Ophthalmic herpes zoster and pain therapy

Effective pain control in cases of ophthalmic herpes zoster infection is essential, first and foremost to alleviate the clinical manifestations, but it is also essential to reduce the risk of postherpetic neuralgia developing.

Recently, neuro-modulation therapy has been put forward as an option for the management of neuropathic pain in the ocular district, which is also increasingly applied in the treatment of systemic shingles pain.

A key factor in the success of neuro-modulation therapy is the targeting of damaged nerve fibres. In particular, a clinical study on a new neuro-modulation strategy for the management of ophthalmic herpes zoster pain, targeting both the peripheral branch and the trigeminal ganglion, has recently been completed.

Pathology

Ophthalmic herpes zoster (HZO) is caused by reactivation of the latent varicella-zoster virus and typically results in a painful eruption with blisters in the area corresponding to the ophthalmic branch of the trigeminal nerve. It is estimated that ophthalmic herpes constitutes about 10-20% of the total herpetic infections.

Risk factors for the development of this infection include advanced age, immuno-compromised conditions and the presence of comorbidities.

A number of studies have recently been published that also report experimental evidence of a potential causal correlation between HZO and vaccination against COVID-19

Symptoms

A characteristic manifestation of HZO is intense pain in the eye, characterised by a stabbing pain that also radiates to the periocular area and localised pain in the acute phase of the vesicular eruption.

Approximately half of HZO patients may develop postherpetic neuralgia with ophthalmic involvement. This condition is characterised by moderate to severe facial pain that may persist for more than 3 months after the onset of the skin lesion.

Specific features of this neuropathy are the presence of a continuous, spontaneous burning pain with electric shock-like twinges in a paroxysmal phase, allodynia (Ed: painful impulse felt by the person following an innocuous stimulus) and hyperalgesia (Ed: increased response to a stimulus capable of provoking painful sensations).

The quality of life in these patients is therefore particularly compromised and it is therefore necessary to find strategies that can alleviate the painful symptoms.

Treatment

In the management of herpes zoster infection, first-line treatment involves the oral administration of acyclovir or systemic antiviral analogues from the early stages of infection, although the ability of these drugs to reduce the risk of postherpetic neuropathy remains controversial.

In addition to antiviral treatment, it is essential to administer specific pain relief therapy, most often with analgesic drugs, including tricyclic antidepressants, antiepileptics, opioids and topical analgesics.

If oral therapy proves insufficient, surgical treatments, such as temporary blockade of local nerve sensitivity to provide immediate short-term pain relief, may also be considered.

In a recent study, Dual-neuromodulation strategy in pain management of herpes zoster ophthalmicus: retrospective cohort study and literature review - PubMed (nih.gov) neuro-modulation therapy was tested by implanting an electrical stimulator of the supraorbital and supratrochlear nerve plexuses, capable of delivering continuous stimulation to cover the areas affected by pain. However, 22.2% of patients with HZO also experience pain in the irradiation area of the second branch of the trigeminal nerve (i.e. the maxillary nerve), which cannot be reached by peripheral ophthalmic stimulation. In very severe cases, patients with HZO may have pain involving all three branches of the trigeminal nerve. Therefore, a dual neuro-modulation strategy has been investigated, which simultaneously targets the peripheral nerve branch and Gasser's ganglion by combining short-term continuous peripheral nerve stimulation (PNS) with pulsed radiofrequency (PRF) of the trigeminal ganglion

The primary outcome was measured in terms of pain intensity before and after neuro-modulation therapy, as measured by the Visual Analogue Scale (VAS)

The VAS scale is one of the best known one-dimensional outcome measures for measuring pain intensity. It corresponds to the visual representation of the extent of pain felt by the patient and consists of a predetermined line 10 cm long, where the left end corresponds to 'no pain' and the right end to 'worst possible pain'. The patient is asked to draw a mark on the line representing the level of pain experienced.

The results show that the dual neuro-modulation strategy is able to ensure superior results in terms of the persistence of the analgesic effect of the therapy, compared to continuous peripheral nerve stimulation alone, which is also very important in view of the fact that herpetic ophthalmic infection tends to be relapsing.

On the subject of herpes virus eye infections see also:

• Current and emerging therapies for herpes simplex eye infections - Oculista Italiano
• Neuropathy after shingles infection: if and when to vaccinate - (oculistaitaliano.it)

• Ma J, Wan Y, Yang L, Huang D, Zhou H. Dual-neuromodulation strategy in pain management of herpes zoster ophthalmicus: retrospective cohort study and literature review. Ann Med. 2023;55(2):2288826. doi: 10.1080/07853890.2023.2288826. Epub 2023 Dec 4. PMID: 38048401; PMCID: PMC10836271.
• Rallis KI, Fausto R, Ting DSJ, et al. Manifestation of herpetic eye disease after COVID-19 vaccine: a UK case series. Ocul Immunol Inflamm. 2022;30(5):1136-1141. doi: 10.1080/09273948.2022.2046795.
• You IC, Ahn M, Cho NC. A case report of herpes zoster ophthalmicus and meningitis after COVID-19 vaccination. J Korean Med Sci. 2022;37(20):e165. doi: 10.3346/jkms.2022.37.e165.
• Martora F, Fabbrocini G, Picone V. A case of herpes zoster ophthalmicus after third dose of comirnaty (BNT162b2 mRNA) vaccine. Dermatol Ther. 2022;35(5):e15411.