Bell's palsy / dental courses

Bell’s palsy
INDIAN DENTAL ACADEMY
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Facial nerve
 7th
cranial nerve
 Nr of 2nd
branchial arch
 Mixed nr
 Sensory root – nervus intermedius

 10,000 neurons
 7,000 (myelinated)
innervate nerves of
facial expression
 3,000-
somatosensory &
secretomotor
and comprise the
{Nervus intermedius}

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Nuclei of facial nerve
 Main motor
 Chief sensory
(tractus solitarius)
 Lacrimatory
 Superior salivatory

Branchial motor (special visceral efferent)
Supplies muscles of facial expression, posterior belly ofSupplies muscles of facial expression, posterior belly of
digastric, stylohyoid and stapediusdigastric, stylohyoid and stapedius..

Visceral motor (general visceral efferent)
Parasympathetic of the lacrimal, submandibular, and sublingualParasympathetic of the lacrimal, submandibular, and sublingual
glands, mucous membranes of nasopharynx, hard and soft palate.glands, mucous membranes of nasopharynx, hard and soft palate.

Taste from the anterior 2/3 of tongueTaste from the anterior 2/3 of tongue

General sensory (general somatic afferent)
General sensation from skin of concha of auricle andGeneral sensation from skin of concha of auricle and
small area behind earsmall area behind ear..

Main motor nucleus
 Part of nucleus that supplies
upper part of face receives
corticonuclear fibres from
both cerebral hemispheres.
Part of nucleus that supplies
lower part receives fibres from
opposite cerebral hemisphere

Upper motor neuron lesion

 Upper motor nerve lesion
 Results from the damage to the neuronal cell bodies in the
cortex or their axons that project via the corticobulbar tract
 Voluntary control of only the lower muscles of facial
expression on the side contralateral to the lesion will be lost
 Voluntary control of muscles of the forehead will be spared
due to the bilateral innervation of the portion of the motor
nucleus of the cranial nerve VII that innervates the upper
muscles of facial expression

 Characteristic of UMN lesion of the facial nerve
 Facial asymmetry
 Atrophy of muscles of lower portion of the face on
affected side
 No eyebrow droop
 Smoothing of nasolabial folds on affected side
 Lips cannot be held tightly together or pursed
 Difficulty keeping food in mouth while chewing on
affected side

Lower motor neuron lesion

Lower motor neuron lesion
 Results from damage to the motor nucleus of
CN VII or its axons
 Results in paralysis of all muscles of facial
expression (including those of the forehead)
ipsilateral to the lesion

Clinical correlation
 A LMN lesion of CN VII
which occurs at or
beyond the
stylomastoid foramen is
commonly referred to
as a bell’s palsy

Bell’s palsy
 Defined as idiopathic paresis or paralysis of
the facial nerve of sudden onset.
 Unilateral lower motor neuron paralysis of
sudden onset, not related to any other
disease elsewhere in the body
 Name ascribed to sir Charles bell, who in
1821, demonstrated the separation of the
motor & sensory innervations

 Incidence : 15 -40 cases per 1,00,000
 Women affected more
 3.3 times more common in pregnant woman
 Prevalent in 3rd
trimester or 1st
week of post
partum
 More in diabetics

 Can occur at any age, more common in
middle age
 Both sides equally affected
 1% bilateral
 8% cases positive family history

Etiology
 Rheumatic hypothesis: Berard in 1936.
rheumatic swelling may press the nerve
against facial canal
 Cold hypothesis: Bell. Exposure to extreme
cold or cold draught
 Ischaemic hypothesis: ischemia from
disturbed circulation

 Factors producing vasospasm
 Cold
 Anoxia
 CO2 excess
 Vasomotor instability
 Injury
 Toxic allergic, hormonal influence

 Immunological hypoyhesis: in vivo
sensitizatiion of lymphocytes to peripheral
nerve myelin
 Viral hypothesis: HSV. Elevated viral antibody
titre & interferons
 Facial palsy + herpes →→ Ramsay Hunt
syndrome

Histology
 Thickened, edematous perineurium &
associated blood vessels
 Diffuse infiltrate of inflammatory cells
between nerve bundles
 Degeneration of myelin sheath

Clinical features
 Sudden onset, usually in morning after
awakening
 Unilateral involvement of entire face
 Corner of mouth droops down, causing
drooling of saliva
 Whistling is impossible
 Excessive tearing

 Inability to close the affected eye or wink or
raise the eye brow
 Bell’s sign: In an attempt to close the eye lid,
the eye balls rolls upward, so that pupil is
covered and white sclera is seen
 Inability to wrinkle the forehead
 Inability to elevate upper or lower lip

 Widening of palpebral fissure
 Loss of blink reflex
 Obliteration of nasolabial fold
 Mask like face
 Slurred speech
 Loss/ alteration of taste occasionally

Prognosis
 Initial weakness of facial musculature →
worsens over 2 to 3 days → maximum by 2
weeks → remission → Spontaneous
recovery

House-Brackman
classification of facial palsy
Grade I – Normal function without weakness
Grade II- Slight facial asymmetry with minor synkinesis
Grade III-Obvious asymmetry with residual forehead movement
Grade IV-Obvious disfiguring asymmetry with lack of forehead motion and
incomplete eyeclosure
Grade V- Asymmetry at rest and only slight facial movement
Grade VI – Complete absence of tone or motion

TREATMENT
 MEDICAL
 Steroids
 Physiotherapy
 Eye care
 Reassurance
 SURGICAL
 Facial Nerve Decompression

Nerve decompression-
 Can be carried out internally or externally
 Internal decompression-the nerve is exposed in the
fallopian canal and pressure in the canal is relieved
by exposing the nerve and the epineural sheath is
opened to visualise the nerve fibres and release
adhesions or reestablish continuity
 External decompression is done by releasing the
epineural sheath from surrounding scar tissue ,bone
or foreign body

Paralyzed eye lid
Non surgical correction
Surgical correction
Gold weight implants

Nerve anastomosis-reanimation-
 anastomosis of the
central end of the
hypoglossal or
spinal accessory
nerve with the distal
end of the facial
nerve is done

 Nerve grafting-
whenever there is
evidence of neuroma or
loss of portion of the
nerve, nerve grafting
can be considered

Bell's palsy / dental courses

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