The Clinical Syndrome
Ramsay Hunt syndrome is the eponym given to acute herpes zoster involvement of the geniculate ganglion. The syndrome results from reactivation of the varicella-zoster virus (VZV) within the geniculate ganglion. VZV is also the causative agent of chickenpox (varicella). Primary infection in the nonimmune host manifests itself clinically as the childhood disease chickenpox. It is postulated that during the course of primary infection with VZV, the virus invades the geniculate ganglia. The virus remains dormant in the ganglia, producing no clinically evident disease. In some individuals, the dormant virus reactivates and travels along the pathways of the geniculate ganglion, producing the pain and skin lesions characteristic of shingles. The reason that reactivation occurs in only some individuals is not fully understood, but it is theorized that a decrease in cell-mediated immunity may play an important role in the evolution of this disease by allowing the virus to multiply in the ganglia and spread to the corresponding sensory nerves, producing clinical disease. Patients with malignancies (particularly lymphoma), patients who are receiving immunosuppressive therapy (chemotherapy, steroids, radiation), and patients with chronic diseases are generally debilitated and much more likely than healthy individuals to develop acute herpes zoster. These patients all have in common a decreased cell-mediated immune response, which may be the reason for their propensity to develop shingles. This decreased immune response may also explain why the incidence of shingles increases dramatically in individuals older than 60 years and is uncommon in individuals younger than age 20.
The first division of the trigeminal nerve is the second-most common site for the development of acute herpes zoster after the thoracic dermatomes. Rarely, the virus may attack the geniculate ganglion, resulting in facial pain, hearing loss, vertigo, vesicles in the ear, and pain. This constellation of symptoms is called Ramsay Hunt syndrome and must be distinguished from acute herpes zoster involving the first division of the trigeminal nerve.
Signs and Symptoms
As viral reactivation occurs, ganglionitis and peripheral neuritis cause pain, which is generally localized to the segmental distribution of the geniculate ganglion. This pain may be accompanied by flu-like symptoms and generally progresses from a dull, aching sensation to dysesthetic neuritic pain in the distribution of the geniculate ganglion. In most patients, the pain of acute herpes zoster precedes the eruption of rash by 3 to 7 days, often leading to erroneous diagnosis (see discussion of differential diagnosis). The clinical diagnosis of shingles is readily made, however, in most patients when the characteristic rash appears. Similar to chickenpox, the rash of herpes zoster appears in crops of macular lesions, which rapidly progress to papules and then to vesicles ( Fig. 14.1 ).
As the disease progresses, the vesicles coalesce, and crusting occurs ( Fig. 14.2 ). The area affected by the disease can be extremely painful, and the pain tends to be exacerbated by any movement or contact (e.g., with clothing or sheets). As healing occurs, the crusts fall away, leaving pink scars in the distribution of the rash that gradually become hypopigmented and atrophic.
In most patients, the hyperesthesia and pain generally resolve as the skin lesions heal. In some patients, pain and neurological findings may persist beyond lesion healing ( Fig. 14.3 ). This most common and feared complication of acute herpes zoster is postherpetic neuralgia. Elderly patients are affected at a higher rate than the general population suffering from acute herpes zoster. The symptoms of postherpetic neuralgia can vary from a mild, self-limited problem to a debilitating, constantly burning pain exacerbated by light touch, movement, anxiety, or temperature change. This unremitting pain may be so severe that it completely devastates the patient’s life, even leading ultimately to suicide. To avoid these disastrous sequelae to a usually benign self-limited disease, the clinician must use all possible therapeutic efforts for the patient suffering from acute herpes zoster in the geniculate ganglion.
Although in most instances the diagnosis of acute herpes zoster involving the geniculate ganglion is easily made on clinical grounds, confirmatory testing is occasionally required. Such testing may be desirable in patients with other skin lesions that confuse the clinical picture, such as patients with acquired immunodeficiency syndrome who have Kaposi’s sarcoma. In such patients, the diagnosis of acute herpes zoster may be confirmed by obtaining a Tzanck smear from the base of a fresh vesicle, which reveals multinucleated giant cells and eosinophilic inclusions. To differentiate acute herpes zoster from localized herpes simplex infection, the clinician can obtain fluid from a fresh vesicle and submit it for immunofluorescent testing.