Peripheral Nerves, Explained

Today's post from healthmeup.com (see link below) is a good and easy to follow description from India of the nervous system; the symptoms when there is nerve damage and the common testing process to make diagnoses. Many people with neuropathy aren't quite sure which nerves are which, what their functions are and why they go wrong - this article provides you with a simple explanation without overwhelming you with information. Definitely worth a read to top up your knowledge.

Understanding Peripheral Nerves : Types, Peripheral Neuropathy, Symptoms and Tests 
By Sobiya N. Moghul posted Aug 20th 2014 Healthy Living

The human nervous system consists of four parts: the brain, spinal cord, autonomic nervous system and peripheral nerves. Peripheral nerves are cord-like structures containing bundles of nerve fibres that transmit signals from the spinal cord to the rest of the body, or to transmit sensory information from the rest of the body to the spinal cord. Your peripheral nerves are the ones outside your brain and spinal cord. Like static on a telephone line, peripheral nerve disorders distort or interrupt the messages between the brain and the rest of the body.

The nerves in our bodies are very similar to electric cables. The brain and spinal cord send electrical signals through the nerves to different muscles. The muscles, in turn, have a specialised mechanism to properly understand the electrical signals and act accordingly, thereby moving different parts of the body.

There are three types of peripheral nerves: motor, sensory and autonomic. Some neuropathies affect all three types of nerves, while others involve only one or two.

Motor nerves send impulses from the brain and spinal cord to all of the muscles in the body. This permits people to perfom activities like walking, catching a ball, or moving the fingers to pick something up. Motor nerve damage can lead to muscle weakness, difficulty in walking or moving the arms, cramps and spasms.

Sensory nerves send messages in the other direction—from the muscles back to the spinal cord and the brain. Special sensors in the skin and deep inside the body help people identify if an object is sharp, rough, or smooth, if it's hot or cold, or if a body part is still or in motion. Sensory nerve damage often results in tingling, numbness, pain, and extreme sensitivity to touch.

Autonomic nerves control involuntary or semi-voluntary functions, such as heart rate, blood pressure, digestion, and sweating. When the autonomic nerves are damaged, a person's heart may beat faster or slower. They may get dizzy when standing up, sweat excessively, or have difficulty sweating at all.

There are various kinds of peripheral nerve disorders. They can affect one nerve( mononeuropathy) or many nerves( polyneuropathy). In some cases, like complex regional pain syndrome and brachial plexus injuries, the problem begins after an injury. Some people are born with peripheral nerve disorders.

Mononeuropathy is usually the result of damage to a single nerve or nerve group by trauma, injury, local compression, prolonged pressure, or inflammation. Examples include: Carpal tunnel syndrome (a painful wrist and hand disorder often associated with repetitive tasks), and Bell's palsy (a facial nerve disorder) .

The majority of people, however, suffer from polyneuropathy, an umbrella term for damage involving many nerves at the same time.

There are many causes of peripheral neuropathy, including diabetes, hereditary disorders, infections, inflammation, auto-immune diseases, protein abnormalities, exposure to toxic chemicals, poor nutrition, kidney failure, chronic alcoholism, and certain medications – especially those used to treat cancer and HIV/AIDS. In some cases, however, even with extensive evaluation, the cause of a person's peripheral neuropathy remains unknown – this is called idiopathic neuropathy.

The symptoms of peripheral neuropathy often include:

• A sensation of wearing an invisible "glove" or "sock"

• Burning sensation or freezing pain

• Sharp, jabbing or electric-like pain

• Extreme sensitivity to touch

• Difficulty sleeping because of feet and leg pain

• Loss of balance and coordination

• Muscle weakness

• Difficulty walking or moving the arms

• Unusual sweating

• Abnormalities in blood pressure or pulse

There are specialised nerve tests like EMG, NCV and SSEP, which are designed to diagnose any abnormality in the functioning of these nerves.

EMG, or Electromyography is a technique used for evaluating and recording the electrical activity produced by muscles. The EMG helps doctors distinguish between muscle conditions that begin in the muscle and nerve disorders that cause muscle weakness.

NCV, or Nerve Conduction Velocity, is an electrical diagnostic test that provides information about abnormal conditions in the nerves.

SSEP, or Somatosensory Evoked Potential, is a test showing the electrical signals of sensation going from the body to the brain and spinal cord. The signals show whether the nerves that connect to the spinal cord are able to send and receive sensory information like pain, temperature and touch.

Treatment aims to treat any underlying problem, reduce pain and control symptoms. Injuries to the Brain and Spinal cord have only a very limited capacity to heal, because nerve regeneration tends not to occur. In contrast, peripheral nerves have a striking capacity for regeneration. Even completely severed peripheral nerves, if repaired in a timely fashion, can regrow, allowing the patients to enjoy complete, or nearly complete recovery in many cases.

The healing process almost invariably requires an extensive amount of time to occur. It is important for patients not to lose hope during this time. It is vital that they exercise, keeping the affected muscles and joints flexible and ready to be used once again when the axons regrow into them. It is not unusual for patients to undergo a lengthy, complex, peripheral nerve reconstruction procedure, only to see no evidence of recovery for a year or more. This can be immensely frustrating for the patient. Unfortunately, currently there is nothing in medical science that can make these axons grow any faster. Perhaps it is best to think of this delay as part of the healing process, paving the road to further recovery.

*Inputs : Dr Harleen Luther – Brain , Spine; Peripheral Nerve Surgeon, Seven Hills Hospital, Mumbai.

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