Stroking the lower abdomen and observing an absent localized twitch suggests a pathologic lesion in which spinal segments?

Stroking the lower abdomen and observing an absent localized twitch suggests a pathologic lesion in which spinal segments?

• A. Thoracic 8, 9, and 10
• B. Thoracic 10, 11, and 12
• C. Lumbar 5 and Sacral 1
• D. Sacral 2, 3, and 4

Answer: (B)

Abdominal reflexes are a spinal reflex that tests the nerves supplying the abdominal wall. When you stroke the skin of the lower abdomen, the response is a localized contraction of the lower abdominal muscles that travels through the spinal cord levels transmitting that region’s sensation and motor output. The lower abdominal region is mainly innervated by the thoracic segments around T10 to T12. If a lesion affects these segments, the reflex arc is disrupted and the localized twitch is absent in the lower abdomen. That’s why absent twitching in the lower abdomen points to a lesion at thoracic levels 10, 11, and 12. The other options involve different regions or levels that would not specifically account for the loss of the lower abdominal reflex.

Abdominal reflexes are a spinal reflex that tests the nerves supplying the abdominal wall. When you stroke the skin of the lower abdomen, the response is a localized contraction of the lower abdominal muscles that travels through the spinal cord levels transmitting that region’s sensation and motor output. The lower abdominal region is mainly innervated by the thoracic segments around T10 to T12. If a lesion affects these segments, the reflex arc is disrupted and the localized twitch is absent in the lower abdomen. That’s why absent twitching in the lower abdomen points to a lesion at thoracic levels 10, 11, and 12. The other options involve different regions or levels that would not specifically account for the loss of the lower abdominal reflex.