Diagnosis and treatment

Diagnosis of neuromuscular disorders may require complex tests such as blood investigations (including relevant DNA or antibody analysis), electrical testing of nerve and muscle and/or biopsy of nerve and muscle.

However, a clinical assessment is the starting point because this can often allow a clinical diagnosis minimising the use of more uncomfortable tests.

If required, we can rely on the help of colleagues with expertise in interpretation of electrical test (neurophysiology), nerve or muscle biopsies (pathologists) and genetic analysis.

Clinical neurophysiology: nerve conduction studies and electromyography

Patients with suspected disorders/diseases of the peripheral nerves or muscles will often require electrical tests which assess their function. These are called nerve conduction studies and electromyography (EMG).

The tests are performed by a consultant clinical neurophysiologist, of which there are four at the Wessex Neurological Centre. Patients are seen either as outpatients or inpatients depending upon the circumstances of their illness. The overall aim of the consultation and tests is to aid or confirm the diagnosis, or to guide management of the patient’s neuromuscular disorder.

Nerve conduction studies and electromyography have a diagnostic role in most of the disorders seen by the service. It is of limited value in some muscle disorders. Specific tests are performed to investigate or distinguish specific conditions and also sometimes to exclude specific conditions. Those in which clinical neurophysiology is important include:

• Peripheral neuropathies, including demyelinating neuropathies
• Motor neurone disease
• Muscle diseases
• Myasthenia gravis, Lambert-Eaton myasthenic syndrome and congenital myasthenic syndromes

More information

• Nerve conduction studies
• Electromyography (EMG)
• Clinical neurophysiology

Edrophonium (or Tensilon) test

An edrophonium (or Tensilon) test may be performed to help confirm a diagnosis of myasthenia. This is usually performed on the neurology day ward. It involves an injection of a medication called edrophonium (trade name Tensilon) which boosts the signal between nerve and muscle.

In most cases of myasthenia, edrophonium improves the muscle weakness but it's effect only lasts a few minutes. During the test you would be connected to a heart monitor as edrophonium tends to slow the heart rate. We usually use another medication, atropine, to minimise this side effect. Other rare side effects include fainting and breathing difficulties which is why the test is performed in a medically supervised setting.