1	Bell’s Palsy: The Most Common Cause of Facial Nerve Paralysis J. Pulnik MD, M. Hollingshead MD, F. Castellano MD, M. Castillo MD Department of Radiology University of North Carolina at Chapel Hill
2	Overview Introduction Review of facial nerve anatomy Clinical and imaging features of Bell’s palsy Typical Atypical Alternative causes of acute facial paralysis References
3	Introduction Bell’s palsy accounts for 75% of cases of acute facial nerve (7^th Cranial Nerve) paralysis⁽¹⁾ Imaging is not needed in patients with acute facial paralysis unless they have atypical features With atypical features, MR & CT may demonstrate other lesions affecting the facial nerves⁽²⁾ The facial nerve can be affected anywhere along its course⁽³⁾
4	Facial Nerve Nuclei Facial nerve nuclei lie in reticular formation of brainstem, ventral to floor (tegmentum) of 4^th ventricle⁽⁴⁾ Motor Nuclei: Surrounded by efferent fibers form small mounds on floor of 4^th ventricle (facial colliculi)⁽⁵⁾ Non-Motor Nuclei: Salivatory Solitary
5	Facial Nerve Efferent fibers surround 6^th CN nucleus & exit at cerebellopontine angle (CPA) Facial nerve fibers course into superior, anterior quadrant of the internal auditory canal (IAC)⁽⁶⁾
6	Facial Nerve Nerve fibers exit the IAC via fallopian canal Narrowest portion throughout entire course Probable culprit in facial nerve compression in Bell’s palsy & other causes of nerve swelling Fibers then course to geniculate ganglion Give rise to greater superficial petrosal nerve Contains taste axons from tongue & somatic fibers⁽⁴⁾
7	Facial Nerve Fibers course posteriorly, under lateral semicircular canal in middle ear (tympanic portion) Fibers angle back & inferiorly at “second genu” diving into the descending canal Here, the last somatic and parasympathetic fibers separate from the facial nerve via the chorda tympani nerve
8	Facial Nerve Facial nerve exits skull base at stylomastoid foramen Facial nerve angles superiorly & anteriorly behind posterior margin of vertical mandibular ramus Just before entering parotid gland, inferior branches arise Posterior auricular, digastric & stylohyoid Within substance of parotid gland, superior branches arise Temporal, zygomatic, buccal, orbicularis oris, mandibular & cervical
9	Clinical Signs Suggest Site of Facial Nerve Lesion Upper face is supplied by bilateral motor cortices Lower face is supplied only by contralateral motor cortex Therefore, unilateral central lesions spare upper face Lesions distal to geniculate ganglion lead to mostly motor abnormalities Lesions proximal to geniculate ganglion lead to motor, gustatory & autonomic abnormalities
10	Typical and Atypical Bell’s Palsy
11	Typical Bell’s Palsy Incidence⁽⁷⁾ 15–30 per 100,000 Usually during winter Etiology not entirely understood ? viral (Herpes Simplex Virus) or idiopathic Viral infection of facial nerve could result in demyelination, inflammation & swelling Trapping nerve in narrow confines of fallopian canal
12	Typical Bell’s Palsy Usually a clinical diagnosis Acute onset unilateral (lower or upper) facial paralysis, posterior auricular pain, decreased tearing, hyperacusis (30%) & disturbances of taste By physical examination, Bell’s palsy divided according to classification by House and Brackman⁽⁸⁾ Grades 1 & 2 have better outcomes with worse outcome as grade increases. Overall 80-90% recover completely⁽⁹⁾ Over age 60, only 40% recover completely^(7,9)
13	Imaging in Typical Bell’s Palsy Imaging in typical Bell’s palsy is not usually necessary When necessary, MRI is exam of choice In normal patients, the facial nerve distal to the geniculate ganglion can enhance However, the facial nerve proximal to geniculate ganglion does not normally enhance⁽¹⁰⁾ In patients with Bell’s palsy, enhancement of facial nerve in fallopian canal & IAC is typical⁽⁶⁾
14	Imaging in Typical Bell’s Palsy
15	Imaging in Typical Bell’s Palsy
16	Atypical Bell’s Palsy Diagnosis suggested by atypical clinical features^(11,7) Slower onset of symptoms, bilateral, or recurrent Numbness is not unusual Progression beyond seven days suggests another cause
17	Imaging in Atypical Bell’s Palsy
18	Alternative Causes of Acute Facial Nerve Paralysis
19	Alternative Causes of Acute Facial Nerve Paralysis Atypical signs & symptoms require imaging Bilateral, recurrent, or slow onset Clinical history is crucial Choice of imaging modality Diagnosis
20	Ramsay Hunt Syndrome^(7,11) Caused by reactivation of varicella zoster virus (herpes virus type 3) A cause of facial paralysis with hearing loss “Herpes Zoster Oticus” Other symptoms Vertigo Rash around ear (66%) Involvement of other cranial nerves (esp. Trigeminal Nerve) Worse prognosis than Bell’s Only 50% recover completely^(7,11) Important cause of facial paralysis in children of 6-15 years⁽¹³⁾
21	Ramsay Hunt Syndrome
22	Ramsay Hunt Syndrome
23	Lyme Disease (Borreliosis) Lyme disease⁽¹²⁾ Endemic areas (Northeast USA, central Europe, Scandinavia, Canada) Consider in children with atypical facial palsy See enhancement of facial & other cranial nerves as well as small white matter lesions similar to multiple sclerosis⁽¹²⁾ Facial paralysis is bilateral in 25% Potentially debilitating disease can be curable early with antibiotics
24	Lyme Disease
25	Other Infectious Causes Acute facial paralysis may result from bacterial or tuberculous infection of middle ear or mastoid & from necrotizing otitis externa⁽⁷⁾ Immune compromised patients are at risk for pseudomonal infection Incidence of facial paralysis with otitis media is 0.16%⁽⁷⁾ Infection extends via bone dehiscence to nerve in fallopian canal leading to swelling, compression & eventually vascular compromise & ischemia⁽¹⁴⁾ Poor prognosis < 50% recover completely
26	Parotid Disease
27	Tuberculosis
28	HIV Infection
29	Trauma Most acute post traumatic facial palsies are due to fractures of temporal bones Historically, fractures are classified as longitudinal or transverse with transverse carrying risk of permanent paralysis⁽¹⁵⁾ Longitudinal fractures usually lead to temporary paralysis from concussion & swelling of nerve Transverse fractures can lead to transection of nerve⁽¹⁶⁾ In all types of paralysis due to fracture, usually the region of the geniculate ganglion is involved
30	Trauma
31	Neoplasms 27% of patients with tumors involving the facial nerve develop acute facial paralysis⁽⁷⁾ Most common causes 7^th CN schwannomas, hemangiomas (usually near geniculate ganglion), perineural spread such as with head and neck carcinoma, lymphoma & leukemia^{(7,11,17,18,19)} Other neoplasms can also involve the facial nerve Adults: metastatic disease, glomus tumors, vestibular schwannomas & meningiomas Children: eosinophilic granuloma & sarcomas
32	Facial Nerve Schwannoma
33	Vestibular Schwannoma Rare cause of facial paralysis unless large, because the facial nerve is resistant to compression
34	Glomus Tumor Glomus tumors arising from jugular bulb (jugulare) and/or middle ear (tympanicum) may involve the facial nerve
35	Hemangioma
36	Hemangioma
37	Perineural Tumor Spread
38	Meningioma Second most common primary tumor of CPA Rarely results in facial paralysis
39	Wegener’s Granulomatosis
40	Rhabdomyosarcoma
41	Hypertrophic Polyneuropathy
42	Other Causes Guillain-Barre Syndrome Ascending paralysis Iatrogenic Temporal bone surgery Excision of vestibular schwannoma has <10% chance of paralysis⁽¹¹⁾ Middle ear surgeries Babies who required forceps delivery >90% recovery
43	Melkersson-Rosenthal Syndrome^(7,21) Very rare Familial but sporadic Usually begins in adolescence Recurrent episodes of facial paralysis Facial swelling Fissured tongue “Scrotal” tongue Leads to facial disfigurement No definite therapy
44	Conclusion While Bell’s palsy does not typically require imaging for diagnosis, radiologic evaluation is important in the work-up of patients with atypical or unusual presentations of acute facial nerve paralysis. Identification of discreet lesions may lead to a change in management of these patients.
45	References (Zalvan CH, Selesnick SH. Bell Palsy. www.emedicine.com/ent/topic719.htm) (Monnell K, Zacahariah SB. Bell Palsy. www.emedicine.com/neuro/topic413.htm) Sim VL, Guberman A, Hogan MJ. Acute bilateral opercular strokes causing loss of emotional facial movements. Can J Neurol Sci 2005; 32(1):119-121 Wilson-Pauwels L, Akesson EJ, Stewart PA, Spacey SD. Cranial nerves in health and disease (2nd edition). Hamilton, Ontario. BC Decker Inc 2002:115-140 Fatterpekar GM, Delman BN, Boonn WW et al. MR microscopy of normal human brain. Magn Reson Imaging Clin N Am 2003; 11(4):641-653 Davidson HC. Imaging of the temporal bone. Magn Reson Imaging Clin N Am 2002; 10:573-613 Jackson CG, von Doersten PG. The facial nerve – Current trends in diagnosis, treatment, and rehabilitation. Med Clin N Am 1999; 83(1):179-195 House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg 1985; 93(2):146-147 Koike Y, Aoyagi M, Ichige A et al. Nationwide investigation on diagnostic methods for facial palsy. Acta Otolaryngol Suppl 1988; 446:30-35 Gebarski SS, Telian SA, Niparko JK. Enhancement along the normal facial nerve in the facial cranial: MR imaging and anatomic correlation. Radiology 1992; 183:319-394
46	References Benecke JE. Facial paralysis. Otolaryngol Clin N Am 2002; 35: 357-365 Coyle PK, Schutzer SE. Neurologic aspects of Lyme disease. Med Clin N Am 2002; 86(2): 261-284 Furuta Y, Ohtani F, Aizawa H et al. Varicella-zoster virus reactivation in an important cause of acute peripheral facial paralysis in children. Pediatr Infect Dis J 2005; 24(2): 97-101 Rizk EB, El-Bitar MA, Matae GM, Saad K, Mikati MA. Facial nerve palsy with acute otitis media during the first 2 weeks of life. J Child Neurol 2005; 20(5): 452-454 Ishman SL, Friedland DR. Temporal bone fractures: traditional classification and clinical relevance. Laryngoscope 2004; 114(10): 1734-1741 Zehnder A, Merchant SN. Transverse fracture of the temporal bone. Otol Neurotol 2004; 25(5): 852-853 Koide R. Acute facial paralysis as the initial presentation of parotid tumor. No To Shinkei 2003; 55(4):374-375 Schattner A, Kozack N, Sandler A, Shtalrid M. Facial diplegia as the presenting manifestation of acute lymphoblastic leukemia. Mt Sinai J Med 2001; 68(6): 406-409 Ho TP, Carrie S, Meikle D, Wood KM. T-cell lymphoma presenting as acute mastoiditis with a facial palsy. Int J Pediatr Otorhinolaryngol 2004; 68(9): 1199-1201 Gerressen M, Ghassemi A, Stockbrink G et al. Melkersson-rosenthal syndrome: case report of a 30-year misdiagnosis. J Oral Maxillofac Surg 2005; 63(7): 1035-1039