Herpes zoster of posterior division of mandibular branch of trigeminal nerve

Abstract

Herpes zoster is a disease caused by the reactivation of dormant varicella zoster virus present in the sensory root ganglion. It presents with a vesicular rash on an erythematous base similar to that seen in classical varicella, however, with only a single dermatomal distribution. The rash is usually seen throughout the affected dermatome as the dorsal root ganglia for each dermatome are clustered together. We present a case of an otherwise healthy male who developed a vesicular rash confined to the distribution of the posterior division of the mandibular nerve. Though the entire mandibular nerve arises from a single ganglion, the skin area supplied by the anterior division of the mandibular nerve was spared. This case provides evidence to show that there is anatomic segregation of cell bodies of nerves traversing anterior and posterior divisions of mandibular division in the trigeminal ganglion and that partial involvement of a sensory root ganglion is possible in immunocompetent patients.

Background

Varicella zoster virus (VZV) causes a primary infection known as varicella (chicken pox), after which it lies dormant in the sensory ganglia.¹ When the cell-mediated immunity declines, the virus gets reactivated and travels along the nerve, causing neuronal damage and vesicular rash. For this reason, the vesicular rash classically patterns the neuronal distribution and is commonly associated with neuralgic pain.¹ The decline of cell-mediated immunity may be due to triggers like increasing age, emotional stress, immunosuppression or malignancy.² The incidence of herpes zoster ranges between 3 and 6 per 1000 person-years in various parts of the world.³ Involvement of trigeminal nerve occurs in 15% of all herpes zoster cases.² Involvement of ophthalmic, maxillary or mandibular division of trigeminal nerve is a common presentation in otolaryngology outpatient clinic. However, partial involvement of the mandibular nerve—only the posterior branch has not been described in the past. Detailed knowledge of trigeminal nerve anatomy is necessary to clinically acknowledge such involvement. Hence we present the case.

Case presentation

A middle-aged otherwise healthy male presented with complaints of throbbing continuous severe pain along the left lower jaw for 5 days in the outpatient clinic. He also complained of vesicular rash along the anterior part of the left ear, temporal region and around the left part of lower lips for the past 3 days. He also complained of oral soreness, and pain along tongue and inner part of lips. There were no complaints of altered taste sensation, decreased hearing, ear discharge or facial weakness. He had no similar history. He did not recall having chickenpox in childhood.

His vitals showed a temperature of 98.6⁰F, respiratory rate of 14 breaths per minute, blood pressure of 110/70 mm Hg and pulse of 70/min. On local examination, there was vesicular rash of various sizes along the anterior part of left pinna, over temporal region (figure 1) and around the left lower lip (figure 2). The rash was present over an erythematous base. Surprisingly, the skin between the ear pinna and lower lip was normal (figure 1). On examination of the oral cavity, erythematous superficial ulcers were seen along the left half of the anterior two-thirds of the tongue, both over its dorsal and ventral surface (figures 3 and 4). Buccal mucosa opposite incisors and canine was ulcerated (figure 5). However, buccal mucosa lateral to premolar and molar was normal. The facial nerve, external auditory canal and tympanic membrane were normal.

Figure 1.

Demonstrates vesicles over incisura terminal and temporal region of forehead overlying erythematous base. The skin overlying mandibular ramus is normal.

Figure 2.

Demonstrates vesicles of various sizes distinctively present over the left half of the lower lip.

Figure 3.

Erythematous mucosal ulcers seen over the left half of the anterior two-thirds of the tongue.

Figure 4.

Erythematous mucosal ulcers with slough-covered base seen over the ventral surface of the tongue.

Figure 5.

Erythematous mucosal ulcers overlying buccal mucosa opposite canine and incisors abruptly stopping to continue as normal mucosa opposite premolars and molars.

Rest of the otolaryngological and systemic examination was normal.

He was clinically diagnosed as a case of herpes zoster of mandibular division of the trigeminal nerve.

Investigations

He underwent pure tone audiometry that showed normal hearing thresholds bilaterally. A complete blood picture showed normal haemoglobin, total leucocyte count and platelets. Test for HIV antibodies was negative. His random blood glucose and glycated haemoglobin were within normal limits. Testing for viral PCR or IgM antibody was not available in the secondary care centre where the patient presented, hence a laboratory confirmation for diagnosis could not be reached.

Treatment

He was treated with 7 days of oral acyclovir 800 mg given five times daily. Pain was managed with oral pregabalin 75 mg. Oral gel of chlorhexidine and lignocaine was used to help keep oral cavity clean and combat oral soreness. Prophylactic antibiotic was provided for 5 days with amoxycillin and clavulanic acid.

Outcome and follow-up

He improved substantially and all lesions resolved 3 weeks post-treatment. There was no residual pain present.

Discussion

Primary infection with VZV commonly occurs in childhood causing a systemic disease called chicken pox or varicella. In uncomplicated varicella, patient develops fever, malaise and generalised vesicular rash all over the body. Child usually improves with symptomatic treatment. Virus is said to remain dormant in the sensory nerve cell bodies. The viral infection may be subtle with patient, who may or may not remember the episode experienced in childhood. In adult years, when the person gets immunosuppressed with possible triggers such as stress, surgery or trauma of affected site, treatment with immunosuppressants, increasing age or malignancy²; the virus gets activated, travels along the sensory nerve causing the vesicular rash along its distribution and neuralgic pain with it. Treatment with antivirals such as acyclovir is recommended within 72 hours of onset of rash. Addition of oral corticosteroids, low-dose tricyclic antidepressants, anticonvulsants, capsaicin, lidocaine patches and nerve blocks are other treatment adjuvants considered on a case-to-case basis.⁴

Reactivation classically occurs in a single ganglia causing lesions along a single dermatome.⁵ Involvement of multiple dermatome or disseminated varicella has been reported in immunosuppressed states.⁶ In our case, partial involvement of a single ganglion was seen. The trigeminal nerve, after its origin from pons, divides into three branches—ophthalmic, maxillary and mandibular. The cell bodies of sensory nerves of these three branches are segregated into three ganglia, resting over the petrous apex in Meckel’s cave. Mandibular nerve, continuing from the ganglia, passes through foramen ovale and gives off meningeal branch and medial pterygoid nerve, before dividing into anterior and posterior divisions. The anterior division is predominantly motor with a single sensory branch called buccal nerve. It provides a general sensory supply to buccal mucosa opposite premolar and molar teeth and skin overlying the mandibular ramus in the corresponding region. Posterior branch is predominantly sensory, giving off auriculotemporal nerve and dividing into lingual nerve and inferior alveolar nerve. Auriculotemporal nerve supplies the skin over temporal region, incisura terminalis and anterior part of external auditory canal. Sensory part of the inferior alveolar nerve provides innervation to skin over mentum, lower lips and the corresponding buccal mucosa. Lingual nerve provides sensory supply to the anterior two-thirds of the tongue on both its ventral and dorsal aspects.⁷ In congruence to this nervous distribution, our case demonstrated oral ulceration and vesicular rash over skin corresponding to the region supplied by the posterior division with sparing of region supplied by anterior branch. Partial involvement of the mandibular ganglion proves the following. First, the cell bodies of anterior and posterior divisions of the mandibular nerve are segregated in the ganglion. Second, in immunocompetent individuals, partial involvement of a sensory ganglion is possible.

Therefore, based on the immune status of the patient, the virus may remain dormant in the sensory root ganglion, if having good cell-mediated immunity. They may have partial involvement of a ganglion when there is a partial drop in immunity. Reactivation along a single ganglion may be seen when there is a drop in immunity due to the use of immunosuppressants or due to the ageing process. Herpes zoster of multiple ganglia or disseminated herpes is possible in severely immunosuppressed individuals. However, this is the only case in the literature reporting partial involvement of a single ganglion. Detailed anatomical knowledge is needed to recognise and report more such cases to come to further conclusions.

Learning points.

• Herpes zoster of a part of a dermatome can occur due to reactivation of varicella zoster in only a part of a sensory ganglion.

• Detailed knowledge of anatomy is essential in making such diagnosis.

• Partial reactivation in a sensory ganglion is possible, possibly in immunocompetent patients.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).