1. Imaging in Acute Facial Nerve Paralysis
M Castillo, MD, FACR
Department of Radiology
University of North Carolina, Chapel Hill

2. Overview of Presentation
Introduction
Review of facial nerve anatomy
Clinical and Imaging features of Bell’s palsy
Typical
Atypical
Other causes of acute facial paralysis

3. Introduction
Bell’s palsy accounts for 75% of cases of acute facial nerve (7th cranial nerve) paralysis
Imaging is not needed in majority of patients unless they have atypical features
W/atypical features, MR & CT may demonstrate potentially treatable lesions affecting facial nerves
Facial nerves can be affected anywhere along their course

4. Anatomy Review
Facial nerve nuclei lie in reticular formation of brainstem, ventral to floor (tegmentum) of 4th ventricle(4)
Motor Nuclei:
Efferent fibers surround nuclei of CN VI & form small mounds on floor of 4th ventricle (facial colliculi)
Non-Motor Nuclei:
Salivatory
Solitary
Facial colliculus

5. 7th nerve courses into internal auditory canal (IAC)
Efferent fibers surround 6th CN nucleus & exit at cerebellopontine angle (CPA)
7th nerve courses into internal auditory canal (IAC)
Within superior anterior quadrant(6)
Ant
Post

6. Exits IAC via Fallopian canal
Narrowest point throughout entire course
Felt to be culprit in facial nerve compression in Bell’s palsy & other causes of nerve swelling

7. Progress to geniculate ganglion
Gives rise to greater superficial petrosal nerve
Contains taste axons from tongue & somatic fibers

8. Fibers then course posteriorly under lateral semicircular canal in middle ear (tympanic portion)
Fibers angle back & inferiorly at “second genu” diving the descending canal
Here last somatic & parasympathetic fibers separate from facial nerve via the chorda tympani nerve
Mastoid segment
Tympanic Portion

9. 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 originate
Posterior auricular, digastric & stylohyoid
Within substance of parotid gland, superior branches arise
Temporal, zygomatic, buccal, orbicularis oris, mandibular & cervical

10. Clinical Signs Suggesting Site of Facial Nerve Lesion
Upper facial territory is supplied by bilateral motor cortices
Lower facial territory is supplied only by contralateral motor cortex
Therefore, unilateral central lesions spare upper face
Lesions distal to geniculate ganglion
Mostly motor abnormalities
Lesions proximal to geniculate ganglion
Motor, gustatory & autonomic abnormalities

11. Typical Bell’s Palsy Incidence Etiology not entirely understood
15–30 per 100,000
Usually during winter
Etiology not entirely understood
Possibly viral (Herpes Simplex Virus) or idiopathic
Viral infection of facial nerve results in demyelination, inflammation & swelling
Traps nerve in narrow confines of fallopian canal
Diagnosis of exclusion
Made only when clinical & imaging (if necessary) findings are supportive

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
Grades 1 & 2 have better outcomes with worse outcome as grade increases.
80-90% recover completely
Over age 60, only 40% recover completely

13. Imaging in Typical Bell’s Palsy
Imaging in typical Bell’s palsy is not usually necessary
When necessary, MRI is best
Normal facial nerve distal to geniculate ganglion may enhance
Facial nerve proximal to geniculate ganglion does not normally enhance
In patients with Bell’s palsy, enhancement of facial nerve in fallopian & ICA is typical

14. C/o Dr. M. Michel, Wisconsin

16. Atypical Bell’s Palsy Clinical features Numbness is not unusual
Slower onset of symptoms
Bilateral
Recurrence
Numbness is not unusual
Progression beyond seven days suggests another cause

17. Imaging in Atypical Bell’s Palsy
C/o Dr. M. Michel, Wisconsin

18. Alternative Causes of Acute Facial Nerve Paralysis
Atypical signs & symptoms which suggest etiology other than Bell’s palsy require imaging
Clinical history is crucial in distinguishing etiologies
Choice of imaging technique depends on clinical suspicion

19. Lyme Disease Lyme disease (borreliosis)
Endemic areas (Northeast USA, central Europe, Scandinavia, Canada)
Consider in children w/atypical facial palsy
Imaging: small white matter lesions similar to multiple sclerosis, enhancement of facial & other cranial nerves
Bilateral facial paralysis: 25%
Important to make diagnosis early because it is curable early w/antibiotics

21. Ramsay Hunt Syndrome
Caused by reactivation varicella zoster virus (herpes virus type 3)
Facial paralysis + hearing loss +/- vertigo
Herpes zoster oticus
Two-thirds of patients have rash around ear
Other cranial nerves, particularly trigeminal nerves (5th CN) often involved
Worse prognosis than Bell’s (complete recovery: 50%)
Important cause of facial paralysis in children
6-15 years old

23. C/o Dr. M. Michel, Wisconsin

24. Infectious causes
Acute facial paralysis may result from bacterial or tuberculous infection of middle ear, mastoid & necrotizing otitis externa
Incidence of facial paralysis with otitis media: 0.16%
Infection extends via bone dehiscences to nerve in fallopian canal leading to swelling, compression & eventually vascular compromise & ischemia
Immune compromised patients are at risk for pseudomona infection
Poor prognosis (complete recovery is < 50%)

25. Tuberculosis

26. Parotid & peri-parotid disease

27. HIV Infection

28. Bezold’s abscess & coalescent mastoiditis

29. Trauma
Most acute post traumatic facial palsies are due to t-bone fractures
Historically fractures classified as longitudinal or transverse with transverse carrying risk of permanent paralysis
Longitudinal fracture usually leads to temporary paralysis from concussion & swelling of nerve
Transverse fracture can lead to transection of nerve
In all types of paralysis due to fracture, usually the region of geniculate ganglion is involved

31. Neoplasms
27% of patients with tumors involving the facial nerve develop acute facial paralysis
Most common causes: schwannomas, hemangiomas (usually near geniculate ganglion) & perineural spread such as with head and neck carcinoma, lymphoma & leukemia
Other neoplasms can also involve the facial nerve
Adults: metatstatic disease, glomus tumors, vestibular schwannomas & meningiomas
Children: eosinophilic granuloma & sarcomas

32. Hemangioma

33. Hemangioma

34. Facial Nerve Schwannoma

36. Perineural Tumor Spread

37. Glomus Tumor
Glomus tumors arising from jugular bulb (jugulare) and/or middle ear (tympanicum) may involve the facial nerve M

38. Rhabdomyosarcoma & squamous cell carcinoma of the EAC
Other tumors
Rhabdomyosarcoma & squamous cell carcinoma of the EAC

39. Vestibular Schwannoma
Common tumor
However, facial nerve is resistant to compression
Therefore, tends to produce facial paralysis mostly when they attain a large size

40. Vestibular Schwannoma
-Common tumor
-However, facial nerve is resistant to compression, thus, tends to produce facial paralysis mostly when they attain a large size

41. Meningioma Second most common primary tumor of cerebellopontine angle
Rarely results in facial paralysis

42. Rhabdomyosarcoma

43. Miscellaneous Causes

44. Hypertrophic Polyneuropathy
Hypertrophic polyneuropathies occasionally lead to facial paralysis

45. Wegener’s Granulomatosis

46. Other Causes Guillain-Barre Syndrome Ascending paralysis Iatrogenic
Temporal bone surgery
Excision of vestibular schwannoma has <10% chance of paralysis
Middle ear surgeries
Babies who required forceps delivery
>90% recovery

47. Melkersson-Rosenthal Syndrome
Acute episodes of facial paralysis
Facial swelling
Fissured tongue
“Scrotal” tongue
Very rare
Familial but sporadic
Usually begins in adolescence
Leads to facial disfigurement
No definite therapy

48. Conclusion
While Bell’s palsy does not typically require imaging for diagnosis, imaging 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.