Facial Paralysis and Bellâ€™s Palsy in Children: Current Diagnostic Concepts and Management Controversies
Dr. Salman is a clinical research fellow in the Division of Neurology at the Hospital for Sick Children in Toronto.
Disclosure: The author reports no financial, academic, or other support of this work.
Acknowledgment: Dr. Salman would like to thank Dr. Daune MacGregor for editing and appraising the manuscript, and for her general and continuous support.
Please direct all correspondence to: Michael S. Salman, MSc, MRCP, Hospital for Sick Children, 555 University Ave, Toronto, Ontario, M5G 1X8; Tel: 416-813-1500; Fax: 416-813-6334; E-mail: firstname.lastname@example.org
How is facial paralysis in children different from adults? Facial paralysis is uncommon in children. Before making the diagnosis of Bell’s palsy (acute idiopathic facial weakness), a prompt search for other causes must be made, especially when the child is <2 years of age, with facial weakness that progresses 3 weeks after onset or fails to improve within a few weeks, and is recurrent or bilateral. There is evidence that implicates herpes simplex virus and, to a lesser extent, varicella zoster virus reactivation in the pathogenesis of Bell’s palsy in children. This may explain its excellent prognosis in that age group. Management includes supportive treatment, such as artificial tears and eye patching. The current medical literature does not provide evidence for significant benefit from the use of steroids in pediatric Bell’s palsy. A trial involving a larger number of children is needed to document if steroids provide moderate benefit in Bell’s palsy. There is not enough information to recommend the routine use of acyclovir in pediatric Bell’s palsy, however, there is some evidence of benefit for using acyclovir in facial paralysis caused by varicella zoster virus reactivation.
Bell’s palsy is defined as acute idiopathic facial muscle paralysis. It is a diagnosis of exclusion and its annual incidence is about 20/100,000.1 Bell’s palsy in the pediatric population has a different natural history, differential diagnosis, and different prognosis than in adults and, hence, deserves special consideration. This review attempts to address these issues with emphasis on establishing the correct diagnosis and reviewing evidence-based medical literature regarding management of Bell’s palsy.
Facial paralysis has been described since ancient times. In 1821, Sir Charles Bell2 drew attention to the anatomical course and function of the facial nerve. His name was linked to facial nerve paralysis at a time when nocause can be found.
Anatomy of the Facial Nerve
The facial corticobulbar tracts descend from the facial cortical motor area through the corona radiata and the internal capsule. The tracts then pass through the ventromedial lower pons, near the corticospinal tract, and descend mainly to the level of the upper medulla. The fibers decussate in the upper medulla and ascend in the dorsolateral medulla to synapse mainly in the contralateral facial nucleus.3
The facial motor nucleus supplying the upper facial muscles receive bilateral cortical innervation from the appropriate motor cortex. The lower facial muscles receive innervation from the contralateral motor cortex. A unilateral cortical (upper motor neuron) lesion spares the upper facial muscles and causes weakness of the contralateral lower facial muscles. This is seen in pediatric strokes caused by middle cerebral artery occlusion. Lesions affecting the facial motor nucleus and nerve cause weakness of all facial muscles ipsilaterally.
The facial nerve nucleus lies dorsolaterally in the caudal pons and upper medulla. The facial nerve leaves the brainstem at the pontomedullary junction. It enters the apex of the petrous part of the temporal bone with the eight cranial nerve and gives branches to the lacrimal gland, and stapedius muscle in the inner ear, sensation to the auricular skin, and the sublingual/submandibular salivary glands, and supplies the anterior two thirds of the tongue with taste fibers. Just before exiting the skull through the stylomastoid foramen, the facial nerve lies close to the inner ear and mastoid air cells. Finally, the facial nerve innervates the muscles of facial expression ipsilaterally.4
Adult Versus Pediatric Facial Paralysis
Children represent approximately 10% of the total number of cases with facial paralysis.5,6 Bell’s palsy accounts for approximately 50% of the adult cases and approximately 35% of the pediatric cases.6
The natural history of Bell’s palsy in adults is less favorable than in children. Adult studies report complete resolution in 70% to 80% of cases,7 compared with 90% to 96% of pediatric cases.8.9 This probably relates to the etiology of the disease, which is likely to be viral in origin in the pediatric population. Therefore, it is not surprising that the disease course and response to treatment in children is different than in their adults counterparts.
Clinical Presentation of Bell’s Palsy
A prodromal viral illness precedes the onset of Bell’s palsy by 1–4 weeks in 60% of cases. The onset of the paresis is abrupt and can progress over 1–7 days (but not weeks or months) to complete paralysis. The paresis involves all the ipsilateral facial muscles, including the forehead muscles. There is no predilection to either side of the face.5 Eyelid closure and blinking are asymmetrical, leaving the cornea vulnerable to dryness and exposure keratitis. The subject’s smile is asymmetrical, which is especially noticeable when looking at the alae nasi (nasal folds between the nares and the corner of the lips). Facial muscle twitching is not seen. The paresis can be accompanied by mild facial pain or otalgia (50%), subjective altered sensation over the affected side of the face (40%) or tongue (20%), and change of taste (50%).10,11
Facial Nerve Function Evaluation
In some case reports, photographs of the face have been used to show the degree of facial paralysis.6,11,12 Few clinical tools have been developed to assess the function of the facial nerve in a more standardized way. This is of particular importance in clinical trials evaluating the effect of different treatment modalities. The Adour/Swanson grading scale gives a facial paralysis recovery profile.13The House-Brackmann Facial Nerve Grading System14 has gained more popularity in clinical trials.15-17 The House-Brackmann Facial Nerve Grading System has six grades; grade I is normal, while there is total paralysis in grade VI.
Another practical tool is the Facial Nerve Cooperative Study Group Score of the Ministry of Health and Welfare of Japan, where it has been used in patients with Bell’s palsy.18 The score is based on 10 clinical observations including asymmetry of the face at rest, wrinkling of the forehead, blinking of the eyes, closing the eyes lightly and tightly, closing one eye, movement of the alae nasi, grinning, whistling, and closing the lip tightly. More recently, the Sunnybrook Facial Grading System was shown to be reliable when applied by novice users.19
When a child presents with facial paralysis, it is important to avoid labeling it as Bell’s palsy until other causes have been considered and excluded (Table 1).20-29 This is especially important in children <2 years of age.A thorough history and clinical examination will help identify congenital, traumatic, and infective causes, which account for the majority of cases in the first 2 years of life.
Important symptoms that may help in localizing the site of the lesion along the course of the facial nerve include lacrimation, which can be quantified using the Schirmer tear test (dry eyes indicate involvement of the facial nerve at or proximal to the geniculate ganglion), hyperacusis (sensitivity to sound), salivation (dry mouth), and loss of taste (indicates distal involvement of the facial nerve).
Congenital absence of the orbicularis oris muscle, found at the corners of the mouth, is a common source of diagnostic confusion in early infancy and is frequently mislabeled as Bell’s palsy. It causes asymmetrical smile or cry. However, forehead muscles, eye closure (seen during crying or sleeping), and blinking are all symmetrical and normal.
Möbius syndrome causes facial diplegia due to aplasia of the facial nerve nuclei. It is associated with bilateral sixth cranial nerve palsy (the eyes are unable to move laterally even with oculocephalic head maneuver), deafness, palatal and lingual palsy, deficiency of the pectoral muscles, and extremities defects (syndactyly, missing or extra digits). Special attention must be paid to examining the central nervous system for evidence of brainstem and other cranial nerves involvement (eg, deafness, vertigo, dizziness, vomiting, difficulty swallowing).
The external auditory canal and tympanic membrane must be examined for evidence of varicalla zoster virus vesicles, seen in Ramsay-Hunt syndrome (herpes zoster oticus). The timing of the vesicle appearance tend be delayed in children.23 Hence, Ramsay Hunt syndrome may be initially indistinguishable from Bell’s palsy.24 The presence of tinnitus, hearing loss, nausea, vomiting, vertigo, and nystagmus, though less common in children than adults with Ramsay Hunt syndrome, may aid in making the correct diagnosis.23
The presence of mastoid bone redness and tenderness should be established or excluded. Bilateral parotid gland inspection and palpation should be done to evaluate asymmetrical enlargement caused by infiltrating mass or tumor recurrence.
Unless the history or clinical exam reveals additional abnormal and unexpected findings, no further tests are indicated for the diagnosis of Bell’s palsy. Some experts suggest doing a complete blood count to exclude the presence of leukemia because facial paralysis is an unusual presenting sign of leukemia. Table 2 lists the investigations that may aid the physician in the diagnosis of facial paralysis.
Recurrent or Bilateral Facial Paralysis
Recurrent or bilateral facial paralysis is uncommon and accounts for approximately 6% to 12% of all cases in both the adult and the pediatric population.10,30 The rate of full clinical recovery is approximately 70%, which is lower than in unilateral Bell’s palsy.30 Prompt search for other causes is recommended, eg, Möbius syndrome, Lyme disease and other infections, Guillain-Barré syndrome, myasthenia gravis, leukemia, and trauma. Melkersson-Rosenthal syndrome is a rare familial disease that causes bilateral, or alternating and recurrent facial paralysis accompanied by facial edema and transversely fissured tongue (cheilitis).
Pathophysiology of Bell’s Palsy
Many patients with Bell’s palsy have been found to have rising antibody titers to herpes simplex virus.31 Different pathophysiological processes have been suggested,31 including active viral invasion or immune processes causing demyelination and facial nerve swelling. Other mechanisms include vascular ischemia and heredity (based on few case reports with familial recurrence of facial paralysis). In early life, the anatomy of the skull makes the facial nerve more susceptible to damage by infections and trauma.32
Treatment of Bell’s Palsy
Supportive measures include the use of artificial tear drops and patching the affected eye especially at night to prevent dryness, exposure keratitis, and subsequent corneal ulceration.
Recent systematic reviews7,33-35 in adult onset Bell’s palsy suggested that steroids are probably effective in improving facial functional outcome, especially if the paralysis is complete.34 A Cochrane systematic review, with stricter inclusion criteria,36 concluded that steroids were not beneficial. These systematic reviews did not analyze the pediatric cases separately.
A recent pediatric systematic review by Salman and MacGregor37 failed to find evidence for benefit from trials involving the use of steroids in pediatric Bell’s palsy. In the only randomized, controlled pediatric trial in Bell’s palsy,17 the outcome was not improved with steroids use. This study was not double-blinded or placebo-controlled.
Acyclovir is an antiviral drug that is used to treat herpes simplex and varicella zoster viral infections. There are reports showing benefits in Ramsay-Hunt syndrome21 and in patients with zoster sine herpete (acute facial paralysis associated with varicella zoster virus reactivation without vesicles).38 The routine use of acyclovir in Bell’s palsy is not proven and cannot be recommended. In one systematic review7 it was concluded that acyclovir in combination with steroids may be possibly effective in improving facial functional outcome in adult patients. A recent Cochrane review on the subject has been retracted.39,40
Steroids and/or acyclovir may confer moderate rather than significant benefits in Bell’s palsy. Such an effect would only be detected in trials with a large large number of participants. The effect of steroids and/or acyclovir should be tested in severely affected patients with complete paralysis. Specific benefits in this group may be seen, but this remains to be established in a purpose-designed clinical trial.
Other treatments have been used in Bell’s palsy and include Vitamin B12,18 acetyl carnitine,41 hyperbaric oxygen,42 and pentoxiphylline.33 These treatments have been previously reviewed.33 There is a lack of evidence for their benefit in pediatric Bell’s palsy.
Many surgical techniques have been advocated to improve facial nerve function in patients with facial paralysis12 and there is no evidence to support surgical decompression in patients with Bell’s palsy.7
In the pediatric age group, the prognosis for full recovery is excellent in approximately 95% of cases. The remainder recover partially, especially if their paralysis was complete at the onset. The blink reflex and electroneuronography (nerve conduction and electromyography) of the facial nerve have been used to aid prognosis.4,8
Long-term complications with facial paralysis may occur (Table 3).43 Surgical techniques aimed at improving function, plastic surgery aimed at improving facial appearance and facial muscle functioning, ie, smiling and cosmesis, are available and have been reviewed recently.4
What is New in Bell’s Palsy?
A significant number of children with Bell’s palsy have rising antibody titers against herpes simplex virus and as such, they are not truly idiopathic. Some cases of herpes simplex virus-seronegative with acute periphral facial paralysis are caused by varicella zoster reactivation in the geniculate ganglion without vesicular rash (zoster sine herpete).44,45 The use of tests for the rapid diagnoses of varicella zoster virus suggests that the early use of acyclovir in the appropriate settings may aid in the full recovery from facial paralysis.38 Magnetic resonance imaging is used to delineate the site of the facial-nerve lesion accurately46 and to aid prognosis.47
Facial paralysis in the pediatric age group has many etiologies, especially during the first 2 years of life. Herpes simplex and, to a lesser extent, varicella zoster viruses may account for many cases of Bell’s palsy (the idiopathic group). The use of acyclovir in such cases is controversial as there is usually a significant time delay before these viruses are detected. The prognosis of pediatric Bell’s palsy without treatment is excellent. The use of steroids in Bell’s palsy does not result in significant benefit. Larger clinical trials are needed to show if steroids confer moderate benefits and better functional recovery. Further trials are needed to investigate the use of acyclovir in pediatric Bell’s palsy. PP
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