Approach Routes to the Orbit

Orbit's pyramidal shape affords five possible anatomical approach routes, namely the anterior, superior, inferior, lateral and medial faces [22, 23]. The neurosurgeon does not need to be familiar with either the anterior approaches (which tend to be restricted to ophthalmologic applications, essentially to access small, anterior neoplasms) nor, as a rule, the medial and inferior approaches (which are the domain of the Ear, Nose and Throat specialist working in collaboration with the ophthalmologist). On the other hand, the neurosurgeon is often called upon to collaborate on techniques based on an approach via either the lateral or the superior routes [9, 19].

The huge number of monographs about the various techniques tends to lead to confusion, even though they generally differ in only relatively minor details. The goal must always be to obtain optimum access while inflicting as little damage as possible, with damage considered in both functional and esthetic terms. It is beyond debate now that no single method is ideal for exploration of the orbit in all cases: the technique to be used has to be chosen in the light of the nature, the location and the size of the lesion.

In neurosurgery, three possible approach routes should be considered namely the lateral approach, the superior approach and a hybrid supero-lateral approach.

Incision

The type of incision to be made will depend on the approach route chosen although a temporofrontal incision is suitable for all three alternatives. For a lateral approach, certain experts prefer an incision in the shape of an elongated S starting at the eyebrow and descending along the lateral edge of the orbit before curving behind along the upper edge of the zygomatic arch. This option is shorter but tends to be more disfiguring. It is important to go no further than 4 centimeters beyond the canthus to preclude damage to the frontotemporal branch of the facial nerve [26]. Both the fascia and the temporal muscle are eventually detached to expose the lateral wall of the orbit.

The temporofrontal incision begins just in front of the tragus at the level of the upper edge of the zygomatic arch and is then carried on in an upward direction. At the level of the temporal line, the incision curves around towards the hair line past the median line. Some experts even prefer bilateral incision [1, 12, 20]. Subsequent detachment of the scalp should preserve the temporofrontal branch of the facial nerve (located between the galea aponeurotica and the temporal fascia) and should avoid in front the bulky temporal muscle mass in order to obtain full access. The detachment procedure starts under the galea and then, 4 cm from the edge of the orbit, an incision is made in the superficial layer of the temporal fascia (which is at this point divided into two layers) in order to pass dissection between the two layers [33]. This leaves the superficial layer in contact with the scalp, and the nerve branch between the two intact. In order to make absolutely sure that this branch is not damaged, it is even better to leave the two layers in contact with the galea, and make dissection between the fascia and the muscle [2]. The fascia and the periosteum are then released from the edge of the orbit and the zygomatic arch. After the fascia and the muscle have been incised at a point 1 cm from the superior temporal line, this muscle can be detached (using a raspatory in order to protect its vasculature [32]) and laid under and behind in order to expose the whole pterional region and the entire lateral wall of the orbit.

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