Facial Palsy
Of all peripheral nerves, the facial nerve is by far the most frequently
affected one. Facial palsy is never a simple problem. The 7th cranial nerve
has been referred to as the nerve of expression. The facial muscles play a
great role in the language of mankind, as the face can express an
international language. So, impairment of their function not only changes the
facial expression but also affects many other activities as the proper
manipulation of food and the sense of smell and taste. Hearing may also be
affected. The facial disfiguration often makes the patient incapable of
performing daily activities; and if his work requires speech or public
appearance, psychological changes will take place as well.
The facial nerve is a mixed nerve as it contains motor, sensory and
autonomic fibers. * The motor part supplies the muscles of expression of the
face as well as four other muscles; platysma, posterior belly of the digastric
muscle, stapedius and stylohyoid. * The sensory part receives taste sensation
from the anterior two thirds of the tongue. * The autonomic part supplies the
lacrimal gland as well as the sub-maxillary and sublingual salivary glands.
Anatomy of the facial nerve:
* Motor part:
The motor nucleus, from which the motor fibers of the facial nerve are
derived, lies deeply in the reticular formation of the caudal part of the pons,
medial to the trigeminal nucleus and anterior to the 6th cranial nerve nucleus.
Its upper part is bilaterally supplied by the pyramidal tracts of both sides,
while the lower part is unilaterally supplied by the pyramidal tract of the
opposite side only.
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From the nucleus, the motor fibers form a loop around the nerve
nucleus then pass laterally to emerge at the lower part of the pons. The nerve
runs laterally between the 6th and 8th cranial nerves, in the sub-arachnoid
space of the angle to enter, through the internal auditory meatus, into the
facial canal.
In the facial canal, the motor part of the facial nerve becomes adherent
to its sensory and autonomic parts. It then leaves the canal through the
stylomastoid foramen, passes through the parotid gland to divide into its five
terminal branches (Table 1).
Table (1): Branches of the facial nerve.
Branch
Muscles
Temporal Its anterior branch supplies the frontal belly of the frontalis, orbicularis
oculi and currugator.
Zygomatic Orbicularis oculi.
Procerus, zygomaticus major, levator labii superioris, levator anguli oris,
Buccal
zygomaticus minor, buccinators, nasalis and orbicularis oris.
Mandibular Resorius, depressor labii inferioris, depressor anguli oris and mentalis.
Platysma.
Cervical
* Sensory and autonomic parts:
In the facial canal lies the geniculate ganglion, which contains
unipolar cells, the process of which divides in a T-shaped manner into a
peripheral part and a central part:
1) The peripheral part runs laterally and divides into the greater superficial
petrosal nerve and chorda tympani. The greater superficial petrosal nerve
passes forward to relay in the sphenopalatine ganglion, where a new set of
fibers give autonomic supply to the lacrimal glands. The chorda tympani
leave the facial nerve before the stylomastoid foramen to supply the
submaxillary and sublingual salivary glands and to convey taste sensation
from the anterior two thirds of the tongue.
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2) The central branch of the unipolar cells passes centrally, joins the motor
part of the nerve then enters the cranial cavity through the internal auditory
meatus as the nervus intermedius. The latter enters the brain stem at the
ponto-medullary junction to terminate in the solitary nucleus in the medulla.
A new set of fibers passes from the nucleus to the opposite side, runs
upwards to terminate in the lower part of the cortical sensory area.
Lesions of the facial nerve:
1. Lesion in the nucleus:
- Paralysis of the facial muscles.
- No impairment of salivation, lacrimation or taste sensation.
- Other cranial nerves may be affected (same side) or hemiplegia (opposite side).
2. Lesion in the cerebro-potine angle:
- Paralysis of the facial muscles.
- Diminished salivation, lacrimation and taste sensation on anterior 2/3rd of tongue.
- Associated 5th, 6th and 8th cranial nerves paralysis on the same side.
3. Lesion in the geniculate ganglion:
- Paralysis of the facial muscles.
- Diminished salivation, lacrimation and taste sensation on anterior 2/3rd of tongue.
4. Lesion between greater superficial petrosal nerve and chroda tympani:
- Paralysis of the facial muscles.
- Diminished salivation and taste sensation on the anterior 2/3rd of tongue.
- No impairment of lacrimation.
5. Lesion in the extra-cranial portion of the nerve:
- Paralysis of the facial muscles.
- No impairment of salivation, lacrimation or taste sensation on the anterior
2/3rd of tongue.
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In some cases when there is lesion between the geniculate ganglia and
the cerebro-pontine angle, there is an abnormal process of regeneration as
there is cross re-innervation between the autonomic fibers of lacrimation and
the motor branch of the facial nerve, “a crocodile tear syndrome” appears.
This syndrome is characterized by tearing from the eyes when the patient
attempts to yawn or do an active facial movement.
Types of facial palsy:
* Upper motor neuron facial paralysis: The affected side will show:
- Dropping of the angle of the mouth.
- Obliteration of the naso-labial fold.
- Inability to blow the cheek or show the teeth properly.
* Lower motor neuron facial paralysis: There will be additional
involvement of the upper part of the face:
- Abolished wrinkles of the forehead on the affected side.
- Widening of the palpebral fissure.
- Inability to raise the eyebrows or close the eye (Table 2).
Table (2): Lesions of the facial nerve.
Upper motor neuron lesion (UMNL)
Affecting the pyramidal tract above the facial
nucleus.
Paralysis of the muscles of the lower quarter of
the face on the opposite side of the lesion.
Paralysis involves voluntary movements, sparing
the emotional and associative movements.
Paralysis is associated with hypertonia and
hyper-reflexia.
There is associated hemiplegia on the same side
of the paralysis.
Lower motor neuron lesion (LMNL)
Affecting the facial motor nucleus or the
terminal branches of the nerve itself.
Paralysis of the half of the face on the same side
of the lesion.
Paralysis involves voluntary, emotional and
associative movements.
Paralysis is associated with hypotonia and hyporeflexia.
If there is hemiplegia, it is on the opposite side
of the paralysis (crossed hemiplegia).
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Bell's Palsy
It is an acute, non suppurative inflammation of the facial nerve at the
stylomastoid foramen. It is the most common lower motor neuron lesion
affecting the 7th cranial nerve with resultant paralysis of the facial
musculature. The etiology of Bell's palsy is unknown, although a viral
inflammatory immune reaction is commonly accepted as the probable cause.
Bell's palsy may also be of rheumatic cause, which is precipitated by
exposure to air draught. The patient is usually noticed with facial weakness
and tenderness or pain may exist in the stylomastoid foramen.
Complete recovery is usually the rule when return of facial function
begins between 10 and 21 days after the onset of paralysis. If the return
appears after 3 weeks but before 2 months, a satisfactory recovery is usually
possible. An outcome often results if the return is noted after 2 to 4 months.
Clinical picture:
The onset is usually acute with or without pain noticed behind and in
front of the ear. One or two days later, there will be:
- Lower motor neuron paralysis of the facial muscles on the affected side.
- Loss of mimetic movement of half of the face on the same side of lesion.
- The face becomes asymmetrical at rest as well as during movement.
- Inability to raise the eye brow, frown or close the eye.
- Widening of the palpebral fissure.
- Bell’s phenomenon: On attempting to close the eye, the eye ball deviates
upward and laterally due to contraction of the superior rectus and relaxation
of the inferior rectus. It is a normal phenomenon but becomes visible when
eye closure is difficult due to weakness of the orbicularis oculi muscle.
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- Reduced or abolished glabellar and blinking (corneal) reflexes, leading to
drying of the cornea followed by its ulceration.
- Loss of habitual wrinkles due to insertion of the facial muscles in the skin.
- Obliteration of the naso-labial fold.
- Dropping of the corner of the mouth on the affected side.
- Deviation of the mouth toward the same side.
- Inability to smile, show teeth, close the mouth to whistle or blow by the
affected side.
- Accumulation of food between the cheek and the teeth.
Physical assessment:
As it has been mentioned before, muscles on one half of the face at
the side of the lesion are partially or completely affected. The facial muscles
differ from the skeletal muscles as the skeletal muscles are held together by
a fascia, while this is not the case for the facial muscles. So in man, traces of
contraction are possible and movement of one single skeletal muscle bundle
can contract completely and separately from the rest of the other skeletal
muscles.
On the contrary, it is not possible to isolate the facial muscles in
action. Moreover, the facial muscles are located directly in the subcutaneous
tissue under the skin and they have the possibility to move freely. Such
insertion into the skin causes wrinkling of the skin and some individuals
have dimples or grooves. The elasticity of the skin and the amount of
subcutaneous structures are additional factors that permit either free,
mimetic movements or that can give an individual a static expression. So,
the facial muscles do not act on joints and there is no role of gravity to act on
them.
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For these previous reasons, facial muscle testing is applied in group as
isolated muscle action is difficult. They are given only three grades; namely
normal, subnormal and zero.
Procedures:
- Assessment should be carried out in front of a large mirror.
- Differentiation between UMN and LMN facial palsy is crucial.
- Test of pain is carried out firstly on the sound side then the affected one
and finally on both sides simultaneously.
- Test of adhesions is then conducted for different facial muscles proceeding
active muscle testing, which are compared with the sound side of the face.
The physical therapist should demonstrate the movement to the child
and his mother. The mother then is asked to repeat it, explaining it to her
child, who is then asked to perform it several times before actual evaluation
is started. Evaluation must be repeated every two weeks.
Stages:
a) Acute stage: from the onset of paralysis till two weeks (if there is no pain)
or as far as there is pain.
b) Quiescent or recovery stage: after the acute stage and extends up to 17 18 months, extending to two years.
c) Chronic stage: after the two years, there is a little hope in recovery or the
case may need surgical interference.
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Physical applications:
After full assessment has been completed, the treatment program may
be started. Rest is given for 3 days from the start of paralysis.
* Short wave diathermy:
Long-duration (10 minutes) low-intensity short wave diathermy (for
young children) is given as an anti-inflammatory and anti-rheumatic agent. It
is applied every other day for two weeks or as long as there is pain, taking in
consideration the principle precautions such as:
- The site of application should be dry.
- All metallic objects are removed.
- Pad electrodes of suitable size fixed over the ears are used for young child,
while he/she is positioned comfortably on the mother's lap to confirm
stability during application. For older children who can maintain head
position, cup electrodes are used to be placed parallel to the patient's ears.
- Short wave diathermy should not be applied on open wounds.
- There must not be crossing of leads of the apparatus.
- The patient or his mother is advised to cover the site of application and rest
until cooling down, not to wash his face especially in cold weather, not to
use cold water for at least two hours after the end of the setting and not to
expose to air draft.
* Massage:
- Effleurage (longitudinal or half circular): It is utilized to stretch the
muscles on the sound side for relaxing them and to regain normal position of
the affected muscles. It can also be used to improve circulation and
encourage venous return of the face.
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- Petrissage (kneading): It may also be used to relax the facial muscles of
the sound side and also improve circulation.
- Vibration: It is applied on both sides of the nose to induce clearness of
nasal air passages.
- Friction: It is used to break down adhesions (if there is).
Different strokes of massage are given from 5 to 10 minutes.
Application of massage should not exacerbate pain, so it is applied in the
convalescent stage as well as a preparatory to the treatment in other stages as
the recovery stage.
* Electrical stimulation:
Low-frequency electrical stimulation may be used to:
- Improve circulation.
- Help the paralyzed or weak muscles to voluntary contract.
- Accelerate muscle functional recovery.
- Regain normal physiological conditions including elasticity, breaking
down adhesions and increasing the number of mitochondria.
Electrical stimulation may continue up to 17 - 18 months, after which
there is a decreasing hope in recovery, which may be attributed to:
- Slowness or increase difficulty in the formation of new motor end plates.
- Abnormality in the pattern of nerve re-innervation, as the axon grows in
parallel with the muscle fibers, instead of being perpendicular on them.
Electrical stimulation may be applied by placing one electrode in front
of the ear where the nerve trunk is present, while the other electrode is
placed on the stimulated muscle. Two muscles may be stimulated
simultaneously by placing one electrode on each of them.
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* Proprioceptive neuromuscular facilitation:
It consists of therapeutic exercises that use a series of facilitation and
synergy patterns to get muscle strengthening, neuromuscular re-education
and over flow from the stronger muscle groups to the weaker ones. In this
system, the weaker muscles work with the stronger ones and not in isolation.
Maximum resistance can be applied against stronger motions (sound
side of the face or upper limbs) in order to stimulate and reinforce weaker
motions. Neck patterns may be used as reinforcement or a type of irradiation
to facilitate weaker muscles. The neck patterns include:
- Isometric neck extension, for the muscles working in an upward direction.
- Isometric neck flexion, for the muscles working in downward direction.
- Isometric neck rotation, for muscles working in sideways.
Jendrassik maneuver may be applied by giving maximum resistance
against a body part as the upper limbs, while the patient is concentrating on
the facial expressional movements. It works via facilitation of the motor
neuron pools of different body parts, including the facial nuclei.
* Active strengthening exercises:
Assistive, free and resistive exercises are applied according to the
facial muscles’ grades. It should be applied in the form of play. As the facial
muscles could not be isolated in action and as all their movements occur
around three pivots; the mouth, nose and eyes, so working on muscles of one
pivot may be accompanied by working on muscles of another pivot.
The active exercises required include raising the eye brows, frowning,
closing the eyes, raising the fascia covering the nose upwards, widening and
compressing the nasal aperture, raising and everting the upper lip, raising the
angle of the mouth upwards and laterally, drawing the mouth angle laterally
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to smile or show the teeth, drawing the mouth angle downwards and
laterally, drawing the lower lip downwards, bringing the lips together and
protruding them and wrinkling the anterior surface of the neck.
* Splinting:
Splinting may be used to maintain normal facial position and
alignment and to prevent stretching of the strong facial muscles on the weak
ones. Hook splint may be used for grown up children. The hook is connected
between the angle of the affected mouth on the affected side and the
ipsilateral ear. Adhesive plaster may be used for small babies, extending
from the corner of the mouth on the affected side to the ear of the same side.
* Mouth hygiene:
Frequent cleaning of the mouth and teeth is required because of
paralysis of the buccinator muscle and/or loss of sensation on the anterior
2/3rd of the tongue, which leads to accumulation of food between teeth.
* Eye hygiene:
Because of the paralysis of the orbicularis oculi and absence of the
blinking and glabellar reflexes, the eye is subjected to drying and ulceration
of the cornea. Frequent care of eyes using antiseptic washes and ointments is
essential. Advice to wear a dark sunglass is also recommended, especially in
the morning. The patients are advised not to be subjected to dusty weather.
Surgical interference:
The surgeries applied include facial nerve decompression or grafting.
Physical therapy program should be conducted pre and post-operatively.
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