendons of the muscles that flex the fingers.

With all things working as they should, the nerve provides sensation to the thumb, index and middle fingers along with half of the ring finger.

As is often the case in medicine, however, things don’t always work as they should. That’s where carpal tunnel syndrome comes in.

This is a common occurrence for people to come to us as GPs complaining of tingling and numbness in their fingers.

While there are a few potential causes for this, carpal tunnel is probably the most common.

In the UK, the incidence of new carpal tunnel symptoms ranges from around 88 per 100,000 for men to 193 per 100,000 for women each year.

Its prevalence appears to be increasing. Whether that is an increase in reporting or a true increase is not clear. The problem occurs when there is a reduction in the volume of the carpal tunnel, either due to a shrinking of the boundaries — for example after trauma — or due to an effective decrease in volume caused perhaps by an increase in inflammatory fluid.

Whatever the underlying cause, the symptoms begin when there is a resulting pressure on the median nerve, causing ischaemia (lack of blood supply) and a reduction in nerve conduction.

I’ve already mentioned the tingling sufferers might experience in the fingers but one might also experience burning discomfort in the affected hand and sometimes an achiness that on occasion will radiate into the forearm and sometimes even up to the shoulders.

One of the real classic features is its propensity to trouble people overnight, interrupting a good night’s sleep, something a vigorous shake of the wrist seems to alleviate upon waking.

This is likely due to our habit of curling our wrists into various flexed positions for long periods of time while we sleep.

Generally speaking, carpal tunnel syndrome is intermittent but more severe cases can result in more persistent symptoms and, with time, the effects — so far reversible — can become more permanent.

Often people describe a loss in grip strength and a difficulty in carrying out daily tasks such as opening jars and doing up buttons.

Carpal tunnel syndrome is a relatively new diagnosis in medical terms. Its classic symptoms were first formally described back in 1854 by Sir James Paget but it wasn’t until about 100 years later that its physiology was properly understood and thus inducted into the medical lexicon.

Before that, the symptoms were often referred to as acroparaesthesia (acro being a rather general term indicating a tip or an extremity). The man responsible for popularising this term was George Phalen, immortalised now by one of the tests we use to diagnose the syndrome.

By placing the backs of your hands together with a 90 degree bend at the wrist for 60 seconds, Phalen’s test — if positive — will induce or worsen the tingling and numbness in a sufferer’s fingers.

GPs often use another test known as Tinel’s test in which they tap on the wrist repeatedly for up to a minute to try and induce the symptoms.

That is frequently all that is needed to reach a diagnosis but in cases where it is not so clear cut, nerve conduction studies might be necessary.

If not carpal tunnel, other conditions must be considered. Entrapment of the nerves further up the arm in the neck, shoulder or elbow, for example, will most likely be obvious in the presence of a stiff neck or a painful shoulder.

A more generalised neuropathy (disorder of a nerve) might present throughout the body in conditions such as diabetes or vitamin B12 deficiency.

The distribution of the altered sensations is key to the detective work. If there is tingling in the little finger, for example, this is more likely to be pressure on the ulnar nerve at the elbow, something known as cubital tunnel syndrome.

There is often a reported link between manual work and carpal tunnel syndrome. It seems likely that those who work on keyboards all day are more prone, although firm evidence is surprisingly in short supply here.

Those who are overweight or have diabetes, rheumatoid arthritis or low thyroid function are certainly more at risk. Pregnant women are also more at risk but where the syndrome occurs in pregnancy the symptoms are commonly transient and tend to resolve after giving birth.

If you think you might be getting a bit of carpal tunnel syndrome, the first step is to ensure that any exacerbating factors are dealt with (weight loss, for example, or practical adjustments if you feel that typing at an odd angle is contributing).

At night-time, it’s a really good idea to wear a splint to keep the wrist in a neutral position.

If this is getting you nowhere your GP might be able to organise an injection of steroid into the wrist. While this doesn’t always work and isn’t something you should be repeating ad infinitum, it can provide some relief by reducing inflammation in the tunnel.

Still not helping? At this stage, it is worth consulting with a hand surgeon to discuss whether a short surgical procedure might be worthwhile to decompress the bottleneck. This is done by putting a small cut in the overlying fibrous tissue in order to release things.

While it is a common condition, carpal tunnel syndrome can be really troublesome and may impact on all sorts of daily activities you would normally take for granted.

While it’s important to seek help if your symptoms are bad, if it is there in the background make sure you try the simple things first. They can often make all the difference.