Age / Sex : 10 / F

Age / Sex : F/ 10

Chief complaint : Extension loss of the right great toe developed 2 months before without any traumatic event.

peroneal nerve entrapment syndrome caused by osteochondroma

Discussion

Findings:

Photograph shows on voluntary extension of toes, an extension loss of right great toe was evident.

Plain film shows that an exophytic bony lesion extending from the lateral aspect of proximal fibua demonstrates a corticomedullary continuity.

Saggital MR scans show a protruding mass surrounded by cartilageous cap with low signal intensity on T1 and high signal intensity on T2 WI.

Serial Gradient echo axial scans demonstrate flattening and thickening of the common peroneal nerve lateral to the extruding mass at the level of the fibular neck.

Diagnosis:  

Peroneal nerve entrapment syndrome caused by osteochondroma

Discussion:

 The peroneal nerve is located behind the bony prominence of the fibular neck. It is superficial and covered primarily by subcutaneous tissue and skin. The peroneal nerve is located behind the bony prominence of the fibular neck. It is superficial and covered primarily by subcutaneous tissue and skin.

 This anatomic course and the increased number of fascicles in this area make the nerve extremely vulnerable to injury. Although injury secondary to a fracture, dislocation, surgical procedure, or application of skeletal traction or a tight cast are the major causes of peroneal palsy, nontraumatic lesions also trigger peroneal nerve neuropathy and include mononeuritis, idiopathic peroneal palsy, intrinsic and extrinsic nerve tumors, extraneural compression by a synovial cyst, ganglion cyst, soft tissue tumor, and osseous mass. Peroneal mononeuropathy in children is uncommon. 

Osteochondroma is a benign tumor consisting of projecting bone (exostosis) capped by cartilage. These tumors may be solitary or multiple. Multiple tumors occur in hereditary multiple exostoses syndrome, an autosomic dominant disorder characterized by the formation of multiple bone prominences and developing from the epiphysis. The exostosis begins to develop in childhood and continues to grow until puberty. Osteochondroma is usually asymptomatic and detected as an incidental finding on radiography. It is considered the most common of all bone tumors. Complications are directly related to tumor size and site and can be extrinsic, intrinsic, or mechanical in origin. Extrinsic complications of osteochondroma, due to its mass effect on adjacent tissues, can be subdivided depending on the tissue involved. Nerve compression caused by this lesion is extremely rare, present in <1% of all cases and usually linked to hereditary multiple exostoses syndrome. Few cases of compression of the peroneal nerve by cartilaginous exostosis have been reported in the literature.

References:

1. Proximal fibular osteochondroma with associated peroneal nerve palsy: a review of six cases. J Pediatr Orthop 15:574–577

2. Gallagher-Oxner K, Bagley L, Dalinka MK, Kneeland JB (1994) Case report 822: osteochondroma causing peroneal palsy-imaging evaluation. Skeletal Radiol 23:71–72