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Two compression cines in short axis confirm the diagnosis. Take a look:
Muscle hernia of the Tibialis Anterior that reduces through the fascial defect under probe pressure. This one was visible at rest but many can only be seen under stress. Sometimes active dorsiflexion is enough but we have also had patients go jog for 10 minutes and then come back to be scanned if that is what elicits their pain and palpable lump. Treatment is based on severity of symptoms and can be conservative or involve surgical repair.
I confess, I've never done US of an acute muscle hernia, but I have never seen much Doppler vascularity related to a muscle hernia. This is just wildly vascular.Just because a blob partially compresses and reduces through a fascial defect into the extensor compartment of the lower leg, can we be sure it's a muscle hernia?Can't there be a vascular mass (not muscle) that is doing the same?I would recommend MRI without and with contrast...would that be wrong?????
ReplyDeleteIt's an important thought and I don't think recommending an MRI would be wrong at all. I think a mass might be expected to invade through the muscular fascia but would be adherent and unlikely to freely herniate back and forth. The vascularity seems explainable by the episodic compression and release of the tissue stimulating perfusion although I agree that it is a lot. The nice thing about MSK ultrasound is that you can confirm the history directly with the patient and in this case it was pretty convincing for muscle herniation: sudden onset dull pain and lump with exertion, relieved with rest. Of course there are always zebra cases.....
ReplyDeleteGreat case!
ReplyDeleteMRI is a great thought. It seems like US is the preferred modality for diagnosis and MRI can be used for further characterization, particularly for preoperative planning.
This case would probably show up well on MRI since there is muscle herniated through the defect even at rest. We have had other cases with negative MRIs that showed large defects on provocative US. Sometimes in retrospect you could see a really subtle defect on the MRI. We haven’t been asked to do this but I’ve wondered if doing a wire loc of the site would be helpful for surgery for cases where the site is completely normal in appearance at rest. We've had several that were impossible to locate until after exercise provocation.
DeleteGreat discussion regarding the utility of MRI in addition/compare with ultrasound. I wonder though, if the lesion appears mass-like and not like normal muscle on ultrasound, whether it would also not have normal muscle signal/morphology on the MRI, which would still show a "mass" (even if it turns out to be a muscle hernia). Does MRI then help narrow the differentiate/exclude a mass?
ReplyDeleteThat's a good thought. I admit Dr. Umans comment made me worry that we were too quick to come down hard on muscle hernia! It's possible that MRI might show confusing mass-like abnormal signal at the site as well. The vascularity is greater than our other cases of muscle hernia but the "neck" of the fascia rent is small and I think the periodic compression and decompression of the muscle is stimulating that hyper-perfusion. The other cases that we've done--although also symptomatic--had much broader rents in the fascia. I think the history is pretty convincing (one of the things I love about MSK ultrasound, you can do a physical exam and history if you want to) and I have to believe that a mass would be more infiltrative and fixed across the fascia. Definitely thought provoking though.
DeleteI wasn't the only one concerned about missing a ST neoplasm here....though it's clearly herniating and the fact that it's neither infiltrating nor tethered is reassuring.
ReplyDeleteI've never scanned an acute muscle hernia, nor do I recall seeing one with such a narrow fascial defect. It's occurring right where most hernias are meant to occur---so I suspect you're right. Would love to hear that anyone else has seen a muscle hernia on US that looks like this. Perhaps they can post it to Blogger????
You're thoughts prompted me to follow up the case. No mass has declared itself but she hasn't undergone a surgical repair or anything either (would love to see intraop photos of this).
DeleteAs an aside, I had reason to make use of your article on digital nerve ultrasound recently. Good stuff! Our pictures did not look that good but it was fun to try something new.
Putting it all together, I doubt a neoplasm would allow itself to be shoved through a very conveniently placed fascial defect. But I agree the amount of flow there is startling. Ultimately I am convinced and if this were my case then I would have signed it out as such and not recommended the MR. But I would have been greedy for the MR. And probably would have slept on the prelim report for a night and shown it around before signing off!
ReplyDeleteIt looks like there is a big vessel that crossed the gap on your Power Doppler. I wonder if you had compressed right there for a few minutes if it would have made it go dusky...
Never wrong to show it around! Maybe we should have billed for a therapeutic procedure since we reduced it with the probe....?
ReplyDelete