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. 2024 Sep;19(6):904-911.
doi: 10.1177/15589447231153233. Epub 2023 Mar 1.

Experience With Proximal Median Nerve Entrapment by the Lacertus Fibrosus

Justin A Cline  1 , Lisa M Frantz  1 , Jessica M Adams  2 , Bernard F Hearon  1   3
Affiliations

Experience With Proximal Median Nerve Entrapment by the Lacertus Fibrosus

Justin A Cline et al. Hand (N Y). 2024 Sep.

Abstract

Background: Unconscious bias of the clinician favors the diagnosis of carpal tunnel syndrome (CTS) in patients with median paresthesia. We hypothesized that more patients in this cohort would be diagnosed with proximal median nerve entrapment (PMNE) by strengthening our cognitive awareness of this alternative diagnosis. We also hypothesized that patients with PMNE may be successfully treated with surgical release of the lacertus fibrosus (LF).

Methods: In this retrospective study, cases of median nerve decompression at the carpal tunnel and in the proximal forearm for the 2-year periods before and after adopting strategies to mitigate cognitive bias for CTS were enumerated. Patients diagnosed with PMNE and treated by LF release under local anesthesia were evaluated to determine surgical outcome at minimum 2-year follow-up. Primary outcome measures were changes in preoperative median paresthesia and proximal median-innervated muscle strength.

Results: There was a statistically significant increase in PMNE cases identified after our heightened surveillance was initiated (z = 3.433, P < .001). In 10 of 12 cases, the patient had previous ipsilateral open carpal tunnel release (CTR) but experienced recurrent median paresthesia. In 8 cases evaluated an average of 5 years after LF release, there was improvement in median paresthesia and resolution of median-innervated muscle weakness.

Conclusions: Owing to cognitive bias, some patients with PMNE may be misdiagnosed with CTS. All patients with median paresthesia, particularly those with persistent or recurrent symptoms after CTR, should be assessed for PMNE. Surgical release limited to the LF may be an effective treatment for PMNE.

Keywords: carpal tunnel syndrome; cognitive bias; diagnostic error; lacertus fibrosus; proximal median nerve entrapment.

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Conflict of interest statement

Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Proximal median nerve compression test, right elbow. With the elbow flexed 70°, the examiner’s right thumb compresses the median nerve beneath the leading edge of the lacertus fibrosus at the elbow flexion crease.
See this image and copyright information in PMC

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