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.