\"My Leg is on Fire\": A Case Study on Spinal and Peripheral Nerve Anatomy Sarah

Question

"My Leg is on Fire": A Case Study on Spinal and Peripheral Nerve Anatomy

Sarah Mitchell is a 68-year-old female who is normally healthy. However, about five days ago she began to feel very fatigued and started to experience a burning and tingling sensation on her right thigh.

You ask to see the area and upon visual inspection you notice 3–4 small, red, swollen areas with vesicles on the posterior aspect of her right thigh. She describes the pain to you, saying “it feels like the back of my leg is on fire and it hurts so bad.” She denies being exposed to any excessive heat sources, any changes in her diet, and any changes in the type of body soap, lotion, or laundry detergent she is using. All other physical findings are within normal limits, but her oral temperature is 100.6F. She complains about being under a lot of stress for the past three months because she has been helping take care of her husband, who is in the end stages of Alzheimer’s disease. She has no known drug allergies, is a non-smoker, and attends a water aerobics class twice a week. You suspect she may be suffering from a particular viral infection, so you ask if she had chicken pox as a child. Sarah confirms that she had chicken pox and measles during childhood. Her answer confirms your suspicions that she is likely suffering from shingles (herpes zoster) due to varicella-zoster virus infection.

Questions:

1.The virus infecting Sarah lies dormant in the dorsal root ganglion. What part of a neuron is located in the dorsal root ganglion?

2.Based on the pattern of skin vesicles and pain, use the map of dermatomes below (or from your textbook) to determine which of Sarah’s spinal nerves could be infected.

Explanation / Answer

Ans 1. The dorsal root ganglion is a cluster of cell bodies (cytons) of the sensory (afferent) neuron of the spinal nerve. The virus infects the sensory neuron and hence the patient feels altered sensations of burning, heat and pain.

Ans 2. Based on the distribution of symptoms, the region is the posterior thigh which is supplied by S1 and S2 dermatomes (spinal nerves). Herpes zoster generally affects one dermatome only. Hence either S1 or S2 could be infected.

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