Ulnar nerve double crush by entrapment of a peri-cubital tunnel ganglion cyst and cubital tunnel: a case report

Abstract

Background

Double crush syndrome (DCS) is a relatively rare nerve compression syndrome among peripheral nerve compression diseases. However, ulnar nerve double entrapment caused by peri-cubital tunnel ganglion cysts has been rarely reported.

Case presentation

Here, we present a case of a 54-year-old woman who experienced occasional pain, numbness and paralysis in her right half hand for 1 year. A B-ultrasound of the right elbow initially revealed cubital tunnel syndrome only. Further Magnetic Resonance Imaging (MRI) showed a ganglion cyst near the cubital tunnel. After evaluation, we performed open surgery to excise the cyst and incise the cubital tunnel, completely decompressing the ulnar nerve entrapment. Ulnar nerve anterior transposition was also performed simultaneously.

Conclusions

The patient was followed up for 1 month, and she experienced a complete recovery with no functional limitations.

Clinical trial number

Not applicable.

Background

Cubital tunnel syndrome ranks the second most common compressive peripheral neuropathy following carpal tunnel syndrome [1]. DCS represents a distinct condition involving compression at two or more locations along the course of a peripheral nerve, which can concurrently exacerbate symptom severity [2]. Since its conceptualization in 1973, cases of DSC alongside cubital tunnel syndrome have mainly been associated coexisting conditions such as Guyon canal syndrome, thoracic outlet syndrome and cervical radiculopathy [3]. Here, we report a case of woman diagnosed with DCS resulting from entrapment of ulnar nerve at two locations around the elbow, along with a brief literature review.

Case presentation

The patient was a 54-year-old female, a housewife, who presented to our hospital in August 2023 with complaints of intermittent pain and numbness in ulnar nerve distribution of her right hand over the past year. There was no history of trauma, and no other pertinent medical related history was reported. Upon specialist physical examination, the patient exhibited a positive Froment’s sign in her right hand, worse than the contralateral side. Additionally, the Tinel sign was elicited over the right elbow, and the patient reported tenderness and muscular atrophy in the hypothenar eminence. Mild claw deformity was noted in the fourth and fifth finger. Electromyography (EMG) examination of both upper limbs showed decreased motor and sensory conduction function of the right ulnar nerve (motor conduction velocities 47.3 m/s, sensory 49.7 m/s). Local B-ultrasound examination of the right cubital tunnel demonstrated significant thickening and edema of the ulnar nerve, suggestive of entrapment and indicative of cubital tunnel syndrome (Fig. 1a-b). MRI of the right elbow joint revealed ulnar neuritis and mass occupying out of the cubital tunnel, although this was not well visualized on B-ultrasound (Fig. 1c-d). The maximum diameter of the cyst was approximately 2 cm on MRI, and the cross-sectional area (CSA) of the ulnar nerve, as shown on B-ultrasound, was 7 mm² in the mid-upper arm and 16 mm² proximal to the cubital tunnel (Fig. 1a, b). Although with no conservative measure for 1 year, according to the patient’s clinical presentation and moderate dysfunction on the cubital tunnel syndrome dysfunction scale, long-term lack of symptom relief indicated the necessity of open surgery [4].

Fig. 1

a-b. B-ultrasound images showed the cross sectional area of the ulnar nerve in the mid-upper arm was 7 mm², and proximal to the cubital tunnel, it was 16 mm²,and within the cubital tunnel the nerve had a reduced thickness of 3.8 mm.; c-d. Display of magnetic resonance imaging before medical intervention showing a giant ganglion cyst (2*1.8*1.5 cm³) occupying the trajectory of the ulnar nerve and a hyperintense lesion at the cubital tunnel on T2-weighted images in sagittal and coronal section; e. The ulnar nerve appeared extremely thin, highly tense, and nearly resembling a flattened transparent straw on the surface of the cyst; f. The edematous ulnar nerve was isolated outside of the cubital tunnel; g. The cyst was completely isolated, and ulnar nerve was fully decompressed; *. ulnar nerve compressed by the ganglion cyst; p. proximal, distal is on the operative area contralaterally

The trajectory of the ulnar nerve was surgically explored with appropriately extended distal incision. At the cubital tunnel, the ulnar epineurium was found to be thickened and adhered. The cyst was discovered underneath the flexor carpi ulnaris, outside of the cubital tunnel. Upon exposure of ganglion cyst surface, the ulnar nerve appeared severely compressed, exhibiting significant tension and resembling a flattened, transparent straw (Fig. 1e-g). The entire cyst stem was excised, releasing the nerve entrapment. External neurolysis of the ulnar nerve and anterior subcutaneous transposition were performed carefully to release the entrapment and relocate the ulnar nerve onto a soft tissue bed. The excised cyst was sent for histopathological examination, and was confirmed as a ganglion cyst (Fig. 2).

Fig. 2

Histopathology of the lesion demonstrating features of a ganglion cyst

The patient was evaluated 2 weeks post-surgery, showing improvement in motor function and some reduction in dysesthesia. A follow-up EMG examination one month later indicated that the motor conduction function of the right ulnar nerve had returned to normal, while the sensory conduction function remained diminished. Nevertheless, the symptoms were significantly alleviated.

Discussions

Examples of double entrapment involving compression and cubital tunnel entrapment unrelated to trauma are rare. DCS refers to a condition when in a peripheral nerve is entrapped in one location, yet symptoms of distal or proximal nerve compression manifest simultaneously [5, 6]. Clinically, combinations such as cervical spondylosis or thoracic outlet syndrome combined with carpal tunnel syndrome, cubital tunnel syndrome with Guyon tunnel syndrome can occur. Despite its recognition, standardized definition of double crush syndrome remains unknown, and consensus on its precise pathophysiology or diagnostic criteria has yet to be reached [7].

Typically, DCS of ulnar nerve is often associated with Guyon canal syndrome, thoracic outlet syndrome, and cervical radiculopathy. However, in our case, the primary cause of ulnar nerve entrapment was attributed to an out-elbow ganglion cyst. During the operation, we observed the thinning of the nerve at cyst site of the cyst and signs of neuritis at the cubital tunnel. Unlike the findings of Chang’s research [8], which identified cubital tunnel syndrome caused by intraneural or extraneural ganglia within the cubital tunnel itself, our case involved the giant ganglion cyst that exerted pressure and extrusion without confinement to a specific tunnel. Similarly, Li [9] reported a case of cubital tunnel syndrome caused by an intraneural ganglion cyst in a 57-year-old female, who underwent ultrasound-guided aspiration and ulnar nerve decompression but had symptom recurrence, leading to open cyst excision, external nerve decompression, and subcutaneous transposition, with complete recovery over two years. Previous studies have indicated that US, EMG, and MRI are commonly utilized preoperative examinations, with open surgical approaches demonstrating favorable clinical outcomes in patients [9,10,11,12,13,14]. This prompted our hypothesis that the mass compression extended the ulnar nerve, and the long-term pulling and friction during elbow joint movements may have contributed to the occurrence of cubital tunnel ulnar neuritis.

In this case, based on clinical manifestations, auxiliary examination, and intraoperative conditions, the patient presented with both cubital tunnel syndrome and double-site entrapment of an intramuscular ganglion cyst in the ulnar forearm. Symptoms caused by peri-cubital tunnel ganglion cysts warrant careful consideration. Not only with B-ultrasound, elbow joint MRI should be performed to exclude space-occupying lesions within the muscle or intermuscular space prior to surgery. Therefore, early diagnosis, careful preoperative imaging assessment and complete decompression can be expected to result in favorable rehabilitation outcomes.