Nerve conduction studies and EMG, read the same day by a consultant clinical neurophysiologist.

Part one

Nerve conduction studies (NCS)

Small surface electrodes are placed on the skin over a peripheral nerve. A brief electrical pulse stimulates the nerve, and recording electrodes downstream capture the response. From that trace the neurophysiologist reads four core numbers.

• Amplitude — the size of the muscle or sensory response. A drop suggests axonal loss.
• Latency — how quickly the signal reaches the recording electrode. A delay across a compression point is the hallmark of carpal or cubital tunnel.
• Conduction velocity — how fast the nerve carries the signal. Slowing points to demyelination.
• F waves and H reflex — long-loop responses that check the proximal nerve and root, useful in early Guillain-Barre and S1 radiculopathy.

Part two

Electromyography (EMG)

A very fine concentric needle electrode is placed into selected muscles. It records the muscle's own electrical activity, first at rest, then during gentle and full contraction. The neurophysiologist listens and watches for four things.

• Insertional activity — a brief burst as the needle enters healthy muscle. Prolonged or absent activity is abnormal.
• Spontaneous activity — fibrillations and positive sharp waves indicate ongoing denervation.
• Motor unit morphology — long, large units suggest chronic reinnervation; small, brief units suggest myopathy.
• Recruitment — how motor units are called into play as effort rises. Reduced recruitment points to a neurogenic cause.

Preparation

What to do the day before.

• Wash the skin with soap and water. Avoid moisturisers, oils and creams on the limbs on the morning of the test.
• Wear loose clothing that lets us access arms and legs.
• Keep your hands and feet warm on the way in. Cold skin slows conduction and distorts the numbers.
• Take all your regular medication as normal. No fasting is needed.
• Tell us about pacemakers, implanted defibrillators and spinal-cord stimulators. Studies remain possible with adjusted technique.
• Tell us about anticoagulants. In almost all cases needle EMG proceeds unchanged.

On the day

What actually happens.

The consultant meets you, reviews the history, and explains the plan. Nerve conduction studies come first, usually 15 to 30 minutes. Each stimulus is a brief tapping sensation. Needle EMG follows, five to ten muscles depending on the clinical question. The needle is very fine and no local anaesthetic is used, because it would blur the traces. Most patients describe it as sharp on entry with a dull ache during activation. You dress, and the consultant talks you through the findings before you leave. The signed report follows the same day.

Indicative cost

What you will pay privately.

• £550 to £950 — focused NCS with EMG of one or two limbs. Covers most carpal tunnel, cubital tunnel and single-limb radiculopathy referrals.
• £850 to £1,400 — four-limb NCS and EMG, or studies with single-fibre EMG or repetitive nerve stimulation for suspected myasthenia gravis or motor neurone disease.
• Consultant follow-up, if needed, is quoted separately.
• Recognised by Bupa, AXA Health, Vitality, Aviva, WPA, Cigna and Healix when medically indicated and pre-authorised. We handle the paperwork.

Where in London

Our neurophysiology partners.

• National Hospital for Neurology and Neurosurgery (UCLH) Private, Queen Square
• King's College Hospital Private, Denmark Hill (specialist MND and neuromuscular unit)
• HCA The Wellington Hospital, St John's Wood
• London Neurology Clinic, Harley Street
• One Welbeck Neurology, Welbeck Street
• Imperial Private Healthcare at Charing Cross Hospital

On the NHS the same test is available in every neurology centre, with waits that vary widely by region. Private is worth considering when timing changes the treatment decision, for example before surgical decompression or when starting immunotherapy.