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

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Presentation on theme: "Imaging in Acute Facial Nerve Paralysis M Castillo, MD, FACR Department of Radiology University of North Carolina, Chapel Hill."— Presentation transcript:

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 (7 th 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 4 th ventricle (4) Motor Nuclei: –Efferent fibers surround nuclei of CN VI & form small mounds on floor of 4 th ventricle (facial colliculi) Non-Motor Nuclei: –Salivatory –Solitary Facial colliculus

5 Efferent fibers surround 6 th CN nucleus & exit at cerebellopontine angle (CPA) 7 th 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 Fallopian Canal

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

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 Tympanic Portion Mastoid segment

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 –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 % 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

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16 Atypical Bell’s Palsy Clinical features –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

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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 (5 th CN) often involved Worse prognosis than Bell’s (complete recovery: 50%) Important cause of facial paralysis in children 6-15 years old

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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

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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

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36 Perineural Tumor Spread

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

38 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.


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