This article describes two cases involving facial (7th) nerve, or Bell’s, palsy, which may prove of great concern, not only to the patient, but also to those nearest and dearest to them. Typically, eye care practitioners may only see these patients some time after onset by which time they may have suffered considerable distress.
Figure 2 caption: Signs of facial palsy after four months of management. 1: wrinkle lines across entire forehead 2: left eye absent blink reflex 3: left lower ectropion absent 4: puffiness of cheek returned 5: smile on right side but not the left (teeth revealed only on right)
Case 1
While watching daytime television with his wife, a 68-year-old male patient suddenly suffered a sharp earache and a severe pain at the back of the head. Immediately, his wife noticed the left side of his face had dropped and he was drooling from the affected side. Fearing he had suffered a stroke, she rang 999 and he was taken to an accident and emergency department.
Fortunately, he was seen by a neurology consultant who undertook a few critical tests and eliminated stroke as the culprit. FAST test for strokes was applicable here:
- Face paralysis
- Arms paralysis
- Speech problems
- Time
Diagnosis
There were no paralysis of the legs or arms and no speech slurring or swallowing issues. The only positive sign was facial paralysis. His final diagnosis was Ramsay Hunt Syndrome, a complication of shingles infection (see later). This was made on the basis of the sharp ear pain, a reported reduction in his taste sensation and the facial paralysis. There were no obvious rash around the ear, as is usually the case with shingles infection affecting the facial nerve. Figure 1 summarises the clinical findings. No MRI or CT scans were undertaken.
Figure 1: Clinical presentation of case 1 patient. The patient
presented with a left 7th nerve palsy and the following signs:
1: absence of wrinkling on the left side of the forehead and a smooth appearance
2: ability to raise the right brow to cause frown lines on this side
3: left inferior ectropion
4: drop of the left side of the face
5: lip frown distorted to the right
6: drooping of left side of the mouth
Management
Treatment was immediately initiated with oral prednisolone and anti-viral acyclovir. Celluvisc preservative-free eye drops (carmellose sodium) were prescribed to use throughout the day to prevent the eyes drying up, and overnight he was given vitamin A eye ointment to prevent corneal erosions.
The patient was also given face massages and ‘funny face’ exercises which he would do regularly with his grandchildren to see who would make the funniest face. He was also recommended acupuncture treatment. Four months later, the improvements were considerable with only a loss of blink reflex, slight drop of the lips and a loss of smile (figure 2). He used the lubricating eye drops two to four times a day to ensure that the eyes did not dry up.
Case 2
A 61-year-old male patient was suffering from a common cold when, one fateful afternoon, in April 2016, he was visiting a wedding venue with his wife and daughter. As they were chatting with the venue host, they all suddenly noticed his speech sounding garbled. The left side of his face had dropped together and there was a drooping of the left lower eyelid. Indeed, the signs were very similar picture to those shown in figure 1. His wife took him immediately to the local accident and emergency department fearing a stroke.
A whole raft of tests was undertaken, including an MRI, and the findings are summarised as follows:
- Left seventh nerve palsy (Bell’s palsy)
- Asymmetric enhancement of the 7th cranial nerve at the apex of the internal auditory meatus (see figure 3)
- The enhancement of the facial nerve was shown to involve both the horizontal section (petrous) as well as the vertical section (stylomastoid) of the nerve
- No obvious infiltration by meningioma or schwannoma was observed
- No ischaemia, infarct or haemorrhage was identified
- No intracranial space occupying lesions were seen
- Bulky and prominent parotid glands were found, though with no focal lesion, inflammation or infiltration
Diagnosis
Left seventh nerve palsy following inflammation of the nerve at the apex of the internal auditory meatus and extending to involve the horizontal section and vertical section of the facial nerve was the final diagnosis.
Figure 3: Enhancement of the left facial nerve at the apex of the internal acoustic meatus (red arrow) and further enhancement of the horizontal petrous section (blue arrow) and vertical stylomastoid of the facial nerve (dashed purple arrow). The geniculate ganglion (GG), which remains unenhanced, is seen as a rounded bulge. The enlarged right and left parotid glands (PG) are highlighted
Management
The patient was prescribed oral corticosteroids to dampen the inflammation and help with the palsy. For his lower left eyelid ectropion, he was given lubricant eye drops to use regularly. It was stressed he should not use massaging or acupuncture so as to prevent any further accentuation of the inflammation.
Four months later, the improvement was excellent with no obvious face palsy remaining. The right eye was able to blink fully while the left was not. He had a good symmetry of the mouth and both the cheeks showed puffiness.
Discussion
Bell’s palsy
Facial nerve palsy (or Bell’s palsy) is usually a unilateral, idiopathic weakness or complete paralysis (loss of movement) of one side of the face of sudden onset. Sir Charles Bell first described sudden facial palsy in 1821. Annually, the incidence of facial nerve palsy is 30 per 100,000 of the population, with equal risk for the right and left sides, and more commonly observed in adults than in children. Bilateral cases represent just 1% of cases with multiple sclerosis being the main cause. Resolution of facial palsy is expected within six to eight weeks, and confirmation of idiopathic facial nerve palsy must be reached following exclusion of the following:
- Neoplastic lesions; these may include a facial tumour, acoustic neuroma, parotid gland malignancy or a brain stem tumour.
- Infections; such as mastoiditis and cholesteatoma (a benign growth in the middle ear as a result of recurrent ear infection)
- Degenerative disease; such as multiple sclerosis
In the main, the mechanism of idiopathic facial nerve palsy is a swelling of the facial nerve due to a viral or immune disorder. Herpes simplex virus is the most common causative agent, while Herpes zoster virus is the second most common. Other causes include middle ear infection, sarcoidosis, Lyme disease, diabetes, cerebellopontine angle tumours and chronic meningitis. If facial paralysis occurs slowly, then a schwannoma (nerve sheath tumour) should be suspected as the cause of compression of the facial nerve.
Symptoms of pain behind the ear often precedes facial paresis, and complete facial paralysis develops within hours with maximal effect within 48 to 72 hours. Patients may feel numbness or heaviness within the face. The affected side of the face drops, becoming expressionless, accompanied by a loss of wrinkling over the forehead, loss of blink and loss of smile. It is helpful to ask the affected patient to smile, blink, raise an eyebrow, pucker lips, puff cheeks and whistle to assess facial nerve function.
Ramsay Hunt syndrome (Geniculate Herpes)
Ramsay Hunt syndrome is due to shingles infection affecting the facial nerve. Herpes Varicella zoster virus, which remains dormant in the geniculate ganglion following chicken pox infection, may reactivate and travel from the ganglion so causing the facial nerve to become inflamed and irritated. Activation of the shingles virus could happen with stress and when the immune system is weakened. Ramsay Hunt syndrome accounts for 20% of all facial nerve palsies, and 80% of sufferers will exhibit the following:
- Vesicular rash of the ear or hair line
- Pain behind the ear
- Taste sensation disturbance on the affected half of the tongue
- Facial pain, usually described as severe, deep, stabbing or ‘electric’ and replicates the dominant symptoms of shingles
- Loss of facial expression
- Speech impediment
- Difficulty with eating as a result of lip and cheek weakness
Fifty percent of cases also report vertigo, dizziness and hearing loss due to vestibular (8th) nerve involvement. Paralysis of the stapedius muscle can result in tinnitus or ringing in the ear.
For facial nerve paralysis, prompt treatment within 48 hours with high dose of steroids (prednisolone 80mg once a day for one week and gradually reduced over the second week) is used. For Herpes simplex infection, antiviral drugs (typically acyclovir 400mg, five times a day for 10 days) are prescribed in combination with prednisolone. Protecting the cornea should also be a priority, with lubricants applied regularly in the daytime and ointment overnight and, if necessary, taping of the eyelids.
Facial nerve course and function
Understanding the anatomy of the facial nerve and its function both in motor (facial muscle movement) and sensory (lacrimation, salivary and taste) is important. The motor part of the facial nerve starts in the pons where it curves around the 6th nerve nucleus and joins the sensory root. The combined facial nerve enters together with the vestibular 8th nerve at the internal auditory meatus in the petrous part of the temporal bone (figure 4). On reaching the medial wall of the middle ear, it swells to form the geniculate ganglion nucleus. Figure 5 then shows the further journey of the facial nerve.
Figure 4: View of the internal auditory meatus looking from the ear inwards. The image on the right shows in detail the position in the left image linked by the yellow arrow. It shows the facial nerve at the top (green arrow), the cochlear nerve inferiorly (blue arrow) and superior and inferior vestibular nerves (red line)
The facial nerve at the apex or base of the internal auditory meatus enters the facial canal and runs laterally through the inner ear. It then bends sharply and descends behind the pyramid to provide branches to the stapedius muscles which protect the ears from loud noise.
Figure 5: The facial nerve journey. The motor facial nerve courses around the 6th nerve nucleus in the pons. It is joined by the sensory root before entering the internal auditory meatus (IAM). On reaching the medial wall, it swells to form the geniculate ganglion nucleus (GG) which releases the greater petrosal nerve (PN) which carries parasympathetic fibres innervating the lacrimal gland to stimulate
Before leaving the facial canal, the chorda tympani (CH TYM) branches from the facial nerve to supply taste sensation to the anterior two thirds of the tongue as well as supplying the salivary glands.
As the facial nerve exits via the stylomastoid foramen, at the base of the skull, it gives off small sensory axons called the posterior auricular nerve (PAN) which supplies a small area behind the ear.
The facial nerve now passes forward through the parotid gland to distribute the five branches that determine facial expression as follows; 1: temporal branch (TN) supplying the frontal muscles allowing the forehead to wrinkle and frown. 2: zygomatic branch (ZN) supplying the superior and inferior orbicularis muscles of the eyes enabling blinking. 3: buccal branch (BUC) allowing movement of the mouth and lips (supporting chewing) and the zygomaticus muscle (allowing smiling). 4: mandibular branch (MAND) supplying the lower lips and chin and allows side to side movement. 5: Cervical branch (CERV) which forms a series of arches across the side of the neck over the suprahyoid region and innervates the posterior belly of the digastric muscle and the stylohyoid muscle.
Figure 6: Stroke on the right side of the brain (a supranuclear lesion) results in paralysis of the left lower face (dashed blue arrow), while the eyelids and forehead are unaffected
Point to remember
Remember that Bell’s or facial nerve paralysis is a lower motor neurone lesion causing the whole one half of the face to lose motor function on the same side as the underlying lesion.Stroke, on the other hand, represents a supranuclear lesion in the motor cortex or the posterior limb of the internal capsule in the brain causing paralysis of the contralateral lower half, with loss of smile and face drop. Eyelid closure and brow movement remain intact due to bilateral innervation (figure 6).
Kirit Patel is an optometrist in independent practice in Radlett, Hertfordshire.