Variations of Ulnar Nerve in the Forearm and Hand: A Review of the Literature and Clinical Significance

Abstract

The ulnar nerve originates from the anterior division of the lower trunk of the brachial plexus which continues as the medial cord and gives off branches to the forearm and the hand with motor and sensory fibers. The objective of the current study is to assemble the recognized anatomical variations of the ulnar nerve (UN) and underline their clinical impact. A literature search was undertaken via PubMed database, using the term: "ulnar nerve AND variations." Classical anatomical textbooks were also used for the normal anatomy of the UN. A total of 23 articles met the inclusion criteria, 16 of which are included in this review. Fifty-four additional articles provided useful information according to the aim of this review. Of great interest is the communication between the UN and the radial nerve (RN) in the forearm, as well as the communication between the UN and the median nerve (MN) in both forearm and hand. Furthermore, variations of the UN were observed in the hand and the classification of the UN compression was also described according to the point of the neuropathy. These collecting data are categorized into five tables. Additional aberrations were also included in this review. According to literature, the UN is characterized by numerous variations of its course and branches. Therefore, good knowledge of the normal anatomy is essential. Moreover, the anomalies are of particular importance due to their significant clinical implications and should be taken into consideration by the surgeons during surgical procedures in this region.

Upper Limb Nerve Variations May Alter Clinical Diagnosis: A Scoping Review

“…described two main types of nerve variations: the first type pertains the course of the nerve itself or its distribution; the second type includes variations in non-nerve anatomies, such as tendons, muscles, or arteries that are related to the course of the nerve. Both types of nerve variations are supposed to have clinical significance (Alraddadi, 2021;Solia et al, 2022). In case the distribution of a nerve differs from its classical distribution, its innervation pattern may partially overlap with that of two different peripheral nerves.…”

“…In general upper limb nerve variations are rather common (Solia et al, 2022). Although the prevalence of specific nerve variations may be quite variable (Ioannis et al, 2015), the variation in the neural architecture of the brachial plexus for example is known to be more the rule than the exception (Johnson et al, 2010).…”