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Abstract., (This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Rationale: The incidence of Martin-Gruber anastomosis ranges from 5% to 34%, which is characterized by crossing over from the median to the ulnar nerve and innervating the first dorsal interosseous, thenar or hypothenar muscles. However, the reverse Martin-Gruber anastomosis, or Marinacci anastomosis, is far less discussed and appears in recent literature., Patient Concerns: A 56-year-old man presented to the clinic of a university hospital because of left neck soreness with numbness radiating to the left lateral shoulder. The neck discomfort was aggravated while the neck rotated or tilted to the right., Diagnosis: Higher compound muscle action potential over the abductor pollicis brevis on elbow stimulation than on the wrist was found during upper limb nerve conduction velocity study. Ulnar to median anastomosis was identified., Intervention: We performed cervical spine X-ray and electrophysiological examinations and monitored the patient., Outcomes: We identified that this patient had left C5 and C6 subacute radiculopathy with active denervation and left subclinical ulnar sensory neuropathy, and verified the existence of ulnar-to-median anastomosis., Lessons: We demonstrated a pure motor ulnar-to-median anastomosis without sensory correspondence and higher CMAP over the abductor pollicis brevis on elbow stimulation of the ulnar nerve than on the wrist. The prevalence might be underestimated in a Chinese population-based published study., Competing Interests: The authors have no conflicts of interest to disclose. Patient consent: The patient provided written informed consent for the publication and use of the report., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

Anomalous innervations are commonly encountered on electrodiagnostic testing and may be mistaken for a pathological process, especially if seen in multiple nerves. While crossover of median-to-ulnar fibers in the forearm (Martin-Gruber anastomosis) has been frequently described, the corresponding ulnar-to-median crossover (Marinacci anastomosis) is much less commonly seen. There have been no reported cases of both of these anomalous innervations occurring together. We describe a novel case of bilateral Martin-Gruber and Marinacci anastomoses in the same patient. The importance of the case lies in the fact that the multiple pseudo-conduction blocks that result from these crossovers could potentially be misinterpreted as being pathological in nature, illustrating the need for electromyographers to be familiar with common anomalous innervations in the upper extremity and with techniques to identify them.

Background: The aim of this study is to determine the prevalence of Martin-Gruber Anastomosis (MGA) in healthy Egyptian subjects, and to discuss the available literature regarding MGA subtypes and their clinical implications. Methods: An electrophysiological study was conducted in both forearms of 140 healthy subjects. This included the ulnar and median nerves. Compound muscle action potentials were recorded from abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles. Other measurements included the compound motor action potential amplitude and its innervation ratio. Results: MGA was found in 56 of the 280 forearms. This included 20 men and 36 women. Type II MGA subtype was the most frequent in both genders. The MGA was bilateral in 6 subjects and more frequent on the right side. The highest mean amplitude and innervation ratio were recorded at first dorsal interosseus muscle. Conclusions: The prevalence of MGA in the studied sample of the Egyptian population is 20%. It is important for Hand, Orthopaedic and Neurosurgeons to be aware of this anatomic variation in order to explain paradoxical motor and sensory loss in patients.

Background: Several anatomical variations of the median nerve recurrent motor branch have been described. No previous reports have described the anatomical variation of the ulnar nerve with respect to transverse carpal ligament. In this article, we present a patient with symptomatic compression of the ulnar nerve found to occur outside the Guyon canal due to a transligamentous course through the distal transverse carpal ligament. Methods: A 59-year-old, right-hand-dominant male patient presented with right hand pain, subjective weakness, and numbness in both the ulnar and the median nerve distributions. Electromyography revealed moderate demyelinating sensorimotor median neuropathy at the wrist and distal ulnar sensory neuropathy. At the time of planned carpal tunnel and Guyon canal release, a transligamentous ulnar nerve sensory common branch to the fourth webspace was encountered and safely released. Results: There were no surgical complications. The patient's symptoms of numbness in the median and ulnar nerve distribution clinically improved at his first postoperative visit. Conclusions: We have identified a case of transligamentous ulnar nerve sensory branch encountered during carpal tunnel release. To our knowledge, this has not been previously reported. While the incidence of this variant is unknown, hand surgeons should be aware of this anatomical variant as its location puts it at risk of iatrogenic injury during open and endoscopic carpal tunnel release.

Median and ulnar nerve interconnections commonly occur in the brachial plexus, forearm, and hand. Each is classified based on location, fiber type (sensory fibers, motor fibers, or both), and directionality (ie, carrying fibers from median to ulnar or vice versa). There are 4 main interconnections found in the forearm and hand: Martin-Gruber and Marinacci anastomoses in the forearm and Riche-Cannieu and Berrettini anastomoses in the hand. The presence of an interconnection may skew electrodiagnostic findings, possibly resulting in misdiagnosis and iatrogenic injury. Clinicians should perform nerve studies of both nerves at proximal and distal stimulation sites to rule out interconnections and guide treatment. This review details anatomy, electrodiagnostic findings, and clinical approach., (Copyright © 2019 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

Aim: To evaluate the existence of nerve innervation of the triceps brachii muscle via the ulnar nerve and its clinical importance in terms of nerve transfer or susceptibility to iatrogenic injuries during surgical procedures., Material and Methods: Thirty-five skeletally mature upper extremities of adult cadavers were included in the present study. The ulnar nerve was revealed from the medial cord to the distal part of the cubital fossa. The existence of the branches of the ulnar nerve and communicant branch of the radial nerve was examined in the brachium. The diameter and length of the variant nerve branches were measured., Results: A nerve branch from the ulnar nerve to the triceps brachii muscle was found in five of the dissected extremities (14.7%). The mean length and diameter of the variant nerve branch were 20.2 mm and 1.46 mm, respectively. The mean distance of the muscle entry point of the variant nerve branch from the bi-condylar line was 8.18 cm., Conclusion: A variant nerve branch via the ulnar nerve can innervate the medial head of the triceps brachii at the distal third of the brachium. This variant nerve branch will be under risk of iatrogenic injury during elbow surgery and it seems to be an option for nerve grafts.

Introduction: The most frequently described anomalous neural connections between the median and ulnar nerves in the upper limb are: Martin-Gruber anastomosis (MGA), Marinacci anastomosis (MA), Riche-Cannieu anastomosis (RCA), and Berrettini anastomosis (BA). The reported prevalence rates and characteristics of these anastomoses vary significantly between studies., Methods: A search of electronic databases was performed to identify all eligible articles. Anatomical data regarding the anastomoses were pooled into a meta-analysis using MetaXL 2.0., Results: A total of 58 (n = 10,562 upper limbs) articles were included in the meta-analysis. The pooled prevalences were: MGA, 19.5% (95% confidence interval [CI], 16.2%-23.1%); MA, 0.7% (95% CI, 0.1%-1.7%); RCA, 55.5% (95% CI, 30.6%-79.1%); and BA, 60.9% (95% CI, 36.9%-82.6%). The results also showed that MGA was more commonly found unilaterally (66.8%), on the right side (15.7%), following an oblique course (84.8%), and originating from the anterior interosseous nerve with a prevalence of 57.6%., Conclusions: As anastomoses between the median and ulnar nerves occur commonly, detailed anatomical knowledge is essential for accurate interpretation of electrophysiological findings and reducing the risk of iatrogenic injuries during surgical procedures. Muscle Nerve 54: 36-47, 2016., (© 2015 Wiley Periodicals, Inc.)

Two patients with an anteriorly positioned ulnar nerve at the elbow, identified during cubital tunnel release, are presented. Upon encountering an empty cubital tunnel, additional dissection found the ulnar nerve to course posterior to and to penetrate through the intermuscular septum 3 to 5 cm proximal to the medial epicondyle. It then ran anterior to the pronator-flexor mass before entering the forearm between the ulnar and the humeral heads of the flexor carpi ulnaris. Although a rare anatomical anomaly, an anteriorly positioned ulnar nerve is potentially an underreported finding. In individuals with cubital tunnel syndrome, diagnosis and surgical treatment may be negatively affected if the surgeon fails to recognize the aberrant anatomy. Upper extremity surgeons should also be mindful of this rare anomaly when performing elbow arthroscopy or medial epicondyle release to prevent inadvertent injury to the nerve., (Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.)

An unusual communication between the radial and ulnar nerves was observed during repair of a fracture of the humerus in an adult patient who presented with unusual physical exam findings. The patient had loss of radial and ulnar nerve motor function, as well as decreased sensation in both nerve distributions. Radial nerve injury following fracture of the humerus is a common condition, and anatomic variations are therefore of importance to clinicians. Communications between branches of the brachial plexus are also not uncommon findings; however there is very little mention of communication between the radial and ulnar nerves in the literature. An appreciation of unusual nerve anatomy is important in explaining unusual finding in patients.

Martin-Gruber anastomosis (MGA) is the most common nerve anastomosis in the upper extremities and it crosses from the median nerve to the ulnar nerve. Proximal MGA is an under recognized anastomosis between the ulnar and median nerves at or above the elbow and should not be missed during nerve conduction studies. We presented two patients with ulnar neuropathy mimicking findings including numbness and tingling of the 4th and 5th digits and mild weakness of intrinsic hand muscles. However, both cases had an apparently remarkable conduction block between the below- and above-elbow sites that was disproportionate to their clinical findings. To explain this discrepancy, a large MGA was detected with stimulation of the median nerve at the elbow. Thus, proximal MGA should be considered in ulnar neuropathy at the elbow when apparent conduction block or/and discrepancy between clinical and electrodiagnostic findings is found.

Purpose: A proximal Martin-Gruber anastomosis (MGA) is an underrecognized anomaly and can mimic ulnar neuropathy at the elbow on electrodiagnostic testing. Martin-Gruber anastomosis is mainly recognized as a crossover from median nerve or its branches to ulnar nerve at the forearm, but may occur at the elbow (proximal MGA). The authors report their experience with MGA at the elbow., Methods: Using standard nerve conduction techniques, the authors prospectively detected electrodiagnostic evidence of a proximal MGA at the elbow over the course of 4 years. An accompanying ulnar neuropathy was diagnosed based on clinical findings, focal conduction slowing, and needle electromyography., Results: A proximal MGA involving branch of ulnar nerve was detected in 16 cases. The detection of proximal MGA to the first dorsal interosseous muscles was more sensitive than to the adductor digiti minimi muscles in their series., Conclusions: A proximal MGA is an underrecognized anomaly. This study is the largest series for proximal MGA in the literature. The authors recommend considering proximal MGA in any cases of ulnar neuropathy at the elbow, especially if the apparent conduction block is not associated with slowing of conduction velocity, and a discrepancy between clinical and electrodiagnostic findings is present.

Numerous causes are reported for ulnar nerve compression at the wrist, known as Guyon's tunnel syndrome. In the present article, a patient with Guyon's tunnel syndrome during pregnancy concomitant with an anomaly of ulnar nerve is described. A 29-year-old Iranian woman presented with clinical features of Guyon's tunnel syndrome (pain and paresthesia in the fifth finger of the left hand and atrophy of the first dorsal interosseus muscle). Symptoms of the patient appeared during the third trimester of pregnancy. Electro diagnostic studies confirmed Guyon's tunnel syndrome. Surgical exploration revealed an anomalous arch of the ulnar nerve passing through the flexor carpi ulnaris (FCU) tendon. The anomalous arch of the ulnar nerve was released by resection of the segment of FCU tendon passing through the ulnar nerve arch. Therefore, in patients with Guyon's tunnel syndrome, the ulnar nerve anomaly should be kept in mind as a cause. Moreover, pregnancy may have a provocative effect on Guyon's tunnel syndrome similar to carpal tunnel syndrome (CTS).

The Riche-Cannieu anastomosis (RCA) is an anatomic variant wherein a deep branch of the distal ulnar nerve innervates muscles of the thenar eminence. A few cases in the literature describe an "all-ulnar hand" when the muscles of the thenar eminence get innervation solely from the ulnar nerve without any contribution from the median nerve. Clinically, patients with ulnar mononeuropathies in the setting of an RCA would also have weakness/atrophy of thenar muscles. Conversely, patients with median mononeuropathies would have sparing of these muscles. This case highlights RCA in the setting of carpal tunnel syndrome and documents the persistent innervation of the second lumbrical by the median nerve. No anatomic dissections have disclosed innervation of the second lumbrical by the deep ulnar nerve, negating the concept of the all-ulnar hand.

Introduction: It is important to understand the presence of Martin-Gruber anastomosis in patients with complete ulnar neuropathy at the elbow., Case Report: We describe a patient with complete ulnar neuropathy at the elbow and Martin-Gruber anastomosis in the forearm, mimicking incomplete ulnar neuropathy with complete conduction block in the forearm segment. Ultrasonography of the ulnar nerve around the elbow demonstrated severe swelling of the ulnar nerve, which was compatible with severe ulnar neuropathy at the elbow., Conclusions: This case report demonstrates that combination of ultrasonography with electrophysiological studies can provide more detailed information about the changes of nerve structures and lesion sites., (Copyright © 2012 Wiley Periodicals, Inc.)

Various nerve anastomoses and anatomic variants in the nervous system have been described. It is important to be familiar with these anastomoses because they can mimic several clinical conditions, possibly leading to misdiagnosis. We report the case of a patient who experienced progressive loss of strength in his left hand without sensory complaints. On neurological examination atrophy was seen in the thenar and first dorsal interosseous muscles of the left hand. Serial electrophysiological studies ruled out motor neuron disease. Electromyography and nerve conduction studies revealed a Riche-Cannieu anastomosis in the left hand. In combination with piso-hamate hiatus syndrome, this anastomosis explained the clinical condition of the patient. It is important to be aware of this anastomosis and this syndrome because it can mimic motor neuron disease.

During a routine dissection we observed an anatomical variation of the median nerve and an atypical anastomosis in the palm region of a male cadaver. There were four distinct recurrent motor branches of the left median nerve, and the palmar cutaneous branch of the ulnar nerve communicated directly with the third common palmar digital nerve. The presence of such an anatomical variant in the hand should keep surgeons alert in the management of hand pathology especially in carpal tunnel syndrome, which is a routine operation for many medical centres.

The incidence of Martin-Grüber medio-ulnar communicating branch (MUCB), from median nerve to ulnar nerve, is about 20%. To avoid operative injury to MUCB, the authors suggest some modifications to the medial approach of the elbow. They suggest medial aponeurotomy of the anterior compartment of the forearm, disinsertion of the medial epicondylar muscles with dissection between the flexor carpi ulnaris (FCU) and the other medial epicondylar muscles, not exceeding 3 cm distally. This allows a valuable exposure of the elbow joint through a medial approach, with FCU disinsertion and ulnar nerve transposition preserving the ulnar nerve vascularization, without injury to the MUCB., (Copyright © 2011. Published by Elsevier SAS.)

We observed in a male cadaver the presence of a new type of very long Cannieu-Riche anastomosis between the proximal portion of the deep branch of the ulnar nerve for the adductor pollicis and ramus of the recurrent branch of the median nerve to the superficial head of the flexor pollicis brevis. The clinical relevance of such a communication is the possible preservation of the function of all or part of thenar muscles from the ulnar nerve in case of median nerve lesion. The ignorance of that anomaly can induce obscure clinical, surgical and electroneuromyographical findings. We report on the incidence, the double innervation and the clinical significance of Cannieu-Riche anastomosis and provide a new classification of the various types of this nerval connection.

Flexor carpi ulnaris (FCU) is an ever-present muscle of the anterior flexor compartment of the forearm. Variations of FCU are uncommon, with additional slips or heads of muscles described, and only one reported case of an accessory muscle. We describe a unique clinical case report in which an accessory FCU was identified and describe the findings of 5,000 cadaveric dissections of the forearm, performed as part of an ongoing institutional study of anatomical variations. An aberrant accessory forearm flexor muscle was identified incidentally at the wrist during surgery for an anterior interosseous to ulnar nerve transfer for management of ulnar nerve palsy. This muscle was seen running superficial to the ulnar nerve and radial to the FCU proper, arising from the common flexor origin and inserting at the triquetral carpal bone. This was therefore suitably acknowledged as an "accessory FCU". The anomaly was identified as bilateral using ultrasound imaging, and was found to be anomalously innervated by the median nerve with nerve conduction studies. A subsequent review of 5,000 cadaveric dissections of the forearm did not identify any such variations related to FCU, despite identifying a range of variations of the other forearm flexor musculature. While the scarcity of this anomaly is thus highlighted, consideration of an accessory FCU, and its aberrant innervation is important in a range of surgical approaches., (2010 Wiley-Liss, Inc.)

The Martin-Gruber anastomosis (MGA) is the most common anatomic variation in the upper extremity. Anomalous superficial radial innervation to the ulnar dorsum of the hand is the most common cause of an absent dorsal ulnar cutaneous (DUC) response. The coexistence of these variants introduces a relatively common yet underrecognized potential pitfall in nerve conduction studies (NCS). We performed confirmatory NCS in two cases referred for ulnar neuropathy in the forearm (case 1) and at the elbow (UNE, case 2). Initial NCS in both cases suggested ulnar nerve injury at the forearm and elbow, respectively, based on an apparent conduction block in ulnar motor fibers in the forearm (case 1) and elbow (case 2), and absent DUC responses. Additional NCS documented an MGA in the mid-forearm (case 1) and high proximal forearm (case 2) with anomalous superficial radial innervation to the ulnar dorsum of the hand (both cases). Failure to recognize the coexistence of these two common variants may lead to misdiagnosis of ulnar neuropathy and inappropriate treatment.

Objective: This study aimed to clarify the morphology of the Martin-Gruber anastomosis (MGA) in Chinese., Methods: One hundred and five Chinese upper limbs (36 males and 20 femalese) were dissected to find the connections between medial nerve and ulnar nerve. The MGA was classified as previously described by Lee., Results: MGA was found in 24 cases (22.9%), in 11 of the 36 male and 5 of the 20 female. There was no obvious difference in the frequency of MGA in both upper limbs. Most MGA ulnar position was located at the medial and distal segment of the forearm., Conclusion: MGA anatomy could play important role in forensic diagnosis of ulnar nerve injury in Chinese population.

Objective: To explore the basis for the Riche-Cannieu anastomosis (RCA) and specifically whether this anomaly is an hereditary characteristic., Methods: Three individuals from the same family were evaluated after initial studies in the index case indicated an RCA. Nerve conduction, needle electromyography (EMG), and axonal excitability studies of the median and ulnar nerves were undertaken in each case., Results: In all subjects onset thresholds for CMAPs from abductor pollicis brevis (APB) were lower with ulnar nerve stimulation, but of similar latencies when compared with median nerve stimulation. Larger CMAP amplitudes were obtained with ulnar nerve stimulation, at lower stimulus intensities. No sensory anomalies were detected. Needle EMG confirmed dual innervation of APB by both median and ulnar nerves. Nerve excitability studies recorded from APB following ulnar nerve stimulation were within previously established normative limits for the median nerve. In the index case, no innervation anomaly was visible on magnetic resonance imaging from the forearm to hand., Conclusions: Dual innervation of APB by the median and ulnar nerves consistent with RCA was demonstrated in all 3 family members without co-existent sensory anomalies., Significance: These findings infer an hereditary basis for RCA, consistent with an autosomal dominant pattern of inheritance.

This describes the indivisible anastomosis of the main stem of median nerve with ulnar nerve through cubital tunnel followed by the anomaly of ulnar artery that appears as superficial ulnar artery. Both anomalies are found during the anatomical dissection of a grown-up male cadaver, on his right arm. Such case is very rare as, in the literature available to us, it has not been described.

We report on a patient with an unusual anatomic variation along the course of ulnar nerve above the elbow who had cubital tunnel syndrome. The variation consisted of a cutaneous neural branch that was originating at a distance of approximately 40 mm proximal to the medial epicondyle, and from the radial aspect of the main trunk of ulnar nerve. The branch had a superficial course and it was passing distally, anterior to the medial epicondyle without penetrating the fascia of the flexor muscles origin. Anterior intramuscular transposition of the ulnar nerve was performed leaving the newly found branch over the fascia between the muscles and the adipose subcutaneous tissue., (Copyright 2006 Wiley-Liss, Inc.)

During a dissection course, an unusual variation in vascularization and nerve supply of the fifth finger of the right hand was found in a 73-year-old human male cadaver. The proper digital palmar artery arose from the superficial branch of the ulnar artery distel to the Guyon's canal. The proper digital palmar artery coursed first palmar to the ulnar nerve then between the abductor minimi and flexor digiti minimi muscles to reach the ulnar side of the fifth finger. Besides this, the ulnar border of the fifth finger was supplied on its palmar side by the dorsal branch of the ulnar nerve, which gave off two tiny twigs for the sensory innervation on the dorsal side of the same finger.

Kaplan's accessory branch is an aberrant branch of the dorsal cutaneous branch of the ulnar nerve that arises proximal to the styloid process of the ulna and courses ulnar to the pisiform. Variations of this anomaly have been described as having an end point of connection to the sensory branch of the ulnar nerve, to the motor branch of the ulnar nerve (rare), to the digital nerve at the level of the midhypothenar eminence, or to the proximal interphalangeal joint of the small finger or as running as an independent branch to the volar aspect of the small finger. We report a variant of Kaplan's accessory branch that coursed through the insertion of the flexor carpi ulnaris, a groove on the ulnar aspect of the pisiform, and connected to the ulnar nerve trunk proximal to its bifurcation into its motor and sensory branch. Based on the findings of the case presented and a review of the literature we offer a classification system for this anomaly.

An ulnar-to-median anastomosis in the forearm is a rare condition, but may be present in any electromyographic case. A thorough approach to this condition is required to avoid misinterpretation of the electrodiagnostic report and confusion during the test. Prior to concluding that an anomaly is present, technical reason should be taken into consideration. The presence of volume-conducted potentials from various nearby muscles may confuse the electromyographer. Therefore, instead of using surface electrodes with unintended supramaximal intensity of stimulation, the needle electrodes may be used (in some cases) to localize specific muscles and to minimize volume-conducted potentials by not utilizing supramaximal stimulation intensity. The authors will discuss ulnar-to-median anastomosis in the forearm. This is the first attempt to put together all the information available in the literature about such an anastomosis.

A case report is presented of a patient found at surgery to have an anomalous neural loop of the ulnar nerve at the wrist. The literature is reviewed. Although previous cases have been reported with compressive symptoms or as a coincidental finding we believe that this is the first case reported where symptoms were directly related to the presence of the loop without evidence of a compressive lesion.

Anastomosis between the median and ulnar nerve in the forearm has been shown to be of clinical significance. We aimed to determine the presence of median to ulnar nerve communications in the forearm of the Greek population by anatomical studies. At the same time we defined the types and patterns of the anastomoses found and compared them to those reported in similar studies that were retrieved after a wide review of the literature. One hundred and sixty three forearms from 100 cadavers (53 males, 47 females, 25-91 years old) were carefully dissected to observe median and ulnar nerve communication. The anastomosis was found in 10 cadavers; it was bilateral in 4 and unilateral in 6, on the right side in four and on the left side in two. It occurred in 7 of the 53 male cadavers (14%) and in 3 of the 47 females (6.5%). Overall, the anastomosis was found in 14 of the 163 forearms (8.6%). No case of ulnar to median nerve anastomosis in the forearm was found in anatomical examination.

This study aimed to clarify the morphologic variations of the Martin-Gruber anastomosis (MGA) by tracing the anastomotic fascicles. We used 102 upper limbs, and MGA was found in 39.2%. Among 12 instances of MGA between the branches innervating the flexor digitorum profundus muscle, eight anastomotic branches solely innervated the muscle without crossover from median to ulnar nerve. The results of the present study showed three morphologic features of MGA that could not be detected by an electrodiagnostic method.

Anatomical variations of the ulnar nerve have been described at the level of the elbow and in Guyon's canal, while the path in the forearm has always been assumed to be constant. We present a case of compressive ulnar neuropathy at the wrist pre-disposed by a presumed congenital variation of the path of the ulnar nerve at the level of the wrist which improved following surgical release of the constriction caused as a result of it.

Symptomatic progression of congenital ulnar nerve hypoplasia in association with an anomaly of the brachial plexus is uncommon. The authors present such a case involving an 11-year-old girl, who presented with a complaint of progressive numbness and hand weakness occurring in less than 6 months' time. Physical examination revealed limb hypoplasia, neurologic abnormalities, and a palpable hypoplastic ulnar nerve at the level of the cubital tunnel. An additional intraoperative finding was an anomalous brachial plexus. This combined case of congenital ulnar nerve hypoplasia, brachial plexus anomaly, and symptomatic progression, is discussed in the context of other literature.

The prevalence of "ulnar hand" is extremely rare. In the ulnar hand, all the intrinsic hand muscles are innervated exclusively by the ulnar nerve; however, all reported cases have been limited to ulnar motor innervation. We present a case that demonstrated exclusive unilateral ulnar motor and sensory innervation. Although the all ulnar hand is extremely rare, an awareness of this variation is essential for the correct interpretation of the findings on electrodiagnostic examination.