Bell’s Palsy

Question 1

… … refers to a unilateral facial nerve palsy of unknown cause.

Answer 1

Bell’s palsy refers to a unilateral facial nerve palsy of unknown cause.

Question 2

The facial nerve is divided into five branches, which collectively control the muscles of facial expression.

Answer 2

The facial nerve is the VII cranial nerve. The nucleus is located in the pons, which is part of the brainstem. The nerve root passes through the internal acoustic canal within the temporal bone in close proximity to the inner ear. It then enters the facial canal giving off several branches before exiting the skull via the stylomastoid foramen. It terminates into five terminal motor branches within the parotid gland.

Question 3

NOTE: A common exam question relates to the cause of hyperacusis in Bell’s Palsy. This occurs due to weakness of the … muscle though this particular sign is often absent.

Answer 3

NOTE: A common exam question relates to the cause of hyperacusis in Bell’s Palsy. This occurs due to weakness of the stapedius muscle though this particular sign is often absent.

Question 4

The facial nerve terminates within the parotid gland giving off five terminal motor branches:

Answer 4

Temporal
Zygomatic
Buccal
Mandibular
Cervical

Question 5

Parasympathetic functions - facial nerve

Answer 5

Greater petrosal nerve: arises in the facial canal. Provides parasympathetic supply to the lacrimal gland via the pterygopalatine ganglion.
Chorda tympani: arises in the facial canal. Provides parasympathetic supply to the submandibular gland and sublingual glands via the submandibular ganglion.

Question 6

….: provides taste to the anterior two-thirds of the tongue.

Answer 6

Chorda tympani: provides taste to the anterior two-thirds of the tongue.

Question 7

Bell’s palsy is the most common cause of facial nerve palsy. Other causes of facial weakness (upper and lower motor neuron - see below) include:

Answer 7

Bell's palsy (click here)
Inner ear disease (Otitis media, cholesteatoma)
Parotid disease (Parotid tumour, parotitis)
Sarcoidosis (click here)
Guillain-Barré syndrome (click here)
Lyme disease
Trauma
Stroke (click here)
Tumours
Encephalitis
Meningitis (click here)
Multiple sclerosis (click here)
Diabetes mellitus related neuropathy (click here)

Question 8

Bell’s palsy typically presents with rapid onset (< … hours) of unilateral facial weakness.

Answer 8

Bell’s palsy typically presents with rapid onset (< 72 hours) of unilateral facial weakness.

Question 9

Symptoms of bell’s palsy

Answer 9

Unilateral facial weakness
Post-auricular/ear pain (50%)
Difficulty chewing
Incomplete eye closure
Drooling
Tingling (cheek/mouth)
Hyperacusis (heightened sensitivity to sound)

Question 10

Signs of Bell’s palsy

Answer 10

Loss of nasolabial fold
Drooping of the eyebrow
Drooping of the corner of the mouth
Asymmetrical smile
Bell’s sign (upward movement of the eye maintained on attempt to close the eye)

Question 11

Differentiating upper and lower motor neuron lesions

Answer 11

Bell’s palsy is a ‘stroke mimic’, but it is differentiated from stroke by the absence of ‘forehead sparing’. Facial weakness can be caused by an upper motor neuron (UMN) or lower motor neuron (LMN) lesion. Examples of UMN lesions include stroke and cerebral tumours.

The frontalis muscle, which is supplied by the temporal branch of the facial nerve, has bicortical innervation. This means it receives information from both hemispheres of the cerebral cortex. Therefore, in UMN lesions leading to unilateral facial weakness, there is ‘forehead sparing’ (i.e. the frontalis can still function). In LMN lesions, the frontalis is affected leading to complete unilateral paralysis.

Question 12

Bell’s palsy is a ‘stroke mimic’, but it is differentiated from stroke by the absence of ‘… …’. Facial weakness can be caused by an upper motor neuron (UMN) or lower motor neuron (LMN) lesion. Examples of UMN lesions include stroke and cerebral tumours.

Answer 12

Bell’s palsy is a ‘stroke mimic’, but it is differentiated from stroke by the absence of ‘forehead sparing’. Facial weakness can be caused by an upper motor neuron (UMN) or lower motor neuron (LMN) lesion. Examples of UMN lesions include stroke and cerebral tumours.

Question 13

… lesions leading to unilateral facial weakness, there is ‘forehead sparing’ (i.e. the frontalis can still function). In … lesions, the frontalis is affected leading to complete unilateral paralysis.

Answer 13

UMN lesions leading to unilateral facial weakness, there is ‘forehead sparing’ (i.e. the frontalis can still function). In LMN lesions, the frontalis is affected leading to complete unilateral paralysis.

Question 14

Bilateral involvement - bells palsy

Answer 14

Bilateral facial nerve palsy is an extremely rare condition that is usually secondary to an underlying diagnosis (e.g. Lyme disease, sarcoidosis, Guillain-Barre Syndrome or HIV among others). Therefore, patients presenting with bilateral facial nerve palsy need specialist neurology input.

Question 15

Acute facial paralysis can be graded using the House-Brackmann system.

Answer 15

The House-Brackmann system was originally created to assess the degree of facial nerve damage following surgery, but is now commonly used to assess functional recovery following an episode of Bell’s palsy.

Question 16

Bell’s palsy is a clinical diagnosis based on unilateral facial weakness, of rapid onset, without forehead sparing.

Answer 16

Investigations may include routine blood tests, neuroimaging or specialists tests (i.e. lumbar puncture, lyme serology). It is important to consider a HIV test in any patient with Bell’s palsy.

When assessing a patient with new onset facial nerve palsy, it is important to consider alternative causes of facial palsy that may prompt further investigations. Features that point to an alternative diagnosis include:

Insidious onset +/- progressive
Overt pain
Systemic illness +/- fever
Vestibular abnormalities
Hearing abnormalities (other than hyperacusis)
Forehead sparing (i.e. suspected UMN lesion)
Mass
Recurrent palsy
Bilateral involvement

Question 17

When assessing a patient with new onset facial nerve palsy, it is important to consider alternative causes of facial palsy that may prompt further investigations. Features that point to an alternative diagnosis include:

Answer 17

Insidious onset +/- progressive
Overt pain
Systemic illness +/- fever
Vestibular abnormalities
Hearing abnormalities (other than hyperacusis)
Forehead sparing (i.e. suspected UMN lesion)
Mass
Recurrent palsy
Bilateral involvement

Question 18

Management is largely supportive, but … may be used in those presenting within 72 hours of onset.

Answer 18

Management is largely supportive, but prednisolone may be used in those presenting within 72 hours of onset.

Question 19

Management of bells palsy

Answer 19

General points: Patients should be reassured that the prognosis is good, but it may take several months to recover. If eating is affected advise a straw for liquids and a soft diet.
Medical therapy: In patients presenting within 72 hours, prednisolone (e.g. 50 mg for 10 days) may be given. Anti-viral treatment (i.e. aciclovir) may be considered in combination with corticosteroids, but this should be discussed with specialists.
Eye care: It is critical to provide good eye care, which includes drops (i.e. lubricating drops and ointments), advice on taping the eye when sleeping, sunglasses outdoors. Any patient with incomplete eye closure (House-Brackmann ≥ IV) should be referred to ophthalmology.

Question 20

Complications

Of Bell’s palsy

Answer 20

The majority of patients with Bell’s palsy will make a full recovery within four months.

Question 21

The majority of patients with Bell’s palsy will make a full recovery within four months.

Answer 21

Referrals should be made if patients develop eye symptoms (e.g. corneal ulcer), show no improvement after three weeks or develop late problems with aberrant reinnervation (e.g. Marcus-Gunn jaw-winking).

Aberrant reinnervation presents with synkinesis, which describes voluntary muscle contraction leading to involuntary contraction of another muscle. It is due to regenerating collateral nerves that have inadvertently supplied another muscle.