How small can small nerves be for diagnostic ultrasonography?

Ultrasonography is the method of choice for imaging the peripheral nervous system [1]. Clinically, imaging especially of small peripheral nerves is relevant for the following purposes: (i) their localization for avoiding harm during surgical or other invasive procedures [2] [3] [4], (ii) the targeting of therapeutics or surgical procedures at these nerves [5] [6] [7] [8] [9], and (iii) the measuring of their caliber for assessing compressive, inflammatory or degenerative neuropathies [12] [13] [14] [15] [16] [17] [18].

• References

• 1 Walker FO, Cartwright MS, Alter KE. et al. Indications for neuromuscular ultrasound: Expert opinion and review of the literature. Clin Neurophysiol 2018; 129: 2658-2679
• 2 Kessler J, Schafhalter-Zoppoth I, Gray AT. An ultrasound study of the phrenic nerve in the posterior cervical triangle: implications for the interscalene brachial plexus block. Reg Anesth Pain Med 2008; 33: 545-550
• 3 Hong MJ, Baek JH, Kim DY. et al. Spinal Accessory Nerve: Ultrasound Findings and Correlations with Neck Lymph Node Levels. Ultraschall in Med 2016; 37: 487-491
• 4 Konschake M, Burger F, Zwierzina M. Peripheral Nerve Anatomy Revisited: Modern Requirements for Neuroimaging and Microsurgery. Anat Rec (Hoboken) 2019;
• 5 Gruber H, Kovacs P, Piegger J. et al. New, simple, ultrasound-guided infiltration of the pudendal nerve: topographic basics. Dis Colon Rectum 2001; 44: 1376-1380
• 6 Blichfeldt-Eckhardt MR, Laursen CB, Berg H. et al. A randomised, controlled, double-blind trial of ultrasound-guided phrenic nerve block to prevent shoulder pain after thoracic surgery. Anaesthesia 2016; 71: 1441-1448
• 7 Aydın T, Şen Eİ, Yardımcı MY. et al. Efficacy of ultrasound-guided suprascapular nerve block treatment in patients with painful hemiplegic shoulder. Neurol Sci 2019; 40: 985-991
• 8 Ellis J, Schneider JR, Cloney M. et al. Lateral Femoral Cutaneous Nerve Decompression Guided by Preoperative Ultrasound Mapping. Cureus 2018; 10: e3652
• 9 Forney MC, Li X, Prayson R. et al. Technically successful ultrasound-guided percutaneous sural nerve needle biopsy in a patient with indeterminate peripheral neuropathy. Skeletal Radiol 2019; 48: 1105-1109
• 10 Wu WT, Chang KV, Mezian K. et al. Basis of Shoulder Nerve Entrapment Syndrome: An Ultrasonographic Study Exploring Factors Influencing Cross-Sectional Area of the Suprascapular Nerve. Front Neurol 2018; 9: 902
• 11 Jang JH, Cho CS, Yang KS. et al. Pattern analysis of nerve enlargement using ultrasonography in chronic inflammatory demyelinating polyneuropathy. Clin Neurophysiol 2014; 125: 1893-1899
• 12 Winter N, Dammeier N, Schäffer E. et al. Nerve Ultrasonography as an Additive Tool to Clinical Examination and Electrodiagnostics in Sporadic Mononeuritis – Imaging is the Key. Ultraschall in Med 2019; (this issue)
• 13 Chaduvula MV, Visser LH, Suneetha S. et al. High-Resolution Sonography as an Additional Diagnostic and Prognostic Tool to Monitor Disease Activity in Leprosy: A Two-Year Prospective Study. Ultraschall in Med 2018; 39: 80-89
• 14 Tsukita K, Taguchi T, Sakamaki-Tsukita H. et al. The vagus nerve becomes smaller in patients with Parkinson's disease: A preliminary cross-sectional study using ultrasonography. Parkinsonism Relat Disord 2018; 55: 148-149
• 15 Pivec C, Sillat T, Moritz T. et al. A Rare Case of Guyon’s Canal Syndrome Caused by Cystic Adventitia Degeneration: High-Resolution Ultrasound Findings. Ultraschall in Med 2017; 38: 556-557
• 16 Lieba-Samal D, Pivec C, Platzgummer H. et al. High-Resolution Ultrasound for Diagnostic Assessment of the Great Auricular Nerve-Normal and First Pathologic Findings. Ultraschall in Med 2015; 36: 342-347
• 17 Lieba-Samal D, Morgenbesser J, Moritz T. et al. Visualization of the Long Thoracic Nerve using High-Resolution Sonography. Ultraschall in Med 2015; 36: 264-269
• 18 Pivec C, Bodner G, Mayer JA. et al. Novel Demonstration of the Anterior Femoral Cutaneous Nerves using Ultrasound. Ultraschall in Med 2018;
• 19 Puma A, Azulay N, Grecu N. et al. Comparison of high-frequency and ultrahigh-frequency probes in chronic inflammatory demyelinating polyneuropathy. J Neurol 2019;
• 20 Coraci D, Gentile L, Tannous Cordenonssi J. et al. Letter to the Editor: "Who seeks finds, who compares discovers". Usefulness of ultrasound to assess small nerve branches. Rom J Morphol Embryol 2018; 59: 1007-1008
• 21 Chang KV, Mezian K, Naňka O. et al. Ultrasound Imaging for the Cutaneous Nerves of the Extremities and Relevant Entrapment Syndromes: From Anatomy to Clinical Implications. J Clin Med 2018; 7: E457
• 22 Causeret A, Ract I, Jouan J. et al. A review of main anatomical and sonographic features of subcutaneous nerve injuries related to orthopedic surgery. Skeletal Radiol 2018; 47: 1051-1068
• 23 Le Corroller T, Santiago E, Deniel A. et al. Anatomical study of the medial plantar proper digital nerve using ultrasound. Eur Radiol 2019; 29: 40-45
• 24 Walter U, Tsiberidou P. Differential age-, gender-, and side-dependency of vagus, spinal accessory, and phrenic nerve calibers detected with precise ultrasonography measures. Muscle Nerve 2019; 59: 486-491
• 25 Geannette C, Lee S, Nwawka O. Sonographic appearance of flexor carpi radialis tenosynovitis associated with a neuritis of the palmar cutaneous branch of the median nerve. Muscle Nerve 2019;
• 26 Flores S, Herring AA. Ultrasound-guided dorsal penile nerve block for ED paraphimosis reduction. Am J Emerg Med 2015; 33: 863.e3–5
• 27 Nielsen TD, Moriggl B, Barckman J. et al. Randomized trial of ultrasound-guided superior cluneal nerve block. Reg Anesth Pain Med 2019;