Facial Nerve Palsy (Bell’s Palsy)

• 11-40/100,000 per year

• 1/60 persons in a lifetime

• Associated with presence of HSV 1 but causal link not proven

• Definition:

o Bells palsy is an idiopathic facial nerve palsy that presents with a typical clinical presentation

- May be best referred to as Bell’s palsy syndrome. If the presentation does not fit the syndrome alternative causes should be sought

Anatomy

Innervates – “Face, ear, taste, tear’

2 components:

• Facial nerve proper – pure motor, innervates muscles of facial expression

• Nervus Intermedius – visceral and somatic afferent fibres + visceral efferent fibres

Anatomically 4 components:

• Intraaxial segment – Facial nerve nucleus, looping around abducens nucleus, course anter-laterally (as well as inferior) to exit at pontomedullary junction

• Cisternal segment – Courses laterally through CP angle together with vestibulocochlear nerve into the internal auditory meatus

• Intratemporal facial nerve – into IAC as the most anterosuperior of the foure nerves

o Labyrinthine segment to anterior genu/geniculate ganglion,

o courses posteriorly under the lateral semicircular canal(as tympanic segment),

o descends in mastoid as the mastoid segment, exits the stylomastoid foramen and enters the parotid gland

• Extracranial facial nerve – ramifies into its terminal motor branches

Functional components:

Motor nerve

• Nucleus in pons, loops around 6^th nerve nucleus

• Branch to stapedius

• Exits via stylomastoid foramen

• Passes under parotid gland

• Innervates muscle of face (sans muscle of mastication)

Somatic sensory nerve

• Innervates skin over the external auditory meatus

• Posterior auricular nerve joins main facial nerve

• Cell bodies in the geniculate ganglion

• Travels in nervus intermedius through internal auditory meatus to spinal nucleus of the trigeminal nerve in the medulla

Special sensory nerve

• Supplies taste to the anterior 2/3 of the tongue

• Initially travel in lingual nerve (branch of mandibular nerve which is branch of trigeminal nerve)

• Travels in corda tympani to cell bodies in the geniculate ganglion

• Travels in nervus intermedius to solitary tract (tractus solitarius) in the medulla

o The posterior 1/3 of the tongue is innervated via the glossopharyngeal nerve which also ends in this nucleus.

Special visceral parasympathetic efferents

• Superior salivary nucleus in the pons

• Travels in nervus intermedius

• Divide at geniculate ganglion to supply:

o Salivary glands (except parotid) – via chorda tympani

o Lacrimal glands – via greater petrosal nerve and pterygopalatine ganglion

Clinical

Core features:

• Unilateral lower motor facial weakness

o Forehead involvement

o Difficulty with eye closure (decreased blink rate)

• Acute, but not sudden, onset

• Maximal weakness within 72 hours (often within 48hrs)

• Recovery begins within 4 weeks

Other features:

• Pain behind the ear ~50%

o Mild-moderate severity

o Before weakness 25%, contemporaneous 50%, after 25%)

• Taste sensation altered/lost unilaterally (anterior 2/3 tongue) 35%

• May be hyperacusis (abnormally acute hearing) ~5%

• Dry eye (Parasympathetic lacrimal involvement) 30%

• Dry mouth (Parasympathetic salivary) 20%

• Sensory symptoms (common)

o Patients often describe altered sensation as an initial sign - ?due to lack of movement, tightness of skin rather than true sensory involvement

Red flags for alternative diagnosis:

• Other cranial neuropathies (including hearing/vestibular)

• Severe pain

• History of cancer

• Fever

• Rash around ear (Ramsay hunt)

• Gradual progression over time

• Lack of any recovery

Prognosis

• ~80% recover with a couple of weeks-months

• Steroid treatment trials – 23% incomplete recovery in steroid group vs 32% in placebo group

• Presence of incomplete paralysis in first week is the best prognostic sign

• Complications

• Synkinesis

• Motor – e.g. smiling leads to eye closure

• Autonomic - e.g. hunger triggers tears

Investigations:

• MRI

o May reveal swelling of geniculate ganglion and facial nerve, and maybe entrapment of swollen nerve in temporal bone

- Facial nerve enhancement within the CPA or IAC is always abnormal

- However enhancement of the labyrinthine segment is generally normal (due to vascular plexus)

o Main role is to exclude alternative diagnosis in atypical presentations

• EMG may be of some prognostic value

• May be mild CSF lymphocytosis

• From radiopaedia:

DDx:

Lower motor neuron facial lesions

• Trauma

• Tumours

o Temporal bone

o Parotid gland

o Acoustic neuroma (most often a complication of surgery for this)

• Infection

o Ramsay Hunt Syndrome (see below)

o Meningitis – TB, lyme, other bacterial, HIV

o Mastoiditis

o Severe otitis media

• Inflammatory/autoimmune

o GBS

o Sarcoid

o Mononeuritis multiplex

o Myasthenia gravis

Upper motor neurone facial lesions

• Brainstem stroke

• Small stroke affecting corticospinal tract

Treatment:

Evidence for steroids and antivirals

• 2 large modern trials with very similar results:

o Swedish trial (Engstrom Lancet Neurology 2008)

- 829 patients, Prednisolone 60mg per day then reduce by 10mg/day +/- valaciclovir

- Full recovery at 12 months – steroids vs no steroids -72% vs 57% (ARR 15%, NNT 7)

- No difference with addition of antivirals

o Scottish trial (Sullivan NEJM 2007)

- 551 patients, Prednisolone 10 days +/- acyclovir

- Full recovery at 9 months - steroids vs no steroids – 94.4% vs 81.6% (ARR 12%, NNT 8)

- No difference in with addition of antivirals

• Both used time frame out to 72hours, previous trials used out to 10 days ?evidence for shorter timeframe unclear

• Both trials had very minimal adverse events (<5%) with possible mild, but not statistically significant increase in GI upset, insomnia.

• Cochrane review – overall there in a also a significant reduction in the proportion of patients getting synkinesis

• Glucocorticoids

o Consistent evidence of benefit

o 60mg during the first 5 days and tapered over the next 5 days

o Or 50mg for 10 days

• Antivirals:

o Use of antiviral alone is not effective.

o Large trials (discussed above) showed no clear benefit of addition to prednisolone

o Subsequent meta-analysis (JAMA 2009) suggested possible borderline benefit (?although skewed by smaller, poor quality studies)

- May be beneficial in combination with steroids in patients with severe facial weakness or pain

- Acyclovir within first 3 days for 10 days may improve outcome.

o Not recommended by therapeutic guidelines

• Eye care

o Frequent lubricating eye drops

o Nocturnal eye ointment

o Consider taping eyelids shut at night to prevent corneal drying

o If severe may need temporary surgical closure of lid (tarsorrhaphy)

o Advise patient to seek review ASAP if pain or bluring

References

Practical Neurology 2016 – Review

Lancet Neurology 2008 7:933

· Prednisone for 10days resulted in faster recovery

· Valaciclovir for 7days did not.

JAMA Meta-analysis

JAMA. 2009;302(9):985-993

· Steroids alone RR 0.69 (of poor outcome), NNT 11

Ramsay Hunt Syndrome

• Herpes Zoster oticus

• Triad of

o Facial paralysis

o Ear pain – often severe

o Vesicles in auditory canal +/- auricle

- May also be anterior 2/3 tongue or hard palate

- Develop after paralysis in 15%

• Can also affect cranial nerves

o VIII – vertigo (30%), nausea, hearing loss (50%), tinnitus (20%)

o V, IX and X

• Vestibular disturbances common

• Worse prognosis for recovery than standard Bell’s palsy

o 50% left with incomplete recovery

• Antivirals in combination with steroids prescribed however data is lacking