Thoracic dermatomes run in a ____ direction and will be evaluated in a ____ direction.

• A. Horizontal, Vertical
• B. Horizontal, Horizontal
• C. Vertical, Horizontal
• D. Vertical, Vertical

Answer: (A)

Thoracic dermatomes form horizontal bands that circle the trunk. Because the boundaries between these dermatomes run horizontally, you map them most effectively by moving the stimulus vertically along the body. A vertical sweep crosses successive horizontal bands, allowing you to identify where one dermatome ends and the next begins. Testing horizontally would keep you within the same belt and wouldn’t reveal the boundaries as clearly. So the correct description is horizontal orientation of the dermatomes with vertical testing direction.