8. The location of the
masseteric artery was
then determined in
relation to 3 points process:
1) the anterior-superior aspect of the condylar neck =
10.3 mm;
2) the most inferior aspect of the articular tubercle =
11.4 mm;
3) the inferior aspect of the sigmoid notch = 3 mm
9. Posteriorly - parotid gland
Superficial temporal vessels
Auriculotemporal nerve
Laterally –
Skin and fascia
Parotid gland
Temporal branches of facial nerve
12. Facial nerve
To locate the facial nerve, an incision is made just in front
of the tragus of the ear from the root of the zygoma to the
angle of the jaw. Here the incision is carried forward about
one finger breadth below the ramus of the mandible as far
as is necessary to obtain adequate exposure.
The incision is carried down through skin and
subcutaneous tissue to the cartilage bounding the anterior
extremity of the external auditory canal. Then, with blunt
dissection, the cartilage of the external auditory canal is
separated from the capsule of the parotid gland as far &
medially as is possible or until a firm bony resistance is
met.
This is the base of the styloid process and is encountered at
a depth of about 1.5 inches (4 em.) from the skin incision. It
is important to remember to stay high just under the root
of the zygoma, so that the base of the styloid process is the
first important structure to be identified.
13. With finger dissection and palpation, the styloid process
can next be identified immediately below its base; a good
headlight and a dry field greatly facilitate this stage of the
operation.
With gentle traction on the capsule of the parotid gland
anteriorly, the facial nerve is brought into view, emerging
from the medial aspect of the styloid process and coursing
sharply upward and laterally to enter immediately the
capsule of the parotid gland.
The nerve usually is heavily invested in fascia and
a.ccompanied by the stylomastoid artery that may prove
troublesome if severed.
14. TheThe length of the facial nerve which is visible
to the surgeon is about 1.3 cm.
15.
16. The distance from the most anterior concavity of the bony
external auditory canal to the most posterior significant
temporal branch of the facial nerve was measured, with a
mean of 2.0 * 0.5 cm and a range of 0.8 to 3.5 cm.
The mean distance from the bifurcation of the main trunk
of the facial nerve to the lowest concavity of the external
auditory canal was 2.3 *0.28 cm, with a range of 1.5 to 2.8
cm.
The mean distance from the bifurcation of the facial nerve
to the postglenoid tubercle was 3.0 + 0.31 cm, with a range
of 2.4 to 3.5 cm.
17. mean distance from most posterior ramus of the temporal
branch of the facial nerve to the most anterior aspect of
the external acoustic canal is 2.12 cm ± 0.21 cm (range, 1.68
to 2.49 cm).
Knowledge of the distances and the range of the facial
nerve branches from fixed bony landmarks within the
surgical field alerts the surgeon to the areas of highest
risk
