History.
A 6-year-old girl evaluated in the consultation for presenting a Steppage gait due to a left EPC nerve palsy.
The patient had no relevant medical history or family history of neurological disorders.
The symptoms began four months ago with progressive distal motor deficit of the left lower extremity, associated with pain in the lateral face of the left foot and foot.
There was no traumatic history in the limb, according to the interview conducted to the patient and his family.
The physical examination revealed a Steppage gait, due to a severe paresis for the dorsal flexion of the foot and the fingers of the left foot, also appreciating a mild deformity of the seal musculature.
On the lateral side of the left side, at the level of the neck of the fibula, a mass in the fibular nerve was observed, whose percussion produced a positive Tinel sign.
The patient had a strength of 0/5 for the dorsal flexion of the ankle, 1/5 for the extension of the toes, while the foot eversion was almost completely conserved (4/5).
Nerve conduction studies revealed prolonged latency of the left EPC nerve at the knee level above the head of the fibula.
Electromyography showed severe denervation of the muscles of the left anterior compartment with loss of motor units, but the long and short peroneal muscles showed no signs of denervation.
The latency to the dorsalis pedis muscle after stimulating the EPC nerve in the fibular neck was increased and a significant difference was observed when nerve stimulation was performed above or below the fibular head.
Magnetic resonance imaging (MRI) of the knee and left ventricle revealed an enlarged CPE nerve due to a cystic lobule mass measuring long in the neck of the fibula.
The cyst content was hypointense on T1 and hyperintense on T2-spin echo muscle with some hypointense areas.
Changes were also observed in the muscle signal in relation to the denervation of the muscles of the anterior and lateral compartments, in comparison to the posterior compartment of the same consonance.
In the axial and coronal sections of the T2-weighted MRI, the existence of a connection between the cystic mass and the superior tibioperoneal joint, the tail sign, was evidenced.
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Surgical intervention.
A S it approach was used, centered on the lesion by palpation.
After dissection of the superficial planes, the proximal fibular tunnel was opened and cystic lesion, CPE nerve and trifurcation were identified in the superficial, deep and articular branches.
The three branches were affected by cyst expansion.
The articular branch was dissected and exposed throughout its extension, confirming the cyst course towards the superior tibioperoneal joint.
After locating a zone on the surface of the cyst free of nerves (by direct visualization with optical magnification and intraoperative stimulation), a clear fascicle cyst was removed through a longitudinal incision epine viscoural.
The cyst wall was not resected.
Finally, the articular branch was ligated to avoid future recurrences.
The upper tibioperoneal joint was left intact.
Anatomopathological examination confirmed the diagnosis of intraneural cyst.
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Postoperative course.
Postoperative MRI at 3 months showed no cyst recurrence.
During the postoperative follow-up, functional recovery grade 4 + was observed for ankle dorsiflexion and toe extension at 6 months and grade 5 - one year after the intervention.
