Clinical neurophysiology · patient guide
Central motor conduction time, transcranial magnetic stimulation to test the corticospinal tract in MS, ALS and myelopathy.
Central motor conduction time (CMCT) uses transcranial magnetic stimulation (TMS) to measure the time taken for a motor signal to travel from the motor cortex to the limb. Used in neurology to detect corticospinal-tract dysfunction — multiple sclerosis, motor neurone disease and cervical myelopathy.
Key facts
- 01
Definition
TMS-based measurement of corticospinal conduction time.
- 02
Detects
Subclinical corticospinal-tract disease.
- 03
Complements
MRI and evoked potentials.
- 04
Painless
30-minute test.
- 05
Interpreted by
Clinical neurophysiologist.
- 06
Used in
MS, ALS and cervical / thoracic myelopathy.
How it works
From referral to report — what happens, in order.
A single 30-minute appointment in the neurophysiology room, painless, no preparation.
- 01
Step 1
Neurology consultation
Referral from a consultant neurologist frames the clinical question the CMCT is being asked to answer.
- 02
Step 2
No specific preparation
Eat, drink and take medication as normal on the day of the test.
- 03
Step 3
Surface EMG electrodes placed
Sticky recording electrodes are positioned on the target muscles (typically hand and leg).
- 04
Step 4
TMS coil over the motor cortex
A magnetic coil is placed on the scalp and delivers brief, painless magnetic pulses.
- 05
Step 5
Peripheral nerve stimulated
A short electrical pulse to the peripheral nerve gives a baseline latency for comparison.
- 06
Step 6
CMCT calculated
Central motor conduction time = total latency minus peripheral latency.
- 07
Step 7
Written report to your neurologist
A clinical neurophysiologist issues a formal report to your referring neurologist.
What it shows
When CMCT is the right test.
CMCT answers a specific question — is the corticospinal tract conducting normally, and where does the delay sit. These are the presentations we see most.
-
Corticospinal delay (MS, ALS)
Prolonged CMCT is a sensitive marker of demyelinating and motor-neurone disease.
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Cervical myelopathy corticospinal slowing
Detects functional cord compromise where MRI changes may be subtle.
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Hereditary spastic paraparesis
Quantifies corticospinal-tract involvement in inherited spastic syndromes.
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Post-stroke corticospinal integrity
Assesses residual pyramidal-tract function relevant to rehab prognosis.
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Prognostic marker in ALS
Adds objective upper motor neurone data alongside clinical examination.
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Post-COVID neurological monitoring
Used selectively where post-viral corticospinal involvement is suspected.
-
Response to disease-modifying therapy
Serial CMCT can track corticospinal-tract response to MS or ALS treatment.
-
Red flag: acute progressive weakness + prolonged CMCT — urgent spinal-cord imaging
Do not wait. Escalate immediately for urgent MRI of the cord.
Next steps
What can follow a CMCT result.
The pathways your referring neurologist will typically consider once the CMCT report is in.
-
MRI brain and spine
The structural companion to CMCT — locates demyelinating, compressive or ischaemic lesions.
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MS disease-modifying therapy
Neurologist-led choice of DMT where multiple sclerosis is confirmed.
-
ALS multidisciplinary review
Coordinated neurology, respiratory, SALT and palliative input for motor neurone disease.
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Neurosurgical decompression
Considered for cervical myelopathy with progressive corticospinal signs.
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Physiotherapy
Targeted rehabilitation for spasticity, gait and upper-limb function.
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Neurorehabilitation
Structured post-stroke or post-MS rehab programme tailored to the deficit.
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Genetic counselling
Offered for hereditary spastic paraparesis and familial motor-neurone disease.
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Serial CMCT follow-up
Objective tracking of corticospinal-tract function over time.
Our vetted London network
A small panel of neurophysiology units, we picked them.
Consultant clinical neurophysiologists across central London. Not listed publicly — introductions are made privately, once we understand your case.
Selection criteria
How we choose every clinic in our network.
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Consultant clinical neurophysiologists using standardised TMS protocols
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Modern figure-of-eight coils with reproducible motor-threshold calibration
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Simultaneous surface EMG of upper and lower limb target muscles
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Written report to your referring neurologist within 5–7 working days
Safety and eligibility
One of the safest tests in neurology.
CMCT is painless and radiation-free — the practical points are the few situations where TMS needs extra screening, and where its limits are.
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Painless
TMS pulses feel like a tap on the scalp — no needles into the brain, no radiation.
-
No preparation
Eat, drink and take medication as normal. Avoid heavy caffeine on the day if possible.
-
Duration
About 30 minutes in the neurophysiology room.
-
Epilepsy caveat
Uncontrolled epilepsy is a relative contraindication — the neurophysiologist will screen carefully.
-
Metal implants
Cochlear implants, deep-brain stimulators and intracranial metal need pre-test assessment.
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Pregnancy
TMS is generally avoided in pregnancy unless the clinical need is compelling.
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Normal CMCT is not a full clear
A normal result reduces but does not eliminate corticospinal disease — clinical context matters.
-
MRI often follows
Prolonged CMCT usually triggers cord and brain MRI for structural correlation.
-
Bring prior neurophysiology
Comparison against previous CMCT, evoked potentials or EMG materially sharpens the report.
Red flags
Presentations that warrant CMCT — or urgent escalation.
The clinical scenarios where corticospinal-tract testing changes management. Rapidly progressive weakness is a 999 / A&E call, not a private outpatient slot.
-
Rapidly progressive weakness
-
Bilateral upper motor neurone signs
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Bladder / bowel dysfunction with myelopathy
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Post-stroke unresolved deficit
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MS relapse with new pyramidal signs
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Cervical spondylotic myelopathy
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Hereditary spastic paraparesis
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Post-radiotherapy myelopathy
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Adrenoleukodystrophy
Reading your report
A CMCT report can look intimidating. It isn’t.
Whatever the finding, the report keeps to the same four parts.
A quiet reminder
The report is written for your neurologist, not for you — and that’s normal.
If you would like us to talk you through it before your follow-up, just ask.
- 01 Header
Indication and referral question
Your details, the referring neurologist and the specific clinical question the CMCT is answering.
- 02 Technique
Coil, muscles and stimulation parameters
The TMS coil type, target muscles, motor threshold and peripheral stimulation used.
- 03 Findings
Latencies and calculated CMCT
Total motor-evoked-potential latency, peripheral latency and calculated CMCT for each limb.
- 04 Impression
The conclusion: read this first
Normal, mildly prolonged or markedly prolonged CMCT — and the concrete next step.
Recognised by major UK insurers
Cover depends on your policy and clinic; we confirm with your insurer before booking.
Frequently asked
Everything we get asked about central motor conduction time.
Quick answers on what CMCT shows, how it compares to MRI, and when it changes management.
-
What does central motor conduction time (CMCT) show?
CMCT measures the time taken for a motor signal to travel from the motor cortex, down the corticospinal tract, to a peripheral muscle. A prolonged CMCT points to disease in the corticospinal tract — commonly MS, motor neurone disease or cervical myelopathy.
-
Is CMCT painful?
No. Transcranial magnetic stimulation feels like a brief tap on the scalp. The peripheral nerve stimulation feels like a small electrical pulse. There are no needles into the brain and no radiation.
-
How is CMCT different from MRI?
MRI shows structure — where a lesion is. CMCT shows function — whether the corticospinal tract is conducting normally. The two are complementary, and prolonged CMCT often triggers a targeted MRI.
-
Who interprets the test?
A consultant clinical neurophysiologist performs and reports the CMCT, and writes back to the referring neurologist.
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When is CMCT used in MS and ALS?
CMCT can detect subclinical corticospinal involvement in MS before it is obvious on examination, and adds objective upper motor neurone data in suspected ALS. Serial CMCT can track response to disease-modifying therapy.
-
When should I go to A&E instead?
Rapidly progressive weakness, bilateral leg weakness with bladder or bowel dysfunction, or any sudden neurological deficit is a 999 / A&E presentation — not a private outpatient neurophysiology slot.
Sources
Clinical references.
- British Society for Clinical Neurophysiology. Guidelines on TMS and motor-evoked potentials.
- European Federation of Clinical Neurophysiology. TMS clinical practice guidance.
- American Academy of Neurology. Assessment: transcranial magnetic stimulation.
- MND Association. Clinical guidance on motor neurone disease.
Reviewed by Pulse Atlas Editorial Board, . Published 2026-07-30. Next review 2027-07-30. Reading time ~6 minutes.
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In practice, in London
Where central motor conduction time sits in a private London pathway
With central motor conduction time, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. Waiting lists on the NHS for central motor conduction time vary widely by borough and by how the GP letter reads. Privately in London, we can normally offer a slot inside the same week, sometimes within 48 hours if there’s a cancellation. The difference isn’t clinical quality — the consultants are frequently the same faces you’d see on the NHS — it’s the calendar.
Once you’re in the private system for central motor conduction time, the pace picks up noticeably. Consultant slots run to time, imaging is usually available in the same building or a short walk away, and the report comes back typed and detailed. It’s the coordination that tends to feel different — one person on the other end of the phone, not a switchboard. For central motor conduction time specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
Honesty about expectations is part of the job. A private central motor conduction time appointment in London won’t change the underlying medicine — the guidelines, the consultants, and the equipment are largely the same as on the NHS. What it changes is speed, continuity, and the amount of time you get to actually talk through the findings. Everyone we route to is GMC-registered and works within CQC-regulated facilities.