A detailed study about facial nerve

1. Facial Nerve Dysfunction After Superficial Parotidectomy With Or
Without Continuous Intraoperative Electromyographic
Neuromonitoring – A Prospective Randomized Pilot Study
Moderator – Dr Vidya BT
Presenter – Dr Medha Krishnamurthy

2. CONTENTS
◦ Relevant anatomy and theory regarding parotid gland and Parotidectomy.
◦ Journal proper
Introduction
Aim
Materials and methods
Surgical and anaesthetic techniques
Electrophysiological monitoring of facial nerve
Facial motricity assessment
Results
Discussion
Limitations of the study
Conclusions
Other studies.

3. RELEVANT ANATOMY

4. EMBRYOGENESIS AND ULTRASTRUCTURE
◦ There are 3 major salivary glands – Parotid, submandibular and sublingual glands and numerous
Minor salivary glands distributed along the oral cavity and pharynx.
◦ Major salivary glands – develop from the 6th to 8th weeks as outpouchings of oral ectoderm into
the surrounding mesenchyme.
◦ Parotid develops first followed by submandibular at 6 weeks and sublingual glands at 8 weeks.
◦ Minor salivary glands – oral ectoderm and nasopharyngeal endoderm.
◦ Parotid last to be encapsulated after lymphatics develop resulting in entrapment of lymphatics
deep to the capsule in the parenchyma.
◦ Made up of secretory acini and ducts. Acini can be either serous, mucous or mixture of both.
◦ Serous acini – small granules with salivary proteins and enzymes.
◦ Mucinous acini – cylindrical in shape, larger granules with mucoproteins.
◦ Acinar ducts Intercalated ducts striated ducts main excretory ducts.

5. CLINICAL ANATOMY – PAROTID GLAND
◦ Largest and mainly serous with few mucous acini.
◦ 15-25g, irregularly lobulated.
◦ 3 sided pyramid.
◦ Four surfaces – superior, superficial, anteromedial, posteromedial.
◦ Three borders – anterior, posterior and medial/pharyngeal.
◦ Apex- posterior belly of digastric and adjoining part of carotid
triangle.
◦ Cervical branch of facial nerve and retromandibular vein emerge
near the apex.
◦ Superior surface /base – EAC, posterior surface of TMJ, superficial
temporal vessels, ATN.
◦ Superficial surface – skin, superficial fascia (anterior branches of
greater auricular nerve, preauricular lymph nodes), parotid fascia,
deep lymph nodes

6. CLINICAL ANATOMY – PAROTID GLAND contd..
◦ Anteromedial surface – masseter, lateral surface of TMJ, medial
pterygoid, branches of facial nerve.
◦ Posteromedial surface – mastoid process, styloid process, ECA
enters the gland through this surface.
◦ Anterior border – parotid duct, terminal branches of facial nerve,
transverse facial vessels.
◦ Posterior border – overlaps SCM.
◦ Medial edge – lateral wall of pharynx.
Structures within the gland – medial to lateral
 Arteries – ECA, maxillary artery, superficial temporal artery gives off
transverse facial artery.
 Veins – retromandibular vein formed within the gland by the union of
maxillary and superficial temporal veins. Divided into anterior and
posterior branches in the lower part.
 Facial nerve – exits from the cranium through the stylomastoid
foramen, enters gland at its posteromedial surface and divides into
terminal branches. Separates the gland into a superficial part and a
deep part.

7. CLINICAL ANATOMY – PAROTID GLAND contd..
 Facial nerve divides into –
 Branches radiate like goose feet – Pes anserinus.
 BRANCHING PATTERNS – Katz and Catalano et al, McCormack et al
and Davis et al, Kwak et al.
 Patey’s faciovenous plane – large superficial and small deep part
connected by isthmus around which facial nerve divides.
Temporofacial Cervicofacial
• Buccal
• Marginal mandibular
• Cervical
• Temporal
• Zygomatic

9. PAROTID DUCT/STENSEN’S DUCT
◦ Named after Danish Anatomist – Niels Stenson in 1660.
◦ Thick walled, 5cm long.
◦ Emerges from middle of the anterior border, runs
forwards and slightly downwards on the masseter.
◦ Superiorly – accessory parotid gland, transverse facial
vessels, upper buccal branch of facial nerve.
◦ Inferiorly – lower buccal branch
◦ At anterior border of masseter, parotid duct pierces –
buccal pad of fat, buccopharyngeal fascia and
buccinators.
◦ Runs forwards between buccinators and buccal mucosa
and opens into the vestibule opposite crown of the
upper 2nd molar tooth.

10. BLOOD AND NERVE SUPPLY
◦ Blood supply – by ECA and its branches. Drains into the external and
internal jugular veins via retromandibular vein.
◦ Preganglionic secretomotor fibres – carried from inferior salivatory
nucleus along the IX nerve, its tympanic branch, tympanic plexus and
lesser petrosal nerve to otic ganglion.
◦ Post-ganglionic fibres carried via auriculotemporal nerve.
◦ Sympathetic vasoconstrictor fibres carried via plexus on the ECA and
middle meningeal arteries from superior cervical ganglion.
◦ Gland receives sensory fibres from ATN and fascia receives from great
auricular nerve (C1).
◦ Lymphatic drainage – first to parotid nodes and from there upper deep
cervical nodes.

11. SALIVA PRODUCTION
◦ 1500 ml/day saliva secreted.
◦ pH of resting saliva is 7; active saliva is 8.0.
◦ Contains lingual lipase secreted from minor glands, alpha
amylase from salivary glands.
◦ Mucin, glycoproteins, IgA, lysozymes, lactoferrin which binds
iron, proline rich proteins protects enamel and binds toxic
tannins.
◦ Parotid saliva – 20% of total secretion/day, serous and watery.
◦ Submandibular saliva- 70%, mucous and moderately viscous.
◦ Sublingual saliva – 5%, mucous and viscous.
◦ Minor and other oral glands – 5%.
◦ Facilitates swallowing, keeps mouth moist, solvent for taste buds,
facilitates speech, keeps oral cavity clean, antibacterial,
neutralizes the gastric acid to relieve reflux heartburn.

12. PAROTIDECTOMY

13. TYPES
◦ Superficial Parotidectomy – removal of entire superficial
lobe. Done in cases of benign diseases.
◦ Total conservative Parotidectomy – done in cases of
benign diseases of parotid either only deep lobe or both
lobes. Both lobes removed with preservation of facial nerve.
◦ Radical Parotidectomy – both lobes removed along with
facial nerve, fat, fascia, muscles (masseter, pterygoids and
buccinator), lymph nodes. Done in carcinoma parotid. Later
facial nerve reconstruction done using greater auricular
nerve graft,
◦ Suprafacial Parotidectomy – done in lower pole tumours
where all branches of facial nerve need not be dissected.

14. STEPS
◦ Lazy S incision – modified Blair’s/ Sistrunk’s approach and raising skin flaps.
◦ Mobilization of the gland
◦ Flap reflected in front just up to anterior margin of the parotid. After identifying SCM,
great auricular nerve identified and can be sacrificed. Posterior belly of digastric identified.
◦ Location of stylomastoid branch of posterior auricular artery anterior to facial nerve trunk
which enters the SMF.
◦ Put the artery forceps 5mm in front of the facial nerve; open the blades for 5mm; lift the
blades for 5mm.
◦ Facial nerve trunk identification.
◦ Dissection of gland off the facial nerve using bipolar cautery.
◦ Removal of the gland.
◦ Haemostasis and closure with a drain.

16. FACIAL NERVE IDENTIFICATION
◦ Facial nerve is 1cm deep and below the tip of the inferior
portion of the cartilaginous canal – Conley’s point.
◦ Nerve stimulator
◦ Inferomedial to Tragal pointer.
◦ Deep to digastric muscle and tympanic plate.
◦ Nerve is just lateral to the styloid process.
◦ Tracing branching from distal to proximal – Hamilton-Bailey
technique.

17. COMPLICATIONS
◦ Facial nerve injury.
◦ Haemorrhage.
◦ Salivary fistulae.
◦ Infection – flap necrosis common.
◦ Frey’s syndrome.
◦ Sialocele.
◦ Numbness over the face and ear – injury to great auricular
nerve. Spontaneous recovery within 1.5 to 2 years.

18. JOURNAL PROPER

19. Facial Nerve Dysfunction After Superficial Parotidectomy With Or
Without Continuous Intraoperative Electromyographic
Neuromonitoring – A Prospective Randomized Pilot Study
◦ Agnaldo J Gracaino, Carlos A Fischer, Guilherme V Coelho, Jose H Steck, Jorge R Paschoal, Carlos T Chone et
al.
◦ Department of Otorhinolaryngology- Head and Neck Surgery, University of Campinas, Brazil.
◦ Study published on – 19 September 2018.
◦ Journal – European Archives of Oto-Rhino-Laryngology.
◦ Study Design – Prospective randomised study.

20. INTRODUCTION
◦ Incidence of salivary gland neoplasm – 0.43/1000,000 to 13.5/1000,000.
◦ Parotid gland – most common site for primary tumour in 62-81%.
◦ Surgery – standard treatment for neoplasms.
◦ Surgical extension – still debated. Some suggest that superficial parotidectomy is one of the most
commonly performed procedures to treat such conditions.
◦ Other minimally invasive procedures with lower functional complications – partial superficial
parotidectomy (limited resection of a segment of superficial part of the gland with dissection of
selected branches of its main divisions) and extracapsular dissection (limited resection of the tumour
within a 2-3 mm margin of normal tissue without intentional dissection of the facial nerve).

21. INTRODUCTION contd..
◦ Transient facial nerve dysfunction (TFD) – most common complication following superficial
parotidectomy (SP), affecting 10-67% of patients.
◦ Most common risk factor for TFD – reoperation, surgery for chronic inflammatory diseases and surgical
extension (more common for total vs superficial parotidectomy).
◦ Facial nerve dysfunction – interruption of axonal conduction due to direct trauma (contusion or
stretching), neural ischemia, secondary to oedema and inflammation.
◦ Dysfunction appears within the first few hours after surgery, indicating that intraoperative events
associated with this condition are often unnoticed.
◦ `facial nerve monitoring via continuous electromyography (EMG) during parotidectomy described in
early 1990s.

22. INTRODUCTION contd..
◦ Various advantages – facilitating nerve location determination and dissection in complex cases,
distinguishing between nerve branches from similar structures and detecting facial nerve trauma
through early and possibly reversible electrophysiological responses.
◦ Intraoperative monitoring (IOM) for facial nerve is increasingly used during parotidectomy.

23. AIM
◦ To compare the incidence and grade of TFD in a homogenous group of patients with benign parotid
tumours exclusively subjected to superficial parotidectomy with or without electrophysiological
monitoring of facial nerve.

24. MATERIALS AND METHODS
STUDY DESIGN – pilot, prospective, randomised, controlled and parallel trial.
Study approved by the institutional research ethics committee.
Written informed consent obtained from all participants.
INCLUSION CRITERIA-
Adult patients (above 18 years) with benign parotid tumours confirmed on definitive HPE.
Exclusively subjected to HPE.
Normal facial motricity on preoperative clinical examination.
EXCLUSION CRITERIA –
Patients with chronic inflammatory diseases
Tumour recurrence
Subjected to parotidectomy for tumours located on the deep lobe of the gland.

25. MATERIALS AND METHODS contd..
Sample size – estimated as 50 patients per group (intervention and control).
Outcome measure – significant reduction in the immediate postoperative rate of facial nerve
dysfunction >/= House- Brackmann II as the main outcome and regional Sunnybrook System was
assessed as a secondary outcome.
Possible Risk factors related to TFD following surgery include –
o Surgical time greater than 120 minutes.
o Tumour size greater than 3-4 cm.
o Tumour location – parotid tail vs central (between mastoid tip and mandible angle) or superior (anterior to EAC).
o Age greater than 40, 60 and 70 years.

26. MATERIALS AND METHODS contd..
Patients randomly allocated at a a ratio of 1:1 to the monitored group (MG) – surgery performed with
continuous intraoperative EMG or the control group (CG) – without the intraoperative EMG.
Assessment of postoperative complications also recorded – hematoma, local infection, salivary fistula
and wound dehiscence.

27. SURGICAL AND ANESTHETIC TECHNIQUES
Patients subjected to SP – under surgical magnifying glasses with 2.5 or 3.3x magnification.
Anatomical reference points – cartilaginous tragal pointer, tympanomastoid fissure and posterior belly
of digastric muscle were used to locate the nerve trunk after its exit from thr stylomastoid foramen
followed by anterograde dissection of all branches of the nerve and complete resection of the
superficial part of the gland.
Retrograde dissection was performed in only 5 patients – difficulty to dissect a large tumour located
over the trunk or the occurrence of EMG events suggestive of neural irritation during antegrade
dissection.
All procedures performed – GA without muscle relaxants.

28. ELECTROPHYSIOLOGICAL MONITORING OF FACIAL
NERVE
The four-channel Neuro-MEP Neuromonitoring system was
used.
Following anaesthesia, paired monopolar needle electrodes
inserted into 4 facial areas - frontalis, orbicularis oculi,
orbicularis oris and depressor anguli oris muscles and the base
electrode was inserted into the ipsilateral trapezius muscle.
System adjusted to record any event with an amplitude over
100mV triggered by nerve irritation (stretching, compression)
or thermal stimuli.

29. ELECTROPHYSIOLOGICAL MONITORING OF FACIAL
NERVE contd..
Events recorded categorised as –
Sporadic peaks and bursts – polyphasic waves usually triggered by contact with the nerve without clinical
relevance.
A train – periodic Electromyographic activity with a sudden onset and end, lasting few seconds.
B train – regular/irregular series of motor potential peaks or bursts lasting for several minutes to hours- possible
neural damage in progression
C train – irregular and continuous EMG activity composed of overlapping elements with large amplitude variation
– established neural damage.
Responses computed during step of identification and confirmation of the facial nerve – visual
inspection and anatomical dissection of nerve during resection.
At the end of the surgery, nerve trunk stimulated again to assess the integrity of the conduction of the
trunk and of all dissected branches.

30. FACIAL MOTRICITY ASSESSMENT
To assess motricity (motor function) – high resolution movies created to evaluate symmetry at rest and
during execution of standardized movements (frowning, closing eyes gently, closing eyes with
maximum effort, smiling wide with lips apart, mouth opening, raising upper lip and puckering lips as if
whistling).
Movies created before surgery and 1 week, 90 days and up to 180 days after surgery.
Facial nerve function graded according to the global House-Brackmann (HB) scale and the regional
Sunnybrook System.
Self-report Facial Disability Index (FDI) – 10 questions distributed across the physical and psychosocial
subscales – to assess the impact of facial dysfunction as perceived by patients.
Applied 30 days after procedure – local edema would not influence the results and 90 days after
surgery (improvement in the degree of facial nerve dysfunction).

31. RESULTS
Total patients – 132 with parotid tumours assessed from March 2015 to September 2017.
Excluded patients – 8 (cytological features suggestive of malignancy = 4 or tumour located in the deep
lobe = 4).
124 patients randomly allocated MG (n=63) or CG (n=61).
Additional 15 excluded (8 – different type of surgery; 9 – whose final HPE revealed malignancy).
106 PATIENTS – with benign parotid tumour subjected to SP.
 Mean duration – 147 mins and 146 mins for MG and CG.

32. RESULTS contd..

33. RESULTS contd..
TFD - 45.3% patients and was the most common complication in the early postoperative period,
followed by tumor spillage (10.3%), salivary fistula (5.6%), hematoma (3.8%), seroma (1.9%), dehiscence
(1.9%) and local infection (0.9%).
Rate of immediate facial dysfunction - lower among the MG vs CG (38.1% vs. 51.8%) - not significant (p
= 0.16).
The rate of late facial dysfunction persisting for up to 6 months after surgery - similar between the
groups (3.8% vs. 5.5%, p = 0.6).
Using the regional Sunnybrook scale - immediate facial dysfunction significantly more severe in the
CG.
Marginal mandibular and buccal branches of the facial nerve - most frequently affected in 80% and
66% of the patients, respectively.
Total facial paralysis - 8.5% of the cases.

34. RESULTS contd..

35. DISCUSSION
TFD – most common complication after SP.
Association of continuous intraoperative EMG with reductions in TFD following SP – debatable.
Present study – immediate facial dysfunction (IFD) in 45% patients.
Rate of IFD lower in MG (38%) than CG (50%) – not significant.
Questionable whether routine use of IOM – associated with reduction in the degree of FND after
parotid surgery.
Beneficial effect of IOM after parotidectomy – lower severity of TFD and reduced perceived disability
by patients in the early post operative period.
Incidence of late facial nerve dysfunction – similar between MG and CG.
Perzik reported – rate of TFD lower with tumours in parotid tail vs in the centre or superior part.

36. DISCUSSION contd…
Tumour size not associated with increased risk of TFD – similar to findings by Mra et al and Sethi et al.
Watanabe et al and Bittar et al – tumours greater than 3-4 cms had increased risk of TFD – series was
heterogenous and patients submitted to total parotidectomy.
Mra et al – increased risk for patients >40 years (no such association in the current study).

37. LIMITATIONS OF THE STUDY
Low sample size.
Not a standard evaluation method for grading facial nerve deficits.
Neither HB scale/Sunnybrook System provides an objective evaluation.
Further studies should consider the association of the Sunnybrook System and an objective tool, such
as postoperative electromyography, for evaluating patients with facial nerve dysfunction following
parotid surgery.

38. CONCLUSIONS
IOM in the present study did not significantly reduce the occurrence of immediate or late facial nerve
dysfunction after SP for benign tumours.
Facial nerve dysfunction – milder in patients subjected to IOM.

39. OTHER STUDIES
Woods et al – reported 41% incidence of IFD among 742 patients who underwent SP.
Grosheva et al – reported that 41 monitored patients and 38 controls subjected to SP had 29% and
42% rate of IFD respectively.
Lopez et al – reported rates of 29.4% and 56.2% respectively for facial paralysis in a small series of 17
monitored and 16 controls.
Savvas et al – evaluated 123 patients subjected to partial SP under IOM and 99 controls and observed
rate of 16% for MG and 46% for CG suggesting that surgical and technical experience accumulated
with routine IOM over 12 years was relevant in obtaining results.
Meta analysis assessing 288 monitored patients and 238 controls – global incidence of IFD was
significantly lower for surgeries performed under IOM.