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Acute Facial Paralysis Evaluation

last modified on: Tue, 02/06/2018 - 13:54

  1. General considerations
    1. 80% of all peripheral facial paralysis is Bell’s palsy
      1. Diagnosis of exclusion
    2. Other etiologies include Ramsay Hunt Syndrome (Herpes Zoster Oticus)
      1. Characterized by otalgia and varicella-like cutaneous lesions that involve the external ear, skin of the ear canal, or the soft palate
      2. Higher incidence of hearing loss or balance dysfunction than Bell’s Palsy
  2. Epidemiology of Bell’s Palsy
    1. 30-45 cases/100,000 per year
    2. Most common amongst 15-45 year olds
    3. Equal laterality
    4. Family history: 10%
  3. Pathogenesis of Bell’s Palsy
    1. Despite evolving evidence, the pathogenesis currently remains ‘idiopathic’, but is most likely a reactivation of herpes virus
    2. Viral hypothesis
      1. HSV reactivation → inflammation → edema → nerve compression → ischemia → nerve injury
      2. Murakami identified HSV-1 DNA in 11/14 patients who underwent decompression for Bells Palsy, no HSV-1 in controls (Annals of Int Med)
      3. Additionally, Burgess et. al, identified HSV-1 in section of human temporal bone after unrelated sudden death of patient with Bell’s Palsy (Ann Otol Rhinol Laryngol)
  4. Natural history of Bell’s Palsy(study by Peiterson of 1011 untreated patients with Bell’s Palsy)
    1. Clinical features:
      1. Complete paralysis (69%)
      2.  Associated symptoms
        1. Taste alteration (83%)
        2. Phonophobia (71%)
        3. Postauricular pain (51%)
        4. Lacrimal dysfunction (12%)
      3. Outcomes (1 year post-diagnosis):
        1. None with permanent complete paralysis
        2. 71% with complete recovery
          1. 94% of those with paresis alone had a complete recovery
        3. 16% developed moderate to severe facial dysfunction
        4. Recovery of associated symptoms:
          1. Taste function: 80%
          2. Stapedial reflex: 86%
          3. Lacrimal function: 97%
        5.  Risk factors for incomplete recovery:
          1. Diabetes
          2. Pregnancy
          3. Post auricular pain
          4. Delayed return of function (>3 weeks from onset)
          5. Age (over 60 have worse prognosis)
  5. Pertinent Facial Nerve Anatomy
    1. 10,000 fibers
    2. Nuclei
      1. Motor nucleus
      2. Superior Salivary nucleus
      3. Solitary Tract nucleus
    3. Segments:
      1. Intracranial
      2. Intratemporal
        1. Meatal (2)
        2. Labrynthine (3)
        3. Tympanic (4)
        4. Mastoid
      3. Extratemporal
    4. Narrowest segment of nerve (0.68mm) occurs at meatal foramen (2) and is presumed site of nerve injury in Bell’s Palsy and therefore is site of facial nerve decompression. Fibrous ligament at meatal foramen contributes to this constriction.
  6. Nerve Injury Classification
    1. Neuropraxia
      1. Axon and supporting tissues remain intact
      2. No Wallerian degeneration
      3. Complete recovery
    2. Axonotmesis
      1. Loss of continuity of the axon
      2. Wallerian degeneration occurs
      3. Complete recovery, no sykinesis
    3. Neurotmesis
      1. Injury involves endoneurium
      2. Wallerian degeneration occurs
      3. Increasing risk of synkinesis and incomplete recovery with increasing Sunderland class
    4. In Bell’s Palsy, there can be a combination of injuries occurring at the same time. Electrodiagnostic testing is useful to demonstrate the most prevalent degree of injury. Electrodiagnostic testing can determine percentage of fibers stimulable (neuropraxia) versus non-stimulable (axonotmesis and neurotmesis).
    5. Unfortunately, no current testing can distinguish between axonotmesis from neurotmesis. More rapid degeneration indicates more severe injury and most likely neurotmesis.
  7. Evaluation
    1. History
      1. Timing
        1. Onset: Sudden, note specific date of onset
        2. Duration: <3-4 weeks, if  >3 weeks r/o neoplasm
      2. Degree of paralysis
        1. If complete, note date of complete paralysis
      3. Symptoms associated with Bell’s Palsy
        1. Otalgia
        2. Taste alteration
        3. Decreased tearing
        4. Facial parasthesia
        5. Hyperacusis
      4. Symptoms NOT associated with Bell’s Palsy
        1. Vesicular eruption: think Ramsey-Hunt
        2. Focal neurological deficits: think stroke
        3. Bilateral disease: think Lyme disease or Guillain-Barre
        4. Recurrent disease: think neoplastic process or Melkersson-Rosenthal syndrome
      5. PMH/PSH
        1. Head and neck cancer
        2. Ear disease, COM, cholesteotoma
        3. Autoimmune disorders
        4. Posterior fossa, temporal bone, parotid surgeries
    2. Physical Exam
      1. Complete head and neck exam
        1. Microscopic ear examination
          1. Cholesteotoma
          2. Middle ear effusion
          3. Vesicles
        2. Cranial nerve exam
        3. Eye exam
      2. Detailed facial nerve exam
        1. Spared branches
        2. Degree of weakness
        3. Synkinesis
        4. Spasticity
      3. House-Brackmann Scale
    3. Audiogram
      1. Conduct prior to any surgical intervention to rule out retrocochlear pathology
      2. 69% have absent ipsilateral acoustic reflex
    4. Electrodiagnostic testing:
      1. Electroneurography (ENoG), most commonly used test
        1. Not useful if paresis present, must wait at least 3 days after total paralysis to perform
        2. Not useful in chronic paralysis, >1 month
        3. Procedure
          1. Stimulating electrode placed at the stylomastoid foramen
          2. Recording electrode placed in the nasolabial fold
            1. Move the recording electrode until you see the maximal amplitude of the compound muscle action potential (CMAP)
          3. Stimulus duration 0.2msec at one per second
          4. Turn up current or voltage until see that amplitude does not grow
          5. Add 10% to ensure maximal stimulation
            1. Make sure no masseter muscle contraction
          6. Stimulate 10-20 times to ensure synchrony
          7. Collect maximal amplitude from normal side of face
          8. Collect maximal amplitude from paralyzed side of face
          9. Calculation of % of degeneration
      2.  Electromyography (EMG)
        1. Complementary to ENoG
        2. Routine EMG
          1. Evidence of degeneration 2-3 weeks following injury
          2. Increased sharp waves on insertion
          3. At rest, spontaneous discharge
          4. Fibrillation and fasciculations
        3. Voluntary EMG
          1. MUST perform if ENoG demonstrates >90% degeneration to detect false positive ENoG results
            1. No response on ENoG may be secondary to desynchronization
          2. Concentric EMG needles in orbicularis oris and occuli and have patient make voluntary, forceful contraction
          3. Detects deblocking of conduction block
          4. Any active motor units within 14 days of paralysis indicate good prognosis and rapid recovery
    5. Topographic tests not very useful to determine the site of lesion, but include:
      1. Submandibular flow
      2. Schirmer’s test – useful to identify dry eye
      3. Stapedial reflex
      4. Electrogustometry
    6. Imaging (not necessary in acute Bell’s Palsy, but if associated symptoms dictate, obtain MRI and CT)
      1. Absolute indications
        1. Focal neurologic deficit or complication of chronic ear disease (ie. cholesteatoma)
        2. Palsy that progresses after 3 weeks
        3. Recurrent facial paralysis
        4. Any patient contemplating surgical intervention
      2. Indications for imaging
        1. No return of any function at 6 months
  8. Treatment
    1. Medical
      1. Most important is the prevention of eye injury
        1. Lacrilube, artificial tears, tape at night, and/or goggles
      2. Prednisone 60-80mg qd x 10 days (1mg/kg)
        1. Sullivan et al. in a randomized, double-blind placebo controlled trial found that early treatment with prednisolone significantly improves changes of complete recovery at both 3 and 9 months. There is no evidence of improvement with acyclovir when given alone or in combination with prednisolone (Sullivan et al., 2007)
      3. Valcyclovir 500mg-1000mg TID x 10 days
        1. Despite mixed evidence for antiviral use, the question of whether patients who are less likely to spontaneously recover would benefit from antivirals remains to be answered and therefore, the use of antivirals should still be considered in patients with total paralysis and severe degeneration on ENoG (Alexander de Rua, et al., 2009)
    2. Surgical treatment
      1. Despite medical management with both prednisone and acyclovir, a small percentage of patients will have poor recovery with medical treatment alone
      2. Esslen and Fisch characterized this ‘poor prognosis group’ by finding that patients with a 95% degeneration on ENoG within 21 days had a 50% chance of poor recovery
      3. Study by Gantz et. al found that patients with >90% ENoG degeneration in 14 days or less and no voluntary motor unit potentials on EMG had significantly better outcomes when treated with surgical facial nerve decompression through the middle cranial fossa (decompression of labrynthine segment) than if treated with steroids only (91% recovery to H-B grade I-II compared to steroid-only group which had 58% chance of recovery to H-B III-IV; p<0.0018)< >Therefore, surgical management is recommended in patients with >90% ENoG degeneration in 14 days or less and no voluntary motor unit potentials on EMG (see treatment algorithm)

        Suggested readings:

        1. de Ru JA, van Benthem PPG, Janssen LM. Is antiviral medication for severe Bell's palsy still useful? The Lancet Neurology. 2009;8(6):509. doi: 10.1016/S1474-4422(09)70114-0.
        2.  Fisch U, Esslen E. Total intratemporal exposure of the facial nerve. Pathologic findings in Bell's palsy. Arch Otolaryngol. 1972;95(4):335-341.
        3.  Gantz BJ, Gmuer AA, Holliday M, Fisch U. Electroneurographic evaluation of the facial nerve. Method and technical problems. Ann Otol Rhinol Laryngol. 1984;93(4 Pt 1):394-398.
        4. Gantz BJ, Rubinstein JT, Gidley P, Woodworth GG. Surgical management of Bell's palsy. Laryngoscope. 1999;109(8):1177-1188. doi: 10.1097/00005537-199908000-00001.
        5. Murakami S, Mizobuchi M, Nakashiro Y, Doi T, Hato N, Yanagihara N. Bell palsy and herpes simplex virus: Identification of viral DNA in endoneurial fluid and muscle. Ann Intern Med. 1996;124(1 Pt 1):27-30.
        6. Peitersen E. The natural history of Bell's palsy. Am J Otol. 1982;4(2):107-111.
        7. Sullivan FM, Swan IR, Donnan PT, et al. Early treatment with prednisolone or acyclovir in Bell's palsy. N Engl J Med. 2007;357(16):1598-1607. doi: 10.1056/NEJMoa072006.