Dermatomes

Snapshot

• A 40-year-old man presents to his primary care physician with bilateral upper extremity weakness and sensory changes. He describes the sensory changes as “numb to pain and heat.” Approximately 8 months ago, he had a multiple sclerosis exacerbation that required hospitalization with intravenous methylprednisolone for 5 days. On physical exam, there is sensory loss to pain and temperature in a “cape-like” distribution of the upper extremity, as well as 4/5 strength. The patient is scheduled for an MRI of the spine. (Post-inflammatory syringomyelia)

Introduction

• Dermatomal maps reflect the sensory distribution for a specific level
  • therefore, one can determine at which level (e.g., brainstem and spinal cord) the lesion is located
    • recall that the primary sensory modalities tested on physical exam includes
      • light touch
      • pain
      • temperature
      • vibration
      • proprioception
• The dorsal root ganglia contain cell bodies of spinal nerve sensory neurons

Head and Neck

Upper Extremity 

Hand

Chest and Abdomen

Important Dermatomal Landmarks of The Chest and Abdomen
Vertebral Level	Sensory Area
T4	Chest at level of nipple”T4 at teat pore”
T7	Chest at level of xiphoid process”T7 at bottom of sternum”
T10	Abdomen at level of umbilicus”T10 at belly button (butTEN)”

Lower Extremity