Pregnancy-Related Carpal Tunnel Syndrome

A high rate of pregnancy-related CTS was highlighted in an article in the Canadian Medical Association Journal in 1983, vol 128, indicating that 25% of 1000 consecutive postpartum women experienced CTS during pregnancy; 3/4 of them that experienced this had bilateral symptoms.  Half of the multigravidas had had similar symptoms in previous pregnancies.

Most recently attention to this gestational complication in an article by Padua et al  in Muscle & Nerve, Nov 2010, pp 697-702 in a thorough patient and literature review.  They discussed some of the literature specifically trying to address the incidence of CTS and performed a metanalysis.  A big problem in assuming rather than confirming CTS with NCS was identified in most of the over 200 papers they reviewed.  They felt that the natural history of pregnancy-related CTS (PRCTS) varies considerably and often fails to resolve after child delivery and lactation, but that only 1/3 of the cases would resolve after 1 year and up to 2/3 after 3 years.

This study coincides with the literature reflecting that about 1/6 adults ultimately will develop CTS about 90% of whom will come in for treatment-if ever-after age 30.  All studies agree that the likelihood of a woman developing CTS is twice that of a man.  This correlates well with congenital narrowness of the carpal tunnel confirmed in previous research by Dekel et al as reported in their article Idiopathic Carpal Tunnel Syndrome Caused by Carpal Tunnel Stenosis, in the British Medical Journal, May 1980, and other reports reflecting sthe strong familial likelihood of developing CTS.  This correlates well with other studies on carpal tunnel size as well as elevated carpal tunnel pressure in people with CTS and elimination of the elevated pressure after carpal tunnel release.  Quite likely, if  followed past age 30 I suspect over 80% of the subjects with NCS proved CTS will go on to require surgery i.e., the increased fluid of pregnancy serves as a challenge in congenitally narrowed carpal tunnels while the remainder of the physiologic triggers evolve by age 30 or so.

Dorsal First Web Space Pain

Ache experienced in the first dorsal web space of the hand, ie the area between the thumb and the index metacarpal, is not a common complaint.  Once arthritis and ulnar nerve entrapment  have been excluded the pain occurring in this area may be related to muscle activity resulting in elevated pressure in this muscle compartment.  I am only aware of three references to dynamic first dorsal interosseous compartment syndrome in the literature.   All three reports occurred within four years of one another in the Journal of Hand Surgery .  The diagnosis can be made with intracompartmental pressure measurement as is done for other sites for compartment syndrome with a wick catheter or Stryker device.  A. Lee Dellon reported the use of a stress test he used in one patient monitoring key pinch for weakening with repetitious pinching in association with development of first dorsal interosseus area pain.  The pain resolved with surgical decompression and the pinch strength was regained,  I have no personal experience in seeing anyone with this diagnosis, but as with other rare entities one must maintain an open mind when establishing a differential diagnosis.

Another Blow to NC-Stat and Other Automated Hand-Held Nerve Conduction Devices

In the most recent study published by Schmidt et al in Muscle & Nerve 2011, Vol 43, the diagnostic accuracy of the NC-Stat system in 50 patients with unilateral leg symptoms and 25 asymptomatic control subjects was studied. The research was done in a rigorous manor by experienced evaluators at the EMG lab of the Mayo clinic. The tests were all performed by technicians blinded to the findings of a standard electrodiagnostic evaluation, which was also performed. The NC-Stat resulted in very low specificity, thus a high false positive rate, in both symptomatic patients and in normal controls with an overall specificity for the NC-Stat of only 0.32.

In the same issue of Muscle & Nerve, John England and Gary Franklin concluded that because of the extremely low sensitivity the NC-Stat cannot be recommended as a diagnostic test for patients with lower extremity complaints. They quoted Armstrong et al from the J. of Occupational & Environmental Medicine, 2008, in the study on median and ulnar nerve conduction studies at the wrist that "NC-Stat is not designed to replace traditional methods of NCS".

From my experience in evaluating the upper extremity and seeing patients come into the office who have had NC-Stat studies, I am underwhelmed with the lack of utility of this tool especially because there is no way to really proof the work that is being done and signed off by a computer in Massachusetts to which all the data is sent. The NC-Stat is very limited with regard to interpretation of ulnar nerve dysfunction with the findings limited to those that can be obtained at the wrist which, for the most part, is a moot point. Most people who have ulnar nerve entrapment at the wrist also have concomitant median nerve entrapment. Carpal tunnel release surgery decompresses both nerves simultaneously. However, entrapment of the ulnar nerve at the elbow occurring in about 1of 5 patients presenting with CTS goes undiagnosed. The NC-Stat relies on f-wave interpretation to suggest "further evaluation". This important diagnosis is hard to confirm even with conventional NCS with or without EMG. Clinical exam by a skilled physician is paramount.

Attention medical office biller: New NCS code

Pre configured electrode "NCS" tests are at best a screening test for high volume HR situations with a revolving door high turnover situation. I have discussed the shortcomings of this testing methodology in the recent past. The new code to be used as of January 1, 2010 is 95905 to distinguish this type of simplified test from conventional, more thorough NCS. Further information can be found under Practice Issues a http://www.aanem.org/. According to the AANEM the Centers for Medicare & Medicaid services (CMS) has assigned a work RVU of 0.05 and a practice expense RVU of 2.04 and a malpractice RVU of 0.02. Thus depending upon practice locale these values will equate with Medicare reimbursement of about $70 per limb. I'm not sure what this will equate to in net terms.

Anyone considering undergoing definitive carpal tunnel release surgery would be well advised to read the article: Touch Allodynia Following Endoscopic or Open Decompression for Carpal Tunnel Syndrome by Povlsen, Tegnell, Revell and Adolfsson published in The Journal of Hand Surgery, British 1997, volume 22B pp 325-327. They performed a prospective, scientific assessment of the amount of soreness present in direct relation to measured palmar pressure in patients undergoing open or endoscopic carpal tunnel release. This clear and concise study is usually overlooked by physicians when debating the optimal treatment. They showed significantly less sensitivity/ soreness in the patients treated endoscopically versus the open "filet of wrist" group of patients both early and late. At three months the endoscopic group was back to control level while the open release group was still significantly abnormal

Annotated Bibliography

I have a huge reference list of good articles regarding all aspects of nerve entrapment, in particular carpal and cubital tunnel syndrome. If you are looking for a very specific topic, perhaps you can ask the question and I can give you the answer and provide some appropriate references for you. Previously I had so much on the internet it was burdensome.

Should ultrasound be the diagnostic test of choice or used interchangeably with nerve conduction studies in the diagnosis of CTS?

Ultrasound has been a tool in search of business as far as I can discern. The only nerve in the body where the ultrasound has seemingly been useful for a diagnosis of entrapment is that of carpal tunnel syndrome. There have been a number of public articles in the medical journals in the past 10 years related to trying to define the potential benefit of ultrasound and the diagnosis of carpal tunnel syndrome and delineating the changes in median nerve size from pressure on the median nerve at the carpal tunnel and subsequent decrease in the size postoperatively. There is extreme patient bias exhibited in those that undergo surgery such as in the article by Smidt and Visser from the Netherlands published in Muscle and Nerve, August 2008, Volume 38, pages 97-101, wherein they were trying to determine the value of postoperative sonogram and the correlation between sonography and the clinical outcome after surgery. Though they initially started with a group of 172 patients, only 88 of them underwent surgery! Additionally, the mean time of symptoms of the patients prior to surgery was a year. Americans generally want results yesterday. They don’t want to wait forever for treatment and, as pointed out in my previous blog, early intervention tends to yield better results overall. Additionally, as Smidt and Visser point out with their limited study which is larger patient volume than the prior publications, “from the available data we conclude that sonography of the median nerve cannot be used to assess whether re-exploration of the carpal tunnel is needed in an individual patient with poor outcome after surgery”. It is particularly important because in their series there were a high percentage of unsatisfied patients. In fact, of the 79 patients that they operated on only 56%, i.e. 44, reported complete recovery or much improvement; 3% reported no change and 12% reported worsening of their symptoms, i.e. bad results in 15% and only excellent results in 56%. This compares unfavorably with the published results for ECTR and in my personal experience with over 5,000 procedures. Indirectly their article supports the application of endoscopic over open carpal tunnel release and early treatment rather than late. It certainly does not support the use of sonography in the evaluation of carpal tunnel patients given the overall inferior results that they had to offer in their patients treated.

Ad sonography to the same junk pile that the Neurometrix NC-Stat on-call belongs in, i.e. worthless.