The Carpal Tunnel Syndrome and the Double Crush Syndrome Hypothesis: Revisited

Abstract
Background: The commonest application of the double crush hypothesis is its association to median nerve entrapment at the wrist. The double crush concept has gained popularity because it provides a reason to evaluate the cervical spine and roots when treating carpal tunnel syndrome (CTS). It is more likely for CTS to occur as DCS rather than occurring by itself. Up to 90% of CTS patients are misdiagnosed, whereas only 10% have the problem at their wrists.
Aim of Study: To examine the validity of DCS hypothesis in CTS patients, to support or disregard the theory.
Patients and Methods: This study was conducted on 80 patients; 40 patients claiming failed carpal tunnel release operation (Group I) and 40 cases presenting with brachialgia (Group II). Diagnostic work up included neurological exam-ination, Phalen test, Tinel sign, electromyographic examination (EMG) and nerve conduction studies (NCS) and cervical MRI. Group I patients had undergone the EMG and NCS at our laboratory pre and post operatively.
Results: EMG and NCS showed 10 cases with CTS (25%), 20 (50%) with DCS and 10 (25%) with cervical radiculopathy in group I, while group II patients showed 10 cases (25%) with CTS and 30 (75%) with DCS. In all patients, 50 cases (62.5%) showed DCS. On comparing the EMG and NCS preoperative results of Group (I), with their postoperative follow-up results, there was a high statistically significant difference (p-value <0.001) with 34 cases (85%) who showed improvement of the NCS results, while 6 cases (15%) deteri-orated postoperatively. There was a high statistically significant difference between both; CTS and DCS (p-value <0.001), denoting a positive correlation between the two syndromes.
Conclusion: The DCS hypothesis was supported, while the concept of frequent failure of CTS release surgery was not supported for the benefit of DC hypothesis.