Juvenile amyotrophy of the distal upper extremity: pathologic findings of the dura mater and surgical management.

STUDY DESIGN

Five cases of juvenile amyotrophy of the distal upper extremity were reviewed retrospectively to elucidate the pathophysiology of spinal cord dysfunction and the results of surgical management.

OBJECTIVES

To clarify the pathogenesis of juvenile amyotrophy of the distal upper extremity and to present the results of a new surgical treatment.

SUMMARY OF BACKGROUND DATA

Hirayama first reported this disorder in 1959. It is characterized by juvenile onset, slow progression, and involvement of the unilateral distal upper extremity. Recently, compression of the cervical spinal cord during neck flexion was implicated as a possible etiology of the disorder, but the exact etiology is still unknown. The value of surgical treatment for patients with juvenile amyotrophy of the distal upper extremity has not been established.

METHODS

The clinical and radiographic characteristics of five patients with juvenile amyotrophy of the distal upper extremity were examined. All five patients were treated surgically with duraplasty in combination with posterior spinal fusion. Dynamic and computed tomographic myelography were performed before and after surgery. Intraoperative ultrasonography and conductive spinal cord evoked potentials were recorded before and after duraplasty. The surgical results and the histology of the resected dura were studied.

RESULTS

Myelograms taken with the neck in a neutral position showed that the spinal cord was flattened in all five patients. When the neck was flexed, the dura and the spinal cord were compressed further. Intraoperative ultrasonography during neck flexion revealed an anterior shift of the spinal cord and decreased spinal cord pulsation. Amplitude of the conductive spinal cord evoked potentials decreased with neck flexion but increased after dural incision. Histologically, the dura appeared abnormal in that it contained few elastic fibers without the normal wavy structure.

CONCLUSIONS

Juvenile amyotrophy of the distal upper extremity was characterized by inelastic dura that constricts and compresses the cervical spinal cord when the neck is in either a neutral or a flexed position. Abnormal dura appeared to be the cause of juvenile amyotrophy of the distal upper extremity. Duraplasty with spinal fusion are proposed as treatments.