Chapter 5 Motor Nerve Blocks in Oculofacial Surgery 21
Figure 5.5. The O’Brien block anesthetizes the facial nerve at a proximal location. Approximately 5 ml of local anesthetic is injected over the condyloid process at a depth of 1.0 cm just anterior to the tragus of the ear.
Retrobulbar and Peribulbar Blocks
Socket reconstruction usually has cosmetic as well as reconstructive goals. To provide anesthesia to this area, an injection of local anesthetic is given in either the intraconal or extraconal space. In the enucleated socket, epinephrine can be used for hemostasis without concern for central retinal artery spasm. However, caution must still be used to avoid intravascular or subarachnoid space injection. After extensive orbital tissue manipulation with an ocular implant, postoperative analgesia can be given locally with a longer-acting anesthetic such as bupivacaine.
However, the volume injected in the retrobulbar space should be kept under 3.5 ml to avoid seizures if accidentally injected into the cerebrospinal fluid space. In the peribulbar space, the volume injected should be kept under 7 ml to allow retention of a conformer under fully closed eyelids.
References
1.Greenbaum S. Anesthesia for eye surgery. In: Tasman W, Jaegar EA (eds.). Duane’s Clinical Ophthalmology on CD-ROM. Philadelphia: Lippincott, Williams, and Wilkins, 2005: Vol 6, Ch 1.
2.Schimek F, Fahle M. Techniques of facial nerve block. Br J Ophthalmol 1995;79:166–173.
6
Regional Nerve Blocks in
Oculofacial Surgery
Vivian Schiedler and Bryan S. Sires
Regional nerve blocks are useful when tissue distortion from anesthetic volume is to be avoided. They are also useful for patients undergoing more invasive procedures such as dacryocystorhinostomy who are poor candidates for general anesthesia.
Sensory Nerve Blocks
Sensory innervation to the orbit and periocular tissues is provided by the ophthalmic and maxillary divisions of the trigeminal nerve. The ophthalmic division enters the orbit through the superior orbital fissure and has three branches: the lacrimal, frontal, and nasociliary nerves. The maxillary division enters the orbit through the inferior orbital fissure and has two branches: the infraorbital and zygomatic nerves.
Lacrimal Nerve Block
This nerve supplies the lateral aspect of the superior eyelid and the lacrimal gland. To block the lacrimal nerve, 1–2 ml of anesthetic is injected close to the internal superotemporal orbital wall approximately 2 cm posterior to the orbital rim behind the lacrimal gland (Figure 6.1).
Frontal Nerve Block
This nerve branches into the supraorbital and supratrochlear nerves. The supraorbital nerve supplies the middle aspect of the superior eyelid, brow, and forehead extending to past the mid-coronal plane. The supratrochlear nerve supplies the medial aspect of the superior eyelid and brow. To block the supraorbital nerve, local anesthetic is injected over the supraorbital notch. It is palpable at the junction of the medial onethird with the lateral two thirds of the superior orbital rim (Figure 6.2). To block the supratrochlear nerve, the needle is inserted along the superomedial orbital wall just above the trochlea to a depth of 1.5 cm (Figure 6.3).
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Chapter 6 Regional Nerve Blocks in Oculofacial Surgery 23
Nasociliary Nerve Block
This nerve branches into the posterior and anterior ethmoidal nerves and the infratrochlear nerve. It innervates the lacrimal sac, inner canthus, and lateral aspect of the nose. To block the infratrochlear nerve, the needle is inserted just above the medial canthal ligament along the medial wall of the orbit to a depth of 1.0 cm (Figure 6.4). If performing local anesthesia for dacryocystorhinostomy, the anterior ethmoidal nerve with its distal external nasal branch should be blocked using the same procedure but to a depth of 2.0 cm posterior to the anterior lacrimal crest.
Infraorbital Nerve Block
The maxillary nerve courses through the inferior orbital canal, giving off the anterior superior alveolar nerve branch within the canal, which supplies the superior incisors, canines, first molar, and gingiva. As it exits the inferior orbital canal through the infraorbital foramen, it becomes the infraorbital nerve, which supplies the skin and conjunctiva of the inferior eyelid, the cheek overlying the maxilla, the lateral nasal skin and septum, and the superior lip skin and mucosa. To block the infraorbital nerve, local anesthetic is injected over the foramen, which is palpable approximately 1.0 cm below the inferior orbital rim at the junction of the medial one third with the lateral two thirds of the rim. This can be done either percutaneously (Figure 6.5) or intraorally (Figure 6.6).
Zygomaticofacial Nerve Block
The zygomaticofacial nerve passes along the inferolateral orbit and exits the foramen by the same name to supply the the skin of the malar eminence and lateral cheek. The foramen can be located over the inferolateral rim below the lateral canthus and blocked with direct in ltration (Figure 6.7).
Figure 6.1. The lacrimal nerve is blocked by advancing the needle along the superotemporal orbital wall and injecting 1–2 ml of local anesthetic behind the lacrimal gland at a depth of approximately
2.0 cm.
24 V. Schiedler and B.S. Sires
Figure 6.2. Injection of 1–2 ml of local anesthetic over the supraorbital notch will block the supraorbital nerve.
Figure 6.3. The supratrochlear nerve is blocked with local anesthetic by inserting a needle just above the trochlea to a depth of approximately 1.5 cm.
Chapter 6 Regional Nerve Blocks in Oculofacial Surgery 25
Figure 6.4. Local anesthetic injection just superior to the medial canthal ligament and along the medial orbital wall to a depth of 1.0 cm will block the infratrochlear nerve.
Figure 6.5. The infraorbital nerve can be blocked percutaneously by direct injection over the infraorbital foramen at the junction of the medial one third and lateral two thirds of the lower lid and 1.0 cm below the orbital rim.
26 V. Schiedler and B.S. Sires
Figure 6.6. Alternatively, the infraorbital nerve can be blocked via an intraoral approach by inserting the needle through the gingiva superior to the canine and aiming toward the infraorbital foramen.
Figure 6.7. The zygomaticofacial nerve can be blocked at the inferotemporal rim inferior to the lateral canthus.