Tests
1st tests to order
clinical diagnosis
Test
Diagnosis is clinical, based on history and physical examination alone.
Result
acute, unilateral facial palsy, with an otherwise normal physical examination
electroneuronography (ENoG) (evoked electromyography)
Test
Indicated in acute cases where physical exam demonstrates complete facial paralysis. Should be performed no sooner than 72 hours to allow for Wallerian degeneration to occur and no later than 14 days following the onset of palsy. Typically performed using skin surface electrodes.
Result
>90% decrease in the amplitude of compound muscle action potential (CMAP) on the affected compared with the healthy side is an indication for confirmatory needle electromyography
needle electromyography
Test
Indicated acutely in patients who demonstrate >90% degeneration in CMAP on the affected side on ENoG, to confirm the absence of voluntary motor unit potentials in facial musculature on the affected side.
Patients meeting both these criteria should be urgently referred to neuro-otology for consideration of neural decompression.
Result
absence of voluntary motor unit potentials
serology for Borrelia burgdorferi
Test
Indicated in patients with facial palsy and recent travel to a Lyme disease-endemic area.[41]
However, do not test for Lyme disease as a cause of musculoskeletal symptoms without a history of exposure and relevant exam findings. Doing so increases the likelihood of false positive results and may lead to unnecessary follow-up and treatment.[42][43]
Result
negative
Tests to consider
pure-tone audiometry
Test
Not routinely ordered in Bell's palsy; indicated when history and physical exam suggest an alternative diagnosis.
An abnormal result suggests an alternative diagnosis.
Result
normal
tympanometry and stapedius reflex
Test
Not routinely ordered in Bell's palsy; indicated when history and physical exam suggest an alternative diagnosis.
Bell's palsy may demonstrate ipsilateral impairment of the efferent limb of the stapedius reflex.
Impairment of the afferent limb suggests an alternative diagnosis.
Result
absent or impaired reflex of the ipsilateral efferent limb
MRI (gadolinium-enhanced fine-cut of facial nerve course)
Test
Not routinely ordered in Bell's palsy; indicated when history and physical exam suggest an alternative diagnosis and neoplasm is suspected. In general, patients with Bell’s palsy need not have any imaging unless the symptoms are atypical, recurrent, or persist for >2 months.[44] When imaging is considered, MRI is the method of choice and is most useful for excluding other causes of facial nerve palsy.[44]
Enhancement of facial nerve without expansion of the fallopian canal is normally demonstrated in Bell's palsy. Neural enhancement may be seen for up to 1 year following onset.
Result
variable abnormal enhancement patterns may be seen in the canalicular, labyrinthine, geniculate, tympanic, and mastoid portions of the nerve
CT (fine-cut, non-enhanced)
Test
Not routinely ordered in Bell's palsy; indicated in those in whom otoscopy suggests middle-ear disease or facial palsy following head trauma. Also helpful in recurrent ipsilateral facial paralysis, which can be a presentation of facial schwannoma.
Result
normal
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