Optic nerve decompression for orbitofrontal fibrous dysplasia: recent development of surgical technique and equipment

Abstract

Objectives: Orbitofrontal fibrous dysplasia often involves the bony orbit and optic canal. Although fibrous dysplasia reportedly produces compression of the optic nerve leading to visual disturbances, optic nerve decompression in patients without clinical signs of optic neuropathy remains controversial. We describe the recent development of surgical techniques and equipment for optic nerve decompression in orbitofrontal fibrous dysplasia.

Methods: Optic nerve decompression was performed prophylactically for five patients and therapeutically for one patient using the transcranial extradural route. A high-speed drill and continuous suction-irrigation system has been used in five patients since 1998, and an ultrasonic bone curette in two patients since 2004.

Results: The continuous suction-irrigation system was particularly effective for decreasing heat transfer and thus preventing thermal injury to the optic nerve from the high-speed drill. The ultrasonic bone curette was also effective, allowing bone removal with minimal pressure from the tip of the handpiece and without catching cotton pledgets or damaging surrounding tissues. Orbital dystopias and craniofacial deformities induced by fibrous dysplasia were also successfully corrected. Postoperatively, disturbance in visual function was present in only two patients. Mean follow-up period was 4.9 years.

Conclusions: This equipment may contribute to the development of new modalities for optic nerve decompression in orbitofrontal fibrous dysplasia.

Figure 1

(A) Lateral view of handpiece and tip of suction-irrigation system. (B) Upper view of handpiece. (C) Flexible tips.

Figure 2

(A) Handpiece and tip of the Sonopet UST-2001 (110 g). (B) Frontal view of tip (width, 1.9 mm). (C) Lateral view of angled tip for resecting bone using a scratching motion.

Figure 3

Patient 5. (A) Preoperative three-dimensional CT. (B) Preoperative axial bone CT. (C) Preoperative coronal bone CT. (D) Optic nerve decompression. White lines: optic nerve canal. (E) Reconstruction of orbital roof. (F) Postoperative axial bone CT. (G) Postoperative coronal bone CT. (H) Postoperative visual field illustration for left eye demonstrating normal visual field. CT, computed tomographic scan.

Figure 4

Patient 6. (A) Preoperative three-dimensional CT. (B,C) Preoperative axial bone CT. (D) Bone resection using ultrasonic bone curette. Black asterisk: continuous suction-irrigation system. White asterisk: ultrasonic bone curette. Arrow: optic nerve canal. (E) Optic nerve decompression. Arrow: decompressed optic nerve canal. (F,G) Postoperative axial bone CT. (H) Postoperative coronal bone CT. (I) Postoperative visual field illustration for left eye showing lower-half hemianopia. CT, computed tomographic scan.