How do you damage a nerve?
The nerves in our bodies are absolutely essential for our survival. Without them, we wouldn’t be able to breathe, walk, talk, or indeed survive at all. Imagine for example, stepping bare foot on a nail sticking up in the ground – as you step onto the nail, your nerves register the damage it does to your foot so without you thinking about it, the nerves in your leg make you recoil your leg away from the nail, the nerves in your arms and hands react so that you might instinctively grab your leg, the nerves in your head, neck and eyes cause you to instinctively look down at what’s caused the pain, the nerves in your voice box activate so that you shout out in alarm at the sudden pain in your foot. The processes that cause all of these reactions to go off at once occurs in less than one second and you did it all self-consciously because your nervous system took control in order for you to ‘survive’. Imagine if you didn’t have that response and you stepped on the nail and didn’t feel it. You’re not aware that it’s there so you carry on as normal. Eventually, the nail may cause infection and damage to the foot that can spread around the body compromising your health and maybe even your life.
The nervous system keeps us alive so when we damage even just one nerve, the change in the body can be quite significant. Sciatica for example, is when the sciatic nerve running through the buttock and down the back of the thigh to the foot becomes compromised and if you’ve ever suffered with sciatica, you’ll know how painful and debilitating it can be. There are three main ways that stop a nerve from working properly and this blogs looks at each of them.
Very basic nerve anatomy
In order to understand how a nerve can get damaged, it is important to have a brief understanding of how they work. A nerve cell is called a neurone. Nerve cells connect together to make a long chain of neurones. This long chain essentially makes up the nerve. The nerves that are in your legs, arms, back etc, all originate from the spinal cord, which is connected to the brain. When a nerve needs to activate (to contract a muscle for example), the brain sends little electrical messages that travel down through the spinal cord and into the nerve needed to make the muscle contract. These little electrical messages travel down through the nerve in a Mexican-wave fashion until they reach their destination. It is a process that happens so quickly that you’re not even aware of it. As I’m typing out this blog, my brain is sending constant electrical messages down my spinal cord and into the nerves going into my hands and fingers which allow me to move my hands across the keyboard and my fingers to type. In order for a nerve to carry electricity to and from the spinal cord, brain and the rest of the body, the nerve must be able to function. Think of the nerve as an electrical cable. As soon as there is a problem with the electrical conduction of a nerve, the nerve/cable stops working properly.
Damage type number one – Temporary compression or ‘squash’
When a nerve becomes squashed, the electrical messages that travel through it, cannot pass as easily to transmit their messages. Compression pressures can occur through things like leaning on a nerve. One common example of compression is the classic pose of being propped up reading or using a phone in bed. The position of having the elbows bent at an angle for a prolonged period of time which allows you to hold your book or phone up, can squash the nerves as they pass the elbow joint and may lead to pins and needles in the arm which can be relieved by straightening the arm out again. Other examples include
· Hanging your arm over the back of a chair – this can squash the nerves going into your upper arm
· Leaning on your elbow on your desk – this can squash the ulnar nerve leading to pins and needles in the ring and little fingers
· Having your blood pressure checked – sometimes the blood pressure cuff can cause temporary pins and needles down the arm whilst it is inflated
When a compression occurs, the nerve stops working properly. Normally the first sign of a nerve compression is the feeling of pins and needles. This occurs due to a lack of blood being able to get to the nerve. Unlike muscles, nerves do not have a big energy reserve. Instead, they rely on a constant blood flow to receive oxygen and even a temporary break in this oxygen (just a few seconds) is enough for the nerve to stop working properly. If oxygen cannot get to the nerve, the nerve is no longer able to transmit its electrical messages so stops working. Neurologists refer to this a conduction block. Once whatever is compressing the nerve is taken away, blood can be restored to the nerve and its function will come back and its activity will resume within minutes.
Damage type number two – Prolonged compression
If the compression is bigger or lasts longer, it can cause further damage than a temporary conduction block. Examples of these types of compressions include a fracture that has caused a nerve to get squashed in the damage, blood clots pressing on the nerve or traumas such as being trapped under something heavy. If the compression is bigger or is applied for longer, it not only creates a conduction block of that nerve, but if the nerve goes too long without oxygen, it will create an anatomical change to the nerve. Once the compression eventually gets removed, the nerve will have to repair itself first before it can resume conducting electricity. Nerves can repair themselves if the damage is not too extreme and regrow at an average rate of 1mm a day. Some nerve fibres will start becoming active within days, some in weeks and some could take as much as six months. Sciatica is often classed under this type of nerve damage. If the compression is not removed at all or is removed too late, it can lead to a permanent nerve loss.
Damage type number three – Nerve cut
If a nerve is cut, it loses its electrical insulation. It’s a bit like having an exposed cable. Nerves can be damaged this way normally through a highly traumatic event e.g. a car accident, falling off a bike, falling over onto an outstretched hand etc. These types of traumas normally result in a trip to A&E as a fracture is likely to be involved. If the cut is just a partial cut, it is possible that the nerve can repair itself. There are tests that can be done to see if a nerve is repairing itself but if after a period of time, these tests show the nerve isn’t repairing, it may mean that the cut was too deep or went completely through the nerve and in these cases, nerve surgery may be required to either suture or graft the affected nerve and to make sure there are no further compressions. Suturing involves stitching the nerve back together and grafting involves taking nerve tissue from a different nerve and using it to bridge the gap between the two ends of the broken nerve.
Nerve pain is very complex and there is still so much we don’t understand. Phantom limb pain for example is still a mystery and there is still much to learn about other nerve diseases such as Alzheimer’s, epilepsy and Parkinson’s etc. Other diseases such as diabetes, if left untreated can also cause nerve damage, as can other conditions such as long term alcoholism and certain types of medication.
Nerve pain is described as feeling different to muscular pain. Muscular pain is often described as a dull ache or throbbing pain whereas nerve pain is more ‘shooting’ and ‘stabbing’. Although pain is necessary to let us know something is wrong, pain left untreated or mismanaged can be very debilitating and affect quality of life. If you are suffering with any type of pain and would like to get it checked out or would like any advice, don’t hesitate to get in touch!