The clinical anatomy of the communications between the radial and ulnar nerves on the dorsal surface of the hand

Causes of Dorsal Cutaneous Branch of the Ulnar Nerve Neuropathy Among Patients Undergoing Electrodiagnostic Studies: A Series of 14 Patients

BACKGROUND

Isolated neuropathy of the dorsal cutaneous branch of the ulnar nerve (DCBUN) is rare and most cases are secondary to trauma, often iatrogenic. The topography of sensory abnormalities and abnormal electrodiagnostic (EDX) findings are crucial in confirming DCBUN neuropathy.  Materials and methods: This is a retrospective study of patients with isolated involvement of the DCBUN from among patients referred for EDX studies for upper extremity symptoms. All patients underwent a focused neurological examination followed by EDX studies. Ultrasound (US) studies were performed in two patients.  Results: Of the 14 patients with DCBUN neuropathy, decreased pinprick sensation in the distribution of the DCBUN was noted in 11 (78%) patients. DCBUN sensory nerve action potential (SNAP) was not recordable in 13 (92%) patients. In one patient who had a recordable SNAP, the latency was prolonged, and the amplitude was decreased. Four (28%) patients had incidental EDX abnormalities suggestive of entrapment of the median nerve at the carpal tunnel. The most common cause of DCBUN neuropathy was trauma in 13 (92%) patients, of which eight were iatrogenic. No specific etiology was detected in one patient (7%). Of the two patients who underwent US studies, one had increased cross-sectional area (CSA) at the wrist with prominent fascicles and hyperechoic scar tissue, while the CSA was normal in the other patient.

CONCLUSIONS

Although rare, DCBUN neuropathy can be readily confirmed by typical clinical features and EDX findings. Surgeons should be aware of the anatomy and clinical features of DCBUN neuropathy and avoid injuring the nerve during surgical procedures at the wrist and forearm.

Comparison of the effectiveness of local anesthesia for the digital block between single-volar subcutaneous and double-dorsal finger injections: a systematic review and meta-analysis of randomized control trials

Local anesthesia is an effective method to perform digital nerve blocks. In this study, we compare the effectiveness of single-volar subcutaneous and double-dorsal injection through a systematic review and meta-analysis of randomized controlled trials (RCTs). A systematic search of PubMed, Embase, and the Cochrane Library from inception to 7 April 2021 was performed. RCTs with the effects of single-volar subcutaneous and double-dorsal injection were eligible. Meta-analysis was performed using random effect models with pooled standardized mean differences (SMDs) and 95% confidence intervals (CI). RoB 2.0 and GRADE of Recommendation Assessment, Development, and Evaluation criteria were applied for evaluating the bias. A total of 2484 studies were initially identified, with 11 eligible RCTs finally included in the meta-analysis (1363 patients). The pooled data of nine studies showed single-volar injection had a statistically significantly lower pain score (pooled SMD: 0.20, 95% CI, 0.01 to 0.39, p = 0.041, I2 = 58%, N = 1187) and higher patient preference but invalid anesthesia at the dorsal proximal digit. No significant differences were observed in the onset of anesthesia, adjacent digit invalid numbness, distal phalanx invalid anesthesia, additional injection rate, and adverse effects. In conclusion, this meta-analysis of RCTs showed that the single-volar injection was associated with a lower pain sensation during injection and higher patient satisfaction with a reduced anesthetic effect over the proximal dorsal phalanx. Further high-quality RCTs with a higher number of cases are needed to validate our results.

Ultrasonography of the Peripheral Nerves of the Forearm, Wrist and Hand: Definition of Landmarks, Anatomical Correlation and Clinical Implications

BACKGROUND

 Peripheral nerve pathologies of the upper extremity are increasingly assessed by high-resolution ultrasonography (HRUS), yet rapid identification of nerve segments can be difficult due to small nerve diameters and complex regional anatomy. We propose a landmark-based approach to speed up and facilitate evaluation and intervention in this region.

METHOD

 Relevant landmarks and section planes for eleven nerve segments of the forearm, wrist and hand were defined by ultrasonography in cadaver arms before cryosection and topographical neurovascular preparation. Information on all nerve segments and a pictorial guide including anatomical cross-sections, topographical preparations and HRUS images are provided. The identification rates of these nerve segments were then assessed in 20 healthy volunteers.

RESULTS AND CONCLUSION

 Sonographic landmarks and guidelines for the rapid identification and assessment of nerves of the forearm, wrist and hand are presented in pictorial and tabular form, including discussion of normal variants. Utilizing this overview should facilitate training, diagnostic examinations and intervention for nerves of the upper extremity.

KEY POINTS

  · High-resolution ultrasound enables assessment of peripheral nerves of the forearm, wrist and hand.. · A landmark-based approach can facilitate and speed up nerve evaluation in these regions.. · High detection rates could be reproduced using the proposed landmark-based approach..

CITATION FORMAT

· Gruber L, Loizides A, Peer S et al. Ultrasonography of the Peripheral Nerves of the Forearm, Wrist and Hand: Definition of Landmarks, Anatomical Correlation and Clinical Implications. Fortschr Röntgenstr 2020; 192: 1060 - 1072.

Diagnostic Accuracy of Sensory Clinical Findings of the Hand Dorsum and of Neurography of the Dorsal Ulnar Cutaneous Nerve in Ulnar Neuropathy at the Elbow

OBJECTIVE

The main objective is to investigate the diagnostic accuracy and the relation of touch sensation and subjective sensory symptoms in the medial aspect of the hand dorsum, and neurography of the dorsal ulnar cutaneous nerve (DUCN) in ulnar neuropathy at the elbow (UNE). Secondary objective is to report the electrophysiological occurrence of anatomical variant of sensory innervation of the medial aspect of the hand dorsum from superficial radial nerve (SRN).

DESIGN

Prospective, cohort study.

SETTING

Electromyography laboratory.

PARTICIPANTS

Consecutive participants (N=282), those with UNE (n=81) and those without UNE (n=201), were enrolled.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Accuracy and agreement between sensory clinical findings of the medial hand dorsum and neurography of DUCN in UNE diagnosis.

RESULTS

DUCN neurographic and sensory findings had high specificity and relatively low sensitivity. Normal or abnormal sensory nerve action potential (SNAP) of DUCN matched with normal or abnormal touch sensation of the medial aspect of hand dorsum. Abnormal DUCN SNAP was related to the clinical severity of UNE and to the axonal damage of the ulnar nerve. Anatomical variant of the innervation of hand dorsum from SRN was demonstrated in 31 of 564 hands (6.2%) belonging to 26 of 282 participants (9.2%). If the variant was present, DUCN SNAP of the same side was more frequently absent or of low amplitude.

CONCLUSIONS

The utility of DUCN neurography and sensory findings of the medial aspect of the dorsum of the hand is limited in the diagnosis of UNE. However, if DUCN SNAP is absent or low in amplitude, it is advisable to check the presence of the anatomical variant of the innervation of the medial aspect of the hand dorsum from SRN.

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

INTRODUCTION

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.

METHODS

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).

RESULTS

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.

DISCUSSION

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.

Connections between radial and ulnar nerve at high humeral level in cadavers: incidence, topography, and literature review

PURPOSE

Although communications between branches and cords of the brachial plexus have been extensively published, there is a scarcity of reports concerning radial and ulnar nerve (RN-UN) communication in the arm. The current study aims to demonstrate the incidence, topography, and length of communicating branches between RN and UN. Any additional coexisted variations were also recorded.

MATERIALS AND METHODS

Two hundred and sixty-six upper limbs collected from one hundred and thirty-three (81 males and 52 females) Greek cadavers were dissected.

RESULTS

Three out of one hundred and thirty-three cadavers, accounting for an incidence of up to 2.3%, were found to have an atypical communicating branch originating at a high humeral level from RN towards UN. In two cadavers, communicating branches were detected on the left side and in one cadaver bilaterally.

CONCLUSIONS

The study of atypical communications between RN and UN attracts great attention for its clinical importance, mainly in cases of peripheral neuropathies with diagnostic dilemma or upper limb nerve injury producing an otherwise unexpected symptomatology due to the aberrant nerve supply. Familiarity with these variations is crucial in avoiding misdiagnosis and preserving valuable communicating branches, thus achieving an uneventful outcome in cases of upper limb nerve injury repair.

Anatomical study of the dorsal cutaneous branch of the ulnar nerve (DCBUN) and its clinical relevance in TFCC repair

The aim of this study was to define a detailed description of the dorsal cutaneous branch of the ulnar nerve (DCBUN) in particular in relevance to triangular fibrocartilage complex (TFCC) repairs. In 20 formalin-embalmed arms, the DCBUN was dissected, and the course in each arm was mapped and categorized. Furthermore, the point of origin of the DCBUN, that is, from the ulnar nerve in association with the ulnar styloid process, was defined. Finally, the distance between the ulnar styloid process and the branching of the radial-ulnar communicating branch (RUCB) and the first branch of DCBUN was measured. The distance between the origin of the DCBUN in relation to the ulnar styloid process ranges from 55 to 111 mm (mean 87 mm; STD 14 mm). The distance between the ulnar styloid process and the RUCB ranges from 1 to 54 mm (mean 19 mm; STD 12 mm). Finally, the distance between the ulnar styloid process and the lateral distal branch shows a range of -6 to 28 mm (mean 10 mm; STD 9 mm). In general, three dorsal digital nerves (medial, intermediate, and lateral branch), run at the dorsal ulnar aspect of the hand. The RUCB is often less abundant and shows a large amount of variation. No complete safe zone could be identified; the course of the DCBUN suggests a longitudinal incision for the 6R portal. In fact, a more dorsal incision also prevents damage to the main branches of the DCBUN.

Anatomical Study of the Ulnar Nerve Variations at High Humeral Level and Their Possible Clinical and Diagnostic Implications

Background. Descriptive evaluation of nerve variations plays a pivotal role in the usefulness of clinical or surgical practice, as an anatomical variation often sets a risk of nerve palsy syndrome. Ulnar nerve (UN) is one amongst the major nerves involved in neuropathy. In the present anatomical study, variations related to ulnar nerve have been identified and its potential clinical implications discussed. Materials and Method. We examined 50 upper limb dissected specimens for possible ulnar nerve variations. Careful observation for any aberrant formation and/or communication in relation to UN has been carried out. Results. Four out of 50 limbs (8%) presented with variations related to ulnar nerve. Amongst them, in two cases abnormal communication with neighboring nerve was identified and variation in the formation of UN was noted in remaining two limbs. Conclusion. An unusual relation of UN with its neighboring nerves, thus muscles, and its aberrant formation might jeopardize the normal sensori-motor behavior. Knowledge about anatomical variations of the UN is therefore important for the clinicians in understanding the severity of ulnar nerve neuropathy related complications.

Communication between radial nerve and medial cutaneous nerve of forearm

Radial nerve is usually a branch of the posterior cord of the brachial plexus. It innervates triceps, anconeous, brachialis, brachioradialis, extensor carpi radialis longus muscles and gives the posterior cutaneous nerve of the arm, lower lateral cutaneous nerve of arm, posterior cutaneous nerve of forearm; without exhibiting any communication with the medial cutaneous nerve of forearm or any other nerve. We report communication between the radial nerve and medial cutaneous nerve of forearm on the left side in a 58-year-old male cadaver. The right sided structures were found to be normal. Neurosurgeons should keep such variations in mind while performing the surgeries of axilla and upper arm.

Anatomical survey of terminal branching patterns of superficial branch of radial nerve in fetuses

BACKGROUND

Regional anesthesia plays a key role in elective as well as emergency orthopedic and other surgeries in children. However, peripheral nerve blocks are quite challenging in children due to lack of precise anatomical knowledge of the course and distribution of these nerves. The purpose of this study was to explore the terminal branches of the superficial branch of the radial nerve in fetuses. The relationship of the superficial branch of the radial nerve with cephalic vein and surrounding tendons was also observed.

METHODS

A total of 60 upper extremities (42 males and 18 females) of 30 spontaneously aborted fetuses (32-40 weeks) were dissected to expose the superficial branch of the radial nerve in the distal forearm and hand.

RESULTS

Three patterns of distribution based on the total area of the dorsum of the hand innervated were observed. Type 1 (66.7%): superficial branch of radial nerve (SBRN) innervated lateral two-and-a-half digits; Type 2 (23.3%): SBRN innervated lateral three digits; Type 3 (10%): SBRN innervated lateral three-and-a-half digits. The cephalic vein was seen to intersect the nerve more than twice along its course.

CONCLUSIONS

Detailed knowledge of the distribution patterns of terminal branches of superficial branch of radial nerve in hand will enhance the success rate of regional blocks or hand surgeries and minimize the postoperative complications due to injury to nerve or vascular structures.

Neural interconnections between the nerves of the upper limb and surgical implications

The knowledge of neural interconnections between adjacent nerves of the upper limb is important to the surgeon as such variations may lead to issues with surgical identification and thus iatrogenic injury. Trauma or entrapment of these nerves may cause functional losses different from those expected and thus result in misdiagnosis. The authors review the literature regarding such nervous system derangements.

Deep palmar communications between the ulnar and median nerves

Innervation of the hand is supplied via the radial, median, and ulnar nerves. A common border of sensory distribution between the ulnar and median nerves is along the fourth digit. However, this sensory distribution may be affected by communication between these two nerves. Among the known communications between the median and ulnar nerves, the deep anastomotic branch in the hand is the least described and rarely illustrated in the literature. This study aims to provide data on the prevalence of a deep communicating branch via cadaveric dissection. We examined 50 hands taken from 25 adult cadavers. Communicating branches were found in 16% of the hands examined, with rami occurring bilaterally in two specimens. By describing the origin and pathway of this communicating branch, we hope to provide surgeons and clinicians with knowledge that may help avoid iatrogenic injuries.