5.7.4Orbital Involvement

5.7.4.1Proptosis

5Orbital enlargement resulting from growth of an optic nerve glioma or neurofibomas is common. It may also be

due to bony cranial abnormalities, typically sphenoid wing dysplasia. The last results in the classic finding of

pulsatile proptosis in the patient with NF1. In addition, buphthalmos, which is often secondary to congenital glaucoma associated with NF1, can lead to pseudoproptosis from an increased axial length. It is not uncommon for patients with significant orbital involvement to have a cluster of findings, including sphenoid wing dysplasia, proptosis, ptosis, buphthalmos with a blind eye, and an optic nerve glioma or orbital neurofibroma (Fig. 5.5).

A multidisciplinary approach is best for the NF1 patient afflicted with these complicated disfiguring problems. Even after neurooncological evaluation and treatment, it is often necessary to intervene surgically to rehabilitate a patient’s appearance. For the child with gross orbital and periorbital deformities, this may be of even greater concern to the family than the preservation of the eye on the affected side despite the opportunity for a reasonable visual potential. The surgeon must thoroughly discuss the realistic limits to keeping a proptotic eye versus complete resection (enucleation, etc.) with subsequent socket reconstruction.

The approach to the proptotic patient with NF1 may require craniofacial or neurosurgical collaboration depending on the need to reach a specific area of the orbit. For posterior apical lesions or the repair of certain bony abnormalities of the orbit and cranium, a transcranial neurosurgical approach may be warranted. Other options for treating proptosis in NF1 are usually available to avoid unnecessarily aggressive intervention, such as orbital exenteration for rehabilitation. As stated, we strongly reject use of this technique except for an extremely unusual case for which malignancy is of documented concern. With a carefully staged approach to multiple surgeries, reasonable results can be achieved to optimize ocular prosthesis retention with acceptable or even good cosmesis in many cases.

5.7.4.2Proptosis Due to Orbital Neurofibromas

Patients with orbital neurofibromas, particularly of the plexiform type, may benefit from possible reduction of tumor with additional chemotherapy. To this date, however, no chemotherapy regimen has proven effective in completely reducing orbital neurofibromas [4]. The main effect, as stated, has been possible slowed growth. At this time, for patients with significant orbital involvement, surgery remains the most hopeful modality for addressing issues of painful proptosis or disfigurement. Patients may suffer from exposure due to proptosis and from orbital or periorbital discomfort secondary to their orbitofacial neurofibromas. The surgeon must obtain adequate imaging in such cases to delineate the presence of any intracranial extension as well as any additional intracranial tumors or other pathology.

5.7.4.3Proptosis Due to Optic Nerve Glioma

The medical management and controversies regarding tumor classification of OPGs in NF1 have been addressed in this chapter. In addition to medical management,

Fig. 5.6 Optic nerve glioma excision: lateral approach. Gliomas can often be excised via a lateral orbitotomy as demonstrated above. Glioma visible in front of retractor (see arrow). Removal of the lateral wall in children may not be necessary due to the shallow orbit in this age group (From Katowitz [23]. With permission from Springer)

tumor resection may be considered. This is both to treat disfiguring proptosis and to remove a lesion that could potentially grow posteriorly. Gliomas of the orbital optic nerve causing proptosis can often be removed by a lateral approach, especially in children, for whom the orbit is shallower and removal of the orbital bone can be avoided (Fig. 5.6). Gliomas directly behind the globe can sometimes be removed by an anterior approach combined with enucleation (Fig. 5.7). For posterior lesions where there is severe proptosis or real concern regarding retrograde progression, a superior transcranial neurosurgical approach may be required (Fig. 5.8).

5.7.4.4Orbital Enlargement with Dystopia and Hypoglobus

Early involvement of NF1 tumors can lead to orbital enlargement (Fig. 5.9). This can present a significant surgical dilemma for reconstruction. Debulking of tumor from the orbit early in life may decrease the stimulus for asymmetric growth to some degree but is usually not sufficient to control this effectively. Orbital bony enlargement, while a problem, is often less noticeable than the soft tissue deformities usually associated with this. For the casual observer, the increase in orbital volume is actually hidden. The periorbital soft tissue changes are what is noticeable, represented by a higher and often more prominent brow, a lengthened lid fissure with lid deformities secondary to tumor growth, as well as an associated mechanical ptosis. Bony sphenoid wing dysplasia or even aplasia permits visible pulsations transmitted from the brain through the orbital defect.

Fig. 5.7 Optic nerve glioma excision: anterior approach. Gliomas can be excised using an anterior approach combined with enucleation if

5 the tumor is adherent to the globe and not in the posterior orbit. (a) Marked proptosis with exposure problems. (b) Tumor visible after removing extraocular muscles. (c) Four years postoperative

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