Table 1.

Measurements of normal cervical nerve roots and nerves by ultrasonography (n = 44, 22 subjects, bilateral)

Cervical nerve	Trunk (mm)	Root (mm)	Intervertebral foramen level (mm)
Cervical plexus
C2	2.46 ± 0.31	5.03 ± 0.70	7.65 ± 1.36
C3	2.75 ± 0.33	5.86 ± 0.82	9.21 ± 1.54
C4	2.83 ± 0.39	6.62 ± 1.13	11.18 ± 7.44
Mean	2.68 ± 0.38*	5.84 ± 1.04*	9.35 ± 4.72*
Brachial plexus
C5	3.09 ± 0.47	7.33 ± 1.22	10.97 ± 2.55
C6	3.48 ± 0.39	7.54 ± 1.72	11.21 ± 2.90
C7	3.82 ± 0.55	7.57 ± 1.09	10.60 ± 2.74
C8	3.79 ± 0.61	7.24 ± 1.10	10.40 ± 2.58
Mean	3.55 ± 0.59	7.42 ± 1.31	10.79 ± 2.68

^*P < 0.05, compared with the mean value of the brachial plexus