Title : Dorsal ulnar hand sensory innervation by anomalous superficial radial nerve: Prevalence and classification in a multiethnic cohort
Abstract:
Objective: To define the prevalence and electrophysiological patterns of an anomalous Superficial Radial Nerve (SRN) contribution to dorsal ulnar hand sensibility and to propose a clinically applicable three-tier classification relevant to hand surgery and peripheral nerve assessment in a large, multi-ethnic cohort.
Background: An absent Dorsal Ulnar Cutaneous Nerve (DUCN) response is used to localise ulnar neuropathy proximal to the wrist, yet anomalous SRN supply to the ulnar dorsum is a recognised, under-quantified cause of absent or reduced DUCN responses. The largest electrophysiological series to date included 100 patients, and no data are available from the Middle East.
Design/Methods: Retrospective review of all consecutive patients undergoing DUCN and SRN sensory conduction studies at the Neurophysiology Laboratory, hamad general hospital, Doha, Qatar (February 2022–January 2026). DUCN sensory nerve action potentials were recorded antidromically at the fourth intermetacarpal space; the SRN was then stimulated at the lateral forearm with the recording electrodes unchanged. Patients were classified as Type I (DUCN present, no SRN response at the DUCN site), Type II (DUCN present, with or without reduced amplitude, plus SRN response, consistent with anastomosis/co-innervation) or Type III (DUCN absent with SRN response: complete SRN replacement). Prevalence was estimated with Wilson 95% confidence intervals; subgroups were compared using the chi-square test.
Results: After removal of 31 duplicate records, 1,026 patients were analysed (746 female and 280 male; 45 nationalities). Type I was found in 838 patients (81.7%), Type II in 130 (12.7%) and Type III in 58 (5.7%). Any anomalous innervation, defined as Type II or Type III, was present in 188 patients (18.3%; Wilson 95% CI, 16.1% 20.8%). Six patients (0.6%) showed discordant bilateral patterns (Type II in one hand and Type III in the other), and the anomaly was unilateral in 147 of 188 affected patients (78.2%). Prevalence was 21.8% in males (61/280) and 17.0% in females (127/746); this difference was not statistically significant by chi-square test (p=0.08).
Conclusions: Anomalous superficial radial nerve contribution to dorsal ulnar hand sensibility is common, occurring in approximately one in five patients undergoing upper-limb nerve conduction studies, with complete electrophysiological innervation of the dorsal ulnar cutaneous nerve in approximately one in twenty. Recognition of this pattern, particularly type III variant, is relevant to surgical planning around the dorsal wrist and hand to avoid iatrogenic cutaneous nerve injury. The proposed three-tier classification is simple and is readily applicable to routine preoperative and diagnostic nerve evaluation.
