Suprascapular Neuropathy
- Author: Jonathan C Reeser, MD, PhD; Chief Editor: Sherwin SW Ho, MD more...
Background
Athletes who participate regularly in overhead sports frequently report shoulder pain. Sports such as baseball, volleyball, and tennis demand skills that place substantial load on the athlete’s shoulder when the upper limb is in an overhead or abducted and externally rotated position (see image below).[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]
Clinically relevant anatomy of the subscapular nerve (SSN) and the structures it innervates. The SSN is vulnerable to entrapment at the superior scapular notch and the spinoglenoid notch, beneath the inferior transverse scapular ligament. The inset depicts the clinical appearance in an individual with predominantly right-sided atrophy of the infraspinatus muscle due to suprascapular neuropathy. Epidemiologic studies have demonstrated that athletes who participate in these and other overhead sports are at higher risk for overuse injuries of the upper limb in general and overuse injuries of the shoulder in particular, including rotator cuff tendinopathy and attritional injury to the glenoid labrum.[6, 22, 23, 24, 25, 26, 27] One often overlooked cause of shoulder pain among such athletes is infraspinatus syndrome.
Infraspinatus syndrome is defined as a condition of frequently painless atrophy of the infraspinatus muscle caused by suprascapular neuropathy. The syndrome typically causes symptoms that mimic those of rotator cuff tendinopathy, and the diagnosis may be overlooked until the symptomatic athlete fails to have a therapeutic response to a traditional rotator cuff treatment program.
For excellent patient education resources, visit eMedicine's Osteoporosis and Bone Health Center. Also, see eMedicine's patient education article Shoulder and Neck Pain.
Epidemiology
Frequency
United States
Although the true incidence is unknown, several authors believe that infraspinatus syndrome is underreported. Although the condition has been described in a variety of athletes, including weight lifters and baseball players (and has been reported as an occupational injury among newsreel cameramen), the prevalence of infraspinatus syndrome appears to be highest among volleyball players.[1, 4, 7, 9, 11, 12, 13, 15, 18, 19, 21, 22, 28, 29, 30] Studies have reported that 13-45% of elite volleyball athletes have signs of suprascapular neuropathy.[7, 9, 11, 12, 13, 15, 18, 19, 21, 30] This observation lends credence to the term “volleyball shoulder.”
Functional Anatomy
The suprascapular nerve (SSN) is a mixed nerve that provides the motor innervation of the supraspinatus and infraspinatus muscles and the sensory and proprioceptive innervation of the posterior aspect of the glenohumeral joint, as well as the acromioclavicular joint, subacromial bursa, and scapula.[31, 32, 33, 34] This nerve carries afferents from approximately 70% of the shoulder joint. The nerve arises from the upper trunk of the brachial plexus and is composed predominantly of C5-C6 level fibers. Some authors suggest that the nerve may also receive contributions from the fourth cervical nerve root in as many as 25% of people. Although the suprascapular nerve is a mixed nerve, it typically carries no cutaneous afferent fibers. The SSN is thought to carry cutaneous afferent fibers in only 15-25% of the general population.
In its initial course, the SSN courses posterior and parallel to the inferior belly of the omohyoid muscle and anterior to the trapezius muscle in the posterior triangle of the neck. The nerve then passes dorsally through the suprascapular notch, where it is retained by the transverse scapular ligament, into the suprascapular fossa, where 2 motor branches to the supraspinatus muscle originate. Just proximal to the suprascapular notch, the SSN gives off the superior articular branch, which travels with its fellow nerve through the notch before proceeding laterally to innervate the acromioclavicular joint and its associated bursa and the coracoclavicular and coracohumeral ligaments (see below).
Clinically relevant anatomy of the subscapular nerve (SSN) and the structures it innervates. The SSN is vulnerable to entrapment at the superior scapular notch and the spinoglenoid notch, beneath the inferior transverse scapular ligament. The inset depicts the clinical appearance in an individual with predominantly right-sided atrophy of the infraspinatus muscle due to suprascapular neuropathy. Cadaveric studies reveal that the suprascapular notch may be either U -shaped or V -shaped, and some physicians believe that this anatomic variation may be related to an individual’s predisposition to SSN entrapment at this level. After supplying the supraspinatus, the nerve subsequently travels inferolaterally to wrap around the spine of the scapula at the spinoglenoid notch.
In roughly 15-80% of cadavers studied, the spinoglenoid (inferior transverse scapular) ligament traverses this notch, creating a tunnel through which the nerve travels. Interestingly, the spinoglenoid ligament is reportedly more common in males than in females; this observation may provide an anatomic basis for any possible sex-related predominance in the prevalence of volleyball shoulder. The inferior articular branch, which contains afferents from the posterior glenohumeral joint capsule, joins the suprascapular nerve at the level of the spine of the scapula. After exiting the fibro-osseous tunnel at the spinoglenoid notch the nerve turns inferomedially before arborizing into 3 or 4 terminal branches that supply the infraspinatus muscle.
Sport-Specific Biomechanics
Anatomic considerations suggest that at least 2 sites of potential SSN entrapment exist: the suprascapular notch and the spinoglenoid notch. Although the distribution of injury at these 2 sites varies in published case series, findings in the available literature suggest that the most common site of entrapment among volleyball athletes is the spinoglenoid notch.[12, 35] Selective involvement of the SSN at this level results in the isolated atrophy and weakness of the infraspinatus muscle that characterizes infraspinatus syndrome. Interestingly, no consensus about the precise mechanism of suprascapular neuropathy exists. There is, however, general agreement that the SSN (like other peripheral nerves) may be vulnerable to injury due to compressive forces or repetitive distraction.
The importance of the scapula in the throwing motion and other overhead sport-specific skills is now well appreciated. As the scapula protracts and retracts with functional use of the upper limb, some traction of the SSN can be expected to occur at 1 or both notches through which it traverses. This concept forms the basis of the “sling effect," which proposes that, in certain functional positions of the upper limb, the SSN is exposed to damaging sheer stress in the suprascapular notch. Similar reasoning leads to the prediction that the nerve is vulnerable to traction injury as it bends around the spine of the scapula at the spinoglenoid notch.
Some authors have proposed that individuals in whom the SSN angles sharply around the spinoglenoid notch may be particularly prone to this mechanism of injury. The so-called "SICK scapula" (defined by Burkhart et al as scapular protraction, inferior border prominence, coracoid tightness, and scapular dyskinesis) that occurs in adaptive response to chronic shoulder overuse and functional instability may also theoretically contribute to the increased tension on the SSN via the sling effect.[6]
Demirhan et al reported that the spinoglenoid ligament, when present, inserts into the posterior glenohumeral capsule.[36] They also observed that the ligament becomes taut when the ipsilateral upper limb is adducted across the body or internally rotated; this motion results in traction of the SSN at the spinoglenoid notch. Other possible mechanisms in which the SSN may be compromised include Sandow and Ilic’s proposal that the SSN nerve is vulnerable to direct compression by the medial border of the spinatus tendons at the spinoglenoid notch when the upper limb is abducted and externally rotated.[18] This mechanism would appear to be a further manifestation of posterior (or internal) impingement.
Ferretti, who has written extensively about volleyball shoulder, hypothesized that the mechanism of selective injury to the terminal portion of the SSN in volleyball players is traction on the nerve due to repetitive, sudden, eccentric activation of the infraspinatus during the deceleration phase of the floater serve.[12, 15, 21]
Several studies have reported that the SSN may be compressed in the vicinity of the spinoglenoid notch by ganglion cysts arising from the glenohumeral joint.[25, 35, 37, 38, 39] These ganglion cysts, like Baker cysts that occur in the popliteal fossa after meniscal degeneration or injury, are likely to be the consequence of an injury to the posterior glenoid labrum with resultant leakage of synovial fluid. Finally, some investigators have also proposed that suprascapular neuropathy can result from ischemia caused by migration of posttraumatic microemboli from the suprascapular artery (which generally follows a course parallel to the companion nerve) to the vasa nervorum.
The shoulder joint, or glenohumeral joint, is the most mobile joint in the human body.[3] Unfortunately, this mobility comes at the cost of stability, of which the bony components in the joint provide little. Ligamentous structures and the fibrocartilaginous glenoid labrum provide additional static stability, particularly at the extremes of glenohumeral motion. The supraspinatus and infraspinatus muscles are part of the rotator cuff, which dynamically stabilizes the shoulder joint through a precise system of force couples and agonist-antagonist coactivation, keeping the humeral head centered in the glenoid socket. SSN dysfunction disturbs this mechanism and could potentially result in proximal migration and elevation of the humeral head, with consequent secondary impingement of the supraspinatus tendon beneath the coracoacromial ligament.
Cummins CA, Schneider DS. Peripheral nerve injuries in baseball players. Neurol Clin. Feb 2008;26(1):195-215; x. [Medline].
Gosk J, Urban M, Rutowski R. Entrapment of the suprascapular nerve: anatomy, etiology, diagnosis, treatment [Polish, English]. Ortop Traumatol Rehabil. Jan-Feb 2007;9(1):68-74. [Medline]. [Full Text].
Kibler WB, Herring SA, Press JM, Lee PA, eds. Functional Rehabilitation of Sports and Musculoskeletal Injuries. Gaithersburg, Md: Aspen Publishers; 1998.
Cummins CA, Messer TM, Schafer MF. Infraspinatus muscle atrophy in professional baseball players. Am J Sports Med. Jan-Feb 2004;32(1):116-20. [Medline].
Ravindran M. Two cases of suprascapular neuropathy in a family. Br J Sports Med. Dec 2003;37(6):539-41. [Medline].
Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: spectrum of pathology Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy. Jul-Aug 2003;19(6):641-61. [Medline].
Witvrouw E, Cools A, Lysens R, et al. Suprascapular neuropathy in volleyball players. Br J Sports Med. Jun 2000;34(3):174-80. [Medline].
Meister K. Injuries to the shoulder in the throwing athlete. Part two: evaluation/treatment. Am J Sports Med. Jul-Aug 2000;28(4):587-601. [Medline].
Kugler A, Krüger-Franke M, Reininger S, Trouillier HH, Rosemeyer B. Muscular imbalance and shoulder pain in volleyball attackers. Br J Sports Med. Sep 1996;30(3):256-9. [Medline].
Jackson DL, Farrage J, Hynninen BC, Caborn DN. Suprascapular neuropathy in athletes: case reports. Clin J Sport Med. 1995;5(2):134-6; discussion 136-7. [Medline].
Côelho TD. Isolated and painless (?) atrophy of the infraspinatus muscle. Left handed versus right handed volleyball players. Arq Neuropsiquiatr. Dec 1994;52(4):539-44. [Medline].
Ferretti A, De Carli A, Fontana M. Injury of the suprascapular nerve at the spinoglenoid notch. The natural history of infraspinatus atrophy in volleyball players. Am J Sports Med. Nov-Dec 1998;26(6):759-63. [Medline].
Holzgraefe M, Kukowski B, Eggert S. Prevalence of latent and manifest suprascapular neuropathy in high-performance volleyball players. Br J Sports Med. Sep 1994;28(3):177-9. [Medline].
Black KP, Lombardo JA. Suprascapular nerve injuries with isolated paralysis of the infraspinatus. Am J Sports Med. May-Jun 1990;18(3):225-8. [Medline].
Ferretti A. Volleyball injuries. Federation Internationale de Volleyball, Lausanne, Switzerland. International Olympic Committee Medical Commission. 1994.
Ringel SP, Treihaft M, Carry M, Fisher R, Jacobs P. Suprascapular neuropathy in pitchers. Am J Sports Med. Jan-Feb 1990;18(1):80-6. [Medline].
Safran MR. Nerve injury about the shoulder in athletes, part 1: suprascapular nerve and axillary nerve. Am J Sports Med. Apr-May 2004;32(3):803-19. [Medline].
Sandow MJ, Ilic J. Suprascapular nerve rotator cuff compression syndrome in volleyball players. J Shoulder Elbow Surg. Sep-Oct 1998;7(5):516-21. [Medline].
Tengan CH, Oliveira AS, Kiymoto BH, et al. Isolated and painless infraspinatus atrophy in top-level volleyball players. Report of two cases and review of the literature. Arq Neuropsiquiatr. Mar 1993;51(1):125-9. [Medline].
Agre JC, Ash N, Cameron MC, House J. Suprascapular neuropathy after intensive progressive resistive exercise: case report. Arch Phys Med Rehabil. Apr 1987;68(4):236-8. [Medline].
Ferretti A, Cerullo G, Russo G. Suprascapular neuropathy in volleyball players. J Bone Joint Surg Am. Feb 1987;69(2):260-3. [Medline]. [Full Text].
Karatas GK, Gögüs F. Suprascapular nerve entrapment in newsreel cameramen. Am J Phys Med Rehabil. Mar 2003;82(3):192-6. [Medline].
Asami A, Sonohata M, Morisawa K. Bilateral suprascapular nerve entrapment syndrome associated with rotator cuff tear. J Shoulder Elbow Surg. Jan-Feb 2000;9(1):70-2. [Medline].
Rossi F. Shoulder impingement syndromes. Eur J Radiol. May 1998;27(suppl 1):S42-8. [Medline].
Chochole MH, Senker W, Meznik C, Breitenseher MJ. Glenoid-labral cyst entrapping the suprascapular nerve: dissolution after arthroscopic debridement of an extended SLAP lesion. Arthroscopy. Dec 1997;13(6):753-5. [Medline].
Berry H, Kong K, Hudson AR, Moulton RJ. Isolated suprascapular nerve palsy: a review of nine cases. Can J Neurol Sci. Nov 1995;22(4):301-4. [Medline].
Pillai G, Baynes JR, Gladstone J, Flatow EL. Greater strength increase with cyst decompression and SLAP repair than SLAP repair alone. Clin Orthop Relat Res. Apr 2011;469(4):1056-60. [Medline]. [Full Text].
Zeiss J, Woldenberg LS, Saddemi SR, Ebraheim NA. MRI of suprascapular neuropathy in a weight lifter. J Comput Assist Tomogr. Mar-Apr 1993;17(2):303-8. [Medline].
Cummins CA, Bowen M, Anderson K, Messer T. Suprascapular nerve entrapment at the spinoglenoid notch in a professional baseball pitcher. Am J Sports Med. Nov-Dec 1999;27(6):810-2. [Medline].
Montagna P, Colonna S. Suprascapular neuropathy restricted to the infraspinatus muscle in volleyball players. Acta Neurol Scand. Mar 1993;87(3):248-50. [Medline].
Ajmani ML. The cutaneous branch of the human suprascapular nerve. J Anat. Oct 1994;185 (pt 2):439-42. [Medline]. [Full Text].
Antoniadis G, Richter HP, Rath S, Braun V, Moese G. Suprascapular nerve entrapment: experience with 28 cases. J Neurosurg. Dec 1996;85(6):1020-5. [Medline].
Aszmann OC, Dellon AL, Birely BT, McFarland EG. Innervation of the human shoulder joint and its implications for surgery. Clin Orthop Relat Res. Sep 1996;330:202-7. [Medline].
Bigliani LU, Dalsey RM, McCann PD, April EW. An anatomical study of the suprascapular nerve. Arthroscopy. 1990;6(4):301-5. [Medline].
Lee BC, Yegappan M, Thiagarajan P. Suprascapular nerve neuropathy secondary to spinoglenoid notch ganglion cyst: case reports and review of literature. Ann Acad Med Singapore. Dec 2007;36(12):1032-5. [Medline]. [Full Text].
Demirhan M, Imhoff AB, Debski RE, et al. The spinoglenoid ligament and its relationship to the suprascapular nerve. J Shoulder Elbow Surg. May-Jun 1998;7(3):238-43. [Medline].
Ticker JB, Djurasovic M, Strauch RJ, et al. The incidence of ganglion cysts and other variations in anatomy along the course of the suprascapular nerve. J Shoulder Elbow Surg. Sep-Oct 1998;7(5):472-8. [Medline].
Moore TP, Fritts HM, Quick DC, Buss DD. Suprascapular nerve entrapment caused by supraglenoid cyst compression. J Shoulder Elbow Surg. Sep-Oct 1997;6(5):455-62. [Medline].
Hashimoto BE, Hayes AS, Ager JD. Sonographic diagnosis and treatment of ganglion cysts causing suprascapular nerve entrapment. J Ultrasound Med. Sep 1994;13(9):671-4. [Medline].
Inokuchi W, Ogawa K, Horiuchi Y. Magnetic resonance imaging of suprascapular nerve palsy. J Shoulder Elbow Surg. May-Jun 1998;7(3):223-7. [Medline].
Gerscovich EO, Greenspan A. Magnetic resonance imaging in the diagnosis of suprascapular nerve syndrome. Can Assoc Radiol J. Aug 1993;44(4):307-9. [Medline].
Chalian M, Faridian-Aragh N, Soldatos T, Batra K, Belzberg AJ, Williams EH, et al. High-resolution 3T MR neurography of suprascapular neuropathy. Acad Radiol. Aug 2011;18(8):1049-59. [Medline].
Shah AA, Butler RB, Sung SY, Wells JH, Higgins LD, Warner JJ. Clinical outcomes of suprascapular nerve decompression. J Shoulder Elbow Surg. Sep 2011;20(6):975-82. [Medline].
Ritchie ED, Tong D, Chung F, et al. Suprascapular nerve block for postoperative pain relief in arthroscopic shoulder surgery: a new modality?. Anesth Analg. Jun 1997;84(6):1306-12. [Medline]. [Full Text].
Jones DS, Chattopadhyay C. Suprascapular nerve block for the treatment of frozen shoulder in primary care: a randomized trial. Br J Gen Pract. Jan 1999;49(438):39-41. [Medline]. [Full Text].
Brown DE, James DC, Roy S. Pain relief by suprascapular nerve block in gleno-humeral arthritis. Scand J Rheumatol. 1988;17(5):411-5. [Medline].
Boardman ND 3rd, Cofield RH. Neurologic complications of shoulder surgery. Clin Orthop Relat Res. Nov 1999;368:44-53. [Medline].
Bredella MA, Tirman PF, Fritz RC, et al. Denervation syndromes of the shoulder girdle: MR imaging with electrophysiologic correlation. Skeletal Radiol. Oct 1999;28(10):567-72. [Medline].
Casazza BA, Young JL, Press JP, Heinemann AW. Suprascapular nerve conduction: a comparative analysis in normal subjects. Electromyogr Clin Neurophysiol. Apr-May 1998;38(3):153-60. [Medline].
Costouros JG, Porramatikul M, Lie DT, Warner JJ. Reversal of suprascapular neuropathy following arthroscopic repair of massive supraspinatus and infraspinatus rotator cuff tears. Arthroscopy. Nov 2007;23(11):1152-61. [Medline].
Cummins CA, Anderson K, Bowen M, Nuber G, Roth SI. Anatomy and histological characteristics of the spinoglenoid ligament. J Bone Joint Surg Am. Nov 1998;80(11):1622-5. [Medline].
Cummins CA, Messer TM, Nuber GW. Suprascapular nerve entrapment. J Bone Joint Surg Am. Mar 2000;82(3):415-24. [Medline]. [Full Text].
Ide J, Maeda S, Takagi K. Does the inferior transverse scapular ligament cause distal suprascapular nerve entrapment? An anatomic and morphologic study. J Shoulder Elbow Surg. May-Jun 2003;12(3):253-5. [Medline].
Kiss G, Kómár J. Suprascapular nerve compression at the spinoglenoid notch. Muscle Nerve. Jun 1990;13(6):556-7. [Medline].
Luo ZP, Hsu HC, An KN. An in vitro study of glenohumeral performance after suprascapular nerve entrapment. Med Sci Sports Exerc. Apr 2002;34(4):581-6. [Medline].
Martin SD, Warren RF, Martin TL, et al. Suprascapular neuropathy. Results of non-operative treatment. J Bone Joint Surg Am. Aug 1997;79(8):1159-65. [Medline].
Padua L, LoMonaco M, Padua R, et al. Suprascapular nerve entrapment. Neurophysiological localization in 6 cases. Acta Orthop Scand. Oct 1996;67(5):482-4. [Medline].
Post M. Diagnosis and treatment of suprascapular nerve entrapment. Clin Orthop Relat Res. Nov 1999;(368):92-100. [Medline].
Post M, Mayer J. Suprascapular nerve entrapment. Diagnosis and treatment. Clin Orthop Relat Res. Oct 1987;223:126-36. [Medline].
Raasch W, Zebrack J. Suprascapular nerve injuries. Curr Opin Orthoped. 2003;14:252-4.
Shaffer JW. Suprascapular nerve injury during spine surgery. A case report. Spine. Jan 1 1994;19(1):70-1. [Medline].
Print
