INVESTIGATION OF Ramsay Hunt Syndrome

Laboratory Studies:

1.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.

2.WBC count, erythrocyte sedimentation rate (ESR), and serum electrolytes are helpful in distinguishing the infectious and inflammatory nature of this syndrome.

3.As CNS complications are suspected (eg, meningitis, meningoencephalitis, myelitis, arteritis [large and small vessel], and ventriculitis), spinal fluid analysis and CNS imaging studies are recommended.

4.Viral studies ,
.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.
The sensitivity of conventional cell culture is 30-40%, with a specificity of 100%.
.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%.
.VZV has been detected by PCR in the tear fluid of patients with Bell palsy (prevalence, 25-35%).
.VZV antigen detection by direct immunofluorescence assay (DFA) is also possible, with sensitivity of 90% and specificity close to 99%.5
.Antibody determinations on paired sera may be helpful in establishing the diagnosis by comparing titers at time of presentation and a few weeks later.

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 [FLAIR]) allow the evaluation of subtle alterations at the level of the blood-labyrinthine barrier.

Tests:
-Audiometry usually reveals sensorineural hearing loss.
-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.

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:

-The affected ganglia of the cranial nerve roots are swollen and inflamed.
-The inflammatory reaction is chiefly of a lymphocytic nature, but a few polymorphonuclear leukocytes or plasma cells may also be present.
-Some of the cells of the ganglia are swollen and others degenerated.