Approaches to the Orbit

Preoperative Considerations ( Figures 36.1 and 36.2 )

• Anatomical pearl: The shape of the orbit is compared to a four-sided pyramid in which the apex is located posteriorly and the base anteriorly.

• Special CT and MRI series centered at the orbit and with thin cuts are useful to study the orbit and to better define any pathology. MRI with fat suppression allows better visualization of the orbital structures decreasing the hyperintensity of the orbital fat.

• Visual fields and fundoscopy examination are important preoperative studies that allow choosing a more appropriate surgical approach considering the optic nerve function.

Indications

• Orbital lesions.

• Orbital lesions with intracranial or intranasal invasion.

• Hemangioma, hamartoma, neurofibroma, osteoma, chondroma, optic nerve glioma, meningioma, mucocele and lymphoma.

• Wide orbital and optic canal decompression are recommended through a transorbital approach.

• For Graves disease (exophthalmos) optic nerve decompression is recommended by an endoscopic approach.

Contraindications

• Management of apex lesions is not recommended by transorbital approaches, because the cranial nerves can be damaged while reaching the apex pathology, causing an iatrogenic orbital apex syndrome or sphenoid fissure syndrome.

• The lateral orbitotomy is avoided for pathologies that extend into the optic canal, because it has the potential complication of lateral rectus muscle paresis, upper eyelid ptosis and orbital hemorrhage.

• Endonasal transorbital approaches are avoided for pathologies that are laterally beyond the mid-orbital or optic nerve axes.

• For monocular patients, extreme care is recommended on the selection of the approach. If the preserved side is being approached, the possibility of loss of remaining vision needs to be discussed with the patient.

Surgical Procedure

The best surgical approach to the orbit is guided by the location of the lesion, as set out in Table 36.1 .

For this section we have selected the most useful transorbital approaches for the neurosurgeon. In the minimally invasive era, the orbit has been used in very selected patients as a natural corridor to access deep areas of the anterior cranial fossa avoiding the use of large incisions and craniotomies. Knowledge of those approaches is important because their indications and uses are expanding (see Figure 36.3 ):

• Supraorbital approach (see Chapter 19 ): Eyelid and eyebrow incisions that were used by ophthalmologist or cosmetic surgeons have been implemented to give access to the anterior cranial fossa, orbital roof and frontal sinus with improved cosmetic results (see Figure 36. 4 ).

  
  

• Transcaruncular approach: This approach can provide access to the anterior cranial fossa, nasal fossa and medial orbital wall.

• Endoscopic endonasal approach (transellar and transorbital variants): Sagittal and coronal expansions of the approach to the sella can provide access to the optic nerve, chiasm and medial orbital wall for pathology extending to those areas or optic nerve decompression.

• Transantral endoscopic approach : Although this approach is more used by ENT surgeons, it is important to understand its use alone or in combined approaches to access the maxillary sinus and orbital floor for pathology extending to those areas.

Transcaruncular Approach