Cord Compression
- Cord compression is anything squeezing the spinal cord itself — and the clock starts the moment it does. Neurologic function lost for too long doesn't come back.
- The job of imaging is to answer three questions fast: is the cord compressed, at what level(s), and by what?
- MRI of the whole spine is the test. Compression can happen at more than one level at once, and missing a second site is a classic, costly error.
- The cord doesn't have to look mangled to be in trouble — effacement of the surrounding fluid against the cord is your earliest tell. A bright T2 signal inside the cord is a worse, later sign.
- Treat the symptoms, not just the picture. New weakness, a sensory level, or bowel/bladder trouble is a "scan now, call someone now" situation.
Imagine your spinal cord as a thick electrical cable threaded down the middle of a bony tunnel, cushioned by a moat of fluid on all sides. As long as the moat is there, the cable floats happily, sending signals between your brain and everything below. Cord compression is what happens when something — a slipped disc, a tumor, a pocket of pus, a shattered vertebra — crowds into that tunnel, drains the moat, and starts leaning on the cable. This is one of the few things in radiology where reading the scan slowly can literally cost someone the ability to walk.
Why this is a "drop everything" diagnosis
Nerve tissue is dramatic and unforgiving. Squeeze it long enough and the damage stops being about pressure and becomes about a lack of blood supply — the cord starts to suffocate. The frustrating part is that there's a window where everything is still reversible, and then the window closes, quietly, with no warning bell.
The deficits a compressed cord causes can become permanent. Loss of bowel and bladder control, leg weakness, and a level below which sensation just stops are the clinical red flags. If those are present, imaging and the consulting team are needed now — not after the morning list.
So when the cord is the question, "I'll get to it" is the wrong answer. This is a hot-seat finding.
What's actually doing the squeezing
It helps to think about where the trouble is coming from, because the cause shapes the whole treatment. Compression comes from three neighborhoods relative to the sac that holds the cord:
| Where it's coming from | Common culprits | The vibe |
|---|---|---|
| Outside the dura (extradural) | Metastatic tumor in a vertebra, a herniated disc, bone fragments from a fracture, an epidural abscess | By far the most common — the squeeze comes from the bony walls or the disc |
| Inside the dura, outside the cord | Certain tumors hugging the cord from within the sac | Less common, often a slow grower |
| Inside the cord itself | Cord tumors, syrinx | Technically "expansion," not external compression |
For the dramatic, sudden cases — the ones that page you overnight — metastatic disease eating into a vertebra and a thoracic disc blowing backward are the headliners. Don't forget infection: an epidural abscess can compress the cord and make the patient septic.
How not to miss it
The test is MRI, and the single most useful sequence is the T2-weighted image, where spinal fluid lights up bright white. On a healthy spine, that bright fluid forms a clean halo around the cord. Compression erases the halo — the fluid gets squeezed out at the level of the problem, and the cord makes direct contact with whatever is pushing on it. That loss of the fluid signal is your earliest, most sensitive sign, and it shows up before the cord itself looks abnormal.
Effacement of the surrounding cerebrospinal fluid (CSF) is the early sign. Bright T2 signal inside the cord (myelomalacia or edema) is the cord telling you it's already been hurt — useful, but later and more ominous.
Now the part everyone learns the hard way. Image the whole spine, not just where it hurts. Pain and the actual compression level don't always agree, and in conditions like metastatic disease, the cord can be pinched in two separate places at once. Scan only the level the patient points to and you may fix one squeeze while ignoring another.
The level of pain is not reliably the level of compression — and a second, asymptomatic compression site is a notorious trap, especially with tumor. When cord compression is suspected, the answer is whole-spine MRI, not a targeted look at one region.
It's also worth knowing what compression is not. A bright signal inside the cord with no external mass and a preserved fluid halo points you away from compression and toward an intrinsic cord problem like transverse myelitis. The cord can be sick without being squeezed; the fluid halo is the detail that keeps those two stories separate.
When MRI isn't an option
Sometimes the patient can't have an MRI — a pacemaker, sheer instability, or the scanner is simply down at 3 a.m. CT myelography is the classic backup: contrast is placed into the fluid space so you can see exactly where the flow of fluid gets blocked, like watching dye fail to get past a clog in a pipe. Plain CT still earns its keep for showing the bone — fracture fragments and the destroyed vertebra behind a compression.
If you want the broader playbook for reading these studies, the approach to spine MRI page walks through the sequences and search pattern in detail.
The one thing to carry out the door
A compressed cord is a stopwatch, not a still life. Find the squeeze, name every level it's happening at by scanning the whole spine, figure out what's causing it, and get the right people moving — all before the window quietly closes.