Ultrasound for carpal tunnel release

In this episode of PodMD, specialist anaesthetist Dr Peter Hebbard will be discussing the topic of ultrasound for carpal tunnel syndrome, including what carpal tunnel syndrome is, how ultrasound can be used in assessment, the limitations of ultrasound, when a GP should refer for ultrasound and more.


  • Transcript
    Please note this is a machine generated transcription and may contain some errors.
    *As always, all in this PODMD podcast is intended for health professionals and the comments are of a general nature. Information given is not intended as specific medical advice pertaining to any given patient. If you have a clinical issue with one of your patients please seek appropriate advice from a colleague with expertise in the area.

    Today I’d like to welcome to the PodMd studio Dr Peter Hebbard.

    Peter Hebbard is a specialist anaesthetist with a particular interest in ultrasound guidance technology, novel techniques and medical device development. Over the last few years, he has been working primarily out of Northeast Health Wangaratta in the northeast of Victoria, and at the Wangaratta Private Hospital.

    After many years of experience, Peter is proud to have developed a system to perform superficial procedures such as carpal tunnel release under ultrasound guidance using a novel needle-based tool called the “micro iBLADE “.

    The “micro iBLADE “ procedure allows patients to get relief from the symptoms of carpal tunnel syndrome with minimal intervention and quicker recovery times. As with any new procedure, it’s carefully introduced and well monitored.

    *We do hope you enjoy this podcast but please remember that the advice here is of a general nature and is not intended as specific advice about a given patient. The views and opinions expressed in this podcast are those of the doctor, not PodMD.
    If you do have a patient on whom you require specific advice, then please seek advice from a colleague with appropriate expertise in that area.

    Peter, thanks for talking with us on Pod MD today.

    Peter: Thank you for having me.

    Question 1
    The topic of today’s discussion is ultrasound for carpal tunnel syndrome. Peter, can you give us a brief overview of carpal tunnel syndrome?

    Peter: Thank you, carpal tunnel syndrome is a syndrome of compression of the median nerve in the wrist under the transverse carpal ligament. Although the symptoms are related mainly to compression of the nerve, I actually look at it as mainly a problem of the tendons and the tendon sheaths, which for one reason or another become inflamed and swollen, causing compression of the nerve, which is what causes the symptoms primarily.

    It usually typically presents with a constellation of pain, tingling, and numbness, although not all three need to be present to make the diagnosis. The pain most typically starts as pain at night, but can increase to pain during the day, particularly with activities.

    Question 2
    How would a patient with carpal tunnel typically present?

    Peter: For patients usually present with carpal tunnel syndrome with pain in the hand, but it can be a presentation with just tingling or numbness of the hand and occasionally in neglected carpal tunnel syndrome, it can present with clumsiness. So the most typical presentation would be a patient in their 40s and 50s, often in a manual occupation.

    Who starts to have problems with waking at night, usually with a burning pain in the hand. Now the pain is often in the lateral 3 1/2 fingers in the distribution of the median nerve, but it’s not always and often patients waking in this fashion have trouble distinguishing exactly where the pain in their hand is.

    Tingling is sometimes the waking symptom associated with numbness. And with tingling and numbness, they’re much more commonly located in the median nerve distribution.

    Question 3
    How can ultrasound be used in the assessment of suspected carpal tunnel syndrome?

    Peter: Thank you. Ultrasound is a very useful first test for patients having a suspected diagnosis of carpal tunnel syndrome, but the first thing I would say is that carpal tunnel syndrome is often made as a primarily a clinical diagnosis, and confirmatory tests such as ultrasound and electrophysiological studies are not necessarily required.

    But ultrasound is very useful to evaluate the median nerve and the typical findings on ultrasound that those of us swollen median nerve proximal to the carpal tunnel. There are specific ultrasound signs of the median nerve because it loses its normal architecture as well as becoming significantly swollen.

    There are other tests for using ultrasound with the for the diagnosis of carpal tunnel syndrome, but I find them less useful, in particular sometimes you’ll see a report of reduced mobility of the nerve, which is a a fairly subjective measure, and also bowing of the transverse carpal ligament.

    I tend not to find that a very useful sign because in carpal tunnel, the transverse carpal ligament is often thickened and in the actual area of compression there can often be very little bowing.

    Question 4
    What are the ultrasound signs of median nerve neuropathy?

    Peter: Yeah, so the cardinal sign is swelling of the median nerve, which is usually accompanied by loss of the normal architecture. So on ultrasound the fascicles of the median nerve can be imaged and due to the blockade in axoplasmic flow, the nerve becomes oedematous and the outlines of those fascicles can be lost.

    A typical median nerve at the wrist in a normal person might be 7 or 8 square millimeters.In carpal tunnel syndrome this can increase to anywhere between 11 and I have seen up to 40 square millimeters at the wrist, in which case the median nerve is often palpable through the skin.

    As well as that, the ultrasound can sometimes pick up the point of compression of the median nerve with the so called hourglass sign where the anteroposterior diameter of the or thhe dimension of the median nerve can be seen to suddenly decrease, and I’d say I see that at about in about 50% of the cases of carpal tunnel syndrome that I see.

    Question 5
    What are the limitations of ultrasound in the evaluation of suspected carpal tunnel syndrome?

    Peter: I find ultrasound to be a very useful confirmatory test. When the typical appearance of nerve swelling can be found, there are other rare potential causes of swollen nerves, but usually that involves swelling of the nerve in the the proximal forearm as well as the distal forearm.

    And certainly ultrasound can distinguish between that because we’re looking for a difference in the size of the median nerve between the proximal and distal forearm.
    As well as that occasionally I see patients who have a severe electrophysiological changes without much in the way of changes in dimension on ultrasound, and I think this is most common in the case of the neglected carpal tunnel syndrome patient. In which case the nerve seems to become fibrotic and reduces in size again over time.

    So sometimes the only sign on ultrasound, maybe a nerve, which in fact rather than being big looks looks normal size but often with an increase in the in the fibrous tissue within the nerve which we see as a white color on the ultrasound.

    The ultrasound does have the advantage that it can also evaluate the carpal tunnel for secondary causes of carpal tunnel syndrome, such as ganglia inside the carpal tunnel, accessory motor bellies accessory, muscle bellies and other space occupying lesions inside the carpal tunnel.

    So you do actually get more information out of the ultrasound than purely whether the patient is likely to have carpal tunnel syndrome or not. But in the presence of symptoms and a swollen median nerve proximal to the carpal tunnel, with or without the hourglass sign is a very strong indication that the patient has a symptomatic median nerve neuropathy.

    Question 6
    What about ultrasound evaluation of recurrent carpal tunnel syndrome?

    Peter: The evaluation of recurrent carpal tunnel syndrome is something that I find fairly tricky, and certainly in my practice, I’m getting referred more and more patients with recurrent carpal tunnel syndrome who’ve had a failure of surgery and sometimes that is an immediate failure of surgery. And sometimes it’s a recurrence after sometime.
    The most straightforward use of ultrasound in evaluating our patients who haven’t got better after carpal tunnel surgery is to evaluate the course of the nerve and the commonest problem I see in that circumstance is that the surgery hasn’t gone approximately far enough and the nerve is still being constructed by a band proximal to the to the general location of the carpal tunnel, which is often defined by a very clear hourglass sign.

    The evaluation of recurrent carpal tunnel syndrome in other cases is much more complicated, and my usual approach in that circumstance is actually to combine the 2D ultrasound evaluation of the nerve with some sort of hydrodissection or probing of the carpal tunnel, so under some local anesthetic coverage, I’ll introduce a stiff needle and some saline or dextrose into the carpal tunnel and actually probe the transverse carpal ligament and test its mobility right through the carpal tunnel to see whether there seems to be any sites of recurrent constriction.

    In the evaluation of recurrent carpal tunnel syndrome, both ultrasound and nerve conduction studies can be very useful. Some of the ultrasound signs of carpal tunnel syndrome actually don’t regress following a successful carpal tunnel release, and in particular you can’t rely on nerve swelling as a sign of ongoing symptomatic carpal tunnel syndrome in those sort of cases.

    So ultrasound is very useful if you can see a clear cause for the recurrent carpal tunnel syndrome. I generally follow that up with some sort of interventional hydrodissection test, distending the carpal tunnel with fluid in order to probe and test the transverse carpal ligament. But that can also be supplemented with nerve conduction studies and nerve conduction studies are in mild to moderate cases of carpal tunnel syndrome will generally return to normal, quicker and more completely than ultrasound. So if the nerve conduction studies are no better or worse than preoperative nerve conduction studies this cannot be another area of evidence that the patient has recurrent carpal tunnel syndrome.

    Question 7
    When should a GP refer for ultrasound?

    Peter: Well, I think ultrasound is a very useful our first Test to confirm the diagnosis of carpal tunnel syndrome, but as I’ve said before, I don’t think that any confirmatory tests are necessary in the case of straightforward clinical presentation. Ultrasound in my hands as a clinical practitioner of ultrasound guided procedures and micro invasive ultrasound guided carpal tunnel release is not necessarily as a as a first investigation, but it does initially confirm the diagnosis and I always perform an ultrasound on those patients that I see in order to plan the subsequent procedure as well as confirm the diagnosis.

    If you are sending the patient to see a surgeon in order to have an open carpal tunnel release. If the ultrasound is positive and the clinical signs are as expected, then I think that’s all the testing that you need to do in order to progress to consider carpal tunnel release.

    Concluding Question
    Thank you for your time here today in the PodMD studio. To sum up for us, could you please identify the three key take home messages from today’s podcast on ultrasound for carpal tunnel syndrome?

    Peter: Thank you. First of all, the cardinal symptom of carpal tunnel syndrome is pain, which is most severe at night and it’s pain in their hands.

    Secondly, a carpal tunnel syndrome is effectively investigated by ultrasound.

    Thirdly, in cases of recurrent carpal tunnel syndrome, an ultrasound examination, particularly in the right hands, can provide a lot of valuable extra information. Thank you

    Thanks for your time and the insights you’ve provided.

    Peter: Thank you

*As always, all in this PODMD podcast is intended for health professionals and the comments are of a general nature. Information given is not intended as specific medical advice pertaining to any given patient. If you have a clinical issue with one of your patients please seek appropriate advice from a colleague with expertise in the area.