Reference values for the cross-sectional area of normal radial nerve at two levels using high-resolution ultrasonography

Abstract

Aim of the study: High-resolution ultrasound is less often used to evaluate the radial nerves. The radial nerve is often involved in entrapment syndromes. The aim of the study is to establish the reference values for the cross-sectional area of the normal radial nerve on high-resolution ultrasonography, and to identify relationships between the cross-sectional area and the subject's age, gender, height, weight, body mass index, and hand dominance.

Material and methods: The study was conducted on 200 subjects of both sexes, between 18 and 75 years of age, who did not have history of peripheral neuropathy or trauma to the upper limb. High-resolution real-time sonographic examination of the radial nerves was performed in both arms at two different levels. Level 1 was taken just proximal to the nerve bifurcation, and level 2 just after the nerve exits the spiral grove.

Results: The mean cross-sectional area measured at level 2 (4.3 ± 0.4 mm²) was greater than that measured at level 1 (2.3 ± 0.3 mm²). No significant relationship was seen with age and hand dominance (p >0.05), but the cross-sectional area values at above mentioned levels were larger in males than in females (p <0.05). In addition, the cross-sectional areas of the radial nerves showed a positive correlation with height, weight, and body mass index (p <0.05).

Conclusion: The established ultrasonographic reference values along with basic clinical data will aid in the diagnosis, response to treatment, and prognostic evaluation of peripheral neuropathies.

Keywords: cross-sectional area; high resolution ultrasonography; peripheral nerves; radial nerve; ultrasound.

Fig. 1.

High-resolution ultrasonography of the radial nerve of the right upper limb done with the patient in supine position using a high-resolution linear transducer (5–18 MHz) at the level of the elbow just proximal to its bifurcation into the superficial sensory nerve and posterior interosseous nerve (level 1)

Fig. 2.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right and left upper limbs in the axial plane at level 1 in a 70-year-old male weighing 60 kg, with a height of 167 cm and a body mass index of 21.4 kg/m². The mean cross-sectional area on the right (A, B, C) and left (D, E, F) sides are 2.4 mm² and 2.5 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 3.

High-resolution ultrasonography of the radial nerve of the right upper limb done with the patient in supine position using a high-resolution linear transducer (5–18 MHz) at the anterolateral aspect of the mid-humerus just after it exits the spiral groove (level 2)

Fig. 4.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right and left upper limbs in the axial plane at level 2 in a 70-year-old male weighing 60 kg, with a height of 167 cm and a body mass index of 21.4 kg/m². The mean cross-sectional area on the right (A, B, C) and left (D, E, F) sides are 4.5 mm² and 4.8 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 5.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 63-year-old female weighing 87 kg, with a height of 162 cm and a body mass index of 33.2 kg/m². The mean cross-sectional areas at level 1 and level 2 are 2.9 mm² and 5.4 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 6.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the left upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 63-year-old female weighing 87 kg, with a height of 162 cm and a body mass index of 33.2 kg/m². The mean cross-sectional areas at level 1 and level 2 are 2.9 mm² and 5.2 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 7.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 64-year-old male weighing 83 kg, with a height of 180 cm and a body mass index of 25.6 kg/m². The mean cross-sectional areas at level 1 and level 2 are 2.9 mm² and 5.8 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 8.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the left upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 64-year-old male weighing 83 kg, with a height of 180 cm and a body mass index of 25.6 kg/m². The mean cross-sectional areas at level 1 and level 2 are 2.9 mm² and 5.4 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 9.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 26-year-old female weighing 53 kg, with a height of 154 cm and a body mass index of 22.3 kg/m². The mean cross-sectional areas at level 1 and level 2 are 1.6 mm² and 3.5 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 10.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the left upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 26-year-old female weighing 53 kg, with a height of 154 cm and a body mass index of 22.3 kg/m². The mean cross-sectional areas at level 1 and level 2 are 1.7 mm² and 3.6 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left, PT – point, VAL – value)

Fig. 11.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the right upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 21-year-old male weighing 55 kg, with a height of 154 cm and a body mass index of 23.2 kg/m². The mean cross-sectional areas at level 1 and level 2 are 1.7 mm² and 3.9 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)

Fig. 12.

Ultrasonographic cross-sectional area values of the normal radial nerve (arrows) of the left upper limb in the axial plane at level 1 (A, B, C) and level 2 (D, E, F) in a 21-year-old male weighing 55 kg, with a height of 154 cm and a body mass index of 23.2 kg/m². The mean cross-sectional areas at level 1 and level 2 are 1.8 mm² and 3.8 mm², respectively (yellow arrow – radial nerve, RT – right, LT – left. PT – point, VAL – value)