Laboratory Studies
The diagnosis of Ramsay Hunt syndrome is usually made without difficulty when the clinical characteristics are present. If necessary, varicella zoster virus (VZV) may be isolated from vesicle fluid and inoculated into susceptible human or monkey cells for identification by serologic means.
WBC count, erythrocyte sedimentation rate (ESR), and serum electrolytes are helpful in distinguishing the infectious and inflammatory nature of this syndrome.
When CNS complications are suspected (eg, meningitis, meningoencephalitis, myelitis, arteritis [large and small vessel], and ventriculitis), spinal fluid analysis and CNS imaging studies are recommended.
Viral studies include the following:
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VZV isolation in conventional cell culture is considered the definite diagnostic test. However, growing VZV in cell culture can be difficult and is usually too slow to be clinically helpful.
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The sensitivity of conventional cell culture is 30-40%, with a specificity of 100%.
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Other tests, including Tzanck test, electron microscopy, and polymerase chain reaction (PCR) are generally more rapid and sensitive. The sensitivity of conventional PCR technique is estimated to be 60%.
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VZV has been detected by PCR in the tear fluid of patients with Bell palsy (prevalence, 25-35%).
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VZV antigen detection by direct immunofluorescence assay (DFA) is also possible, with sensitivity of 90% and specificity close to 99%. [15]
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Antibody determinations on paired sera may be helpful in establishing the diagnosis by comparing titers at time of presentation and a few weeks later.
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VZV DNA in cerebrospinal fluid (CSF) may help to predict degree of nerve damage, however, it is not correlated with clinical outcomes. [16]
Imaging Studies
Structural lesions can be ruled out by CT scan, MRI, or magnetic resonance (MR) angiography.
Gadolinium enhancement of the vestibular and facial nerves on MRI has been described in Ramsay Hunt syndrome.
Recent advances in clinical MRI images (eg, 3-Tesla MRI, multichannel phased array coil, 3-dimensional fluid-attenuated inversion recovery [3D-FLAIR]) allow the evaluation of subtle alterations at the level of the blood-labyrinthine barrier. [17] Precontrast hyperintesity and postcontrast enhancement 3D-FLAIR in facial nerve, vestibulococlea nerve and inner ear are correlated with clinical presentation. [18]
Transcranial magnetic stimulation (TMS) may be clinically useful in gaining additional information about the prognostic status of the facial nerve. [19]
Other Tests
Audiometry usually reveals sensorineural hearing loss in high frequency ranges. [11]
Unilateral caloric weakness may be present on electronystagmography (ENG).
Electrodiagnostic methods, such as facial motor nerve conductions studies (electroneurography), electromyography of facial innervated muscles, the blink reflex, and nerve excitability testing, could add information regarding the extent of seventh cranial nerve (CN VII) involvement, as well as prognostic factors. [6, 20, 21]
Procedures
In the setting of a peripheral facial palsy, cerebrospinal fluid (CSF) rarely is analyzed. Although lumbar puncture is not recommended in the diagnosis of this disease, CSF findings can be helpful in confirming the diagnosis. In one study, CSF findings were abnormal in 11% of 239 patients with idiopathic peripheral facial palsy, in 60% of 17 patients with Ramsay Hunt syndrome (abnormal finding was pleocytosis), in 25% of 8 patients with Lyme disease, and in all 8 patients with HIV infection. Thus, if the CSF is abnormal, a specific cause should be sought.
Temporary relief of otalgia in geniculate neuralgia may be achieved by applying a local anesthetic or cocaine to the trigger point, if in the external auditory canal.
Histologic Findings
See the list below:
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The affected ganglia of the cranial nerve roots are swollen and inflamed.
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The inflammatory reaction is chiefly of a lymphocytic nature, but a few polymorphonuclear leukocytes or plasma cells may also be present.
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Some of the cells of the ganglia are swollen and others degenerated.
Staging
Several scales have been developed to quantify the degree of facial muscle weakness. Of those, the House-Brackmann scale is most commonly used. [6] However, the Yanagihara facial nerve grading scale is also clinically helpful. [22]
The House-Brackmann facial neuropathy scale is as follows:
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1- Normal
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2 - Mild dysfunction (slight weakness only noticeable on close inspection)
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3 - Moderate dysfunction (obvious weakness, but not disfiguring differences between both sides)
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4 - Moderately severe dysfunction (obvious weakness and disfigurement)
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5 - Only barely perceptive motor function
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6 - Complete paralysis
The Yanagihara facial nerve grading scale is as follows:
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At rest 0 - 2 - 4
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Wrinkle forehead 0 - 2 - 4
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Close eyes normally 0 - 2 - 4
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Close eyes forcefully 0 - 2 - 4
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Close eye on involved side 0 - 2 - 4
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Wrinkle nose 0 - 2 - 4
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Blow out cheek 0 - 2 - 4
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Wristle 0 - 2 - 4
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Grin 0 - 2 - 4
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Depress lower lip 0 - 2 - 4
Each function is scored 0 (complete palsy), 2 (partial palsy), or 4 (nearly normal).
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Herpes zoster oticus, day 6. Image courtesy of Manolette Roque, MD, ROQUE Eye Clinic.
