History.
A 9-year-old boy complained of pain on the lateral side of the foot and lack of strength on the right side when practicing sports.
Three months later, there was evidence of a clear paresis for the dorsal flexion of the foot, which was initially evaluated by neurology and then by neurosurgery.
The patient had no history of trauma in the affected limb.
Physical examination revealed a steppage gait, with severe paresis for extension and eversion of the foot and extension of the toes (grade 1/5).
A mass was clearly seen at the level of the fibula neck, with a sign of Tinel present.
Nerve conduction studies of the right lower limb evidenced acute and chronic denervation of muscles innervated by the superficial and deep branches of the EPC nerve.
The amplitude and latency of the peroneal nerve were pathological at the level of the fibula neck.
Magnetic resonance imaging of the right knee showed a cystic mass along the course of the EPC nerve at the level of the fibular neck, with an extension of 52 mm, starting from the lateral part of the popliteal fossa.
As in case 1, the cyst content was hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences, with hypointense areas.
Changes related to muscle denervation of the anterior and lateral compartments were also observed.
There was no evidence of the tail sign on MRI images, but the presence of an intraneural cyst was suspected due to the presence of a slow-growing non-solid mass in the external sciatic nerve path.
Surgical intervention.
Similar to patient 1, in this case the approach allowed the identification of the three nerve branches, as well as cystic lesion content.
Intraoperative stimulation identified both motor branches.
The resection of the lesion was complete and included ligation and subsequent section of the small joint branch.
Postoperative course.
The evaluation one year later showed a complete recovery of the previous deficit, and MRI ruled out any sign of lesion recurrence.
