Module 35, Pediatric Orthopaedist Level

1, 2, 3, 4, 5, 6, 7

A 2 year and 6 month old white male presented to clinic with a 2-3 month history of limping on the right lower extremity. There was no history of trauma to the extremity, or a history of constitutional symptoms such as fever, chills, sweats, malaise or weight loss. Prenatal, perinatal and postnatal course were all normal. Examination of the right lower extremity was significant for a distinct absence of ankle dorsiflexion and eversion activity to motor testing. Plantar flexion strength was graded as 5/5. Sensation was intact on the entire plantar aspect of the foot, with patchy sensation on the dorsum of the foot, including the first web space. Radiographic examination of the left knee revealed no osseous abnormalities (images 1 and 2). A fullness of the soft tissues was evident over the fibular head. MRI examination of the left knee displayed a 2 cm. by 0.8 cm. lobulated mass in the region of the common peroneal nerve with no enhancement (images 3and 4). On the T-2 weighted sequences there was abnormal increased signal of the tibialis anterior, extensor digitorum longus and peroneus longus muscle bellies suggesting atrophy (images 5, 6 and 7).

Question 35A

Electrodiagnostic tests of the peroneal nerve would be expected to show a definite non-functioning nerve.

Question 35B

Based on this imaging, the differential diagnosis should include all the following: Neurilemmoma, 2) Neurofibroma, 3) Ganglion, 4) Hemangioma, 5) Neuroma.

Question 35C

Based on the above information you would do a biopsy of the most prominent part of the mass and wait for permanent microscopy results.

Question 35D

Surgical exploration revealed a lobulated mass compressing and encompassing the peroneal nerve. The stalk of the cyst was found to be originating from the proximal tibio-fibular joint. This sounds like a benign joint ganglion and you would inform the parent that you expect the nerve to return to full function.

Question 35E

The following is a result of the biopsy.. This is most likely a Neurilemmoma.

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