Can trauma cause tibial intraneural ganglion cysts at the superior tibiofibular joint? (2012)

Our group recently described an association between trauma and common fibular intraneural ganglion cysts arising from the anterior aspect of the superior tibiofibular joint (STFJ) (Spinner et al.,2012). While direct trauma to the proximal leg seems obvious as a potential cause, indirect trauma from torsional injury to the ankle (particularly of an inversion type), though less obvious, should also be considered as a mechanism by extension of translational forces along the interosseous membrane (IOM) to the proximal leg. At that time, although we considered the possibility of tibial intraneural cysts in the popliteal fossa forming in the same manner because of certain similarities of the common fibular and tibial nerves, we could find no evidence to support our hypothesis. The similarities of the common fibular and tibial nerves include: (1) their respective innervation of the STFJ and their articular branch anatomy; (2) their potential compressive sites at the fibular neck and soleus sling, respectively (Williams et al.,2012); (3) the analogous formation of intraneural ganglion cysts from the STFJ as anterior and posterior counterparts (Spinner et al.,2007); and (4) the effect of nerve mechanics (i.e., strain) in the leg (Coppieters et al.,2006; Alshami et al.,2008). Two months after our paper was published online, a case of interest was featured on a radiology list server (One Case a Day): “29-year-old twisted ankle 5 months ago; knee pain.” Images of a tibial intraneural ganglion cyst that originated from the posterior aspect of the STFJ were displayed (Fig. 1). The radiologist who uploaded the images (F.C.) provided us with some additional clinical information that was obtained from the referring orthopedic surgeon. The ankle injury occurred 2 months before the onset of knee pain and mild tibial neuropathy. Because of the relatively minor symptomatology, the patient declined further evaluation or surgery and did not return for additional treatment. This radiologist also allowed the other authors the opportunity to review the complete MRI studies electronically. We present this case to suggest that the same mechanisms described for the formation of ganglion cysts within the common fibular nerve should apply to those within the tibial nerve as well. The abbreviated description by itself provides the basis for exploring a mechanism for a shared injury. The relatively young age of this patient compared to the older age when a degenerative cause is present would support a contributing role of trauma. MRIs. A: Sagittal T2-weighted image with fat suppression just lateral to the intercondylar notch shows the tibial intraneural cyst (asterisks) arising from the posterior aspect of the superior tibiofibular joint (arrow) and extending proximally to the tibial nerve and into the tibial division of the sciatic nerve (arrowhead). The most proximal extension of the cyst was not imaged. B,C: Proton density weighted axial images at the level of the proximal tibia and fibula show the tibial intraneural cyst (asterisks). In (C), the connection along the articular branch (*) to the posterior aspect of the superior tibiofibular joint (arrow) is seen. As has been seen in other cases of tibial intraneural ganglion cysts, the branch to the popliteus muscle is characteristically affected, resulting in selective denervation atrophy of this muscle (+). The tibialis posterior muscle was normal on more distal images. T, tibia; F, fibula; f, femur. Tibial intraneural cysts in the popliteal fossa are rare, especially compared to common fibular nerve intraneural cysts. Excluding rare examples of tibial intraneural ganglion cysts arising from the knee joint, there have been ∼15 reported cases either definitely or presumptively originating from the STFJ (Friedlander,1967; Jacobs et al., 1975; Spinner et al., 2000; Ogata and Hayashi, 2002; Tseng et al.,2006; Gosk et al.,2007; Suh and Moon,2009; Spinner et al.,2009; Davis and Cox,2011; Jose et al.,2011). Only one had a traumatic association: a 40-year-old male manual laborer who sustained direct trauma from a fall, developed immediate symptoms of a tibial neuropathy and was found to have a large tibial intraneural ganglion cyst (Spinner et al.,2000). This patient was supported for a worker's compensation claim at the time based on the apparent cause-effect temporal relationship. In this new case, indirect trauma from an ankle injury could well be envisioned with transmission of the forces along the IOM to the posterior aspect of the STFJ (Fig. 2). Furthermore, we believe that the mechanism of proximal extension of forces from the ankle and along the IOM to the fibular neck in patients with common fibular neuropathy in the absence of cysts (Lalezari et al.,2012), would also apply to injury resulting in tibial neuropathy in the proximal leg. Despite the fact that there are only scattered case reports of combined ankle injuries and tibial neuropathy in the knee region, one group established a strong association with severe ankle sprain, raising the question that this combination of injuries has been underreported (Nitz et al.,1985). Although we are unaware of a similar case of indirect trauma to the ankle resulting in a tibial intraneural or extraneural ganglion cyst from the STFJ, it would seem to be a logical extension. Postulated mechanisms (with permission, Mayo Foundation, 2011). Direct and indirect trauma potentially can lead to a tibial intraneural ganglion cyst in the popliteal fossa, analogous to the mechanisms for those developing posttraumatically in the common fibular nerve at the fibular neck region. Torsion at the ankle translated along the course of the interosseous membrane can cause tension/traction of the tibial nerve in the proximal leg and result a tibial intraneural ganglion cyst arising from the superior tibiofibular joint. In intellectual honesty, we fully acknowledge the lack of supportive science in this letter and the difficulty in “proving” a new mechanism with a single case or two in a rare condition. We realize that the combination of the cysts and trauma in these two cases, particularly, the ankle injury and cyst in the illustrated example, may, in fact, be totally coincidental. The cyst may have been present at a subclinical level before the trauma. The cyst could have enlarged and become symptomatic; the space through which the nerve passes may have decreased in size. The cyst without a change in dimensions still could become symptomatic, if the space the nerve passed through narrowed from inflammation. Alternatively, the cyst and the neuropathy could have predisposed to the ankle injury (Spinner et al.,2012). In the absence of imaging of the ankle and leg, we have no proof that the IOM was abnormal. There are more questions than answers. We present this case and this argument to raise awareness about the possibility of a possible causal association between trauma and tibial intraneural ganglion cysts. Clearly more work is necessary to better define these translational forces and their role on STFJ pressures. Robert J. Spinner**, Frank Crnkovich , Mohanad Ahmed Ibrahim Kobeal*, Kimberly K. Amrami , * Department of Neurologic Surgery Mayo ClinicRochester, Minnesota, Health Images South ParkLittleton, Colorado, Departments of Radiology and Neurologic Surgery Mayo ClinicRochester, Minnesota.