Compression of the ulnar nerve in Guyon's canal by an arteriovenous malformation

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.

Clinical and Ultrasonographic Features of Distal Ulnar Neuropathy: A Review

Focal ulnar neuropathy at the wrist is a rare but problematic disorder often associated with the unique anatomy of this nerve as it courses through Guyon's canal, a superficial fibro-osseous tunnel in the proximal ulnar palm. The electrophysiologic features of this disorder have been well-characterized, but the sonographic anatomy of the nerve across the wrist and palm has yet to be systematically described in normal and abnormal states. In this review, we describe the basic anatomy and the sonographic appearance of the nerve in the wrist and palm in normals and individuals with pathology. The value of using US in conjunction with electrodiagnostic testing is emphasized as the two tests together provide critical information regarding etiology, predisposing factors, and functional significance. Furthermore, ultrasound is useful as a patient educational tool to promote behavioral changes that assist in nerve recovery when pathology is related to repetitive stress.

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.

Vascular Malformations, Rare Causes of Sciatic Neuropathy: A Case Series

BACKGROUND:

Sciatica is typically a clear-cut symptom complex commonly related to an impingement at the spinal nerve level. Etiologies of sciatic neuropathy outside the neural foramina are uncommon.

OBJECTIVE:

To describe 4 patients presenting with radiating leg pain due to sciatic nerve involvement, all with a vascular etiology.

METHODS:

Four patients presenting with neuropathic pain were retrospectively reviewed. Preoperative 3 Tesla magnetic resonance imaging was used to identify these lesions, which most commonly showed diffuse T2 changes with nerve enhancement upon administration of contrast.

RESULTS:

Exploration revealed vascular lesions. All patients went on to external and limited internal neurolysis of the involved sciatic nerve segment. Intraoperative histological study confirmed the presence of a venous angioma, an arteriovenous malformation, a venous malformation associated with Klippel-Trenaunay syndrome, and a capillary hemangioma. Follow-up demonstrated stable neurological examinations with reduction in pain at 1 year or greater.

CONCLUSION:

In patients with sciatic distribution symptoms and signs, after initial negative spine imaging, high-resolution imaging of the sciatic nerve itself should be undertaken to address rarer causes such as vascular abnormalities. In these cases, exploration and fascicular biopsy provided a diagnosis; external and limited internal neurolysis improved pain.

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.

Lipoma of Guyon's canal causing ulnar neuropathy

Lipoma is a benign soft tissue tumor which rarely causes neuropathy. In closed compartments such as Guyon’s canal, even small volume loss can lead to compression of nerve. Hence in such areas, even innocuous tumors such as lipomas can cause neuropathy and warrant surgery. We present one such case of ulnar neuropathy caused by lipoma of Guyon’s canal.

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.