Letter to the editor

Abstract

I read with interest the recent report by Fujita et al (1Fujita I. Matsumoto K. Minami T. Kizaki T. Akisue T. Yamamoto T. Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve report of 2 cases and review of the literature.J Foot Ankle Surg. 2004; 43: 185-190Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar) of 2 cases of tibial epineural ganglia at the ankle. These cases supplement the several previously reported cases of intraneural tibial nerve ganglia found within the tarsal tunnel region (2Loeffler F. Volkmann J. Ein seltener Befund bei angeblichen Plattfussbeschwerden (ganglion des Nervenscheide des Tibialis).Zbl Chir. 1920; 47: 1339-1340Google Scholar, 3Jacobs R.R. Maxwell J.A. Kepes J. Ganglia of the nerve. Presentation of two unusual cases, a review of the literature, and a discussion of pathogenesis.Clin Orthop. 1975; 113: 135-144Crossref PubMed Scopus (29) Google Scholar, 4Penkert G. Moringlane J.R. Lorenz R. Intraneurales ganglion des nervus tibialis im tarsaltunnel.Nervenarzt. 1984; 55: 552-555PubMed Google Scholar, 5Høgh J. Benign cystic lesions of peripheral nerves.Int Orthop. 1988; 12: 269-271Crossref PubMed Scopus (24) Google Scholar, 6Poppi M. Giuliani G. Pozzati E. Acciarri N. Forti A. Tarsal tunnel syndrome secondary to intraneural ganglion.J Neurol Neurosurg Psych. 1989; 52: 1014-1015Crossref PubMed Scopus (12) Google Scholar, 7Boyer M.I. Hochban T. Bowen V. Tarsal tunnel syndrome an unusual case resulting from an intraneural degenerative cyst.Can J Surg. 1995; 38: 371-373PubMed Google Scholar) and the nearly 200 total cases of intraneural ganglia occurring in all locations. The pathogenesis of intraneural ganglia has been extremely controversial. Despite the fact that these ganglia occur universally near joints, the most popular theory for many has been a degenerative rather than a synovial explanation. Recent publications (8De Schrijver F. Simon J.P. De Smet L. Fabry G. Ganglia of the superior tibiofibular joint report of three cases and review of the literature.Acta Orthop Belg. 1998; 64: 233-241PubMed Google Scholar, 9Malghem J. Vande Berg B.C. Lebon C.H. Lecouvet F.E. Maldague B.E. Ganglion cysts of the knee articular communication revealed by delayed radiography and CT after arthrography.Am J Roentgenol. 1998; 170: 1579-1583Crossref PubMed Scopus (98) Google Scholar, 10Malghem J. Vande B.B. Lecouvet F. Lebon Ch. Maldague B. Atypical ganglion cysts.JBR-BTR. 2002; 85: 34-42PubMed Google Scholar, 11Spinner R.J. Atkinson J.L.D. Scheithauer B.W. Rock M.G. Birch R. Kim T.A. Kliot M. Kline D.G. Tiel R.L. Peroneal intraneural ganglia the importance of the articular branch. Clinical series.J Neurosurg. 2003; 99: 319-329Crossref PubMed Scopus (126) Google Scholar, 12Spinner R.J. Atkinson J.L.D. Tiel R.L. Peroneal intraneural ganglia the importance of the articular branch. A unifying theory.J Neurosurg. 2003; 99: 330-343Crossref PubMed Scopus (199) Google Scholar, 13Rezzouk J. Durandeau A. Nerve compression by mucoid pseudocysts arguments favoring an articular cause in 23 patients.Rev Chirurg Orthop Reparatrice L’Appareil Moteur. 2004; 90: 143-146Crossref PubMed Google Scholar) have documented compelling evidence supporting a strong link between intraneural ganglia and a joint-related source. As such, I believe that the vast majority, if not all, of the intraneural ganglia are joint-related in nature. A unified theory (12Spinner R.J. Atkinson J.L.D. Tiel R.L. Peroneal intraneural ganglia the importance of the articular branch. A unifying theory.J Neurosurg. 2003; 99: 330-343Crossref PubMed Scopus (199) Google Scholar) that was substantiated to explain joint-related cysts involving the peroneal nerve at the fibular neck region (the most common type of these intraneural ganglia) can be extrapolated to other nerves affected at other sites. In this theory, cyst fluid is produced within a joint, egresses intraneurally (or extraneurally), and propagates along the path of least resistance. For intraneural ganglia, it would appear that dissection may occur either epineurially or intrafascicularly, as described by Fujita et al (1Fujita I. Matsumoto K. Minami T. Kizaki T. Akisue T. Yamamoto T. Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve report of 2 cases and review of the literature.J Foot Ankle Surg. 2004; 43: 185-190Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar). For peroneal intraneural ganglia, in particular, fluid, made in the superior tibiofibular joint, can dissect along the articular branch when subjected to increased intraarticular pressure. This articular branch serves as the conduit between the superior tibiofibular joint and the deep peroneal nerve, from which the articular branch is derived. Once within the articular branch, cyst fluid tends to propagate proximally up the deep peroneal nerve branch, and into the common peroneal nerve, at times, even extending up the sciatic nerve. Joint-related connections for intraneural ganglia have been established for other nerves at varied sites, including the tibial nerve at the knee (14Spinner R.J. Atkinson J.L.D. Harper Jr, C.M. Wenger D.E. Recurrent intraneural ganglion cyst of the tibial nerve. Case report.J Neurosurg. 2000; 92: 334-337Crossref PubMed Scopus (54) Google Scholar), the ulnar nerve at the elbow (13Rezzouk J. Durandeau A. Nerve compression by mucoid pseudocysts arguments favoring an articular cause in 23 patients.Rev Chirurg Orthop Reparatrice L’Appareil Moteur. 2004; 90: 143-146Crossref PubMed Google Scholar, 15Hori S. Surgimura I. Muraoka H. Tatsukawa K. Kuori H. [Intraneural ganglion of the ulnar nerve. Report of two cases.].Orthop Surg Trauma Surg. 1986; 35: 269-273Google Scholar), and the median or ulnar nerve at the wrist (13Rezzouk J. Durandeau A. Nerve compression by mucoid pseudocysts arguments favoring an articular cause in 23 patients.Rev Chirurg Orthop Reparatrice L’Appareil Moteur. 2004; 90: 143-146Crossref PubMed Google Scholar, 16Jaradeh S. Sanger J.R. Maas E.F. Isolated sensory impairment of the thumb due to an intraneural ganglion cyst in the median nerve.J Hand Surg. 1995; 20B: 475-478Crossref Scopus (25) Google Scholar, 17Zielinski C.J. Intraneural ganglion of the ulnar nerve at the wrist.Orthopedics. 2003; 26: 429-430PubMed Google Scholar), for example. A connection of an intraneural ganglion to a joint at the foot or ankle region has been reported in only one instance. Notably, Høgh (5Høgh J. Benign cystic lesions of peripheral nerves.Int Orthop. 1988; 12: 269-271Crossref PubMed Scopus (24) Google Scholar) described a case of a tibial intraneural ganglion with an ankle joint connection via a pedicle. Based on this unified theory and by extrapolation, I believe the “pedicle” in Høgh’s case represented a neural connection to the joint (namely an articular branch). Therefore, it seems quite plausible that tibial intraneural ganglia could form in this way, arising from a neighboring joint in the vicinity of the tarsal tunnel, and gaining access to the tibial nerve or one of its branches directly from an articular branch. It seems unlikely that increased pressure from a ganglion arising from a tendon sheath could penetrate the epineurium or induce an associated degenerative phenomenon leading to an intraneural ganglion, (1Fujita I. Matsumoto K. Minami T. Kizaki T. Akisue T. Yamamoto T. Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve report of 2 cases and review of the literature.J Foot Ankle Surg. 2004; 43: 185-190Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar) although it may result in extrinsic neural compression as reported by several other authors. It is quite understandable that joint connections for tibial nerve ganglia at the ankle have not been identified. These intraneural ganglia are extremely rare and are often reported retrospectively as isolated case reports of “surgical curiosities.” A joint connection of intraneural ganglia is not widely known by surgeons and is easily missed. Those unaware of the possibility of a joint connection do not look for one at surgery. However, even those surgeons knowledgeable of the articular branch connection may not identify it when it is extremely small. Imaging studies were not performed in earlier reports. In fact, in other examples of intraneural ganglia in which routine imaging modalities did not display an obvious joint connection, specialized imaging techniques (high resolution and even delayed imaging studies) performed by and interpreted by experienced radiologists were necessary to reveal occult joint connections for intraneural ganglia (8De Schrijver F. Simon J.P. De Smet L. Fabry G. Ganglia of the superior tibiofibular joint report of three cases and review of the literature.Acta Orthop Belg. 1998; 64: 233-241PubMed Google Scholar, 9Malghem J. Vande Berg B.C. Lebon C.H. Lecouvet F.E. Maldague B.E. Ganglion cysts of the knee articular communication revealed by delayed radiography and CT after arthrography.Am J Roentgenol. 1998; 170: 1579-1583Crossref PubMed Scopus (98) Google Scholar, 10Malghem J. Vande B.B. Lecouvet F. Lebon Ch. Maldague B. Atypical ganglion cysts.JBR-BTR. 2002; 85: 34-42PubMed Google Scholar, 11Spinner R.J. Atkinson J.L.D. Scheithauer B.W. Rock M.G. Birch R. Kim T.A. Kliot M. Kline D.G. Tiel R.L. Peroneal intraneural ganglia the importance of the articular branch. Clinical series.J Neurosurg. 2003; 99: 319-329Crossref PubMed Scopus (126) Google Scholar, 12Spinner R.J. Atkinson J.L.D. Tiel R.L. Peroneal intraneural ganglia the importance of the articular branch. A unifying theory.J Neurosurg. 2003; 99: 330-343Crossref PubMed Scopus (199) Google Scholar). Little attention has been paid to the importance of the articular innervation of joints of the foot and ankle region from nerves in the tarsal or plantar tunnels (18Sarrafian S.K. Anatomy of the Foot and Ankle. ed 2. 1993Google Scholar). This anatomy is fundamental to understanding the intraneural ganglia. As additional cases of tibial intraneural ganglia are seen, radiologists need to look specifically for an articular connection preoperatively and surgeons, intraoperatively, and then document these findings. Comprehending the pathoanatomy and pathogenesis of intraneural ganglia is the first step in their successful treatment. Our lack of understanding of this entity is highlighted by the high postoperative recurrence rate in patients with intraneural ganglia (located at other sites). Ironically, it is at reexploration of intraneural recurrences that joint connections are first established, after an initial surgery that did not reveal a connection.