Abstract
Patients undergoing foramen magnum decompression for Chiari malformation may experience severe postoperative pain in the area innervated by the greater occipital nerve (GON). We developed a modified dissection to lessen this pain. A midline skin incision was extended 2 cm in a cephalad direction to the inion and the skin was minimally retracted. After exposing the occipital bone, the semispinalis capitis and the trapezius muscles were detached subperiosteally in a caudal-to-cephalad direction. Consequently, the muscles and skin containing the GON were retracted in a single layer. We retrospectively compared the intensity of postoperative pain recorded on the visual analogue scale (VAS) by patients who underwent decompression using our (group A, n = 5) and the conventional layer-by-layer dissection technique (group B, n = 5). The VAS scores were not different on the day of surgery, but subsequently they fell faster in group A. Group A patients received a mild analgesic for a short period. Group B patients required a stronger analgesic for prolonged periods. Postoperative GON numbness/tenderness was observed only in group B. With respect to most evaluation criteria, the difference between the two groups was significant. Our anatomically rational dissection that protects the GON results in less postoperative pain.