Bell's palsy Flashcards
definition of Bell’s Palsy
idiopathic lower motor neuron facial (CN7) nerve palsy
acute, unilateral facial nerve weakness or paralysis of rapid onset (less than 72 hours) and unknown cause
aetiology of bell’s
idiopathic
60% preceded by upper resp tract infection = suggesting viral/post-viral aetiology
weakness and paralysis may be from inflamm and oedema of CN7 = nerve compression and damage as pass through the temporal bone
Herpes simplex virus, varicella zoster virus, and autoimmunity may contribute to the development of Bell’s palsy, but the exact pathogenesis is controversial and the significance of these factors remains unclear
RF for bell’s
dm
immunocomprimised
obesity
hypertension
upper resp conditions
pregnancy
CN7
special secretory innervation to the lacrimal gland
- greater superficial petrosal branch
- Schirmer’s test may be used to identify facial nerve lesions in relation to the geniculate ganglion
motor innervation to stapedius - contracts with loud stimuli - protective dampening reflex
epidemiology of bell’s
most common diagnosis associated with CN7 weakness or paralysis
8/10 facial mononeuropathies
overall relatively uncommon: 20-30 per 100000
equally effect men and women
most cases aged 20-50yrs
sx of bell’s
Prodrome of pre-auricular pain in some cases followed by acute (hours/days)onset unilateral facial weakness (involve upper and lower part of face) and droop (<72hrs). max severity in 1-2 days
- reduction in movement on the affected side, often with drooping of the eyebrow and corner of the mouth and loss of the nasolabial fold.
- unilateral mouth sagging
50% get ipsilateral facial, neck, ear pain or numbness
numbness or tingling in cheek/mouth
hypersensitivity to sounds - hyperacusis caused by stapedius paralysis
loss of taste - ageusia (uncommon)
Difficulty chewing, dry mouth (in 20%), food trapped between the gum and cheek
speech articulation problems, drooling
incomplete closing, ear pain, tearing or drying of exposed eye, injury from foreign bodies, conjunctivitis
ectropion - sagging and turing out of the lower eyelid
signs of bell’s
do otoscopy, palpation of parotid gland and neck and assess movement of facial muscles
- CN7 runs from skull base, within middle ear cavity and temporal bone to emerge via the stylomastoid foramen and then within the substance of the parotid gland
- hemifacial paralysis: need to assess external auditory canal and tympanic membrane, palpation of the parotid gland and neck, assessment of the muscles of facial expression to grade the severity of the palsy and ascertain which branches of the facial nerve are affected
LMN weakness of facial muscles - affects all ipsilateral msucles of facial expression ie non-forehead sparing
unable to whistle - tests buccinator
bell’s phenomenon
ear examined to rule out other causes - otitis media, herpes zoster infection
bell’s phenomenon
eyeball rolls up but eye stays open when trying to close eye
face numbness reported by pt, but sensation testing is normal
Ix for Bell;s
rule out other causes
Blood
- ESR
- glucose
- raised borrelia Ab in lyme disease
- raised VZV Ab in Ramsay Hunt syndrome
CT/MRI
- space occupying lesions
- stoke
- MS
CSF - rarely done, for infections
EMG
- May show local axonal conduction block in facial canal.
- Only useful>1 week after onset.
Mx for Bell’s
protection of cornea with protective glasses/patches and artificial tears (hypermellose)
encourage regular eyelid closure by pulling lid down by hand
tape to close eye at night
high dose corticosteroids (prednisolone 60mg/d PO for 5dasy, tailing by 10mg/d) - beneficila within 72hrs = speeds recovery, 95% make full recovery (only if Ramsay Hunt’s syndrome is excluded)
little guidance of treatment >72hrs - corticosteroids often used allow SE
surgery
surgery for bell’s
lateral tarsorrhaphy (suturing the lateral parts of the eyelids together) if imminent or established corneal damage
if eye closure remains a long term problem (lagophthalmos) or ectropion is severe
complications of bells
corneal ulcers
vision loss
eye infection
facial pain and parasthesia
dry mouth - loss of PNS to submandibular and sublingual salivary glands
intolerance to loud noise
aberrant reinnervation may occur eg blinking may cause contraction of angle of mouth because of simultaneous innervation of obicularis oculi and ori
PNS may also aberrantly reinnervate = crocodile tears while salivating
psychological effect - reduced social connections
Px of bell’s
85-90% recover function in 2-12wks with or w/o treatment
incomplete paralysis w/o axonal degeneration = full recovery in weeks
complete paralysis
- approx 80% full spontaneous recovery
- 15% have axonal degeneration (50% in preg) - recovery delayed, after 3mo, may have aberrant connections
