Herpes Zoster (Shingles)

Herpes Zoster (Shingles) is usually diagnosed by the distribution of the rash it causes. In the image above, the rash affects the right side of the face. A frontal view would show that the rash stops exactly in the midline of the chin and does not continue onto the left side of the face. Note also the distribution of the rash over the skin when compared to the diagram on the right. It corresponds exactly to the distribution of the mandibular branch of the trigeminal nerve.

This is an important diagnostic feature of herpes zoster. The distribution of the rash always corresponds to the distribution of a single major nerve branch. The distribution of any major sensory nerve on the skin is called a dermatome. In this case, the nerve branch was the mandibular branch of the right trigeminal nerve, and the associated dermatome is marked in yellow on the diagram above. Any other major nerve branch could be effected, including dermatomes on the chest and the back (on one side) when a somatic spinal nerve is infected.

Below is the same image, but with the outline of the rash emphasized for clarity.

This is a generic diagram of the dermatomes associated with the spinal nerves. When a person has a herpes zoster infection in a spinal nerve, the distribution of the rash usually involves exactly one half of one of the cervical or thoracic dermatomes, wrapping from the midline of the back, around to the midline on the front of the body. When the infection involves the lumbar or sacral dermatomes, the rash involves only one of the effected limbs. (Note: On the diagram, the three branches of the trigeminal nerve are labeled V1, V2 and V3. The trigeminal nerve is also referred to as the fifth cranial nerve, and the "V" label stands for the Roman numeral five. These labels are used as standard medical terminology when referring to the branches of the trigeminal nerve.)

Herpes zoster is the same virus that causes chicken pox. After the initial chicken pox infection, usually occurring in childhood, the virus remains in an inactive form inside the nerve branch. It is an opportunistic infection, manifesting later in life when the immune system of the host is compromised. It is found very frequently in AIDS patients due to the HIV induced compromise of the immune system. Prior to AIDS, it was common only in the elderly.

This presentation is Herpes zoster in an AIDS patient. One would be hard pressed to tell it from any other form of herpes infection, all of which present simply as a cluster of itchy, tiny blisters which eventually break and crust over. Note, however, that the redness associated with the rash actually extends around from the hairline to about the midline of the throat indicating that the virus infection is associated with the somatic dermatome C2. This distribution is a clear diagnostic indication that the infection is actually herpes zoster, as opposed to herpes simplex. --- (See also intraoral herpes.)

Is shingles contagious?

Shingles (herpes zoster) is not considered to be contagious. This is because a healthy person who is exposed to a person suffering an active shingles infection will not contract shingles. On the other hand, he or she may become infected with chickenpox if he/she has never been inoculated against it, either by having had chickenpox during childhood, or being inoculated with the vaccine.

Post herpetic pain

After a shingles infection, the affected areas may have prolonged sensitivity and pain, even though all visible signs of the infection have disappeared. This hypersensitivity and deep aching may be controlled with certain anticonvulsant drugs such as Neurontin (gabapentin), Tegretol (carbamazepine) and Lyrica (pregabalin).