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Epidural fat in spine
I know there is epidural lipomatosis and prominence of the epidural fat related to obesity and possible steroid use among other things.
But if the spinal canal is narrowed as a result of the increase fat is that considered spinal stenosis? No disc herniation or facet changes etc.. Do you just describe it? If so do you follow it by saying there is severe spinal stenosis?
Thinking since it is fat, which is also seen in the neuroforamen, does it really cause any symptoms?
Yes, I tried searching the web, but wasnt getting clear answers. -
31 Replies
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Yes, great question. You frequently see this at L5/S1. If you have a 3mm thecal sac that is narrowed by fat only, is that “stenosis?”
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“Tapered spinal canal distally due to epidural lipomatosis
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I haven’t ever read the answer to this but a neurosurgeon once told me that he doesn’t consider it spinal stenosis if from hypertophied epidural fat.
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Neuroradiologist here. I use the term thecal sac effacement. When combined with spondylosis it can result in mass effect on the cauda equina, and you may see buckling of the rootlets in the same fashion as true spinal canal stenosis. In isolation it usually only results in mild effacement.
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I call it stenosis, qualitatively grade it, but make sure to highlight that it is from epidural lipomatosis.
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I don’t tend to say severe “stenosis” if the AP dimension of the thecal sac is 4 mm but it’s all related to fat. Effacement better if you want to pick term I think.
I think being descriptive with measurements (AP dimension of the thecal sac for example) and any nerve root issues is the best way to do it. Sometimes I’ll say if there is or is not bony spinal canal stenosis. Not all “bone” of course by they know what you mean.
If its just at L5-S1, I usually say tapering of the thecal sac related due to prominent epidural fat. Quite common.
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I’m a proponent of labeling it thecal effacement in the lumbar spine.
However for some reason it tends to behave more like osseous stenosis in the dorsal epidural spine, I’ve proven a couple of effective canal blocks from bad lipomatosis with myelos.
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Dorsal thoracic spine epidural space, that is
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Good thread. Something Ive been wondering myself. Definitely clinically, if only narrowing from fat in the canal, rarely seems to have consequences.
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“…generalized broad-based narrowing of the spinal canal at the XYZ level from protuberant epidural lipomatosis…”
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I trained at a very spine centric MSK fellowship. The spine surgeons there said that epidural lipomatosis was never an indication for surgical decompression. I think that’s a little dogmatic, but you get the idea. If you’ve ever done a midline epidural, you know that injecting into epidural fat is free flowing as the fat is loose and soft. That’s why epidural fat doesn’t really cause radicular symptoms.
Prominent epidural fat does not narrow the spinal canal (spinal canal refers to the osseous canal). If you really want to, you can say thecal sac effacement. But calling it spinal canal stenosis is factually incorrect.
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Very interesting. But by that logic wouldnt a large disc would not be spinal canal narrowing but thecal sac effacement? It may be factually incorrect but it would be strange to me to call start saying mild/moderate/severe thecal sac effacement rather than spinal canal stenosis. Also to differentiate each level between facet osseous canal narrowing,etc. Great thread.
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I say “constriction of the thecal sac by epidural fat without significant central canal stenosis.” Might start using “effacement” though based on this thread. Sounds less menacing.
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You make a good point bricky. I hadn’t thought of it that way. Maybe the reason our surgeons preferred that verbiage was that it was rooted in the indication for surgical intervention. A disc or ligamentum flavum hypertrophy can be symptomatic, so those cause spinal canal stenosis vs epidural fat which generally is not symptomatic.
Another quick point – we were taught never to use the term “central canal” to discuss stenosis because the central canal is a tiny CSF filled space within the spinal cord, distinct from the spinal canal. Just food for thought.
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raddood1.
I agree the central canal is the space inside the spinal cord. the ‘spinal canal’ is outside the cord.
definitions do matter. -
We were shown a case of this that had happened relatively rapidly in a younger athlete pt who had taken steroids or binge eaten to bulk up and had severe symptoms from it.
I truly believe it could be symptomatic although I haven’t figured out my sweet spot for how to couch the findings/impression.
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Generally speaking most surgeons don’t think it’s likely to be symptomatic. But importantly, this doesn’t mean it will never be symptomatic, you have to look at the whole picture.
The majority of times I have seen it become an issue, it’s in combination with other findings. Facet and discogenic disease that might have otherwise not been too bad, but combined with epidural lipomatosis ends up causing problems. Don’t think you can make a blanket rule that it is or is not important to the surgeons, just have to describe accurately. -
I’m getting lots of opinions but it is ‘spinal stenosis’ or not? saying ‘thecal sac encroachment’ sounds like hedge. If a PCP ask you is there spinal stenosis, yes or no. what is the answer?
“well there is some fat with effacement of the thecal sac, you need to correlate with exam’?
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Politely thank the PCP for the referral and tell him/her the patient should be evaluated by someone else 🙂
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It’s fluffy squishy loose fat. It may efface the thecal sac but it doesn’t create compression of the nerve roots.
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Quote from fw
It’s fluffy squishy loose fat. It may efface the thecal sac but it doesn’t create compression of the nerve roots.
In isolation, this is almost always true. As others mentioned above, there are severe cases. And it’s also often not the only thing going on.
If you have a normal or near normal spine with typical “moderate” effacement without nerve root buckling… generally I agree it’s pretty safe to say it’s not doing anything important. -
It does not make my impression. At the most, I’ll say thecal sac effacement without spinal canal stenosis because it’s highly rare to be symptomatic. Put another way, if there is a disc bulge, facet arthropathy, and prominent epidural fat, it is not the epidural fat causing the radiculopathy.
If the PCP calls and asks if there is spinal canal stenosis, the answer is no.
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Quote from raddood1
Put another way, if there is a disc bulge, facet arthropathy, and prominent epidural fat, it is not the epidural fat causing the radiculopathy.
I agree in these cases the discs and facets are usually the main issue and what the surgeons care about. But the epidural fat can be contributory, in a “straw that breaks the camels back” sort of way. Sometimes the nerve root impingement really is exacerbated by the fat when things are already tight (i.e. if the epidural fat was normal, the roots actually wouldn’t be buckled or displaced by the other pathology)
Quote from raddood1
If the PCP calls and asks if there is spinal canal stenosis, the answer is no.
I agree but am hesitant to tell a random PCP this type of thing without some caveats. We don’t see the patient, and they may not be qualified to do a good exam. Often these are not even ordered by an MD or DO.
If there is enough concern to get the MRI, I have a low threshold to suggest a legit neuro workup if there is still clinical concern. I guess if you live in a rural area and specialists are hard to come by, maybe the situation is different. -
I don’t think your perspective is unreasonable at all.
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Gonna hi jack this thread a bit to ask , what are peoples thoughts on congenitally narrow canals is there a cutoff you use and does it effect your interpretation in other ways?
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<= 10 mm. If their canal is like 14 mm at L1 and then narrows way down in the inferior levels it seems pretty clear. does not affect the arbitrary criteria levels for what is x level of stenosis.
and prominent epidural fat which contributes to spinal canal narrowing. this stuff never occurs in a vacuum, almost everyone that you’re going to do an MRI on for radiculopathy/myelopathy has facet degen and disc pathology. -
I like to say moderate canal narrowing at L4-5 predominantly due to prominent epidural fat
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<14mm in the lumbar spine, <0.8 x vertebral body AP dimension in cervical spine.
I would hesitate to say spinal canal stenosis if all you see is epidural fat. That's going to result in a lot of unnecessary spine surgery consults and the spine surgeons are going to roll their eyes every time they see it.
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No on the fat question.
Congenital stenosis is a gestalt thing, but the numbers above are all reasonable.
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I call it narrowing or effacement of thecal sac. I do not call it stenosis unless there is narrowing of the bony spinal canal or disc herniation.
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Taken from STATdx:
Excessive accumulation of intraspinal fat causing cord compression and neurologic deficits.
Most common signs/symptom – Weakness: > 85%
Other signs/symptoms – Back pain, sensory loss, polyradiculopathy, altered reflexes, incontinence, ataxia
Clinical profile – Gradual progression of symptoms
Natural History & Prognosis – Presurgical low steroid dose and idiopathic cases have better prognosis, > 80% with postsurgical symptomatic relief
Treatment – Correction of underlying endocrinopathies, Weight reduction in case of general obesity, Multilevel laminectomy and fusion, Indicated when cord compression and radiculopathy present
