Overview and Pathophysiology
Bell’s palsy is also called idiopathic peripheral facial paralysis and affects the facial nerve (CN VII), which provides parasympathetic innervation to the submandibular salivary glands, sublingual salivary glands, and lacrimal glands, controls the muscles of facial expression, and conveys taste sensations from the anterior two-thirds of the tongue via sensory fibers.
The right facial nerve controls the right side of face, and the left facial nerve controls the left face. The upper muscles of facial expression are innervated by fibers from both the ipsilateral as well as contralateral cortex. Therefore, a peripheral lesion should completely affect one side of face, while a central lesion should spare the motor function of the forehead, since the contralateral cortex supplies fibers to the affected side.
The incidence of Bell’s palsy is 15-40/100,000, affects men and women equally, and all ages are affected with peak incidence in the 30s to 50s.
Risk factors include pregnancy, diabetes, and previous episode of Bell’s palsy, hypertension, migraine, and psychological stress. Recently, epidemiological studies have revealed that the incidence of Bell’s palsy is also related to extreme temperature exposure. Especially when the head and face was long exposed to an extremely cold or hot temperature environment, the sharp temperature changes will easily lead to microenvironment changes of the microvascular neuron, which may be a high-risk factor of Bell’s palsy.
To date, most Bell’s palsy cases have been detected without determining a definite cause. Although various causes have been proposed including viral, inflammatory, autoimmune, and vascular, the only broadly authenticated findings are inflammation and edema of the facial nerve leading to entrapment within the facial canal. As Bell’s palsy is a clinical syndrome, it is completely possible that more than one disease entity produces the idiopathic facial palsies.
Prognosis is generally good. Recovery is 90% with those moderately affected and 78% in those severely affected. The palsy recurs in 7% of patients with equal incidence of ipsilateral and contralateral recurrence.
Clinical Features
- Weakness or paralysis of the upper and lower facial muscles of the affected side.
- Drooping of ipsilateral side.
- Inability to close the eye completely.
- Dry eye and excessive tearing of the eye (epiphora)
- Drooping of the corner of the mouth.
- Ipsilateral impaired/loss of taste sensation.
- Difficulty with eating due to ipsilateral muscle weakness causing food to be trapped on the affected side of the mouth.
- Dribbling of saliva.
- Altered sensation on the affected side of the face.
- Pain in or behind the ear.
Differential Diagnosis
- Upper motor neuron lesion.
- Herpes zoster oticus (Ramsey Hunt syndrome).
- Rare causes including otitis media, HIV infection, sarcoidosis, autoimmune disorders, and tumors of parotid gland.
Complications
- Motor synkinesis (involuntary muscles occurring at the same time as deliberate movement, e.g. involuntary mouth movement during voluntary eye closure).
- Crocodile tears (tears when eating).
- Incomplete recovery.
- Contractual of facial muscles.
- Reduction or loss of taste sensation.
- Problems with dysarthria due to facial muscle weakness.
Integrative Therapies
- PT including tailored facial exercises. Early facial exercise may reduce recovery time and long-term paralysis.
- Massage with some benefit.
- Thermotherapy is a key to hasten recovery at the early stage of Bell’s palsy.
- Electrical stimulation also is beneficial at the early stage of the palsy.
- Corticosteroids: the maximum benefit is seen when steroids are commenced within 72 hours of the onset of symptoms.
- Antiviral drugs: both acyclovir and valacyclovir have been used in clinical trials. There is currently no evidence to support the use of either antiviral drug on its own.
Acupuncture
- Local points: LI 20, ST 2, 3, 4, 6, 7, SI 18, BL 2, TH 23, GB 2, 14, GV 24, 26, and Tai Yang
- Distal points: LI 4, 11, ST 36, 40, SP 6, 10, HT 8, SI 3, BL 67, PC 8, TH 5, LV 3
- All local points have the effect of eliminating wind and invigorating circulation. LI 4, 11, and LV 3 are effective in eliminating pathogenic wind in the head and facial region.
- Acupuncture can be effective for acute and chronic Bell’s palsy in improving functional and cosmetic outcome.
Cupping Therapy
- Repetitive dry cupping followed by wet cupping over the affected side of face in the same session is the most effective approach with two weeks intervals between treatments for total of three to four visits. Cupping placement varies depending on the area of face most affected.
- Combination of cupping therapy and acupuncture is superior to cupping therapy alone.
- Intensity of cupping: weak to medium.