Blocks of Nerves Supplying Facial Sensory Innervation
The face is supplied by the three division branches of cranial
nerve V (i.e., trigeminal nerve): the ophthalmic nerve (V1
), the maxillary
nerve (V2
), and the mandibular nerve (V3
).[286]
Most branches of these nerves are purely sensory nerves (precluding the use of a
nerve stimulator) and they are not usually blocked in children. However, three infiltration
techniques are easy to perform, safe, reliable, and recommended for analgesia for
surgery involving facial skin in an emergency (e.g., skin lacerations) or for superficial
elective procedures.
Block of the Supraorbital and Supratrochlear Nerves
The supraorbital and the supratrochlear nerves are the two terminal
branches of the frontal nerve that supply sensory innervation to the forehead and
scalp. These nerves can easily be blocked by a single-injection technique used on
each side. The landmark is the supraorbital foramen, located by palpation at the
junction of the lateral two thirds with the medial one third of the superior orbital
rim, in line with the centered pupils and the infraorbital and mental foramina ( Fig.
45-26
). An intradermal needle (25 gauge and 25 mm long) is inserted 0.5
to 1.5 cm below the foramen and on the vertical line uniting the three foramina.
As the tip of the needle reaches the lower border of the foramen, 0.1 mL/kg (up
to 3 mL) of local anesthetic is slowly injected to block the supraorbital nerve.
The needle then is slightly withdrawn and redirected medially and toward the angle
formed by the union of the orbital rim with the nasal bone. The same
Figure 45-26
Blocks of nerves supplying the face (supraorbital, infraorbital,
and mental nerve blocks), showing the sites for block of the supraorbital nerve (1),
block of the infraorbital nerve (2), block of the mental nerve (3), and block of
the supratrochlear nerve (4) and identifying the ophthalmic nerve (5), maxillary
nerve (6), and mandibular nerve (7).
volume of local anesthetic is injected while slowly with-drawing the needle (i.e.,
infiltration along the medial upper border of the orbit). If necessary, the same
procedure is repeated on the other side to obtain complete anesthesia of the upper
eyelids, forehead, and scalp.
Block of the Infraorbital Nerve
The landmark is the infraorbital foramen, which is easily palpable
on the line joining the centered pupil and the supraorbital and mental foramina,
below the junction of the medial and the middle thirds of the lower border of the
orbit. The puncture site lies on this line, at the crossing with the perpendicular
line passing just below the nostrils (see Fig.
45-26
). The intradermal needle is directed cephalad toward the lower border
of the infraorbital foramen (which must not be entered), and 0.1 mL/kg (up to 3 mL)
of local anesthetic is injected. Alternatively, the block can be performed using
an endobuccal route. The needle is inserted just above the upper canine tooth and
then aimed upward and laterally in the direction of the infraorbital foramen while
palpating the canal orifice to avoid needle penetration into the foramen.
Block of the Mental Nerve
The landmark for a block of the mental nerve is the mental foramen,
in line with the centered pupil and the supraorbital and infraorbital foramina and
at the level of the second premolars in adolescents or the second deciduous molar
teeth in younger children. The mental foramen is directed backward and upward.
The puncture site lies 0.5 cm above the mental foramen (see Fig.
45-26
).
The simplest procedure consists of inserting the needle pointing caudally in the
direction of the mental foramen and injecting 0.1 mL/kg (up to 3 mL) of local anesthetic.
The endobuccal route is more reliable. The needle first is inserted perpendicular
to the mucosa and then redirected at a 45-degree angle in the direction of the mental
foramen until bony contact is felt or paresthesia occurs. The local anesthetic is
then injected slowly. The main indication for a mental nerve block is surgery involving
lower incisor and canine teeth. Bilateral blocks allow procedures on the lower lip.
