The balloon sign: Adn M, Hamlat A, Morandi X, Guegan Y (2006) Intraneural ganglian cyst of the tibial nerve. Acta Neurochir (Wien) 148: 885-890

Tarsal Tunnel Syndrome Due To Three Different Types of Ganglion During a 12-Year Period: A Case Report

A 52-year-old male complained of numbness and radiating pain affecting the plantar region of his left foot. He was found to have recurrent tarsal tunnel syndrome due to posterior tibial nerve compression by 3 different types of ganglion during a 12-year period. To the best of our knowledge, a similar case has not been documented. At the first operation, flexor retinaculum release and simple excision of an epineural ganglion were performed without injuring the nerve fascicles; however, an intrafascicular ganglion developed approximately 2 years later. At the second operation, the ganglion cyst was resected completely to prevent recurrence, despite the risk of nerve fiber injury. The cyst originated from the subtalar joint; thus, the joint was closed, and a free fat graft was placed to prevent adhesion formation. However, an extraneural ganglion occurred about 3 years later. At the third operation, the cyst was resected completely, and a free periosteal graft was used to close the joint more effectively. No recurrence had developed at 6 years after the third operation. The findings of the present case show the need for long-term monitoring of patients with tarsal tunnel syndrome caused by a ganglion owing to the possibility of recurrence related to different ganglion types.

THE UNIFYING ARTICULAR (SYNOVIAL) ORIGIN OF INTRANEURAL GANGLIA

THE PATHOGENESIS OF intraneural ganglia has been an issue of curiosity, controversy, and contention for 200 years. Three major theories have been proposed to explain their existence, namely, 1) degenerative, 2) synovial (articular), and 3) tumoral theories, each of which only partially explains the observations made by a number of investigators. As a result, differing operative strategies have been described; these generally meet with incomplete neurological recoveries and high rates of recurrence. Recent advances in magnetic resonance imaging and critical analysis of the literature have clarified the mechanisms underlying the formation and propagation of these cysts, thereby confirming the unifying articular (synovial) theory. By identifying the shared features of the typical cases and explaining atypical examples or clinical outliers, several fundamental principles have been described. These include: 1) a joint origin; 2) dissection of fluid from that joint along an articular nerve branch, extension occurring via a path of least resistance; and 3) cyst size, extent, and directionality being influenced by pressures and pressure fluxes. We believe that understanding the pathogenesis of these cysts will be reflected in optimal surgical approaches, improved outcomes, and decreased frequency, if not elimination, of recurrences. This article describes the ongoing process of critically analyzing and challenging previous observations and evidence in an effort to prove a concept and a theory.

Intraneural ganglion cyst: a 200-year-old mystery solved

We describe the first reported case of an intraneural ganglion cyst, an ulnar ("cubital") intraneural cyst, which, on literature review, dated to 1810. For over 80 years, its original brief description by Beauchêne was wrongly attributed to Duchenne, effectively making the reference and specimen inaccessible to scrutiny. Fortunately, the intact cyst had been safely housed in the Musée Dupuytren, Paris, France, thus permitting its examination. Although originally described as a "serous" cyst, our present understanding of the anatomy of the ulnar nerve and of peripheral nerve pathology allowed us to reinterpret it as a mucin-filled, elbow-level, ulnar intraneural ganglion cyst. In addition to its description as a fusiform cystic enlargement of the nerve, we documented similar enlargement of a lumen-bearing branch, the articular branch at the level of the elbow. Based on our assessment of the specimen and with a modern perspective, we concluded that the origin of the cyst was from the postero-medial aspect of the elbow joint and that its fluid content, having dissected through a capsular defect, followed the path of the articular branch into the parent ulnar nerve. The purpose of this report is to clarify historical misconceptions regarding the pathogenesis of this controversial entity.

Magnetic resonance imaging of a deep peroneal intraneural ganglion cyst originating from the second metatarsophalangeal joint: a pattern of propagation supporting the unified articular (synovial) theory for the formation of intraneural ganglia

A deep peroneal intraneural cyst of the first web space of the foot is presented. Analysis of the magnetic resonance image scans revealed not only a connection with the medial aspect of the second metatarsophalangeal joint, but also the presence of an interconnected cyst within the lateral digital branch of the hallux. These characteristic magnetic resonance image findings are consistent with those previously described for a peroneal intraneural ganglion cyst that arose from the superior tibiofibular joint, and include (1) origin (ascent) from the second metatarsophalangeal joint with propagation along the articular branch and into the dorsal digital branch of the second toe, (2) cross-over within the shared epineurial sheath of the deep peroneal nerve, and (3) further propagation (descent) within the dorsal digital branch of the hallux. The analogous features between intraneural ganglion cysts affecting small and large-caliber nerves support the fundamental principles of the unified articular (synovial) theory for the formation of intraneural ganglia, including (1) a connection to a synovial joint, (2) dissection of joint fluid through a capsular rent along the articular branch into the parent nerve, and (3) intra-epineurial, pressure-dependent propagation of cyst fluid along paths of least resistance.

LEVEL OF CLINICAL EVIDENCE

4.

Patterns of intraneural ganglion cyst descent

On the basis of the principles of the unifying articular theory, predictable patterns of proximal ascent have been described for fibular (peroneal) and tibial intraneural ganglion cysts in the knee region. The mechanism underlying distal descent into the terminal branches of the fibular and tibial nerves has not been previously elucidated. The purpose of this study was to demonstrate if and when cyst descent distal to the articular branch-joint connection occurs in intraneural ganglion cysts to understand directionality of intraneural cyst propagation. In Part I, the clinical records and MRIs of 20 consecutive patients treated at our institution for intraneural ganglion cysts (18 fibular and two tibial) arising from the superior tibiofibular joint were retrospectively analyzed. These patients underwent cyst decompression and disconnection of the articular branch. Five of these patients developed symptomatic cyst recurrence after cyst decompression without articular branch disconnection which was done elsewhere prior to our intervention. In Part II, five additional patients with intraneural ganglion cysts (three fibular and two tibial) treated at other institutions without disconnection of the articular branch were compared. These patients in Parts I and II demonstrated ascent of intraneural cyst to differing degrees (12 had evidence of sciatic nerve cross-over). In addition, all of these patients demonstrated previously unrecognized MRI evidence of intraneural cyst extending distally below the level of the articular branch to the joint of origin: cyst within the proximal most portions of the deep fibular and superficial fibular branches in fibular intraneural ganglion cysts and descending tibial branches in tibial intraneural ganglion cysts. The patients in Part I had complete resolution of their cysts at follow-up MRI examination 1 year postoperatively. The patients in Part II had intraneural recurrences postoperatively within the articular branch, the parent nerve, and the terminal branches, although in three cases they were subclinical. The authors demonstrate that cyst descent distal to the take-off of the articular branch to the joint of origin occurs regularly in patients with fibular and tibial intraneural ganglion cysts. The authors believe that parent terminal branch descent follows ascent up the articular branch from an affected joint of origin. This mechanism for bidirectional flow explains cyst within terminal branches of the fibular and tibial nerves and is dependent on pressure fluxes and resistances. This new pattern is consistent with principles previously described in a unified (articular) theory, is generalizable to other intraneural ganglion cysts arising from joints, and has important implications for pathogenesis and treatment of these intraneural cysts.

A posttraumatic, joint-connected sural intraneural ganglion cyst-with a new mechanism of intraneural recurrence: a case report

Intraneural ganglion cysts are rare in occurrence and most commonly involve the peroneal nerve at the fibular neck. We present a case of a traumatically induced intraneural ganglion cyst of the sural nerve that developed after a nondisplaced posterior malleolus ankle fracture. The intraneural ganglion cyst was connected to the subtalar joint by its articular branch and ascended several centimeters into the distal fourth of the leg. It was resected from the sural nerve proper and the posterior branch of the lateral calcaneal nerve, and the articular trunk was ligated. The patient developed subclinical intraneural recurrence, which was detected on a postoperative magnetic resonance imaging (MRI). Retrospective reinterpretation of the preoperative and postoperative MRIs revealed that ligation of the articular trunk proximal to a major branch (ie, the anterior branch of the lateral calcaneal nerve) led to increased intraneural cyst propagation distally: within the blind stump of the articular trunk and within several anterior branches of the lateral calcaneal nerve but not within the parent sural nerve or its continuation, the lateral dorsal cutaneous nerve. This mode of intraneural, but extraparental nerve recurrence can be easily understood by considering the altered fluid dynamics, particularly the increased resistance. This case report provides further evidence not only supporting the articular theory of intraneural ganglion formation but also highlighting the importance of searching for, identifying, and treating the pathologic articular branch connection near its joint connection in all cases.

LEVEL OF CLINICAL EVIDENCE

4.