Objective: To describe the anatomy of dorsal root entry zone (DREZ) of brachial plexus for microsurgical DREZ lesioning in Thai population.

Material and Method: Two hundred DREZ of 20 formalin-fixed adult human cadaveric spinal cords from C5 to T1 were collected for study. Measured parameters at each spinal cord segment include number of dorsal rootlets, DREZ length, segmental length, distance from posterior median sulcus to posterolateral sulcus, and angle and depth of DREZ.

Results: Two hundred DREZ were evaluated. The average number of dorsal rootlets was 6.7±1.48 (4 to 11). The average DREZ length was 11.41±1.62 (6.9 to 16.2) mm. The average segmental length was 12.92±1.96 (8 to 18.4) mm. The average distance from posterior median sulcus to posterolateral sulcus was 3.64±1.29 (2.2 to 4.9) mm. The average angle of DREZ was 34.84±1.00 (32.2 to 37.7) degrees. The average depth of DREZ was 1.41±0.31 (0.6 to 2.2) mm.

Conclusion: The authors recommended the starting point for DREZ lesioning at the posterolateral sulcus, which is about 3.64 mm from the posterior median sulcus with the angle of about 34.8 degrees and depth of about 1.41 mm. However, there was rather high variation in term of distance from posterior median sulcus to posterolateral sulcus and depth of DREZ.

Keywords: Anatomy, Dorsal root entry zone, Brachial plexus, DREZ lesioning