Testing the spinothalamic tract

The sensory fibres of pain and temperature enter the spinal cord and cross to the opposite spinothalamic tract a few segments up. The tract then ascends to the brainstem.

• pain testing - use a new pin. The sharpness of the pin is demonstrated to the patient, e.g. by gently touching his anterior chest wall. The limbs - either arms or legs - are then tested by touching the patient with a pin in a position approximating to a dermatome and asking whether the patient feels the pin as sharp or dull. When testing the limbs, sensation is first tested proximally and then more distally. Always compare right limb with left limb for each dermatome. Pain testing may also be used to ascertain a spinal level of a lesion that affects the trunk.
• temperature testing - this is not routinely undertaken. The procedure involves using test tubes filled with hot and cold water and testing in a similar pattern to pain testing.