Ulnar nerve compression in Guyon's canal in the presence of a tortuous ulnar artery

Uncommon Anatomical Causes of Ulnar Compression: A Narrative Review

OBJECTIVES

Some patients develop ulnar nerve compression due to rare anatomical variations or malformations. The aims of this review are to provide a comprehensive overview of anatomical structures and variations that can cause ulnar nerve compression and to evaluate treatment options.

METHODS

Case reports and case series about rare cases of unusual ulnar nerve compression published from January 2000 until April 2022 were obtained from databases Embase, MEDLINE, and Web of Science. A total of 48 studies describing 64 patients were included in our study.

RESULTS

The following structures have proven to cause ulnar nerve compression: anconeus epitrochlearis, accessory abductor digiti minimi, vascular anomalies, palmaris longus, fibrous bands, and flexor carpi ulnaris. All cases except one have had a surgical release of the ulnar nerve resulting in diminished symptoms or complete recovery at follow-up.

CONCLUSIONS

In addition to considering common compression points, it is important to be aware that proximal compression symptoms, such as pain and a positive Tinel sign at the medial elbow, may be attributed to a hypertrophic AE or vascular anomaly. Distal compression symptoms encompass swelling, along with pain and a positive Tinel sign at the distal forearm. Various structures contributing to distal compression include an accessory abductor digiti minimi muscle, an accessory or anomalous palmaris longus muscle, or an accessory or hypertrophic flexor carpi ulnaris muscle. The occurrence of fibrous bands exhibits variability, manifesting in diverse locations across the arm.Level of Evidence: IV.

Prospective outcome analysis of ulnar tunnel syndrome: Comparing traumatic versus non-traumatic etiologies

BACKGROUND

Ulnar tunnel syndrome (UTS) is relatively uncommon compared to the carpal tunnel or cubital tunnel syndromes. Few reports dedicated to the functional outcomes after surgical intervention of the UTS exist. Herein we compare the outcomes of patients with UTS of different etiologies.

METHODS

Patients diagnosed with UTS between 2016 and 2020 were recruited. Ulnar tunnel release was performed in all patients, along with other necessary osteosynthesis or reconstructive procedures in the traumatic group. Patients were followed-up every six months post-operatively. Outcomes measured include: objective evaluations, subjective questionnaires, records of clinical signs, and grading of the British Medical Research Council scale for intrinsic muscle strength.

RESULTS

21 patients were recruited, and favorable results were noted in all of them after surgery. Traumatic UTS patients had a worse initial presentation than the non-traumatic cases, but had a greater improvement after surgery and yielded outcomes comparable with those of the patients without trauma. Patients with aberrant muscles in their wrists had better outcomes in some objective measurements than those without aberrant muscles.

CONCLUSIONS

Ulnar tunnel release improves the outcome of patients regardless of the etiology, especially in patients with trauma-induced UTS. Thus, a proper diagnosis of the UTS should be alerted in all patients encountering paresthesia in the ulnar digits, ulnar-sided pain, weakness of grip strength, or intrinsic weakness to ensure good outcomes.

Tortuous ulnar artery presenting as left distal forearm mass

Knowledge of anatomic variation in vasculature is critical to safe medical intervention as conduits vary in morphology, architecture, and course. Tortuosity is a common anatomic variant in certain arterial beds; however, its prevalence in ulnar arteries is not well documented in the literature. Here we report two cases of tortuous ulnar arteries in patients being evaluated for upper extremity hemodialysis access.

Isolated Compression of the Ulnar Nerve Motor Branch: A Case Series With 3 Unique Etiologies

BACKGROUND

Although ulnar neuropathies are commonly encountered, isolated involvement of the motor branch is exceedingly rare. Previous reports of this entity describe compression as the deep motor branch passes through the piso-hamate hiatus and the adductor pollicis hiatus. This case series described 3 cases of motor branch compression due to unique etiologies which resolved after surgery.

METHODS

A retrospective chart review identified patients with compression of the ulnar nerve motor branch. From these patients, 3 were selected with a unique etiology for compression. Patient demographics, objective and subjective findings, and pathology identified during surgery were recorded and analyzed.

RESULTS

Eight patients had compression of the ulnar nerve motor branch and 3 unique etiologies were selected; an intraneural ganglion, a constricting leash of vessels, and a series of compressing fibrous bands. All required surgery, and each patient had full resolution of symptoms by 1 year postoperatively.

DISCUSSION

Patients presenting with complaints of weakness with a positive Froment and Egawa signs but a negative Wartenberg sign and no sensory complaints can be a diagnostic dilemma. Compression of the ulnar nerve motor branch must be considered, and here we present 3 unique cases. Activity modification in those presenting early may be curative, although many ultimately require surgery. In the cases presented here, all patients experienced full resolution of their symptoms by 1 year after surgery.

Looped and Tortuous Ulnar Artery - An Erratic Unilateral Vascular Presentation in the Proximal Forearm

Precise and detailed knowledge of possible anatomical variations of the arterial pattern in the upper extremity is vital during reparative surgery in this region. Scientific literatures witnessed several reports on variant origin and branching pattern of ulnar artery. But report on looped and tortuous ulnar artery is lacking in the literature. We report here a unique case of ulnar artery having double loop at its commencement giving it an appearance of sigmoid shape and its undue tortuous course in the forearm. Such an unusual and unpredictable variation of ulnar artery is vulnerable for life threatening hemorrhage during clinical approaches. It could also lead to misinterpretation of CT scans as presence of tumours. Awareness on such exceptional anatomical discrepancy of ulnar artery is important to clinicians, neuroradiologists and radiologists in general.

Ulnar tunnel syndrome

Ulnar neuropathy at or distal to the wrist, the so-called ulnar tunnel syndrome, is an uncommon but well-described condition. However, diagnosis of ulnar tunnel syndrome can be difficult. Paresthesias may be nonspecific or related to coexisting pathologies, such as carpal tunnel syndrome, cubital tunnel syndrome, thoracic outlet syndrome, C8-T1 radiculopathy, or peripheral neuropathy, which makes accurate diagnosis challenging. The advances in electrodiagnosis, ultrasonography, computed tomography, and magnetic resonance imaging have improved the diagnostic accuracy. This article offers an updated view of ulnar tunnel syndrome as well as its etiologies, diagnoses, and treatments.

Uncommon upper extremity compression neuropathies

Hand surgeons routinely treat carpal and cubital tunnel syndromes, which are the most common upper extremity nerve compression syndromes. However, more infrequent nerve compression syndromes of the upper extremity may be encountered. Because they are unusual, the diagnosis of these nerve compression syndromes is often missed or delayed. This article reviews the causes, proposed treatments, and surgical outcomes for syndromes involving compression of the posterior interosseous nerve, the superficial branch of the radial nerve, the ulnar nerve at the wrist, and the median nerve proximal to the wrist.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

T2-signal of ulnar nerve branches at the wrist in guyon's canal syndrome

OBJECTIVE

To evaluate T2-signal of high-resolution MRI in distal ulnar nerve branches at the wrist as diagnostic sign of guyon's-canal-syndrome (GCS).

MATERIALS AND METHODS

11 GCS patients confirmed by clinical/electrophysiological findings, and 20 wrists from 11 asymptomatic volunteers were prospectively included to undergo the following protocol: axial T2-weighted-fat-suppressed and T1-weighted-turbo-spin-echo-sequences (3T-MR-scanner, Magnetom/Verio/Siemens). Patients were examined in prone position with the arm extended and wrist placed in an 8-channel surface-array-coil. Nerve T2-signal was evaluated as contrast-to-noise-ratios (CNR) from proximal-to-distal in ulnar nerve trunk, its superficial/sensory and deep/motor branch. Distal motor-nerve-conduction (distal-motor-latency (dml)) to first dorsal-interosseus (IOD I) and abductor digiti minimi muscles was correlated with T2-signal. Approval by the institutional review-board and written informed consent was given by all participants.

RESULTS

In GCS, mean nerve T2-signal was strongly increased within the deep/motor branch (11.7±4.8 vs.controls:-5.3±2.4;p = 0.001) but clearly less and not significantly increased in ulnar nerve trunk (6.8±6.4vs.-7.4±2.5;p = 0.07) and superficial/sensory branch (-2.1±4.9vs.-9.7±2.9;p = 0.08). Median nerve T2-signal did not differ between patients and controls (-9.8±2.5vs.-6.7±4.2;p = 0.45). T2-signal of deep/motor branch correlated strongly with motor-conduction-velocity to IOD I in non-linear fashion (R(2) = -0.8;p<0.001). ROC-analysis revealed increased nerve T2-signal of the deep/motor branch to be a sign of excellent diagnostic performance (area-under-the-curve 0.94, 95% CI: 0.85-1.00; specificity 90%, sensitivity 89.5%).

CONCLUSIONS

Nerve T2-signal increase of distal ulnar nerve branches and in particular of the deep/motor branch is highly accurate for the diagnostic determination of GCS. Furthermore, for the first time it was found in nerve entrapment injury that T2-signal strongly correlates with electrical-conduction-velocity.

Ulnar tunnel syndrome

Ulnar tunnel syndrome could be broadly defined as a compressive neuropathy of the ulnar nerve at the level of the wrist. The ulnar tunnel, or Guyon's canal, has a complex and variable anatomy. Various factors may precipitate the onset of ulnar tunnel syndrome. Patient presentation depends on the anatomic zone of ulnar nerve compression: zone I compression, motor and sensory signs and symptoms; zone II compression, isolated motor deficits; and zone III compression; purely sensory deficits. Conservative treatment such as activity modification may be helpful, but often, surgical exploration of the ulnar tunnel with subsequent ulnar nerve decompression is indicated.

Subluxation-related ulnar neuropathy (SUN) syndrome related to distal radioulnar joint instability

Ulnar neuropathy coexistent with distal radioulnar joint (DRUJ) instability has previously been observed in our practice. The aim of this study was to define this phenomenon and investigate the hypothesis that the cause of this intermittent, positional ulnar neuropathy is related to kinking of the ulnar nerve about the DRUJ. Ulna neuropathy was present in 10/51 (19.6%) of a historical cohort of patients who presented with DRUJ instability. Nine subsequent patients with DRUJ instability and coexistent ulnar neuropathy underwent 3-T magnetic resonance imaging to better understand the mechanism of the observed syndrome. Both 3D qualitative and quantitative analyses were used to assess the presence of nerve 'kinking', displacing the nerve from its normal course and causing nerve compression/distraction in the distal forearm and Guyon's canal. Results of the quantitative analysis were statistically significant (p < 0.05). The clinical features of the condition have been delineated and termed subluxation-related ulnar neuropathy or SUN syndrome. The imaging study was a level II diagnostic study.

The arcade of Struthers: An anatomical study with potential neurosurgical significance

BACKGROUND

Significant controversy exists regarding the existence of the so-called arcade of Struthers and whether this structure is involved in some cases of proximal ulnar nerve entrapment. Therefore, the aim of the present study was to further elucidate this anatomy.

METHODS

Fifteen cadavers (30 sides) underwent dissection of the medial arm with special attention to the course of the ulnar nerve and its relationships to the soft tissues of this region.

RESULTS

We identified a thickening in the inferior medial arm that crosses the ulnar nerve and is consistent with the so-called arcade of Struthers in 86.7% of sides. On 57.7% of the sides, the arcade was found to be due to a thickening of the brachial fascia and was classified as a type I arcade. On 19.2% of the sides, the arcade was due to the internal brachial ligament and these were classified as type II arcades. On 23.1% of the sides, the arcade was due to a thickened medial intermuscular septum and these were classified as type III arcades. The mean length of the arcade was 4.3 cm and the distal end of the arcade was, on average, 6.8 cm above the medial epicondyle. Although the presence of an arcade of Struthers was slightly more common in female specimens, this did not reach statistical significance. However, arcades were found more often on right side (P < 0.001).

CONCLUSIONS

Based on our findings, the arcade of Struthers is an anatomical band of connective tissue in the medial distal arm that crosses the ulnar nerve. This structure was found in the majority of our specimens and may need to be evaluated in proximal ulnar neuropathies. We believe that past studies that have not observed the arcade and past studies with varied findings are due to the various definitions used for this anatomical structure. Using the classification system as demonstrated in the present study may make future communications regarding the arcade of Struthers more exact.

Guyon's canal syndrome: a rare case of venous malformation

This paper describes an unusual case of parasthesia in the medial two fingers of the hand in a 56-yearold lady. MRI suggested a space occupying lesion and on exploration this proved to be a venous malformation causing a pressure neuropathy of the ulnar nerve.

Ulnar Nerve Compression at Guyon's Canal by an Arteriovenous Malformation

Guyon's canal at the wrist is not the common site of ulnar nerve compression. Ganglion, lipoma, anomalous tendon and muscles, trauma related to an occupation, arthritis, and carpal bone fracture can cause ulnar nerve compression at the wrist. However, ulnar nerve compression at Guyon's canal by vascular lesion is rare. Ulnar artery aneurysm, tortous ulnar artery, hemangioma, and thrombosis have been reported in the literature as vascular lesions. The authors experienced a case of ulnar nerve compression at Guyon's canal by an arteriovenous malformation (AVM) and the patient's symptom was improved after surgical resection. We can not easily predict vascular lesion as a cause of ulnar nerve compression at Guyon's canal. However, if there is not obvious etiology, we should consider vascular lesion as another possible etiology.