Dorsal Ulnar Nerve Research Articles

Neurophysiological study of the radial nerve variant in the innervation of the dorsomedial surface of the hand.

Sensory innervation of the dorsomedial surface of the hand usually depends on the dorsal ulnar nerve (DUN). Innervation in this area by the superficial radial nerve (SRN) has been described as a normal variant. We studied 358 patients using nerve conduction of the DUN and SRN with dorsomedial recording. Each hand was classified into usual innervation (only DUN response), mixed variant (response of both nerves), or complete variant (only SRN response). Mixed innervation was found in 14.2% of hands and complete innervation was found in 6.8% of hands, mostly unilaterally. No statistically significant differences were observed in age, sex, or clinical suspicion between usual and variant innervation. The potential amplitude after SRN stimulation was greater in the complete variant. It is important to know the characteristics of this variant in order to avoid diagnostic errors and to prevent iatrogenic lesions in surgery performed on the dorsum of the wrist. Muscle Nerve 58: 732-735, 2018.

The Hidden Variability of the Ulnar Nerve and Its Importance for Hand Function

The dorsal branch of the ulnar nerve, which is vital for hand function, provides feeling to the back of the hand. The anatomical variations in the origin of this branch on the ulnar nerve may have an impact on upper limb surgical procedures. This paper investigates the dorsal ulnar nerve branch's hidden variability and its practical implications for hand function.

Safety of dorsal wrist arthroscopy portals: A magnetic resonance study

In wrist arthroscopy, the standard dorsal portals are the most commonly used. However, their placement can be associated with injuries to the neurovascular structures of the radiocarpal joint. The present study assessed and compared the distance of commonly used dorsal portals to radial and ulnar neurovascular structures.Forty patients (20 males, 20 females) were evaluated with T1-weighted spin-echo (SE) magnetic resonance (MR) sequences. We measured the distance between 1–2 and 3–4 portals and radial vascular bundle and the nearest branch of the superficial branch of radial nerve (SBRN). We also measured the distance between 4 and 5, 6/U and 6/R and ulnar vascular bundle and the nearest branch of the dorsal ulnar nerve (DUN).The median age of patients was 39 years (95% IC 36.97–43.32 years). The 3–4 portal was farther away from the vascular structure than the 1–2 portal (P < 0.0001), 4–5 portal (P = 0.008), 6/R (P < 0.0001), and 6/U portals (P < 0.0001). Moreover, the 3–4 portal was farther away from the nerve branch than the 1–2 portal (P < 0.0001), 4–5 portal (P < 0.0001), 6/R (P < 0.0001), and 6/U portals (P < 0.0001). No statistical significant differences were found between the two genders.The 3–4 and 4–5 portals are the farthest away from the neurovascular structures, and likely reduce the risk to damage these structures. On the other hand, the 1–2 and 6/U portals likely increase the risk of neurovascular damage, because of their proximity to neurovascular structures.Level of evidence: Diagnostic study; Level III.

Le rameau transverse de la branche dorsale du nerf ulnaire : anatomie et rapports avec les voies arthroscopiques du poignet: Quarante-cinq dissections

Purpose of the study We conducted an anatomic study of the transverse branch of the dorsal ulnar nerve to describe its morphology and position in relation to arthroscopic exploration portals. Material and methods Forty-five non-side-matched anatomic specimens of unknown age and gender were preserved in formol. The dorsal branch of the ulnar nerve was identified and dissected proximally to distally in order to reveal the different terminal branches. The morphometric analysis included measurement of the length and diameter of the transverse branch and measurement of wrist width. We also measured the smallest distance between the transverse branch and the ulnar styloid process, and between the branch and usual arthroscopic portals (4-5, 6R, 6U) in the axis of the forearm. Results The transverse branch was inconstant. It was found in 12 of the 45 dissection specimens (27%). In two-thirds of the specimens, the branch ran over less than 50% of the wrist width, tangentially to the radiocarpal joint. Mean nerve diameter was 1 mm. It was found 5-6 mm from the ulnar styloid process and was distal to it in 83% of the specimens. The dissections demonstrated two anatomic variants. Type A corresponded to a branch running distally to the ulnar styloid process, parallel to the joint line (10/12 specimens). Type B exhibited a trajectory proximal to the ulnar styloid process, crossing the ulnar head (2/12 specimens). The relations with the arthroscopic portals (4-5, 6R, 6U) showed that the mean distance from the branch to the portal was 3.75 mm for the 4-5 portal (distally in 11/12 specimens), 3.68 mm for the 6R portal (distally in 10/12 specimens), and 4.83 mm for the 6U portal (distally in 7 specimens and proximally in 5). Discussion To our knowledge, there has been only one report specifically devoted to this transverse branch. Two other reports simply mention its existence. According to the literature, the transverse branch of the dorsal ulnar nerve occurs in 60-80% of the cases. We found two anatomic variations different than those described in the literature. Based on our findings and data reported previously, we propose a new classification, describing two main types. In Type 1, the transverse branch arises proximally to the ulnar styloid process; type 1A and type IB are described in relation to the direction of the branch. In Type II, the branch arises distally to the ulnar styloid process; type IIA and type IIB again being described in relation to the direction of the branch. On the tangential trajectory over the radiocarpal joint, the morphometric data show a zone of risk described by a rectangle measuring 10 mm wide (6 mm distal and 4 mm proximal to the ulnar styloid process) and covering 50% of the wrist width. The relations with arthroscopic portals describe a zone of risk corresponding to a 5-7 mm radius circle centered on the portals (4-5, 6R, 6U), which includes 83% of the transverse branches.

The projection pattern of forepaw nerves to the cuneate nucleus of the raccoon.

The transganglionic transport of horseradish peroxidase (HRP) was used to determine the projection pattern within the cuneate nucleus of the 4 major nerves innervating the forepaw of the raccoon, a carnivore noted for its tactile and manipulative abilities. The two nerves innervating the dorsal, hairy skin and claws (the radial and dorsal ulnar nerves) projected to the marginal rim of the cuneate nucleus, but not to the middle cluster region or to the caudal region of the nucleus. The two nerves innervating glabrous skin (median and ulnar) projected heavily to the cluster region as well as to rostral and caudal levels of the nucleus. This organization, with dorsal nerves ending above the ventral nerves, is similar in the raccoon, rat and tree squirrel, but reversed in the cat. However, the medio-lateral topography is similar in all species with the ulnar and dorsal ulnar nerves projecting medially within the nucleus compared to the median and radial nerves.

Sensory innervation of the raccoon forepaw: 1. Receptor types in glabrous and hairy skin and deep tissue.

Electrophysiological recordings were made from the median, ulnar, radial, and dorsal ulnar nerves to determine the types of mechanosensory receptors serving glabrous and hairy skin surfaces of the raccoon forepaw. In addition to the cutaneous mechanoreceptors, fibers innervating deep tissues were also recorded from each of these nerves. These included sensory fibers innervating muscles, joints, claws, and the subcutaneous pulp. The array of receptors serving raccoon glabrous skin was the same as found in monkeys and humans: Rapidly adapting (RA), slowly adapting (SA), and Pacinian (Pc) fibers were characterized. Pacinian fibers have been rarely described in previous physiological studies of the raccoon peripheral nerves, but in the present study they composed between 14% and 18% of the glabrous skin mechanoreceptors recorded. A distal-proximal gradient in the density of skin innervation was evident for all three types of receptors. Receptors characterized in the hairy skin of the dorsal paw were similar to those described in other mammals, and included both down and guard hair afferents, non-hair-associated RA fibers, and SA I and SA II fibers. The relative proportions of these fibers differed from those generally reported for the hairy skin of other mammals. SA hair-associated afferent fibers, which have been reported previously only in primate hairy skin, were also found in large numbers in the raccoon. Similarities and differences in the frequency and types of receptors innervating the raccoon forepaw, the forepaws of other mammals, and the hands of primates (including humans) are discussed.

USE OF THE ARTICULAR BRANCH OF THE ULNAR NERVE TO THE WRIST FOR A LOCAL NERVE GRAFT

The use of articular branch of the dorsal sensory ulnar nerve as a nerve graft is discussed. A case of traumatic neuroma of the dorsal ulnar nerve which was treated by this method is presented.