Post Herpetic Neuralgia (PHN)
Shingles affects millions of adults in their later years. Each year some one million adults in the US develop shingles and with increasing age, approximately twenty per cent go on to suffer post herpetic neuralgia and intractable pain. Shingles is a viral infection of the nerve roots causing pain and a band of rash that usually spreads on one side of your body. The shingles infection can be divided into three phases namely:
- The pre-eruptive phase – early symptoms of burning, itching and generally feeling unwell
- The acute eruptive phase – skin lesions appear and there may well be severe pain and
- The chronic phase – persistent pain lasting 30 days or more after the lesions have crusted
It is this last phase which is post herpetic neuraligia (PHN) and it is during this last phase where the sufferer can have persistent or recurring pain for thirty days or more after the rash itself has crusted. PHN is the most common complication of shingles and it is a condition that can be more painful than shingles and in some cases intolerable. This is why it is so important to treat shingles itself in the early stages to shorten the length of the illness and reduce both the severity of the symptoms and the risk of these complications.
PHN is caused by damage to the nerves. The varicella zoster virus causes this damage to the nerves. Nerve fibers send messages from the skin to the brain but if the nerve fibers are damaged during an outbreak of shingles, they are not able to send messages in the normal manner. The body then perceives these mixed messages as pain. However in most people who develop PHN, the pain will gradually resolve with time even though it may take months or, in the very worst cases, years.
Post Herpetic Neuralgia and “Flower Power"
As most PHN sufferers are over 60, they may well remember the Flower Power years of the 1960s (and San Francisco in particular) with fondness. Now in the 2000s, there are anecdotal testimonies from patients who have suggested that smoking marijuana relieves the pain in much the same way as it relieves the pain of multiple sclerosis.
From a medical point of view, cannabinoids (which are the compounds in marijuana or cannabis and which may have properties that protect nerve cells) are being studied for a number of nerve disorders, including chronic nerve-related pain. So far in one study, it was effective in reducing pain and had no major side effects.