MINISTRY OF EDUCATION AND TRAINING

MINISTRY OF DEFENCE

108 INSTITUTE OF CLINICAL MEDICAL AND
PHARMACEUTICAL SCIENCES
--------------------------------------------------------

BUI MAI ANH

ANATOMICAL RESEARCH AND CLINICAL
APPLICATIONS OF MASSETER NERVE IN INTERMEDIATE
DURATION FACIAL PARALYSIS TREATMENT

Speciality: Odonto-Stomatology
Code: 62720601

ABSTRACT OF MEDICAL PHD THESIS

Hanoi – 2019


Thesis is completed at:
108 INSTITUTE OF CLINICAL MEDICAL AND
PHARMACEUTICAL SCIENCES

Supervisor:
1. Prof.PhD. Nguyen Tai Son

Reviewer:
1.

In Vietnam, surgery for facial paralysis treatment has been carried out for a
long time. However, there has not been any study on surgery and applications
of masseteric nerve in a systematic way, so we conduct research on the topic
”Anatomical research and clinical applications of masseter nerve in
intermediate duration facial paralysis treatment” for the following
purposes:
1. Course of masseteric nerve anatomy.
2. Evaluate results of the applications of masseteric nerve in surgical
treatment of intermediate durationfacial paralysis.


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Chapter 1
OVERVIEW

1.1. Masseteric nerve
The nerve that regulates masseter musclemovement is called
masseteric nerve (MN), a branch from the anterior trunk of mandibular nerve.
- Branching: According to some studies, MN has branching in some
cases.
- Location: According to Kun Hwang, MN is located at 33 ± 5.6 mm
from the lower limit of masseter muscleon the longitudinal line 1/3 before the
masseter muscle and 47 ± 5.5 mm from the lower limit on the vertical line 1/3
after.
- Microscopic anatomy: Through microscopic anatomical results, it
can be seen that the number of MN axons is much larger than other nerves,
which is one of the good conditions for recovering nerve transmission when it
is used as a source.
1.2. Surgical methods to restore facial muscles by the time of paralysis

treatment
1.3.1. Masseteric nerve transfer in intermediate durationfacial paralysis
treatment ( 2 years)
Like the direct transfer of MN, the use of MN for muscle
transplantation has many advantages such as ease of surgery, short recovery
time, the used nerve does not affect the function.
However, the authors also said that the use has disadvantages such as
when lifting the edge, it is necessary to bite with the bitting and the time to
create a natural smile must be 2-4 years after surgery. To overcome this
problem, some authors have used dual nervous joint with two places: MN and
facial nerves with the movement nerves of the grafted muscle to create
spontaneous and natural laughs. In 2012, Biglioli reported a series of free

- Research on fresh cadaver: 22 specimens /11 fresh cadaver (including 6 men
and 5 women) from 35-73 years old, 9 fresh cadaver were studied in Ho Chi
Minh City University of Medicine and Pharmacy, 02 fresh cadaver at Viet
Duc Hospital, unknown age (unidentified cadaver)
- Clinical research: Patients with facial paralysisdue to various causes
in the period from 3 weeks to 24 months had surgery to transfer one-sidedness
MN at the Department of Maxillofacial Surgery-Plastic Surgery-Aesthetics,
Viet Duc Hospital from 11 / 2009-12 / 2017.
2.1.1. Selection criteria and exclusion of patients
- Criteria for selection on cadaver: The specimens on the fresh cadaver
are intact in the face area, have not been surgically or previously injured.
Exclude specimens that are not properly preserved, face areas are injured.
- Criteria for patients selection: Patients with facial paralysisaccording
to FNGS 2.0 classification from grade 4 to grade 6 for not more than 24
months

paralysis;

The

patients

were

diagnosed

with

intermediate


+ Measure the index of masseter muscle as below.
+ Continue operating the layers of masseter muscle, peeling according to the
layers.
+ Find donor nerve and masseter muscle arteries in the deep layer of masseter
muscle.
+ Measure indicators.


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- Clinical research:
+ Clinical examination of the patients: assessing injury status of the nerve VII
according to House and Brackmann score (FNGS 2.0); measure commissure
excursion amplitude; assessment of facial nerve injury; masseteric muscle
function; classify causes of injury; body situation.
+ Subclinical assessment: MRI, CT to search for causes of the nerve VII
injury; EMG to determine vulnerability; do tests to exclude other diseases.
+ Perform the surgery
2.2.3. Improved content in surgery to find MN
Through clinical and anatomical researches on the fresh cadaver, we map out
the "MN zone” as follows:
+ Upper limit: zygomatic branch.
+ Lower limit: buccal branch
+ Posterior limit: the parallel line and measure the distance from the tragus to
the branching position of MN.
+ Anterior limit: the line parallel to the posterior limit and about 1cm from the
posterior limit.
MN zone is limited when connected 04 lines above and in the deep layer of
masseter muscle.
2.2.4. Follow uppost operation

patients can have a natural, spontaneous smile after the practice from 24-72
months.


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2.3. Data processing
- Analysis on software STATA 12.0
- Research classification is as follows:
Type 1: Very good
- FNGS 2.0: Grade I, Grade II.
- Electromechanics: There are signs of the movement unit of the facial muscle
(optional conditions).
- Spontaneaous smile
- Difference in amplitude from the healthy side is
point under MN is 7.8 ± 0.8; The distance from the zygomatic arch to the
branching point under MN is 5.8 ± 0.8; The distance from the jaw corner to
MN is 54.2 ± 12.6; The distance from the mouth branch of the nerve VII to the
branching point under MN is 11.2 ± 3.0. There are no statistically significant
differences in men and women. There is difference, but not statistically
significant between the MN location on the corpse and on the surgery, the
distance from the tragus to MN on the corpse is larger than on the surgery but
not significant. MN was found in the deep layer of the masseter muscle and
between the cheekbone branch and the mouth branch of the nerve VII, before
the tragus 29.9 ± 2.5 mm.
3.2. Surgical results
3.2.1. Short term results
Complications after surgery: Infection, fluid accumulation, saliva
leakage are not seen in any case. The effect of the proximal results is
calculated on the time of time onset of vibrationand the commissure excursion
movement when biting after surgery.
Table 3.13.Onset-vibration muscle time with the bitting (n = 32)


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Time of the first muscle vibration
(month)

Mean ± SD

Min
Max

Coaptation to the buccal branch (n=23)

Table 3.14 Onset motion time with the bittingand grading according to
FNGS 2.0
Mean ± SD
Min – Max
Mean ± SD
Min – Max
Mean ± SD
Min – Max
Mean ± SD
Min - Max
The first commissure excursion on Mean ± SD
the paralysis side with bitting Min – Max
(n=30)
Grade I
Grade II
Grade III
Coaptation to the buccal branch
(n=23)
Coaptation to the buccal and
zygoma branch (n=4)
Coaptation to the main trunk
(n=5)
All the cases (n=32)

5.6 ± 3.8
3 – 24
5.75 ± 0.5
5-6
5.4 ± 0.9
4–6

commissure excursionmovement on the paralysis side is 5.4 ± 2.1 mm. The
majority of patients with FNGS 2.0 results reached the grade III (70.0%). In
this results table, there is 01 patient who had surgery at the age of 18 months,
so he does not cooperate to move the muscle when biting with the bitting, until
after 24 months he accepted to cooperate and had the oral movement. The
results from 3-6 months of 06/36 patients who only sent pictures after surgery
so it was only possible to identify patients who could clearly move their
mouths when biting with the bitting but it is not scored according to the FNGS
2.0 score and not measured oral movement amplitude calculated from the
middle of the upper lip.
3.2.2. Long term results
Table 3.20.Long term results according to the House-Brackmann 2.0 score
on each factor (n = 36)
Characteristics
Eyebrow (point)
Eye (point)

Nasolabial fold(point)

Mean ± SD
Min – Max
Mean ± SD
Min – Max
Mean ± SD
Min – Max

Frequency
(n)
5.1 ± 0.8
3–6

24
66,7
Grade
III
9
25.0
Grading by point
FNGS 2.0
Grade IV
3
8.3
Grade V
0
0
Grade VI
0
0
Remark: After surgery 6-72 months, the majority of patients had the
surgery result of grade II (66.7%); then grade III (25.0%); only 8.3% of
patients had a result of grade IV.

Grade I: Very good
Grade II: Good
Grade III: Fairly

Figure 3.1. The long term result according to the classification of the studies
Remark: According to the grading standard of the studies, the patients with
grade I results were very good, accounting for 38.9% and good for 27.8%,
only 8.3% of the patients had the average grade IV results.


Through our studies of over 22 fresh corpse specimens of Vietnamese
people, masseter muscle anatomy has a length of 64.4 mm, width of 37.4 mm,
masseter muscle divided into 03 classes. According to Hwang's studies with
96 specimens that had a masseter muscle length of 66 ± 5.6 mm. In the
studies, we did not measure the length of MN but only measured the distance
from the Sigma hollow of 5.8 ± 0.8 mm to the point of branding under MN,
because this is the point that we choose and cut MN inferior branch to joint
microsurgery. We also measured the distance from the jaw corner to the
subdivision point under MN of 48.7 ± 16.9 mm (Table 3.4), compared with
Hwang's result from the jaw corner to the lower branch of 3.2 ± 4.1 mm.
Brenner and Schoeller studied on more than 36 cadaver specimens
and summarized that when MN entered the muscle, divided into 2 branches, is
seen in 47% of the specimens, only 1 branch is seen in 5% of the specimen, 3
branches seen in 25%, 2, 8% is divided into 4 branches. Cotrufo et al only saw
02 anatomical changes: only 1 branch in 14/17 specimens, 2 branches found in
3/17 specimens. In addition, more than 96 corpse specimens of Kun Hwang
and colleagues are divided into 03 anatomical changes: 1 branch, 2 branches
and 3 branches. According to our analysis results: 20/22 specimens had 2
branches, 02/22 had a branch. Thus, most of the results according to reports
are mainly MN divided into two upper branch and lower branch. This
anatomical feature is quite important because based on this result, we often
choose the nerve lower branch, used to joint microsurgery to the oral branch to


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recover MN because this branch usually has large size and length. .
According to our analysis on 22 MN specimens located at the depth
layer of the masseter muscle, this is different from the author Hwang when he
found MN in the middle layer and the deep layer of the masseter muscle. This

when we operate on patients (please refer to the surgical section).
The diameter we measured on the corpse specimens between the two
ends of the nerve, the oral branch and MN,is relatively similar: 1.1 mm and
1.2 mm. In previous studies by foreign authors, we do not see the presentation
of MN headdiameter, although this is also an important factor in
nervouscoapted technique. However, in clinical practice we found that the MN
inferior branch is always very small and there is only one nervousfiber bundle
so we try to joint all nervous fiber bundles of the nerve VII branches or the
suralnerve with the fiber bundle of MN inferior branch.
4.2. Surgical results
4.2.1. Short-term results
Our assessment of recent postoperative results is based on the time of
the time onset of vibrationafter surgery, the time of the first commissure
excursion movement at paralysis side after surgery with the bitting, the
amplitude of the first movement at paralysis side, compared with the healthy
side and FNGS 2.0 score. According to Murphey, in 10 articles, the time of
the time onset of vibrationin themain body coaptedgroup were 5.76 months on
average, while in the branchcoapted group it was 3.76 months. Therefore, we
choose the time to evaluate the recent results for 3-6 months after surgery. In
our studies, the time of the time onset of vibrationof the buccal branchcoapted
patient was 3.5 months, of the two branchcoapted was 4.3 months, of the main
body was 4.6 months.Compared with some other authors, we have the average


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time of the time onset of vibrationsimilar to results of other authors. The
authors Biglio and Bianchi do not join the branch VII directly to the MN
branch but join nerve roots through a compound. According to the author
Bianchi, this is why the time for neurotransmitter recovery is longer (8

According to Hontanilla's studies, it was 7.8 mm. Many authors do not
measure the oral movement amplitude calculated from the upper lip middle at
the beginning but usually after 6-12 months of surgery when the muscles are
strong and clear.
According to the score, we found that the mouth branch was restored
to its earliest transmission, followed by the zygoma and eyehole branches. The
patient will have the first commissure excursionmovement and then close his
eyes. Many authors share the same comments with us,Biglio found that the
first visible nervous movement recovery is from large zygoma muscle. The
reason for this result has not yet been shown by any author, but in our opinion,
the mouth branch and the zygomaand eyehole branches are usually large and
are connected in the branches VII and dominate many facial muscles so when
recovering the nerve is usually faster than other branches.
4.2.2. Long-term results
Our follow-up period from a distance after surgery is from 12 to 96
months, Author Wang: 6-12 months; Klebuc: 7-84 months; Faria: 6-18 months
and Bianchi: 12-72 months. For nervous transmission reconstruction surgery
we find that the longer the follow-up time, the more likely the recovery will be
completely evaluated as well as the possible sequeleas of the nerve are the
source. Therefore, we will see advantages and disadvantages of the nerves.
According to the research results in our patient group, 100% of patients
hadmovement re-transmission and reached the research score: Very good is


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38.9%, Good is 27.8%, Fairly is 25%.
In 36 patients with a follow-up period of 12 months or more, 91.7%
had a quite stable balance compared to the time before surgery, this rate was
16.7%. The rate reduced and the end of dryness, corneal redness, or

+ Upper limit: lower cheekbone branch.
+ Lower limit: upper mouth branch
+ Posterior limit: the parallel line and the distance from the tragus to
the MN branching position, taken according to the smallest value of the two
researchlots (on fresh cadaverand clinical bodies) is 28mm.
+ Anterior limit: The line parallel to the anterior limit and from the
tragus according to the maximum value of the two research lots (on fresh
cadaver and clinical bodies) is 40 mm.
2. Surgical results
The patient had the average time of the time onset of vibrationwith his