Motor Neurone Disease (MND)
Motor neurone disease (MND) is a condition that affects the nerves in the brain and spinal cord which control movement (motor neurones). The disease causes progressive degeneration of the motor neurones and over time, the muscles they control become weaker, which may affect daily activities such as walking, speaking, swallowing or breathing.
It is important to recognise that MND affects everyone differently. Some people notice weakness in a limb first, whilst others may notice changes in speech or swallowing. The disease usually progresses over time, but the speed and pattern can vary from person to person. MND does not usually affect the senses such as sight, hearing or touch, though some people may experience changes in thinking or behaviour. MND is also categorised into different subtypes and the aim of the consultation with your consultant and the investigations planned, are part of this diagnostic work-up.
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What is a Nerve Conduction Study (NCS) and Electromyography (EMG)?
When investigating possible MND, one of the key tests is a combination of Nerve Conduction Studies (NCS) and Electromyography (EMG).
NCS looks at how well the nerves carry electrical signals. Small electrical impulses are used to stimulate the sensory and motor nerves, and sensors measure how quickly and strongly the signal travels. This helps show whether the nerves that carry messages to muscles are working normally.
EMG looks directly at the electrical activity inside the muscles. A very fine needle is gently placed into a muscle, and you are asked to relax and then contract the muscle. The test records the electrical patterns in the muscle, which can reveal whether the muscle weakness is due to a problem with the nerves supplying it.
These tests are generally safe and well tolerated. The EMG needle may cause some mild discomfort, but typically there are no significant complications beyond mild bruising at the needle insertion sites. It is important however to inform your doctor if you are taking blood thinners. Click here for more information on NCS and EMG.
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How do these tests fit into the diagnosis?
Ultimately, MND is a clinical diagnosis. There is no single test that can confirm MND. The diagnosis is made by your Consultant Neurologist based on a thorough medical history and neurological examination, supported by diagnostic tests such as NCS/EMG, blood tests and brain/spine imaging. These tests serve to exclude other conditions that can mimic MND. The diagnosis of MND is based on diagnostic criteria such as the Awaji criteria or the Gold Coast criteria.
The NCS/EMG is particularly important because it can show patterns of nerve and muscle involvement typical of MND, which increases the diagnostic confidence when applied to the diagnostic criteria. It can also help rule out other conditions, such as nerve entrapments or peripheral neuropathies, which may cause similar symptoms.
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For more information on NCS and EMG, please visit here