Visualization of the Long Thoracic Nerve using High-Resolution Sonography

Abstract

Purpose: The long thoracic nerve (LTN) innervates the serratus anterior muscle (SA) which plays an important role in shoulder function. Evaluation of the LTN has so far been restricted to clinical assessment and partly electromyography and neurography. Progress of high-resolution ultrasound (HRUS) increasingly enables visualization of small peripheral nerves and their pathologies. We therefore aimed at (a) clarifying the possibility of visualization of the LTN from its origin to the most distal point in the supraclavicular region visible and (b) developing an ultrasound protocol for routine use. We further present two cases of patients with LTN pathology.

Methods: The study consisted of two parts: Part 1 included 4 non-enbalmed human bodies in whom the LTN (n = 8) was located and then marked by ink injection. Correct identification was confirmed by anatomical dissection. Part 2 included 20 healthy volunteers whose LTN (n = 40) was assessed independently by two radiologists. Identification of the LTN was defined as consensus in recorded images.

Results: LTN was clearly visible in all anatomical specimens and volunteers using HRUS and could be followed until the second slip of the serratus anterior muscle from the supraclavicular region. In anatomical specimens, dissection confirmed HRUS findings. For all volunteers, consensus was obtained. The mean nerve diameter was 1.6 mm ± 0.3 (range 1.1 – 2.1 mm) after the formation of the main trunk.

Discussion: We hereby confirm a reliable possibility of visualization of the LTN in anatomical specimens as well as in volunteers. We encourage HRUS of the LTN to be part of the diagnostic work-up in patients presenting with scapular winging, shoulder weakness or pain of unknown origin.

Zusammenfassung

Ziel: Der Nervus thoracicus longus (LTN) innerviert den Musculus serratus anterior (SA), der eine wichtige Rolle für die Funktion des Schultergelenks spielt. Seine Evaluierung war bisher auf klinische Untersuchung und teilweise Elektroneurografie und Elektromyografie beschränkt. Der Fortschritt des hochauflösenden Ultraschalls (HRUS) ermöglicht zunehmend die Darstellung kleiner peripherer Nerven und deren Pathologien. Ziel der vorliegenden Arbeit war es (a) die Visualisierbarkeit des LTN vom Ursprung bis zum distalsten einsehbaren Punkt supraklavikulär zu dokumentieren und (b) ein Ultraschallprotokoll für den Routineeinsatz zu erstellen. Darüber hinaus präsentieren wir zwei Fälle mit LTN-Pathologien.

Material und Methoden: Die Studie bestand aus zwei Teilen: Teil 1 umfasste die Ultraschalldarstellung des LTN, seine Markierung mittels Tinte und anschließende Sektion in 4 frischen anatomischen Präparaten (n = 8). Teil 2 umfasste die Darstellung des LTN in 20 gesunden Freiwilligen (n = 40). Die Identifikation erfolgte im Konsens durch zwei Untersucher.

Ergebnisse: Der LTN konnte in allen anatomischen Präparaten und Probanden identifiziert werden. Die Darstellung von supraklavikulär aus gelang bis zur zweiten Zacke des SA. Die korrekte Identifikation wurde in den Präparaten durch Dissektion bestätigt. Für alle Probanden wurde Konsens erzielt. Der durchschnittliche Durchmesser des LTN lag bei 1,6 mm ± 0,3 (Range 1,1 – 2,1 mm) nach der Formierung des Hauptstammes.

Schlussfolgerung: Die Ergebnisse dieser Studie bestätigen die zuverlässige Visualisierbarkeit des LTN mittels HRUS und legen den zukünftigen routinemäßigen Einsatz in der Diagnostik bei PatientInnen mit Scapula alata, Schwäche oder Schmerzen unklarer Genese im Schultergelenk nahe.

Key words

normal variants - long thoracic nerve - scapula alata - shoulder pain

• References

• 1 Bertelli JA, Ghizoni MF. Long thoracic nerve: anatomy and functional assessment. J Bone Joint Surg Am 2005; 87: 993-998 DOI: 10.2106/JBJS.D.02383.
• 2 Tubbs RS, Salter EG, Custis JW et al. Surgical anatomy of the cervical and infraclavicular parts of the long thoracic nerve. J Neurosurg 2006; 104: 792-795 DOI: 10.3171/jns.2006.104.5.792.
• 3 Wang JF, Dang RS, Wang D et al. Observation and measurements of long thoracic nerve: a cadaver study and clinical consideration. Surg Radiol Anat 2008; 30: 569-573 DOI: 10.1007/s00276-008-0368-8.
• 4 Yazar F, Kilic C, Acar HI et al. The long thoracic nerve: Its origin, branches, and relationship to the middle scalene muscle. Clin Anat 2009; 22: 476-480 DOI: 10.1002/ca.20794.
• 5 Dvir Z, Berme N. The shoulder complex in elevation of the arm: a mechanism approach. J Biomech 1978; 11: 219-225
• 6 Eisler P. Die Muskeln des Stammes. Fischer; 1912
• 7 Hamada J, Igarashi E, Akita K et al. A cadaveric study of the serratus anterior muscle and the long thoracic nerve. J Shoulder Elbow Surg 2008; 17: 790-794 DOI: 10.1016/j.jse.2008.02.009.
• 8 Martin RM, Fish DE. Scapular winging: anatomical review, diagnosis, and treatments. Curr Rev Musculoskelet Med 2008; 1: 1-11 DOI: 10.1007/s12178-007-9000-5.
• 9 Foo CL, Swann M. Isolated paralysis of the serratus anterior. A report of 20 cases. J Bone Joint Surg Br 1983; 65: 552-556
• 10 Gregg JR, Labosky D, Harty M et al. Serratus anterior paralysis in the young athlete. J Bone Joint Surg Am 1979; 61: 825-832
• 11 Johnson JT, Kendall HO. Isolated paralysis of the serratus anterior muscle. J Bone Joint Surg Am 1955; 37-A: 567-574
• 12 Saeed MA, Gatens Jr PF, Singh S. Winging of the scapula. Am Fam Physician 1981; 24: 139-143
• 13 Wiater JM, Flatow EL. Long thoracic nerve injury. Clin Orthop Relat Res 1999; 17-27
• 14 Martin JT. Postoperative isolated dysfunction of the long thoracic nerve: a rare entity of uncertain etiology. Anesth Analg 1989; 69: 614-619
• 15 Wood VE, Frykman GK. Winging of the scapula as a complication of first rib resection: a report of six cases. Clin Orthop Relat Res 1980; 160-163
• 16 Oware A, Herskovitz S, Berger AR. Long thoracic nerve palsy following cervical chiropractic manipulation. Muscle Nerve 1995; 18: 1351
• 17 Kauppila LI, Vastamaki M. Iatrogenic serratus anterior paralysis. Long-term outcome in 26 patients. Chest 1996; 109: 31-34
• 18 Duncan MA, Lotze MT, Gerber LH et al. Incidence, recovery, and management of serratus anterior muscle palsy after axillary node dissection. Phys Ther 1983; 63: 1243-1247
• 19 Sumner AJ. Idiopathic brachial neuritis. Neurosurgery 2009; 65: A150-A152 DOI: 10.1227/01.NEU.0000345355.59438.D1.
• 20 van Alfen N. Clinical and pathophysiological concepts of neuralgic amyotrophy. Nat Rev Neurol 2011; 7: 315-322 DOI: 10.1038/nrneurol.2011.62.
• 21 Toshkezi G, Dejesus J, Jabre JF et al. Long thoracic neuropathy caused by an apical pulmonary tumor. J Neurosurg 2009; 110: 754-757 DOI: 10.3171/2008.10.JNS08755.
• 22 Petrera JE, Trojaborg W. Conduction studies of the long thoracic nerve in serratus anterior palsy of different etiology. Neurology 1984; 34: 1033-1037
• 23 Goodman CE, Kenrick MM, Blum MV. Long thoracic nerve palsy: a follow-up study. Arch Phys Med Rehabil 1975; 56: 352-358
• 24 Fardin P, Negrin P, Dainese R. The isolated paralysis of the serratus anterior muscle: clinical and electromyographical follow-up of 10 cases. Electromyogr Clin Neurophysiol 1978; 18: 379-386
• 25 Läsionen peripherer Nerven und radikuläre Syndrom. 8 ed. Mumenthaler M, Stöhr M, Müller-Vahl H, ed Stuttgart: Thieme; 2003
• 26 Martinoli C, Gandolfo N, Perez MM et al. Brachial plexus and nerves about the shoulder. Semin Musculoskelet Radiol 2010; 14: 523-546 DOI: 10.1055/s-0030-1268072.
• 27 Koscielniak-Nielsen ZJ, Dahl JB. Ultrasound-guided peripheral nerve blockade of the upper extremity. Curr Opin Anaesthesiol 2012; 25: 253-259 DOI: 10.1097/ACO.0b013e32835069c2.
• 28 Vermeylen K, Engelen S, Sermeus L et al. Supraclavicular brachial plexus blocks: review and current practice. Acta Anaesthesiol Belg 2012; 63: 15-21
• 29 Halaszynski TM. Ultrasound brachial plexus anesthesia and analgesia for upper extremity surgery: essentials of our current understanding, 2011. Curr Opin Anaesthesiol 2011; 24: 581-591 DOI: 10.1097/ACO.0b013e32834aca03.
• 30 Hanson NA, Auyong DB. Systematic Ultrasound Identification of the Dorsal Scapular and Long Thoracic Nerves During Interscalene Block. Reg Anesth Pain Med 2012; DOI: 10.1097/AAP.0b013e31826f0a63.
• 31 High-Resolution Sonography of the Peripheral Nervous System. Baert AL, ed Berlin Heidelberg: Springer-Verlag; 2010
• 32 Nath RK, Lyons AB, Bietz G. Microneurolysis and decompression of long thoracic nerve injury are effective in reversing scapular winging: long-term results in 50 cases. BMC Musculoskelet Disord 2007; 8: 25 DOI: 10.1186/1471-2474-8-25.
• 33 Bianchi S. Ultrasound of the peripheral nerves. Joint Bone Spine 2008; 75: 643-649 DOI: 10.1016/j.jbspin.2008.07.002.
• 34 Koenig RW, Pedro MT, Heinen CP et al. High-resolution ultrasonography in evaluating peripheral nerve entrapment and trauma. Neurosurg Focus 2009; 26: E13 DOI: 10.3171/FOC.2009.26.2.E13.