Bell’s palsy is the sudden onset of weakness (paresis) or complete loss of movement (paralysis) of the one side of the face. It is very traumatic for patients and should be regarded as a medical emergency. The correct management in the first 14 days is crucial to improve the outcome. Although still regarded by some as an idiopathic disorder (unknown cause) overwhelming evidence exists that Bell’s palsy is caused by the herpes simplex virus (cold sore virus). It is not a stroke. In the majority of cases the face will recover to normal but in some cases it may not recover fully. Early decompression surgery (within 14 days), utilizing the middle cranial fossa approach may benefit this subset of patients and prevent the poor long-term outcome. Electrodiagnostic testing is indicated in those patients with complete loss of function. Dr Hofmeyr has experience and has performed numerous middle cranial fossa surgeries for the facial nerve for different indications.
Every facial palsy should be regarded as an emergency
What is Bell’s palsy?
Bell’s palsy is the most common cause of sudden facial palsy. Scottish anatomist, Sir Charles Bell, first described it in 1821. Bell’s palsy occurs on one side of the face, sudden in onset and is often preceded by pain behind the ear.
The annual incidence of Bell’s palsy is 15-40 per 100 000 of the population. There is an equal male to female ratio and a three times greater incidence in pregnant females. Familial inheritance has been found in 4-14% of cases with a recurrence rate of 10-12%. The left and right sides are equally involved and less than 1% of cases are bilateral. It is also considered to be four to five times more likely to occur in diabetics. It is more common in adults than in children. It has a poorer long-term outcome in older patients.
The facial nerve
Bell’s palsy is a condition or disorder of the facial nerve. The facial nerve is the seventh cranial nerve (CN VII) and is the nerve that travels the longest distance within a bony canal of all the nerves in the human body. The facial nerve controls the muscles of facial expression. Other functions of the facial nerve include taste sensation of the front part of the tongue, facial sensation and the production of tears and saliva.
Facial nerve palsy, paralysis and paresis
According to Wikipedia the term “palsy” refers to various types of paralysis. A “paralysis “ is the loss of muscle function for one or more muscles and a “paresis” a condition typified by a weakness of voluntary movement, or partial loss of voluntary movement or by impaired movement. In Bell’s palsy the weakness of the facial muscles is not due to the muscles itself, but due to an injury of the facial nerve.
Although the impaired movement of the face is by far the most distressing symptom it should be realized that the other functions of the nerve are also affected.
Out of a clinical, prognostic and management viewpoint it is important to distinguish between patients with paresis and those with a paralysis.
Diagnosis of Bell’s palsy
Bell’s palsy is a diagnosis of exclusion, by elimination of other reasonable possibilities. It is a clinical diagnosis and no confirmatory test exists. It is of sudden onset, temporary duration, lack of progression and clinically complete resolution of the inflammation. If a taste disturbance and pain behind the ear are present it is caused by a virus. Regular meticulous clinical examination in the first 14 days will distinguish between patients with a paresis (weakness) and a paralysis (complete loss of movement). A standardized grading system such as the House Brackmann facial nerve grading system should be used to record observations.
Patients often report the following symptoms:
- Pain behind the ear
- Taste disturbance (dysgeusia)
- Increased sensitivity to touch (somatophobia)
- Increased sensitivity to loud sounds (hyperacusis)
- Reduced sensation of the cheek and the cornea of the eye
- Dizziness and vertigo
- Increased tearing of the eye
- Reduced tearing and a dry eye (sometimes both sides)
- Choking and irritation on swallowing
The following tests may be of use to exclude other conditions and to treat Bell’s palsy:
- Diagnostic hearing tests including speech discrimination scores
- Immittance and reflex testing of the ear
- Computed tomography (CT scan) of the temporal bone
- Magnetic resonance imaging (MRI) with gadolinium to exclude central causes and tumours
- Blood tests
- Plain X rays of the lateral skull base to exclude marble bone disease.
- Electrodiagnostic testing (MST, ENOG or EMG)
- Topographic tests
- Auditory brainstem response audiometry (ABR)
- Balance and vestibular testing (VNG, DVA, VHIT)
Other causes of facial palsy
- Ramsey Hunt syndrome (Herpes zoster oticus)
- Mobius syndrome, congenital lower lip paralysis, Melkersohn Rosenthal syndrome, marble bone disease (e.g. sclerosteosis)
- Birth trauma, temporal bone fractures, facial lacerations, penetrating facial wounds
- Acute otitis media, otitis media with effusion (OME), malignant otitis externa, syphilis, tuberculosis, HIV/AIDS, glandular fever, Lyme disease
- Cholesteatoma, acoustic neuroma, facial nerve neuroma, haemangioma, haemangioblastoma, meningioma, paraganglioma (glomus tumour), leukemia, parotid tumour, rhabdomyosarcoma.
- Diabetes mellitus, thyroid problems, pregnancy, auto-immune disease
- Multiple sclerosis and Guillain-Barre syndrome
Why perform electrodiagnostic testing?
Patients with complete paralysis may have different grades of injury to the nerve. In some cases the nerve may degenerate which will result in a less satisfactory outcome. Recovery may take longer, be incomplete and lead to abnormal function. Electrodiagnostic testing can help to differentiate patients with intact conduction (better outcome) and those with degeneration (poorer outcome). Nerve stimulation tests using surface electrodes are used. It is recommended that the first stimulation test be done on day three after the onset of the palsy. The maximum stimulation test (MST) and electroneurography (ENOG) are two tests that are performed. It can help to monitor the progression of nerve damage in the first few days. With the information obtained a more accurate prognosis can be given to a patient. It is mandatory for those patients in which decompression surgery is contemplated. Patient participation is good because when the worried patient feels the muscles contract on stimulation, it is an immense relief.
Visual observation with electro stimulation
A variation of the ENOG test is to observe the muscle contractions produced at the same time as measuring the compound action potentials. Additional information is obtained and this test can be called ‘visual ENOG’. This method of testing is especially suitable for use with a small nerve stimulator. If the evoked muscle contractions drop to 50% of normal, the patient can be referred for ENOG testing.
Topographic tests for Bell’s palsy
Topographic tests are of historical interest and have not been found to be of much use clinically for determining the site of the lesion in facial paralysis or for predicting the outcome. These include the Schirmer’s test for lacrimation, stapedial reflexes, electrogustometry and salivary flow testing.
Every facial palsy should be regarded as an emergency.
After excluding other causes of facial paralysis, treatment of Bell’s palsy is medical at first. Fortunately, 85% of patients with Bell’s palsy have full return of facial function.
Steroid treatment should be started immediately by the referring doctor and not delayed until a specialist is seen. When requesting an appointment with a specialist, the urgency should be stressed and the specialist should see the patient within 1-2 days.
- Systemic steroids: Prednisone is prescribed initially for the duration of five days for both complete and incomplete palsies. Depending whether it is a weakness (paresis) or total loss of movement (paralysis) the dose and duration of treatment is then adjusted accordingly. Prednisone should never be stopped abruptly because rebound inflammation can lead to further injury to the nerve.
- Antivirals may be of benefit if started within 3 days of the onset.
- Analgesics: The steroids usually help to reduce the pain, but additional analgesics may be required.
- Eye care is of major importance. Because the eye cannot close, natural tears or a tear gel should be prescribed. The eye should also be protected at night.
- Serial electrodiagnostic testing is indicated for all patients with paralysis. Due to limited value it is not performed earlier that 3 days after the onset.
- Decompression surgery: The consensus is that, if surgery is performed, the labyrinthine segment of the nerve and meatal foramen should be decompressed via a middle cranial fossa (MCF) approach.
- Physiotherapy: Most facial nerve researchers do not recommend physiotherapy treatment. The argument that muscle atrophy during the time of total paralysis is prevented does not apply to the facial muscles. Experience gained with patients who needed nerve grafts many months after the onset of the paralysis have shown that excellent movement recurs, even after many months of inactivity of the muscle, by utilizing physiotherapy.
- Mime therapy is a form of physiotherapy that has shown promising results in limiting long-term complications of Bell’s palsy such as involuntary simultaneous movement of different facial muscles (synkinesis) and spasm.
- Botulinum toxin injections may help to reduce established synkinesis and asymmetric movements in some patients.
If there is no return of facial movement within four months after the onset of Bell’s palsy, the diagnosis should be reconsidered.
In South Africa, marble bone disease should be excluded in children who present with Bell’s palsy.
Surgery for Bell’s palsy
The aim of early (within 14 days) decompression surgery for Bell’s palsy is to reduce the poor long-term outcome, which can occur in some patients. One predictor of poor long-term outcome is age. In several studies it have been shown that in patients older than 60 a poor outcome is to be expected in at least 66%. For younger patients with paralysis a poor long-term outcome ranges from 10 to 25%.
Poor long-term outcome may include to any degree:
- Permanent weakness
- Permanent complete loss of movement
- Involuntary simultaneous movement of different facial muscles (synkinesis)
- Spasm of facial muscles
- Contractures of facial muscles
- Facial asymmetry
- Dry eyes, corneal abrasion and blindness
- Reduced ability to close the mouth
- Impaired taste (dysgeusia)
- Impaired speech (dysarthria)
- Psychological problems
The challenge is to identify the subset of patients who will have a poor outcome, early enough. Meticulous regular clinical examination, using a grading system such as the House Brackmann facial nerve grading system, will help to identify patients with a paralysis. Electrodiagnostic testing (ENOG) will then quantify the percentage of degeneration compared to the intact side.
In selected patients surgical decompression of the meatal foramen and labyrinthine segment of the facial nerve, utilizing a middle cranial fossa (MCF) approach has proven to improve the outcome. If performed by appropriately trained surgeons it is effective, safe, preserve hearing and improve long-term facial motor function in patients.
Decompressing the nerve through the mastoid (transmastoid) has been abandoned and is not effective since the narrowest and critical point of compression and conduction block of the facial nerve is at the meatal foramen and labyrinthine segment.
Dr Hofmeyr’s experience
Dr Hofmeyr has experience and has performed more than 100 middle cranial fossa surgeries for the facial nerve for different indications. He trained internationally at the House Ear Institute (Los Angeles) and Prof Ugo Fisch (Zurich). Working with Dr H Hamersma vital experience was gained performing the middle cranial fossa approach in difficult cases of patients with marble bone disease.