What is Herpes Zoster (shingles)?
Herpes Zoster, also known as shingles, is a virus infection of the nervous system and is accompanied by pain occurring after a herpes infection (post herpetic).

Causes
Herpes zoster occurs when a childhood virus, which at the time caused chickenpox, becomes active again.

After recovery from chickenpox, the virus settles into a particular part of the nervous system, such as dorsal root ganglion. As people grow older, resistance to viral infections decreases, until the moment when the herpes zoster virus can gain control. Consequently, the virus spreads from the nerve button(s) to the skin and shingles results, with its characteristic one-sided skin rash in one or more areas of a nerve(s). The little blisters contain the virus and are therefore contagious to anyone who has not built up natural resistance to it.

Pain during shingles is due to inflammation of a sensory nerve in the skin.The associated inflammation in the peripheral nerves leads to demyelination, Wallerian degeneration and fibrosis. Thus, as a result, uninhibited and amplified activity in unmyelinated primary afferents leads to pain associated with post-herpetic neuralgia.

PATHOPHYSIOLOGY

Varicella zoster virus is a highly contagious double stranded DNA virus of the herpes family. Primary varicella manifests commonly as chickenpox in a non-immune or incompletely immune person. During the primary infection, the virus gains entry into the sensory dorsal root ganglia. Reactivation of the virus occurs following depression of cell-mediated immunity and in advance-aged patients. The reactivated virus replicates and migrates down the sensory nerve leading to the dermatomal distribution of pain.

Complaints/Symptoms
Patients with shingles report one-side symptoms in a skin area(s) corresponding to an infected nerve knot(s).

Since nerve buttons are present all over the body, the pain can occur anywhere within the skin, e.g., face and trunk.Unilateral thoracic dermatomes and the trigeminal nerve, especially the ophthalmic branch, are most frequently affected.

Moreover, outside pain, pins and needles, changed skin sensation and itching can also occur. The pain is experienced as burning, pulsating, dull and itching.
Pain after a herpes zoster infection can be continuous, with shooting sensations in the scar area. Clothes can be uncomfortable or even painful.
Apart from this, patchy allodynia, hyperesthesia, and hypoesthesia can present to varying degrees in the affected region. Allodynia refers to the precipitation of pain by a non-painful stimulus, such as touch or pressure.

It is often a distressing feature of PHN. Sleep disturbance and clinical depression are not uncommon.

How is the pain diagnosis made?
The diagnosis is based on the pattern of the pain complaints, together with physical and neurological examination.

Do I need any additional examinations?
Physical Examination
At the start of the disease, there is a typical skin rash with redness, pimples and blisters in the painful area. Healed blisters are covered in scabs.

The skin rash is generally located on one side of the body and does not cross to the other side. Sensory disturbances, such as dullness, unpleasant pain after pricking or touching the infected skin are frequent. Additional examinations

What are the treatment possibilities?

A.TREATMENT DURING THE ACUTE PHASE

There is good evidence that prompt antiviral treatment can prevent development of PHN and reduce severity when it does occur. Options include aciclovir and the newer antiviral drugs valaciclovir (now a generic medication) and famciclovir. All three are equally effective though the newer agents appear to be better tolerated and have more evidence to support their use: demonstrated benefits include a reduction in the incidence of PHN at 6 months and a faster resolution of pain symptoms.

The early use of aciclovir has also been shown to reduce the incidence and severity of PHN. The optimum window seems to be within 72 hours of appearance of the rash but observational studies suggest even treatment outside 3 days may be of benefit. This is particularly so for patients at high risk of morbidity such as those affected by herpes zoster ophthalmicus and HIV.

B.TREATMENT OF ESTABLISHED POST HERPETIC NEURALGIA

Pharmacological agents
Simple analgesics are unlikely to be effective on their own but may contribute to improved overall analgesia. Paracetamol (either alone or in combination with codeine) is recommended by two sets of guidelines but no evidence exists to support this. It is worth trying but do not expect more than modest benefit in isolation. NSAIDs have no evidence to support their use.

Anti neuropathic drugs
These drugs are the main stay of management in post herpetic neuralgia. They include Amitriptyline, Nortriptyline, Gabapentin and Pregabalin. The main limiting factor is the side effect profile of these drugs and hence patient compliance tends to be generally low.

C.Topical treatments
Capsaicin 0.075%
This topical treatment is licensed for the symptomatic relief of PHN after lesions have healed. Two studies have demonstrated benefit over placebo in PHN. The preparation should be applied four times a day. Benefit may be delayed for up to 4 weeks. The commonest side-effect is a burning sensation; patients should be advised that this decreases with continued use, but if it remains problematical, lidocaine 5% ointment applied 10 minutes beforehand can alleviate this. Mixing the capsaicin with GTN paste or EMLA cream has proved useful.

5% Lidocaine plasters
These plasters have to be applied over the painful area, and are used in a 12 hours on, 12 hours off regimen. If tolerated, clinical experience has found that some patients benefit from wearing the plasters 36 hours out of 48, reducing any pain associated with its application/removal. The plasters can be used as 1st line treatment where allodynia is prominent and distressing or where patients are particularly sensitive to side effects of systemic pharmacotherapy. In a study on pain resulting from PHN and diabetic neuropathy, the 5% lidocaine plaster had an incidence of drug related adverse events of under 6% (half were skin reactions) versus 42% for pregabalin.

Qutenza treatment
Qutenza is a high-potency capsaicin (8%) topical patch available for treating pain associated with postherpetic neuralgia. The efficacy of a single 60-minute application to the affected locations has been shown in controlled clinical trials conducted in patients with PHN. Pain reduction was observed as early as week one and was maintained throughout the 12-week study period. Qutenza decreases pain sensation by reducing transient receptor potential vanilloid 1 (TRPV1) expression and decreasing the density of epidermal nerve fibers in the application area. Qutenza must be administered by a nurse or a physician or under the close supervision of a physician. It is not available for self-use.

The most common adverse drug reactions occurring with capsaicin 8% are application site erythema (63%) and application site pain (42%). Some patients experienced transient increases in blood pressure during Qutenza application.

D.INTERVENTIONAL TREATMENTS FOR POST HERPETIC NEURALGIA

Interventional treatments should be considered in patients with refactory pain, where the quality of life is significantly affected by the severity of pain.

1. Intercostal Nerve Block
Intercostal nerve block should be considered in patients who do not respond to conservative management. The procedure is done on an outpatient basis. The procedure is performed under ultrasound guidance to ensure accuracy of needle placement. Generally a mixture of local anaesthetic and steroid is injected. The local anaesthetic is probably responsible for immediate pain relief, whereas steroids are believed to be responsible for pain relief 2–6 days after their administration.

2. Intercostal nerve ablation
Patients who get temporary relief from intercostal nerve block may be suitable for intercostal nerve ablation (pulsed radiofrequency treatment). This is likely to provide longer-term pain relief.

Patients who get temporary relief from intercostal nerve block may be suitable for intercostal nerve ablation (pulsed radiofrequency treatment). This is likely to provide longer-term pain relief.

3. Dorsal root ganglion block and pulsed radiofrequency treatment
Lesioning of the dorsal root ganglion (DRG) using pulsed radiofrequency (PRF) has shown pain reduction in patients with severe post-herpetic neuralgia. In an open, nonrandomized study, 49 patients with PHN, refractory to conservative therapy, were subject to PRF, performed thrice, adjacent to the DRG of the corresponding levels at 42°C for 120 seconds, under the fluoroscopy. There was excellent pain relief (about 55%) at four weeks, with the effect lasting till the 12-week follow-up. (Kim YH, Lee CJ, Lee SC, Huh J, Nahm FS, Kim HZ, et al)

4. Sympathetic Block
5. Neuromodulation (Spinal Cord Stimulator)
6. BOTOX therapy

Non-physical Treatments
If the results of your pain questionnaire are abnormal, your pain specialist will suggest one of the non-physical treatments listed below:

GENERAL ADVICE TO PATIENTS

Explanation that symptoms can resolve after a few months, or may persist for longer. Interventions may not completely resolve the pain, but may reduce it.

Wear loose clothing or cotton fabrics, as these will usually cause the least irritation. Consider protecting sensitive areas by applying a protective layer (such as cling film or a plastic wound dressing such as Opsite®).

Consider frequent application of cold packs, unless this causes pain (allodynia)

What is trigeminal neuralgia?
Trigeminal neuralgia is a painful disorder of one of the nerves in your face, the trigeminal nerve

Cause
The precise cause of trigeminal neuralgia is unknown.

Experts think that it may be due to overstimulation of the trigeminal nerve, but in most cases, it is not known what causes this overstimulation.

The most common cause is thought to be a blood vessel pressing on the nerve.

In some cases, the cause may be a tumour, an inflammation (as in Multiple Sclerosis) or Postherpetic Trigeminal Neuralgia

Signs and symptoms

Trigeminal neuralgia occurs more often in women than in men and mostly seen in people over 40.

Patients with trigeminal neuralgia suffer brief but very severe stabbing pains in a particular part of their face, often near a corner of the mouth or a nostril.

Patients sometimes describe the pain as being like an electric shock, or like a stab with a hot needle.

The pains can be triggered by various stimuli or causes, such as wind blowing in one's face, washing, shaving, cold or heat, but also by chewing, speaking or swallowing.

Trigeminal neuralgia often leads to weight loss, as patients may be too afraid to eat. Some patients have specific sensitive sites ('trigger points') on their face where even a light touch may provoke a pain attack.

The complaints may be so serious that they seriously affect the patient's quality of life. The pains often occur over a particular period, after which they may disappear for a while.

Some patients only have a few of these pain periods in their whole lifetime, while others have them far more often.

How is trigeminal neuralgia diagnosed?
The diagnosis is based on the pattern of the patient's symptoms.

Do I need additional examinations?

What are my treatment possibilities?
Physical Treatments
1. Medication

2. Interventional Pain Treatments

What is a Gasserian Ganglion block (RFTC)?
A ganglion is a bundle of interconnected nerves that are important for pain in a certain area of the body. One such ganglion is the Gasserian ganglion or trigeminal ganglion - this ganglion is important in the treatment of some types of facial pain.

It is possible to relieve pain by blocking the Gasserian ganglion. The Gasserian ganglion is found inside the skull next to the brainstem and has three nerve branches known as the trigeminal nerves. These three branches are responsible for sensation on one side of the face.

A block in one part of the Gasserian ganglion is achieved by applying electrical current to the Gasserian ganglion via a needle that heats the ganglion. This stops it from passing on any more pain signals.

Only the thin nerves in this ganglion are blocked. Since the thick nerves of the ganglion are not blocked, the remaining function of the ganglion remains intact. This Gasserian ganglion block is also known as the Sweet procedure.

When do I need a Sweet procedure?
Patients with classical facial pain, also named trigeminal neuralgia, are suitable for treatment with a Sweet procedure.

What should I be aware of before undergoing a Sweet procedure?
There are a number of situations that you should report your pain specialist if he proposes you a Sweet procedure:

How should I prepare for a Sweet procedure?

How does the Sweet procedure work?

What are dangers and side effects of a Sweet procedure?
After a Sweet procedure, the following complications or side effects can occur:

When can I expect pain relief after the treatment?