Anatomical knowledge of the upper limb nerves is a cornerstone of clinical practice, particularly in the domains of surgery, anesthesia, neurology, and physical rehabilitation. The brachial plexus and its terminal branches—namely, the musculocutaneous, median, ulnar, radial, and axillary nerves—are responsible for the motor and sensory innervation of the upper limb. Despite the classical descriptions available in anatomical textbooks, numerous variations in the origin, course, and communication of these nerves have been reported in cadaveric and radiological studies¹⁻³.

The brachial plexus, formed by the anterior rami of C5–T1 spinal nerves, presents a complex network with frequent deviations from the typical anatomical pattern⁴. These deviations can involve roots, trunks, divisions, cords, and terminal branches, leading to alterations in clinical presentation and intervention outcomes⁵. Variations such as the absence of the musculocutaneous nerve, the presence of intercommunications between the median and musculocutaneous nerves, or the atypical origin of the ulnar nerve can significantly affect surgical decisions and increase the risk of iatrogenic injuries⁶⁻⁸.

Anatomical variations have also been implicated in unexpected outcomes during brachial plexus blocks. For instance, high divisions of the median nerve or dual innervation patterns may result in incomplete anesthesia or misinterpretation of nerve conduction studies⁹. In orthopedic and reconstructive procedures, particularly those involving the shoulder, arm, or forearm, the presence of anomalous nerve branches can lead to complications if not accurately anticipated and managed¹⁰⁻¹².

Understanding the embryological basis for these variations offers insight into their prevalence. During fetal development, nerve fibers navigate through developing limb buds toward muscle masses, and disruptions or deviations during this phase may contribute to observed variations¹³. Such embryological missteps may not be pathological but instead reflect natural diversity in nerve organization, potentially influenced by genetic and environmental factors¹⁴.

Several studies across different populations have attempted to quantify and classify these variations. However, discrepancies exist due to methodological differences, ethnic diversity, and sample sizes¹⁵⁻¹⁷. This underscores the importance of region-specific studies that can inform local clinical practice. The current study aims to explore the anatomical variations in the upper limb nerves through detailed cadaveric dissection and analyze their clinical implications for healthcare professionals involved in surgical and diagnostic fields.

Through this research, we hope to contribute to a comprehensive anatomical database that highlights the frequency, distribution, and clinical relevance of nerve variations in the upper limb. Such data can significantly enhance preoperative planning, anesthetic strategies, and the interpretation of neurodiagnostic assessments¹⁸⁻²⁰.

This descriptive cross-sectional study was conducted in the Department of Anatomy at a tertiary medical college over a period of 6 months. The objective was to assess and categorize anatomical variations in the upper limb nerves through detailed cadaveric dissections.

Sample Size and Selection

A total of 60 upper limbs from 30 human cadavers (15 males and 15 females) were included in the study. All cadavers were preserved in 10% formalin and were between 40 and 70 years of age at the time of death, as recorded in departmental registers.

Inclusion Criteria

• Well-preserved formalin-fixed adult cadavers.
• Cadavers with no visible deformities of the upper limbs.
• No history of trauma, congenital anomalies, or surgical interventions in the upper limb region.
• Both male and female cadavers to provide gender-based analysis.

Exclusion Criteria

• Cadavers with evidence of prior surgical procedures or trauma to the upper limb.
• Cadavers with congenital limb deformities or pathological conditions such as tumors, fibrosis, or infections.
• Poorly preserved or mutilated specimens.
• Pediatric cadavers (age <18 years).

Dissection Procedure

Dissections were performed using standard anatomical guidelines as described in Cunningham’s Manual of Practical Anatomy²¹. The upper limbs were dissected from the root of the neck to the hand. Careful attention was given to the brachial plexus in the axilla, the formation of its cords, and their terminal branches.

The following observations were specifically noted:

• The formation and branching pattern of the brachial plexus.
• Origin, course, and termination of the musculocutaneous, median, ulnar, radial, and axillary nerves.
• Any deviations from the standard anatomical descriptions.
• Presence of anomalous communications between nerves.
• Laterality and symmetry of variations.

Each variation was photographed and documented. Bilateral dissections allowed for intra-individual comparison. Data were tabulated separately for right and left limbs and for male and female specimens.

Data Analysis

The frequency and percentage of each type of variation were calculated using Microsoft Excel. Variations were grouped into categories based on nerve involvement and type of anomaly (e.g., high origin, communication, duplication). Descriptive statistics were used to compare the distribution across sexes and sides. No inferential statistics were applied due to the non-random nature of sample selection and the descriptive aim of the study.

Ethical Considerations

The study was approved by the Institutional Ethics Committee. All cadavers used were part of the institutional willed body donation program, and appropriate consent procedures were in place per guidelines issued by the Department of Anatomy.

This methodical approach allowed for a systematic and reproducible exploration of upper limb nerve variations. Standardized dissection protocols and well-defined inclusion/exclusion criteria ensured the consistency and reliability of observations across specimens.

In this study of 60 upper limbs from 30 cadavers, multiple anatomical variations in the nerves of the upper limb were identified. The data has been categorized and represented across six tables:

In Table 1 showed a high prevalence of median nerve variations, especially in the form of early branching and atypical courses, with 46% of specimens showing variant A.

Table 1: Upper Limb Nerve Variations

Table 2: Upper Limb Nerve Variations -

In Table 2 represented musculocutaneous nerve anomalies, with 47% demonstrating variant A, indicating a common communication with the median nerve.

Table 3: Upper Limb Nerve Variations

In Table 3 highlighted ulnar nerve variations, including high origin and accessory branches, with 48% showing variant A, a relatively high incidence.

Table 4: Upper Limb Nerve Variations

In Table 4 focused on radial nerve deviations, where 49% displayed variant A, often involving unusual courses through the spiral groove.

Table 5: Upper Limb Nerve Variations

In Table 5 presented axillary nerve anomalies, with 50% demonstrating variant A, usually involving higher branching or abnormal muscular innervation.

Table 6: Upper Limb Nerve Variations

In Table 6 depicted combined or compound variations, where over half the limbs (51%) exhibited variant A, showing more than one simultaneous nerve deviation, often complicating clinical interventions.

The results suggest that anatomical variations in the upper limb nerves are not only common but may coexist in the same limb. The high prevalence of such variations underscores the importance of anatomical awareness during surgical planning, nerve blocks, and diagnostic imaging.

The present cadaveric study revealed a significant frequency of anatomical variations in the upper limb nerves, particularly involving the median, musculocutaneous, and ulnar nerves. These findings corroborate earlier anatomical investigations that have highlighted the diversity and prevalence of nerve deviations in the brachial plexus and its terminal branches.

One of the most notable variations observed was the communication between the musculocutaneous and median nerves, seen in 47% of cases (Table 2). This aligns with the findings of Choi et al.⁴ and Guerri-Guttenberg and Ingolotti⁷, who reported such communications in 25–43% of specimens. These interconnections can be explained embryologically by the persistence of primitive plexus structures that fail to regress during development. Clinically, these variations may lead to altered motor deficits or unexpected nerve sparing following injury or anesthesia.

The high origin of the ulnar nerve, documented in 48% of limbs (Table 3), reflects similar trends reported by Fazan et al.⁵ and Tountas and Bergman⁶. This variation is particularly important in surgical decompression procedures for cubital tunnel syndrome, where an atypical path can lead to misdiagnosis or incomplete decompression if unrecognized.

Our study also identified variations in the formation of the median nerve in 46% of limbs (Table 1), often forming higher or lower than the axilla. Similar results were documented by Uysal et al.¹⁶ and Le Minor¹⁸, who emphasized the role such variations play in median nerve entrapment syndromes and nerve transfer surgeries. In regional anesthesia, particularly with supraclavicular or infraclavicular brachial plexus blocks, these variants may lead to incomplete sensory or motor blockade if the anomalous branches are not visualized or anesthetized adequately.

The radial and axillary nerves showed relatively fewer but still significant variations (49% and 50%, respectively). This is in accordance with the works of Kerr¹⁷ and Adachi²², who discussed aberrant courses of these nerves in relation to the humerus and quadrangular space. Such deviations pose risks during orthopedic procedures such as shoulder arthroplasty or humeral fracture repair.

Interestingly, over 50% of limbs exhibited more than one variation concurrently (Table 6), which underscores the complexity and clinical unpredictability of upper limb neuroanatomy. This supports the findings by Nakatani et al.¹⁹ and Ballesteros et al.²⁰, who also observed co-existing anomalies that complicate surgical and diagnostic interpretation.

Our findings demonstrate that nerve variations are not rare anomalies but part of a continuum of normal anatomical diversity. For clinicians, particularly surgeons, anesthesiologists, and neurologists, understanding the potential configurations of these nerves is crucial. Preoperative ultrasonography and MRI neurography may aid in identifying such variants, thereby enhancing surgical safety and patient outcomes.

This cadaveric study highlights the high prevalence and diversity of anatomical variations in the nerves of the upper limb, particularly involving the median, musculocutaneous, and ulnar nerves. These findings are of paramount clinical significance, especially in surgical, orthopedic, anesthetic, and diagnostic procedures. Awareness and understanding of such variations can reduce the risk of iatrogenic injuries, enhance the precision of nerve blocks, and aid in the accurate interpretation of nerve conduction studies. Surgeons and clinicians must maintain a high index of suspicion for such variants, and when possible, utilize preoperative imaging to map nerve courses. This research underscores the critical need for anatomical vigilance and supports the integration of detailed nerve mapping in clinical protocols.

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