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Pattern of The Buccal Branch of Facial Nerve Among A Sample of Sudanese Subjects: A Multicenters Study
It is well known in the vast
majority of the literature; the buccal branch can be single or double in
number. It has a close relationship to the parotid duct, and it was divided to
superficial and deep branches, which can be further divided to upper and lower
branches as they cross the face horizontally, they predominantly supply a
clinically significant part of the face [1]. For successful surgery for parotid
field area, it is extremely essential to have a tremendous knowledge of the
topography of the buccal branch and its relation to the parotid duct. It’s
worthwhile to mention that, careful selection of the surgical technique and
suitable incision is highly relevant in these sorts of surgeries in relation to
the parotid duct as it is essential in elucidation the pattern of the buccal
nerve branch of the facial nerve [1]. A study on the relationship of the buccal
branch of the facial nerve to the parotid duct was carried by Pogrel MA et al.
[2], in California. In 85% of the cadavers there was a single buccal branch of
the facial nerve, whereas 15% had two branches. In 75% of cases, the nerve was
inferior to the duct as it emerged from the parotid gland, whereas in 25% of
cases the nerve crossed the duct, usually from superior to inferior [2].
In 2006 Saylam et al. [3], studied
the anatomic landmarks of the buccal branches of the facial nerve among a
sample of Turkish subjects. Thirty cadaver heads 60 specimens were dissected.
The vertical and horizontal relationships between the buccal branches of the
facial nerve and tragus, and parotid duct were recorded and analyzed. The
buccal branches of the facial nerve were classified into four types:
Methodology
A total of 90 facial nerves were
dissected, [40 cadavers (bilateral) and 10 patients (unilateral)]. Out of these
50 cases, 41 were males (37 cadavers and 4 patients) and 9 were females (3
cadavers & 6 patients). Forty-six (51%) were left and 44 (49%) were right
facial nerves. The study was conducted in Khartoum Teaching Dental Hospital and
the Dissection Rooms at the Department of Anatomy, medical campuses of
different Universities and Bashair mortuary in Khartoum state, Sudan. Ethical
approval was obtained from the University of Khartoum Faculty of Dentistry,
Ethical Committee Review Board, research unit at Khartoum Teaching Dental
Hospital and a signed written consent was obtained from the patients. Previous
damaged intraparotid facial nerve in cadaveric dissection, patients with
history of previous surgical operations in the parotid region and subjects with
history of maxillofacial trauma which damaged the facial nerve were excluded
from the study. Data were entered in a computer master sheet using SPSS version
16. All statistical analysis was set at 95% confidence level, 0.2the width of
the confidence interval and the level of significance alpha 0.05.
Pattern of the buccal branch was
classified according to Saylam classification. In all cases an incision was
made anterior to the tragus of the ear and extending down below the lobule of
the ear. An inverted S-shaped incision was extended behind the ear and
inferio-posterior to the angle of the mandible. In case of anterior parotid
lesion, the incision was extended further down the neck. After elevating the
flaps, the anterior border of sternocleidomastoid muscle was dissected to the
mastoid process. The posterior belly of digastric muscle was visualized. The
cartilaginous portion of external auditory canal was dissected to the bony
portion. So, in an orthograde approach the facial nerve was identified using
the two standard anatomic landmarks (the tragal pointer and the posterior belly
of digastric muscle). The facial nerve was visualized and dissected
peripherally, and tracing of the buccal branch was carried out. For the
retrograde approach the buccal branch was used as a guide to reach the main
trunk. Following dissection, schematic illustrations and photographs of the
buccal branch in relation to the parotid duct were done and according to the
branching pattern they were classified into groups as described by Saylam.
Discussion
A precise identification,
localization and preservation of the facial nerve branches must precede the
excision of an involved gland by proper exposure and handling that attains by
means of meticulous careful dissection unless the nerve branches are to be
sacrificed because of invasion by a tumor [4]. The area of greatest
vulnerability for the buccal nerve is the area between the anterior border of
the parotid gland before it innervates the lip elevators and a line drawn from
the lateral canthus to the oral commissure anterior. Patients with facial
paralysis, may experience tremendous psychosocial distress and stigma about
their condition [5]. The pattern of the buccal branches of the facial nerve was
classified by Saylam et al. [3] into four types according to the vertical and
horizontal relationships between the buccal nerve branch and the parotid duct.
Few studies were performed to record and analyse the pattern of the buccal
nerve branch in relation to the parotid duct and most of them on Turkish
specimens. According to Saylam classification: Type I where a single buccal
nerve branch inferior to the parotid duct. Type II where a single buccal nerve
branch superior to the parotid duct.
In the present study the most
common pattern of the buccal nerve branch in relation to the parotid duct was
type II (43.3%) followed by type I (32.2%). These findings were different from
studies carried by Saylam et al. [3], who reported that type I was the most
common pattern of buccal branch accounting for (52%), followed by type II (35%)
respectively. So, the current study highlights a major variation in this
pattern topography in relation to the saylam study, which is the main reference
study, this may be due to the difference in sample size and anatomogeographical
variations. Type III where the buccal nerve branch and other branches of the
facial nerve formed a plexus was found in one cadaveric case in the left side
of the face, which is an important surgical point as its difficult to approach
this complex type during surgical dissection.
Type IV where two branches of
buccal branch; one superior and one inferior to the duct at the point of
emergence from the parotid gland was found in 23.3% of the present study.
Saylam et al. [3] reported that 13% of the cases where found to have mixed
patterns of the buccal nerve branch. There were no reported studies in the
literature that recorded and analyzed the gender distribution of the pattern of
the buccal branch. The present study revealed that type I and II were the most
prevalent types among males accounting for 36 and 25 cases respectively. Type
IV and type I were the most common types among females accounting for 5 and 4
cases respectively.
Also, there were no reported
studies in the literature on the distribution of the pattern of the buccal
branch according to the side of dissection. The present study showed that type
II was the most common pattern on the right and left sides of face (58.9% and
41%) respectively. Moreover, bilateral buccal nerve branch pattern
configuration (40 cadaveric cases) of the present study was found different on
the two sides of the face in 42.5% and similar in 57.5% of the specimens. In
the literature there were no previous reports related to the bilateral buccal
nerve branch pattern configuration.
Conclusion
It is extremely crucial for the
surgeons to have familiarity and basic knowledge with the different pattern
types of buccal branch of the facial nerve in order to avoid injury of it and
the parotid duct during surgery, avoid the functional loss of the acting
muscles which supply and enhance the quality of life. Another surgical benefit.
it could describe the way of selection of parotid surgical approach
specifically the retrograde one which depends commonly on the buccal branch
taking the parotid duct as essential landmark. The study recommended further
large cadaveric study on this field using the micro-loups which will be a major
forward leap to have a challenge of detection of any tiny nerve twigs and
reporting of a new pattern variation.
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