Epineurial ganglion cyst at the cubital tunnel: A rare cause of ulnar neuropathy
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.246248
Source of Support: None, Conflict of Interest: None
Epineurial ganglion cysts are uncommon lesions., Among these, the peroneal nerve at the fibular head is most commonly involved. Ulnar nerve involvement at the elbow is rare and, till date, only a handful of cases have been reported in literature.,,,,, These patients commonly present with motor weakness and pain in the distribution of the involved nerve. Magnetic resonance imaging (MRI) is the best imaging modality for its diagnosis. Surgical excision offers good-to-excellent results.,,, A case of an ulnar nerve epineurial ganglion cyst at the cubital tunnel has been described below, with a literature review, briefing the salient operative steps.
A 63-year old male patient presented to our outpatient services with complaints of a gradually progressive swelling noted in the medial aspect of the distal left arm since 1 month, as well as tingling and shooting pain at the elbow radiating along the medial aspect of the forearm up to the little finger for 3 weeks. The pain was severe and hampered his daily activities considerably. The swelling per se was non-tender but the shooting pain described above was noted on pressing/tapping the swelling. On examination, severe sensory loss (pinprick, light touch, and temperature) was present in the ulnar nerve distribution in the hand (medial aspect of the hand and fourth and fifth digits) and Tinel's sign was positive at the cubital tunnel over the ulnar nerve. At the initial presentation, there were no signs of motor weakness. However, within a span of a few days, he developed clawing of left little and ring fingers, and on examination, there was intrinsic hand muscle (palmar and dorsal interossei, and third and fourth lumbricals) weakness. Nerve conduction studies showed a reduced ulnar nerve conduction velocity across the elbow. On ultrasonography, an anechoic cystic mass was seen apposed to the ulnar nerve along its course in the distal arm extending till the elbow joint. Neither internal echoes were seen nor was there any evidence of blood flow on color Doppler sonography [Figure 1]a and [Figure 1]b. MRI revealed a cystic lesion on the medial aspect of the distal one-third of arm closely apposed to, and coursing along the ulnar nerve, although the nerve could be separately visualized. The cyst was located anteromedial in relation to the nerve, was uniformly hypointense and hyperintense on T1 and T2 sequences, respectively, and showed a rim enhancement. There were also a few small cysts seen distally along the nerve, with no obvious extension to the ulnohumeral joint [Figure 2]a,[Figure 2]b,[Figure 2]c,[Figure 2]d. With a diagnosis of an epineurial ganglion cyst, under a regional anesthetic block, surgical exploration was considered. Intraoperatively, an 8-cm long, cystic lesion containing a clear mucoid, jelly-like content was seen arising from the epineurium and encapsulating the entire ulnar nerve, which seemed flattened and thickened with a normal-appearing nerve being visible superiorly and inferiorly [Figure 3]a and [Figure 3]b. The capsule was fragile but could be dissected off from the underlying epineurial tissue. There was no intraneural extension. Complete excision of the cyst along with the involved epineurium was achieved using standard microsurgical methods [Figure 3]c,[Figure 3]d,[Figure 3]e,[Figure 3]f. There were small cysts extending along the nerve distally, which were also removed in toto. There was no evidence of communication of the cyst with the elbow joint seen during surgery. The nerve was adequately decompressed in its entire length. Histopathology revealed features consistent with a ganglion cyst. He had an excellent relief of his pain immediately after the surgery, that showed gradual recovery over time. At a follow-up of 20-month duration, there was a complete pain resolution, the sensory loss had improved remarkably, and a significant improvement in his motor weakness of intrinsic hand muscles was noted. No clinical evidence of recurrence was noted at follow up visits.
Ganglion cysts are benign lesions most commonly seen along the tendons or joint capsule synovium in the hand or foot. Ganglion cysts can affect the peripheral nerves as well and were first described in 1901.,, These cysts are commonly seen in middle-aged males and affect the dominant hand frequently., They usually present with pain and motor weakness of the involved nerve. Their benign appearance is often misleading. These lesions are often associated with significant motor deficits on presentation, in contrast to milder deficits seen with nerve tumors., In our case too, there was severe sensory loss and wasting of the intrinsic hand muscles.
Three different types of cysts have been described in relation to the peripheral nerves—epineurial (located in the epineurial sheath) or intraneural (located within the nerve between the nerve fascicles) or extra-neural (arising from the adjacent structures and compressing the nerve secondarily). Of these, epineurial cysts are the least common., In the largest review of 38 cases of medial elbow ganglia by Kato et al., all the cysts included in the study originated from the adjacent ulnohumeral joint and none of them were epineurial. In terms of location, peroneal nerve involvement at the fibular head is the most common, occurring in 50% to 75% of cases, followed by ulnar nerve at the wrist.,,,, The ulnar nerve at the elbow is a very rare location for such epineurial cystic lesions. Till date, only a handful of cases have been reported in the literature [Table 1].,,,,, They are mostly found in the fifth-sixth decades and males predominate. A connection with the elbow joint may or may not be present. In our case, we explored the nerve distally up to the joint level where a few small cysts that were found were removed but no connection to the joint was seen. Hence, an exploration needs to be performed distally for a few centimeters to rule out any such joint communications.
The exact etiopathogenesis is not clear; however, multiple theories have been proposed for the occurrence of these cysts. These include cystic degeneration of neurilemmomas, cystic degeneration of the epineurium or perineurium, metaplasia of the connective tissue of the nerve trunk, expansion of synovial rests displaced during embryological development, tracking of ganglion from articular or paraarticular tissue along the sheath of a small articular nerve to its final position in the sheath of a major nerve, traumatic intraneural hemorrhage, and repetitive microtrauma.,,,,
The diagnosis includes a thorough clinical examination, electrophysiological studies and imaging. Nerve conduction studies are often the first investigations to be performed, and in a few reported cases, surgical exploration was considered based only on these nerve conduction findings.,, They uniformly reveal a reduction in the conduction velocities of the affected nerve distal to the site of the lesion. Imaging plays a significant role in the diagnosis of these lesions; however, the importance of a thorough clinical workup cannot be overemphasized. Imaging methods include ultrasonography and MRI. A good ultrasonography with a color Doppler scan is fairly sensitive to visualize and characterize these lesions. These lesions appear well-lobulated, markedly hypo/anechoic, and are located immediately beneath the nerve, with no internal flow voids. MRI helps in confirming these findings, and provides excellent details of the nerve morphology and its relationship to the surrounding structures. It also reveals the extent and possible communication with the adjacent joint., On MRI, these lesions are usually multilocular, hypointense on T1 and hyperintense on T2 images, and show minimal/no enhancement., The important differential diagnoses include nerve sheath tumors, lipomas, and rarely glomus tumors.
The mainstay of treatment is surgery with the goals of stabilizing or improving the preoperative deficits. The ideal treatment is complete surgical resection, but this is, however, difficult and often not possible in an intraneural GC, for fear of causing new deficits. In such cases, an incision and drainage has been recommended by many authors, probably at the cost of increased recurrence rates. In the cases of intraneural cysts manifesting with severe deficits, resection and grafting might also be a viable option. Other treatment methods reported include drainage and partial removal of the cyst wall, CT-guided aspiration, and in cases of extension to adjacent joints, curettage of the joints to prevent recurrences.,,
The outcome depends on several factors that include the severity of preoperative deficits, the duration of symptoms, and whether or not, the lesion has an epineurial/intraneural location. A short duration of symptoms (less than 1 year) with mild deficits at presentation and an epineurial location have been found to be favorable factors for recovery.,,,, As a thumb rule, pain and sensory changes recover faster and more consistently than motor deficits. There seems to be a difference in outcome in patients who present early (<1 year) than those with delayed presentations.,, Hence, an early recognition by electrophysiological and imaging studies, and prompt surgery is recommended to optimize the outcome.,
Recurrences are known, ranging from 17% to 25%, with the mean time to recurrence being 16 months, as quoted in one report. Reexpansion of the residual duct or growth of a new duct/cyst from the joint capsule are possible explanations for the recurrence. A recurrence of symptoms is thought to herald the recurrence of the cyst. Long-term follow-up is, however, recommended, as delayed recurrences have been noted to occur many years after the primary surgery.
To conclude, epineurial ganglion cysts of the ulnar nerve at the cubital tunnel are very rare lesions. Pain and motor weakness are the predominant symptoms. A thorough clinical workup with appropriate imaging studies assist in arriving at a correct diagnosis. Early and prompt surgery is mandatory to optimize outcome. A short duration of symptoms and milder preoperative deficits correlate with a good outcome. Long-term follow-up is required to detect delayed recurrences.
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[Figure 1], [Figure 2], [Figure 3]