Terminal Sensory Branches of the Trigeminal Nerve

Clinical Applications

Blockade of the terminal branches of the three divisions of the trigeminal nerve is primarily used for diagnosis of trigeminal neuralgia. Individual nerve blocks can also be used for minor surgical procedures.

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Figure 44-21 Blockade of the terminal sensory branches of the trigeminal nerve. A vertical line connects the supraorbital notch, infraorbital foramen, and mental foramen (see Plate 1 and Plate 2 in the color atlas of this volume).

Technique: Supraorbital and Supratrochlear Nerves

The supraorbital and supratrochlear nerves, branches of the ophthalmic nerve (i.e., cranial nerve V₁ ), are derived from the frontal nerve, which supplies the skin of the medial upper eyelid and forehead. The supraorbital notch can be easily palpated. This landmark lies on a vertical line with the pupil (when the eye is looking directly forward), the infraorbital foramen, and the mental foramen ( Fig. 44-21 ; see Plate 1 and Plate 2 in the color atlas of this volume).

A 25-gauge, 2-cm needle is inserted immediately superior to the supraorbital notch, and 2 to 4 mL of local anesthetic solution is injected. A paresthesia is sometimes elicited, but it is not essential. The supratrochlear nerve can be blocked by extending the supraorbital injection site medially with an additional 2 to 4 mL of solution.

Technique: Infraorbital Nerve

This nerve can be blocked to provide anesthesia of the upper lip and skin of the cheek. The infraorbital notch lies on the line connecting the supraorbital and mental foramina and the pupil of the eye. The nerve can be blocked by advancing a 25-gauge, 3-cm needle laterally and cephalad toward the foramen from a point 1 cm inferior. A paresthesia is frequently elicited. When the needle tip is in the region of the foramen, 3 to 4 mL of solution is injected. It is not essential that the needle enter the foramen (see Fig. 44-21 ).

Technique: Mental Nerve

Blockade of the mental nerve as it exits the mental foramen provides anesthesia of the lower lip and chin. The mental foramen lies on the vertical line connecting the pupil of the eye with the foramina of the peripheral nerves of V₁ , V₂ , and V₃ . The foramen is palpated in the mandible, and a 25-gauge, 3-cm needle is inserted inferomedially. Infiltration of 2 to 4 mL of solution after elicitation of a paresthesia or in the region of the foramen results in anesthesia of the mental nerve (see Fig. 44-21 ).

Side Effects and Complications

Direct injection of the peripheral nerves within the bony foramina may result in nerve damage.