Herpes zoster oticus is an infection of the geniculate ganglion (seventh cranial nerve), characterized by a vesicular eruption of the skin of the external ear.
It may occur in varying degrees of severity:
1. herpes auricularis
(an isolated herpes infection of the skin of the external ear canal and pinna
2. herpes auricularis with facial palsy
(herpes auricularis with facial palsy and involvement of the eighth cranial nerve causing hearing loss and/or loss of balance)
This condition may also be associated with a herpes infection of the upper cervical roots or the glossopharyngeal nerve, the latter producing vesicles on the soft palate.
The causative organism is the herpes zoster virus, which is also responsible for chickenpox.
Initially the patient experiences a hot feeling within the ear, which develops into pain of increasing severity. Malaise may be present in the early stages.
Hearing loss, tinnitus or giddiness may be present when the inner ear is involved.
Long after the infection has resolved, many patients continue to suffer severe pain in the previously involved area (post herpetic pain).
The vesicles may appear on the superficial pinna within the conchal bowl, along the skin of the external canal and sometimes even on the tympanic membrane.
A pure tone audiogram should be done to determine whether there has been involvement of the cochlear portion of the inner ear.
Tests of vestibular function may be required if there are signs or symptoms, such as nystagmus or vertigo, suggesting vestibular involvement.
The eye should be carefully examined to ensure that the patient is not developing a herpes infection of the eye.
Tympanometry with measurement of the stapedial reflexes is useful in localizing the lesion in those cases where the facial nerve is involved (after the canal has healed).
A haemorrhagic bleb is present on the tympanic membrane overlying the short process of the malleus.