Dr Brython Hywel

Nerve conduction studies and electromyography are an extension of the neurological examination. They help with the diagnosis of nerve and muscle diseases. For nerve conduction studies, small electrical impulses are passed through nerves and the responses are picked up and analysed to assess how well the nerves are working. Electromyography involves a needle being inserted into muscle whilst connected to the nerve conduction machine. The inherent electrical signal within the muscle is analysed. It can give detail as to how well the nerve supply to that muscle is working and can give clues to whether the underlying problem is within the muscle itself (myopathy). In general, the consultation involves history and examination followed by the nerve conduction tests then EMG. A report is provided to the referring clinician.

Common conditions that these tests can look for include:

Carpal tunnel compression

This is where the median nerve that runs through the centre of the wrist can be compressed in the narrow canal formed by the wrist. Nerve conduction tests can help prove the presence of carpal tunnel compression and grade its severity from very mild to extremely severe. This can help target appropriate treatment.

Ulnar neuropathy at the elbow

This is where the ulnar nerve, that supplies sensation to the little finger and half of the ring finger, is irritated as it passes around the elbow. This is the nerve that is irritated when we hit our funny bone. Identifying ulnar neuropathy at the elbow can lead to treatment which ranges from conservative measures to protect the nerve, such as taking care not to apply too much pressure to the nerve, to operations to protect the nerve (decompression or transposition). Nerve conduction studies can help differentiate ulnar neuropathy at the elbow from ulnar neuropathy at the wrist, which is less common.

Radiculopathy

This is where the nerve roots are irritated as they leave the spinal canal, most commonly by spinal discs that have moved due to wear and tear. Nerve conduction tests and EMG can help show that nerve symptoms in the limbs are due to radiculopathies leading referrers to targeted imaging such as MRIs of the spine.

Peripheral polyneuropathy/peripheral neuropathy

Peripheral polyneuropathy is a process that affects the functioning many of the peripheral nerves. There are many different forms and causes, including low B12, diabetes, high alcohol intake, and infections such as HIV. There are a substantial number of people with genetic polyneuropathies, and whilst many are diagnosed in childhood there are cases picked up in adulthood. In many cases of polyneuropathy, the exact cause isn’t found.

Mononeuritis multiplex

This is where more than one nerve, not connected to each other, are affected. It can be caused by an inflammation of the blood vessels (vasculitis). This is rare, but important not to miss as it can be treatable and early treatment can reduce disability.

Motor Neurone Disease

Also known as Anterior Horn Cell Disease, this is a disease where the motor nerves, that tell the muscles when to move, degenerate. It is a degenerative disease. EMG can help diagnose this condition, to aid management.