Bell’s Palsy [Facial Nerve Palsy] (OSCE Guide)
Facial nerve palsy can be either UMN type or LMN type. It can be unilateral or bilateral. The most common scenario would be LMN type unilateral facial nerve palsy (Bell’s Palsy) you would encounter at the exam. LMN lesions affect both upper & lower parts of the face in contrast to the UMN lesions.
You should be thanking your destiny if you got Bell’s palsy as one of your cases at the exam because it is one of the easiest short cases you would ever get at the neurology station. Though it is a pretty straightforward case, just diagnosing Lower Motor Neuron (LMN) type of facial nerve palsy may not be enough for you to acquire higher marks. Always think about the possible aetiology & try to localize the site of the lesion whenever possible once you detect LMN type of facial nerve palsy.
The general instruction would be to “Examine the lower motor crannial erves” or “Examine the motor cranial nerves”. Always follow the instruction of the examiner.
BELL’S PALSY – EXAMINATION
DIAGNOSE BELL’S PALSY
- Facial asymmetry (involving affected half of the face – both upper & lower parts)
- Delayed / Absent Blinking of one eye (affected side)
- Loss of facial expressions
- Drooping of the corner of the mouth (affected side)
- Deviation of the mouth to the opposite side when the patient is asked to clench teeth.
- Widened palpebral fissure (affected side)
- Flattened nasolabial fold (affected side)
LOCALIZE THE LEISON
1. At Parotid gland (Parotid Neoplasm)
- Palpate the gland enlargement (Neoplasia).
- Elicit parotid tenderness (Parotitis).
- Look for surgical scars on the parotid gland (Previous Surgery).
2. At External Acoustic Meatus (Ramsey Hunt Syndrome, Infection)
- Look for vesicles in external auditory canal & soft palate.
- Look for pus discharge from the ear.
3. At Middle Ear (CSOM, Cholesteatoma)
- Look for hyperacusis – A tuning fork would sound louder in the affected ear.
4. At Internal Acoustic Meatus (Acoustic Neuroma)
- Look for hearing impairment (Associated 8th nerve palsy when entering together with the facial nerve at internal acoustic meatus).
5. At Cerebellopontine Angle (CP angle tumour)
- Associated 5th nerve palsy – Look for ipsilateral facial numbness along with hearing impairment (8th nerve palsy), 6th nerve may also be involved.
- Ipsilateral Cerebellar Signs.
6. At pons (Pontine infarction / Hemorrhage)
- Associated 6th nerve palsy (Lateral Rectus Palsy) of the affected side. Check eye movements.
Facial Nerve Palsy (Bell’s Palsy) – CASE PRESENTATION
This patient is having left side facial asymmetry involving both upper and lower parts of the face. There is absent blinking of the left eye. The mouth is deviated to the right side when an attempt to clench the teeth. There is reduced facial expressions with widened palpebral fissure and flattened nasolabial fold on the left side.
The parotid gland is not enlarged or tender. There is a vesicular rash involving the left external auditory meatus and soft palate. Other cranial nerve examination is unremarkable.
He is having left LMN type Facial nerve palsy secondary to reactivation of Varicella-Zoster Virus; that is Ramsay-Hunt Syndrome.
FREQUENTLY ASKED QUESTIONS
In UMN lesions of Facial nerve (“Central Seven”) only the lower part of the face on the contralateral side is affected whereas in LMN lesions of Facial nerve (“Bell’s Palsy”) both upper and lower parts of the face on the ipsilateral side are affected.
Intracranial Branches • Greater Petrosal nerve • Communicating branch to Otic ganglion • Nerve to Stapedius • Chorda Tympani Extracranial Branches • Posterior auricular nerve • Nerve to Digastric muscle • Nerve to Stylohyoid muscle • Five major facial branches (Temporal, Zygomatic, Buccal, Marginal mandibular & Cervical)
1. Corneal Reflex - efferent arc. 2. Palmomental reflex
1. Bell’s Palsy (Idiopathic) 2. Parotid Tumours 3. Ramsy-Hunt Syndrome 4. Otitis Media 5. Cerebellopontine Angle Tumours 6. Acoustic Neuroma 7. Mononeuritis Multiplex 8. Basal Skull Fractures
1. Guillain Barre Syndrome 2. Sarcoidosis
It indicates involvement of nerve to Stapedius muscle in inner ear and suggests the lesion is proximal to this level.
It is upward and outward movement of the eye when an attempt to close the eyes. It is a normal defense reflex and becomes noticeable when the orbicularis oculi muscle is weak as in Bell’s palsy.
It is the idiopathic LMN type facial nerve palsy.
Diabetes accounts for 10% of Bell’s palsy.
1. FBC, ESR, CRP 2. Nerve Conduction Studies (if GBS suspected) 3. MRI brain (if SOL suspected)
• Physiotherapy • Corneal Protection (Eye lubricant and covers) • Oral Acyclovir • High Dose Oral Prednisolone (5 days)
1. Persistent facial weakness 2. Corneal abrasions 3. Pain 4. Hemifacial Spasms
It is the LMN type facial nerve palsy caused by reactivation of VZV (Herpes Zoster) affecting the facial nerve.