Question 1

What is the clinical significance of dermatomal overlap?

Accepted Answer

Dermatomes overlap significantly, so a single nerve root lesion usually produces hypoaesthesia rather than complete anaesthesia. The zona exclusiva areas (C5, C6, C7, C8, T4, T10) are most reliable.

Question 2

What is the pattern of dermatomal involvement in shingles?

Accepted Answer

Shingles typically involves 1-3 adjacent dermatomes unilaterally without crossing the midline. Thoracic dermatomes are affected in 50-60% of cases.

Question 3

How are dermatomes used in spinal cord injury classification?

Accepted Answer

The ASIA classification uses 28 key sensory points per side. The sensory level is the most caudal dermatome with normal sensation.