07.14.22|Posted by Paul Carson

Understanding the upper limb nervous system

Ascenti physiotherapist Paul Carson explores the upper limb nervous system and shares his advice for treating injuries to the two types of nerves within it.

The neck is commonly referred to as the cervical spine and consists of seven bones known as vertebrae. In between the vertebrae are joints known as the intervertebral discs. The nerves branch off from the cervical spine (neck) into the shoulder and all the way down to our fingertips. 

To understand why we are getting nerve related symptoms, it helps to understand the anatomy of the body. When we think of nerves it can be helpful to split them into two categories depending on what they do: dermatomes and myotomes.

What is a dermatome? 

A “dermatome” is the area of your skin that is supplied by a specific nerve root, (single nerve as it leaves the spinal cord). They are responsible for our ability to feel different textures and sense changes in temperature at the skin.

When you rub something on your hand or touch something warm, that sends a stimulus from the skin to the spinal cord and into the brain; at which point we react to that stimulus. (For example, noticing that something is hot and experiencing pain or touching something soft and experiencing feelings of comfort.)

There are lots of different nerves that supply (innervate) various parts of your skin, and after an accident the strength of the signal can be impaired as the nerve has been injured. 

What are some common symptoms?

Some common examples of symptoms you may experience when the nerves that supply your skin are damaged, swollen or bruised are:

  • You do not feel objects/textures in the same way when compared to the other side
  • You are unable to detect changes in temperature hot or cold increasing the risk of damaging the skin
  •  You might be getting pins and needles after certain movements

What is a myotome?

A “myotome” is the group of muscles supplied by a specific nerve root (single nerve as it leaves the spinal cord). When you want to perform an action, such as picking up a cup, there is communication between the brain, spinal cord and associated nerves with the muscles required to perform that action. Each spinal nerve root or origin can be associated with a movement of the arm or leg.

Similarly, as with dermatomes, your myotomes can also be impaired when the nerve that supplies them is injured after a traumatic event such as a Road traffic accident. However, when the nerves that innervate our muscles have been affected, you are more likely to experience weakness and pain associated with the injured nerves. 

What are some common symptoms?

Symptoms of a damaged/bruised or swollen nerve root supplying a group of muscles include: 

  • Weakness of shoulder, arm or hand
  • Twitching of the muscle
  • Dropping items when they are picked up
  • Struggling with buttons/fine motor tasks

When nerve roots are injured, they become painful and swollen, just like your ankle if you were to sprain or injure that. The pain from a nerve root can be sharp and shooting, but can also be a constant, deep pain which makes it difficult to find a position which is comfortable.

What can a physio do to help problems with nerve root injuries?

Physiotherapists are trained to ask the appropriate questions to identify if you are having problems with your nerve roots, and whether this is affecting your skin or muscles or both (dermatomes and myotomes). 

When examining your dermatomes, your physio will screen the affected area by performing a light touch test with something soft such as tissue or cotton wool and compare your sensation side to side. This will allow your physio to identify the specific dermatomes that have been affected.

When examining your myotomes, your physio will test the strength of both of your arms and will be looking for a weakness in the muscle. This allows your physio to identify the specific myotome/s that have been affected.

What can I do to help my physiotherapy treatment for these issues? 

Nerves are fascinating and can heal themselves (generally speaking), through a process called neuroplasticity.  

Evidence suggests that people with nerve pain coming from the cervical spine will have improvements in sensation and a reduction in pain regardless of the type of treatment provided.

However, there are things you can do to aid the process that will help improve function and quality of life during the rehabilitation.

How to help stimulate your dermatomes

The best thing to do is to give the area that has been affected as much external stimulus as possible.
What this means is to rub the area with different textures throughout the day. This sends lots of messages back up to your brain with the aim of increasing neuroplasticity.

Will sensation come back after an injury with nerve damage?

This is a common and valid question; however, it is very difficult to say and varies from each patient depending on the type, location, and severity of the injury. Most people will find some degree of improvement in sensation - to a full recovery of normal sensation. This process varies in terms of time as well, so patience is a virtue.

How to help strengthen your weak muscles

Your muscles will regain strength as the nerve heals itself and the messages to the muscle return. However, it’s important to try and maintain the movement, flexibility and activation of your muscles while your body is repairing itself to try and prevent further weakness. Since some of your muscles feel weaker, one of the best treatments can be activation exercises. It is usually best to begin with isometrics – when you activate your muscles and maintain the same muscle length throughout the exercise.

Then you can progress onto strengthening exercises when you have full movement of the joint that the weak muscles act on, for example when you can bend your elbow fully without anything in your hand, you are ready to start introducing some light resistance and build up slowly from there – bending and straightening the elbow.

There are lots of different options here, so be sure to discuss this with your physiotherapist so you can work together to create a programme suited to you.

Managing pain with nerve injuries

Living with pain is no easy task, and when you start exercising again you may notice that it hurts when you perform them. But no need to panic because pain does not mean damage!

Part of the management of nerve injuries is working out how to get back to the things you enjoy. In fact, avoiding doing the things you normally do will only make things worse. Your physiotherapist will be there to help you manage all this – it’s more about modifying the activities you do rather than stopping them.

Will my symptoms go away?

This is a very common question, but difficult to answer as once again this will vary from person to person. Most of the research shows that after a year you should see significant improvements in your quality of life and function as well as a reduction in your pain.

   Top tips:

  • Rub various textures such as cotton wool (soft) kitchen towel (coarse). A bowl of dried rice can also be effective for the hand and fingers
  • Use your other hand or a get a friend or family member to massage the affected area
  • Be careful with temperature at the affected area - hot oil when cooking- avoid putting ice packs or heat packs on that area for long periods of time unless advised by a professional
  • Set a pain scale for your exercises. Use the Numerical Rating for pain (NRS) - pick a range that is tolerable for you for example 1-4/10 NRS. If you go to the gym or whilst walking you find your pain falls between these numbers, it’s a good indicator you aren’t pushing yourself too hard.

If your pain does exceed this scale, then it means you need to modify your programme: reduce the amount of time, the number of days or change the exercises. Your physiotherapist will be able to help you with this.

Nerve pain can be a scary thought, but it tends to improve over time and just because you are in pain it does not mean you are doing any damage to your body; you might just have to modify your activities. If you do go to see a physiotherapist, they will be able to identify where your sensation, weakness and pain is coming from and create a specific plan tailored to your needs.

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