Initial infection with the varicella-zoster virus causes a disseminated vesicular rash with fever, known as chickenpox. During the acute phase of this infection, the virus is spread by respiratory droplets. After the viremia and exanthem have resolved, the virus can remain dormant in cranial nerves and dorsal root ganglia. During times of physiological stress or immunocompromise, reactivation of the virus within the distribution of the nerve in which it has been dormant can occur. The rash is infectious, and the virus is shed from the vesicles; VZV can also be cultured from tears and saliva or identified on polymerase chain reaction (PCR) testing.
During an episode of zoster, vesicular rashes tend to appear within a single dermatome. In Ramsay Hunt syndrome, the virus reactivates along the seventh cranial nerve via the geniculate ganglion. According to Coulson et al., The initial presenting symptom is typically pain in the ipsilateral ear (55% of patients), with facial paralysis and vesicles appearing within 2 to 3 days. In 23% of patients, facial paralysis is the presenting symptom, and in only 2%, vesicles appear first. While 86% of their patients reported that the rash occurred only on the auricle, 7% only had vesicles in the oral cavity, and 8% had them in both locations. Rashes have also been reported on the scalp and the cheek.
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The proximity of the facial nerve to the vestibulocochlear nerve can result in hearing loss, tinnitus, and vertigo. Sensorineural hearing loss was present in 43% of patients in Coulson’s series, imbalance or vertigo in 51%, and tinnitus in 20%. Vagal nerve involvement is also probably more common than it appears to be. Unless the patient is symptomatic with hoarseness or aspiration, vocal cord paralysis is not usually noted because it requires mirror or fiberoptic laryngoscopy to discover. Less frequently, other cranial nerves can be involved as well, including the trigeminal, glossopharyngeal, and hypoglossal, although cranial polyneuropathy is more likely to present in immunocompromised patients, such as those with diabetes mellitus or human immunodeficiency virus infection.
The facial paralysis resulting from Ramsay Hunt syndrome has a worse prognosis than that seen in Bell’s palsy, with only 70% regaining normal or near-normal facial function compared with over 90% in Bell palsy. After Bell palsy, the rate of synkinesis development is roughly 16%, but it is closer to 40% after Ramsay Hunt syndrome. The neuritis associated with Ramsay Hunt syndrome appears to be more severe than that of Bell’s palsy, given that more than twice as many patients present with complete hemifacial paralysis with Ramsay Hunt syndrome as in Bell palsy.
When patients fail to recover premorbid function, synkinesis is a common sequela, in which aberrant reinnervation connects axons with neuromuscular junctions different from the ones to which they were connected prior to the inflammation. Severe neuritis can cause an injury similar to a traumatic one, wherein Wallerian degeneration of facial nerve axons occurs along with varying degrees of damage to the internal architecture of the nerve. When the endoneurium, perineurium, or epineurium are disrupted (as in Sunderland class III-V injuries), the axons no longer have a physical structure in place to guide reinnervation and may ultimately connect with the incorrect muscle or end-organ. In many cases, newly regenerated axons will also terminate on multiple neuromuscular junctions, which has the effect of further increasing dyscoordination as well as raising the resting tone of the muscles that subsequently have more associated axons than they did before the injury. Patients with synkinesis often complain of eye closure with mouth movements and vice versa, as well as facial tension and pain. Because the facial nerve supplies parasympathetic fibers to the lacrimal glands, patients may also develop gustatory lacrimation, or Bogorad syndrome, due to aberrant reinnervation; this causes tearing with eating. All of these issues, as well as the difficulties associated with acute facial palsy, can have a serious negative impact on patient quality of life.