Ultrasound Imaging of Median and Ulnar Nerves After Carpal Tunnel Surgery

Abstract

33-yr-old female patient was seen for hypoesthesia of the fourth and fifth fingers in her left hand 3 mos after an open surgery for ipsilateral carpal tunnel syndrome. The medical history was otherwise noncontributory. The findings from the physical examination revealed weakness in the abduction and the adduction of the second, third, fourth, and fifth digits and weakness in the adduction of the first digit. The findings from nerve conduction studies of the ulnar and median nerves were normal bilaterally. The result of the needle electromyography of the first dorsal interosseosus muscle was consistent with partial axonal injury and regeneration of the left ulnar nerve (a few fibrillations.increased polyphasia, and decreased recruitment were observed). Thereafter, ultrasound imaging of the median and ulnar nerves was performed. The operated median nerve was still edematous and accompanied by a persistent median artery (Figs. \A~B, 2A-B). Further, the left ulnar nerve also seemed to be injured (Figs. M-B). The patient was diagnosed with a mild iatrogenic ulnar neuropathy and a healing median nerve after carpal tunnel surgery.Median neuropathy at the wrist is the most common entrapment neuropathy, and decompression surgery can be performed for its treatment. However, there may be certain early postoperative complications such as injury to the median nerve (and its branches), the ulnar nerve/Guyon canal, the superficial palmar arch, and the ulnar artery and incomplete release of the transverse carpal ligament.Ĉ omplications associated with the ulnar nerve are relatively rare, and the relevant literature comprises only anectodal cases.^ Moreover, the diagnosis is generally based on clinical and electromyographic findings. The authors know of only one case report whereby ultrasound was used for such a diagnosis.T he diagnostic value of ultrasound in peripheral nerve lesions is well established.^ Particularly in entrapment syndromes, it can confirm the diagnosis morphologically and it may be used to guide an onward intervention/surgery or assist with close follow-up thereafter.^ In the described subject, the ultrasound detected the postoperative edema in the ulnar nerve and, additionally, it depicted the persistent median artery as the likely cause of the carpal tunnel FIGURE 1 Comparative ultrasound imaging of the patient's median nerves. On longitudinal view, the median nerve (white arrowheads) is observed as an anechoic long tubular structure. The (operated) left median nerve is, however, significantly enlarged proximally (B). Healthy side (A).

Diagnostic Considerations in Compressive Neuropathies

“…Additionally, scarring necessitating revision may be observed along with perineural fibrosis with changes in nerve gliding during dynamic observation. 23 , 24 , 25 In combination with each other, US and EDS are useful diagnostically, with 1 study reporting 100% sensitivity and 92.5% specificity. 26 …”