17-18mm
Typical
What it means
The usual front-to-back width of the canal at mid-cervical levels in an adult.
Significance
Ample room. The cord has fluid all around it and tolerates normal movement easily.
Cervical spinal stenosis: when the canal runs short of room
The spinal cord travels through a bony canal in your neck. Stenosis simply means that canal has narrowed. On its own that is a measurement, not a diagnosis: plenty of people have a narrow canal and no symptoms at all. What matters is whether the narrowing has started to affect the cord.
What you need to know in 30 seconds
Stenosis means the spinal canal has narrowed. It describes available space, not symptoms.
A mid-cervical canal is typically 17 to 18mm front to back. Symptoms commonly begin below about 13mm.
Narrowing can be silent. In 1,211 symptom-free volunteers, 5.3 per cent had cord compression on MRI.
Stenosis is the setting; myelopathy is the problem. The important question is whether the cord is being affected.
Some people are born with a narrower canal, which leaves less margin when age-related change is added.
Significant stenosis is worth knowing about, because it makes a neck injury more consequential.
17-18mm
The typical front-to-back width of the canal at mid-cervical levels.
Under 13mm
The point below which symptoms commonly start to appear. Under 10mm is considered severe.
5.3%
Of people with no neck symptoms had cord compression on MRI, rising after age 50.
Space, not pain
Stenosis is a measurement. Whether it causes trouble depends on what the cord is experiencing.
WHAT IT IS
Less room than the cord would like
The canal has a fixed bony outline, and everything that thickens or bulges into it takes space the spinal cord cannot get back. Stenosis is the cumulative result.
1
The space available to the cord, measured front to back
2
Spinal cord, with fluid comfortably around it
3
Bone, disc and thickened ligament encroaching on the canal
4
Cord flattened against the walls, with little fluid left
01
Stenosis is not the same as myelopathy
This is the distinction that matters most. Stenosis is narrowing. Myelopathy is what it is called once that narrowing is actually affecting how the spinal cord works. You can have the first for years without the second.
02
Some canals start out narrower
Canal size varies naturally between people. Someone with a congenitally narrow canal has less reserve, so a modest amount of age-related change or a single disc herniation can matter more than the same change would in a roomier neck.
03
It can be genuinely silent
Among 1,211 people with no neck symptoms, 5.3 per cent had cord compression visible on MRI, and that proportion rose after the age of 50. Narrowing found incidentally is not automatically something to operate on.
THE NUMBERS
How much room is enough
These figures are a guide, not a threshold for treatment. Two people with the same measurement can be affected completely differently, which is why the examination carries more weight than the millimetres.
Under 13mm
Relative stenosis
What it means
Narrowed enough that the reserve space around the cord is meaningfully reduced.
Significance
The range in which symptoms commonly begin, though many people at this width have none.
Under 10mm
Absolute stenosis
What it means
Severely narrowed, with very little or no fluid left around the cord.
Significance
Higher likelihood of symptoms, and a neck injury at this width carries more risk.
Ratio
A rough guide
What it means
The canal width compared with the width of the vertebral body, sometimes quoted as a ratio.
Significance
A value under about 0.82 suggests a congenitally narrow canal, but it is unreliable on its own.
WHEN TO ACT
The signs that narrowing has become a problem
Stenosis on a report needs no urgent action by itself. These symptoms suggest the cord is now involved, and they change the timeline.
1
Both hands becoming clumsy
Fumbling buttons, keys and coins, or handwriting deteriorating, particularly in both hands together.
2
Balance or walking changing
Feeling less steady, or walking more carefully than you used to, without another obvious explanation.
3
Weakness or spreading numbness
New weakness in an arm or leg, or numbness that is extending rather than staying put.
4
After any neck injury
If you know you have significant stenosis, a fall or impact followed by new symptoms should be assessed promptly.
Seek urgent care
Sudden or rapidly worsening weakness or numbness, a sharp decline in walking or hand function, or any new loss of bladder or bowel control needs emergency assessment. Call 000 or go to your nearest emergency department. GPs with an urgent concern can phone the rooms directly on (07) 3870 3708.
WHAT CAUSES IT
What takes up the space
01
Bony spurs
The commonest contributor. Spurs formed as part of cervical spondylosis grow into the canal over years.
02
A congenitally narrow canal
Some people simply start with less room. It causes no trouble for decades, but it removes the buffer that absorbs later change.
03
Thickened ligament
A ligament at the back of the canal can thicken with age, and in some people a spinal ligament hardens, taking up space directly.
04
Disc bulging
A disc pushing backward reduces the canal at that level, sometimes tipping a marginal canal into a symptomatic one.
HOW IT IS ASSESSED
Measuring the space, then testing the cord
01
MRI
The key test. It shows the canal, the fluid around the cord, and whether the cord itself shows any change from the pressure.
02
CT and X-ray
Useful for bone detail, spur size and alignment, and for measuring canal dimensions where MRI is not available or is unclear.
03
Neurological examination
The part that determines what the measurement means. Reflexes and specific hand and gait tests reveal whether the cord is being affected.
A number on a report never decides treatment by itself. Two people can have identical canal measurements and be in entirely different situations, because what counts is how the cord is functioning. That comparison of imaging against examination is the substance of the consultation.
WHAT TO EXPECT
Narrowing without symptoms is a watching brief
Not automatic
Stenosis found incidentally, with a normal examination, does not mean you need an operation. It means it is worth knowing what to look out for, worth reviewing if things change, and worth taking sensible care to avoid a significant neck injury. Where the cord has started to be affected, that is a different conversation, and the guidance on timing is set out on the myelopathy page.
TREATMENT
Treating the consequence, not the measurement
IF SILENT
Monitoring and sensible care
No symptoms means no operation. Know the warning signs, stay active, and take reasonable care with contact sport and fall risk.
IF PAINFUL
Non-surgical treatment
Where stenosis coexists with neck pain or nerve pain, physiotherapy, medication and sometimes injections are the first approach.
IF THE CORD IS AFFECTED
Decompression is considered
Once there are signs of myelopathy, surgery to give the cord room is the mainstay, and timing matters.
THE OPTIONS
From the front or the back
Which approach suits depends on how many levels are involved and where the narrowing is coming from.
ACDF
Removing the disc and spurs from the front and fusing the level. Suits narrowing coming mainly from in front of the cord.
About ACDF ›Laminectomy
Removing bone from the back of the canal to give the cord room, often across several levels, sometimes with a fusion.
About cervical spine surgery ›Laminoplasty
Reshaping rather than removing the bone at the back to widen the canal, an option in suitable multilevel anatomy.
About cervical spine surgery ›The decision rests on your symptoms and examination far more than on the millimetres. Cervical myelopathy covers what happens when narrowing does start to affect the cord, and do I need neck surgery? sets out how the call is made.
Narrowing on a scan is not the same as a problem to be fixed
In an MRI study of 1,211 people with no symptoms at all, 5.3 per cent had compression of the spinal cord. A finding on a report is a starting point for the examination, not a conclusion on its own.
COMMON QUESTIONS
The things people ask most
Is cervical spinal stenosis serious?
It depends entirely on whether it is affecting the spinal cord. Narrowing with a normal examination and no symptoms is common and often needs nothing but awareness. Narrowing that has begun to affect the cord is myelopathy, which does warrant prompt attention.
Does stenosis always need surgery?
No. Surgery is directed at symptoms and at cord compromise, not at a measurement. Many people with stenosis on a report never need an operation for it.
Can stenosis be reversed without surgery?
The narrowing itself cannot be reversed by exercise or medication, because it is structural. What can be managed well is pain and function, and surgery is the only way to physically create more room when that is required.
Should I avoid certain activities?
With significant stenosis it is sensible to be cautious about contact sports and high fall-risk activities, because a neck injury has more consequence when there is less space around the cord. General exercise remains beneficial.
What does the millimetre measurement mean for me?
It gives context, not a verdict. A mid-cervical canal is typically 17 to 18mm, symptoms commonly appear below about 13mm, and under 10mm is considered severe. Plenty of people sit in the narrower ranges without symptoms.
Will it get worse over time?
Age-related change tends to continue, so canals generally narrow slowly rather than widen. Whether that translates into symptoms varies a great deal, which is why review is based on how you are rather than on repeat scans alone.
RELATED CONDITIONS
Closely connected to this one
Cervical myelopathy
The condition that develops when narrowing starts to affect how the spinal cord works. The reason stenosis is worth understanding.
Read about myelopathy ›Cervical spondylosis
Age-related wear in the discs and joints, and the source of most of the bone and ligament that crowds the canal.
Read about spondylosis ›Cervical disc herniation
A disc pushing backward can narrow the canal at a single level, sometimes enough to matter in an already tight neck.
Read about disc herniation ›About this information
This page is general information about the cervical spine. It is not a substitute for an individual assessment and it cannot tell you what is happening in your own neck. Where figures are given, they come from the published research listed below and describe groups of people rather than individuals. Please discuss your own circumstances with your GP or a specialist. More about Dr Tollesson.
References
Cervical Stenosis, knowledge base of the American Academy of Physical Medicine and Rehabilitation, for normal canal dimensions and the relative and absolute stenosis thresholds.
Abnormal Findings on Magnetic Resonance Images of the Cervical Spines in 1211 Asymptomatic Subjects. Spine, 2015, for the prevalence of cord compression in people without symptoms.
A narrow canal is worth understanding, not worth panicking about.
A consultation will tell you where you actually stand, what to watch for, and whether anything needs doing now. A GP or specialist referral is needed for a Medicare rebate.