Functional anatomy

The neuroanatomy involved in Ramsay Hunt syndrome is more complex than cases of shingles of a single dermatome elsewhere in the body.

There are four cranial nerve nuclei involved in facial nerve functions. They are the motor nucleus of VII, the nucleus of the solitary tract, the superior salivatory nucleus and the spinal nucleus of V:

Motor nucleus of VII - special visceral efferent motor fibres from the motor nucleus of VII leave the brain stem and travel through the internal acoustic meatus to the bony facial canal to supply facial muscles. In Ramsay Hunt syndrome, these fibres are affected as they pass through the geniculate ganglion, impairing motor supply of the facial nerve.

Nucleus of the solitary tract - the solitary tract receives special visceral afferent taste fibres from the anterior two thirds of the tongue. These fibres travel with the chorda tympani. The cell bodies of these special visceral afferent fibres are in the geniculate ganglion which is the site of virus reactivation when vesicles erupt on the tongue. The fibres reach the brain stem via the nervus intermedius and can be affected by local inflammation as they pass the geniculate ganglion.

Superior salivatory nucleus - special visceral efferent parasympathetic fibres to the lacrimal and salivary glands come from the superior salivatory nucleus, travel in the nervus intermedius and branch at the geniculate ganglion into the greater petrosal and chorda tympani nerves. Decreased lacrimation may result from involvement of these fibres as they branch at the level of the geniculate ganglion. Special visceral efferent sympathetic fibres originate from the carotid plexus on the internal carotid artery and join the greater petrosal nerve as they pass through the foramen lacerum. The sympathetic fibres supply the same areas as the parasympathetic fibres.

Spinal nucleus of V - this receives general somatic afferent fibres from the geniculate zone of the ear via the chorda tympani. Cell bodies of these neurons lie in the geniculate ganglia and are the site of viral reactivation in classic Ramsay Hunt syndrome, causing vesicular eruptions in geniculate zones.

Epidemiology

• Herpes zoster is seen as a disease of older people (most commonly over 60 years old)^[1] but it can affect all ages, including children. There has been a case report of varicella infection in utero and presentation in infancy with this syndrome.^[2]
• The incidence and severity increase with age. In one study about 50% of cases were aged 60 or older.^[3] This may be due to a decline in cellular rather than humoral immunity.^[4]
• The overall incidence of all types of herpes zoster is estimated to be 3.6 cases per 1,000 person-years.^[3] However, the increased incidence with age is apparent in the following annual figures:^[3]
  • Age under 50 years - 2.0 cases per 1,000 persons.
  • Age 50 to 60 years - 5.0 cases per 1,000 persons.
  • Age 60 to 70 years - 7.0 cases per 1,000 persons.
  • Age 70 to 80 years - 10.0 cases per 1,000 persons.
  • Age over 80 years - 12.0 cases per 1,000 persons.
• About 20% of people will have shingles at some stage in their lives.
• Of patients presenting with lower motor neurone facial palsy, 12% have Ramsay Hunt syndrome^[5] but the diagnosis can be missed if there is no rash.
• The rate of recurrent shingles within 3 years was 1.4%.^[3]

People who are immunocompromised are much more susceptible to shingles in all forms. It tends to be more severe and may present at a comparatively young age. If shingles affects more than one dermatome, consider immune compromise.

Presentation

Symptoms

The presenting feature is often pain deep within the ear. It may be paroxysmal at first but, after a day or two, the pain often radiates outward into the pinna and there is a more constant, diffuse and dull background pain.

The following may also be presenting features:

• Vertigo and ipsilateral hearing loss.
• Tinnitus.
• Facial weakness or face drop.
• The patient also complains of rash or blisters which may be on the skin of the ear canal, auricle or both, and may become infected secondarily, causing cellulitis

Signs

• There is a rash or herpetic blisters in the distribution of the nervus intermedius.
• The distribution of the rash varies, as does the area innervated by the nervus intermedius. It may include the following:
  • The anterior two thirds of the tongue.
  • The soft palate.
  • The external auditory canal.
  • The pinna.
• An ipsilateral face drop or weakness may be obvious or it may be elicited on testing.
• There may be hyperacusis on that side due to paralysis of the stapedius and tensor tympani.
• The patient may have associated ipsilateral hearing loss and balance problems.

The weakness of the facial nerve will show a lower motor neurone pattern as with Bell's palsy. Ask the patient to give a big grin showing his teeth. Ask him to screw up his eyes. Ask him to raise his eyebrows. The upper motor neurone (UMN) innervation of the forehead is bilateral, so that in an UMN lesion of the face, the muscles of the forehead are spared.

Differential diagnosis

• The unilateral facial weakness is very similar to Bell's palsy but the rash is the characteristic diagnostic feature to differentiate the two.
• There is not always a rash, especially in younger patients. In children aged 5 to 15, acute facial palsy, like a Bell's palsy and without a rash, may be produced by the varicella-zoster virus.^[6]
• Making the diagnosis is very difficult when the presentation is simply pain in the ear. If vesicles are seen in the auditory canal or on the palate, this will help make the diagnosis.
• If it presents as vertigo, viral labyrinthitis will be considered or possibly a stroke of the posterior inferior cerebellar artery region.
• Trigeminal neuralgia is paroxysmal and tends to be precipitated by a stimulus such as a cold wind or washing the face.
• Other conditions in the differential diagnosis include postherpetic neuralgia, persistent idiopathic facial pain and temporomandibular disorders.^[7]
• You may also consider otitis (external, media),^[8] referred pain (eg dental abscess) and carcinoma of the nasopharynx.^[7]

Investigations

Virological studies are available but usually the diagnosis is clinical. Audiometry may be performed. Occasionally, nerve conduction studies may be done to determine the extent of damage to the facial nerve and potential for recovery.

Associated diseases

The varicella-zoster virus has been detected by polymerase chain reaction in the tear fluid of 25%-35% of patients with Bell's palsy.^[7] Beware of possible immune compromise.

Management

The management of herpes zoster is discussed in the separate Shingles article, including when it is appropriate to use antiviral agents to reduce the risk of postherpetic neuralgia. The relative merits of adding corticosteroids to antivirals is also discussed there.

In essence, although prompt treatment (within 72 hours) has been shown to be beneficial in patients with shingles, more generally there is a paucity of data regarding the efficacy of specific antivirals^[9] and the role of steroids^[1] in Ramsay Hunt syndrome.

A proportion of patients with 'Bell's palsy' have Ramsay Hunt syndrome zoster sine herpete (without a rash). Treatment of these patients with acyclovir and prednisolone within 7 days of onset has been shown to improve the outcome for recovery from facial palsy.^[10] In view of this occurrence, especially if paresis appears to be complete rather than partial, a case can be made for adding antivirals to the treatment of such apparent cases of Bell's palsy. The latter is thought to be caused by herpes simplex. The number of patients with peripheral facial nerve palsy who really have zoster sine herpete appears to be small but varies between series. However, they do have a better outcome if given antivirals too.

If there is problem with closing the eye, a pad will protect the cornea and eye lubricants should be prescribed.

Complications

• If closure of the eye is compromised, abrasions may occur.
• Lesions may acquire secondary bacterial infection.
• Postherpetic neuralgia may occur. The condition, risk factors and management are described in the separate Postherpetic Neuralgia article.

Prognosis

• Early diagnosis and initiation of treatment within 72 hours of the onset of symptoms improves outcome.^[1]
• The shingles will resolve but, unlike Bell's palsy, the rate of complete recovery (notably of facial function) is only 75% if treatment was initiated within 3 days.^[1]
• Scarring of deep lesions may occur.
• Hearing loss usually recovers well but prognosis is poorer in elderly males.^[11]
• Age, diabetes and hypertension appear to be poor prognostic features.^[12]

Historical aspects

James Ramsay Hunt was born in Philadelphia in 1872 and graduated M.D. from the University of Pennsylvania in 1893. After studying in Paris, Vienna and Berlin, he returned to New York to practise neurology at Cornell University Medical School from 1900 to 1910. He described the syndrome that bears his name in 1907.^[13] His research interests were the anatomy and disorders of the corpus striatum and the extra-pyramidal system. He was consulting physician at several New York hospitals and was appointed professor of neurology at Columbia University College of Physicians and Surgeons, New York, in 1924. He died in 1937.