The diagnosis of motor neurone disease is often clinically difficult, and sometimes it is necessary to review a person for some time before the diagnosis becomes relatively certain. A general practitioner may suspect a neurological problem, and organise referral to a neurologist.
Several other neurological conditions resemble motor neurone disease, especially in the early stages, and need careful exclusion.
The diagnosis can be assisted through a range of tests, including some which eliminate other conditions. Nerve conduction studies (NCS) and electromyography (EMG) are often performed and may help in establishing the diagnosis.
A nerve conduction study (NCS) analyses neural function by electrical stimulation of nerves and recording muscle activity. Sometimes a patient may have to undergo nerve conduction studies & EMG on more than one occasion so that any changes over time can be identified.
EMG consists of inserting a needle electrode into various muscles to measure their electrical activity. Electromyography (EMG) is a diagnostic procedure that evaluates the health condition of muscles and the nerve cells that control them. These nerve cells are known as motor neurons. They transmit electrical signals that cause muscles to contract and relax.
There is no blood test to diagnose MND. However, blood tests might be performed to look for evidence of damage to the muscle (called CK, or creatine kinase), to look for causes of inflammation in the spinal cord (such as vitamin B12 levels) or to look for supportive evidence of damage to the motor nerves (such as anti-ganglioside antibodies). The appropriateness of each test is determined on a patient-by-patient basis and as all patients are different all the tests may not be performed on every patient.
Muscle biopsy is needed only rarely but may be considered if the presentation of MND is atypical. The results will confirm the presence of signs of denervation and reinnervation or may lead to an alternative diagnosis.
A lumbar puncture cannot diagnose motor neurone disease but can look for evidence of other causes of a patient's symptoms (such as inflammation in the spinal cord and brain).