Introduction

An anatomical structure resembling a pully is known as a trochlea; "trochlea" is a Greek word, the English meaning of the trochlea is pully.

In the human body, many pulley-like structures are known as a trochlea; for example, the medial part of an articular area at the lower end of the humerus is called the trochlea. A ligamentous structure attached to the hyoid bone acts as pully for the digastric muscle.[1] The superior surface of the talus is also known as the trochlear surface.[2]

In the ocular orbit, trochlea is a fibrous cartilaginous pully like structure on the nasal aspect of the frontal bone through which superior oblique muscle passes.[3][4] 

Structure and Function

The trochlea is a spine-like structure present at the medial angle of the orbit; the trochlea is a part of the orbital surface of the frontal bone. The orbital part of the frontal bone forms roof of the orbit and ethmoidal sinus.[4][5]

The supratrochlear nerve and tendon of the superior oblique muscle pass through the trochlea, while the supratrochlear artery passes posterior to the trochlea.[4] 

Embryology

The frontal bone develops from neural crest cells controlled by Msx1 and Dlx5 genes; during development, the frontal bone passes under membranous ossification.[6][7]

The development of trochlea is not clear; recent studies describe the trochlea developing with superior oblique muscle tendon. It moves with the tendon and then develops as the fibrocartilaginous pully at 12 weeks of gestational age.[8][9][4] One hypothesis describes the trochlea potentially originating from the common anlage with the sclera.[8]

The supratrochlear nerve originates from the neural crest cell.[10][11] 

Blood Supply and Lymphatics

Supratrochlear artery (Image 2): The supratrochlear artery is a terminal branch of the ophthalmic artery (intracranial branch of the internal carotid artery).

Course: After emerging from the ophthalmic artery, the supratrochlear artery crosses trochlea along with the supratrochlear nerve; then, it crosses the supraorbital margin, pierces the orbital septum and enters the forehead. In the forehead, it runs between corrugator supercilii, orbicularis oculi, and the frontalis muscle.[12][13][14][15][3] Above the level of the mid-forehead, it pierces frontalis muscle and becomes subcutaneous.[16][17][12]

Supratrochlear artery anastomoses with the branches of the supraorbital and superficial temporal artery, both ipsilateral and contralateral, to form a rich vascular network.[16][17][12]

Branches and area of distribution: the bony branches of the supratrochlear artery supply the periosteum of the supraorbital rim and glabella. Muscular branches supply the muscle of the upper eyelid, corrugator supercilii, frontalis, and procerus muscle. Cutaneous branches supply the glabellar skin and skin of the medial forehead.[16][17][12][13][14][15][3]

A study by Kleintjes describes nine branches of the supratrochlear artery:(i) the medial communicating branch that communicates with the contralateral artery, (ii) the lateral communicating branch that communicates with the supraorbital artery, (iii) Superior palpebral artery supplying the upper eyelid, (iv) branch to the brow, (v) periosteal branch, (vi) cutaneous branch supplying the skin of the glabella and median forehead, (vii) oblique branch, (viii) a vertical branch, (ix) medial and lateral vertical branches.[15][12]

Supratrochlear vein: The supratrochlear vein drain the medial forehead, glabellar complex, and periosteum of the medial part of the supraorbital margin. It divides into two branches; one branch accompanies the supratrochlear artery, another branch unites with the supraorbital vein, and forms the angular vein.[18][14][19]

Nerves

Supratrochlear nerve: The supratrochlear nerve is a branch of the frontal nerve (branch of the ophthalmic division of the trigeminal nerve).

Course: The supratrochlear nerve passes forward relative to levator palpebrae superioris muscle; turns medially above the trochlea. Here it gives a descending branch to the infratrochlear nerve then enters into the forehead through the frontal notch.[20][21][22][23][24][25][14] Once it exits the foramen, the supratrochlear nerve ascends to the forehead and runs close to the frontalis and corrugator supercilia muscles. At this junction, it divides and supplies the lower skin of the forehead next to the midline, conjunctiva, and the skin of the upper eyelid.[14][26][27][20][22]

Branches and area of distribution: The descending branch of the supratrochlear nerve combine with the infratrochlear branch of the nasociliary nerve.[20][21][22] The supratrochlear nerve gives sensory branches to the cornea, conjunctiva, the skin of the upper eyelid, the bridge of the nose, and the skin of the forehead. The supratrochlear nerve carries touch, pain, and temperature sensation from the area of the distribution.[23][24][25][14][10]

Muscles

The superior oblique muscle attaches to the trochlea, where it changes direction to insert on the eyeball. The origin of the superior oblique muscle from the body of the sphenoid near the margin of the optic canal. It changes direction at the trochlea. Then it runs backward and laterally on the superior surface of the eyeball behind the equator.[4][28]

The action of the superior oblique muscle is intorsion, depression, and abduction of the eyeball.[4]

Physiologic Variants

Robert et al. reported that in 36% of cases, the supratrochlear nerve originated from the frontal nerve at the distal half of the orbit, while in 64% of cases, the supratrochlear nerve origin was from the frontal nerve at the proximal half the orbit.[10] The supratrochlear nerve may exit the orbit through the supraorbital notch/foramen along with the supraorbital nerve.[10][29][30][31] The supratrochlear nerve gives branches at 4 to 10 mm distance from the supraorbital rim; sometimes, it does not divide.[31] In some cases, the supratrochlear nerve was absent, while in some instances an accessory supratrochlear nerve is also present.[31][32]

The supratrochlear artery branches from the ophthalmic artery in 85 to 90% cases, while in 10 to 15% of cases, the supratrochlear artery and the supraorbital artery emerge as a single branch from the ophthalmic artery and then divide into supratrochlear and supraorbital arteries.[33][12] In some cases, the supratrochlear artery is absent, where the paracentral artery may replace it.[15][12] The branching pattern of the supratrochlear artery also has variation; in most cases, it divides into superficial and deep branches, whereas in some cases, the deep branch was not present. The supratrochlear artery also shows a variation in the number of branches.[12][33][15]

Surgical Considerations

For the midline forehead flap, the supratrochlear artery and its branches play a critical role along with the supraorbital artery. The supratrochlear artery forms anastomoses with the contralateral supratrochlear artery, the supraorbital artery, and the superficial temporal artery. Because of the rich vascularization, the skin supplied by the supratrochlear artery is often used as a skin graft/pedicle to repair the defect at the bridge of the nose or upper facial defect also.[15][34][35]

Fracture of the roof of the orbit may lead to injury of the trochlea, which complicates as a compromised action of the superior oblique muscle; in severe injury, the position of the eyeball is also affected, leading to exophthalmos or enophthalmos.[36][37][38][39][40]

The supratrochlear nerve block is performed in combination with a supraorbital nerve block as regional anesthesia, local infiltration, or field anesthesia for procedures such as repairing of scalp lacerations, craniotomies, and scalp lesion excision.[41][42][43] Between 2 and 3 ml of 1% lidocaine is injected 1 cm medial to the supraorbital foramen to block the supratrochlear nerve.[41]

Clinical Significance

The supratrochlear nerve may become entrapped at the supraorbital margin, supraorbital foramen, or within the corrugator supercilii muscle; the condition may present as chronic frontal migraine. The nerve is relieved by endoscopically or by injecting the botulinum toxin to relieve the migraine.[22][44][45][46]

Embolia Cutis Medicamentosa (ECS) is a phenomenon following an intra-arterial filler injection. The drug or fluid may accidentally enter the supratrochlear or supraorbital artery while injecting the glabellar skin. Injecting fluid in the supratrochlear artery has been found as one of the causes of embolism of the ophthalmic artery and central artery of the retina; embolism of the central artery of the retina may lead to blindness.[47][48][49][50][51]

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References

1.

Gordon A, Alsayouri K. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 24, 2023. Anatomy, Shoulder and Upper Limb, Axilla. [PubMed: 31613503]

2.

Badalahu, Qin B, Luo J, Zeng Y, Fu S, Zhang L. Classification of the subtalar articular surface and its matching situation: an anatomical study on Chinese subtalar joint. Surg Radiol Anat. 2020 Oct;42(10):1133-1139. [PubMed: 32112282]

3.

Luibil N, Lopez MJ, Patel BC. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 24, 2023. Anatomy, Head and Neck, Orbit. [PubMed: 30969665]

4.

Abdelhady A, Patel BC, Aslam S, Al Aboud DM. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Aug 7, 2023. Anatomy, Head and Neck: Eye Superior Oblique Muscle. [PubMed: 30725837]

5.

Singh O, Varacallo M. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 24, 2023. Anatomy, Head and Neck: Frontal Bone. [PubMed: 30571045]

6.

Chung IH, Han J, Iwata J, Chai Y. Msx1 and Dlx5 function synergistically to regulate frontal bone development. Genesis. 2010 Nov;48(11):645-55. [PMC free article: PMC2995851] [PubMed: 20824629]

7.

Tyler MS. Development of the frontal bone and cranial meninges in the embryonic chick: an experimental study of tissue interactions. Anat Rec. 1983 May;206(1):61-70. [PubMed: 6881551]

8.

Katori Y, Rodríguez-Vázquez JF, Kawase T, Murakami G, Cho BH, Abe S. Early fetal development of hard tissue pulleys for the human superior oblique and tensor veli palatini muscles. Ann Anat. 2011 Mar;193(2):127-33. [PubMed: 21334866]

9.

Rodríguez-Vázquez JF, Honkura Y, Katori Y, Murakami G, Abe H. Fetal development of the pulley for muscle insertion tendons: A review and new findings related to the tensor tympani tendon. Ann Anat. 2017 Jan;209:1-10. [PubMed: 27693602]

10.

Haładaj R, Polguj M, Topol M. Anatomical Variations of the Supraorbital and Supratrochlear Nerves: Their Intraorbital Course and Relation to the Supraorbital Margin. Med Sci Monit. 2019 Jul 13;25:5201-5210. [PMC free article: PMC6647930] [PubMed: 31301129]

11.

Freter S, Fleenor SJ, Freter R, Liu KJ, Begbie J. Cranial neural crest cells form corridors prefiguring sensory neuroblast migration. Development. 2013 Sep;140(17):3595-600. [PMC free article: PMC3742142] [PubMed: 23942515]

12.

Agorgianitis L, Panagouli E, Tsakotos G, Tsoucalas G, Filippou D. The Supratrochlear Artery Revisited: An Anatomic Review in Favor of Modern Cosmetic Applications in the Area. Cureus. 2020 Feb 29;12(2):e7141. [PMC free article: PMC7105260] [PubMed: 32257686]

13.

Shumrick KA, Smith TL. The anatomic basis for the design of forehead flaps in nasal reconstruction. Arch Otolaryngol Head Neck Surg. 1992 Apr;118(4):373-9. [PubMed: 1554465]

14.

Walker HM, Chauhan PR. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 24, 2023. Anatomy, Head and Neck: Glabella. [PubMed: 32310453]

15.

Kleintjes WG. Forehead anatomy: arterial variations and venous link of the midline forehead flap. J Plast Reconstr Aesthet Surg. 2007;60(6):593-606. [PubMed: 17485046]

16.

Cai XY, Li ZM, Xu YB, Cheng G, Luo P. [The anatomic features of supratrochlear artery]. Zhonghua Zheng Xing Wai Ke Za Zhi. 2009 Nov;25(6):456-9. [PubMed: 20209940]

17.

Brodland DG. Paramedian forehead flap reconstruction for nasal defects. Dermatol Surg. 2005 Aug;31(8 Pt 2):1046-52. [PubMed: 16042928]

18.

Germann AM, Jamal Z, Al Khalili Y. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jan 13, 2023. Anatomy, Head and Neck, Scalp Veins. [PubMed: 31082005]

19.

Cai X, Li Z. [Applied anatomy study of supratrochlear vein in reconstruction of nasal defect]. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2009 Feb;23(2):219-21. [PubMed: 19275108]

20.

Janis JE, Hatef DA, Hagan R, Schaub T, Liu JH, Thakar H, Bolden KM, Heller JB, Kurkjian TJ. Anatomy of the supratrochlear nerve: implications for the surgical treatment of migraine headaches. Plast Reconstr Surg. 2013 Apr;131(4):743-750. [PubMed: 23249981]

21.

Gras-Cabrerizo JR, Martel-Martin M, Garcia-Lorenzo J, Rodríguez-Álvarez F, Montserrat-Gili JR, Mirapeix-Lucas R, Massegur-Solench H. Surgical Anatomy of the Medial Wall of the Orbit in 14 Human Cadavers. J Neurol Surg B Skull Base. 2016 Dec;77(6):439-444. [PMC free article: PMC5112172] [PubMed: 27857868]

22.

Ortiz R, Gfrerer L, Hansdorfer MA, Nealon KP, Lans J, Austen WG. Migraine Surgery at the Frontal Trigger Site: An Analysis of Intraoperative Anatomy. Plast Reconstr Surg. 2020 Feb;145(2):523-530. [PubMed: 31985652]

23.

Kikuta S, Yalcin B, Iwanaga J, Watanabe K, Kusukawa J, Tubbs RS. The supraorbital and supratrochlear nerves for ipsilateral corneal neurotization: anatomical study. Anat Cell Biol. 2020 Mar;53(1):2-7. [PMC free article: PMC7118260] [PubMed: 32274242]

24.

Olinevich VB, Ziangirova GG. [Embryogenesis and structural-and-functional specificity of corneal nerves in health and pathology]. Vestn Oftalmol. 2004 Jul-Aug;120(4):47-50. [PubMed: 15384854]

25.

Eghrari AO, Riazuddin SA, Gottsch JD. Overview of the Cornea: Structure, Function, and Development. Prog Mol Biol Transl Sci. 2015;134:7-23. [PubMed: 26310146]

26.

Konschake M, Burger F, Zwierzina M. Peripheral Nerve Anatomy Revisited: Modern Requirements for Neuroimaging and Microsurgery. Anat Rec (Hoboken). 2019 Aug;302(8):1325-1332. [PubMed: 30951264]

27.

Bradford BD, Lee JW. Reconstruction of the Forehead and Scalp. Facial Plast Surg Clin North Am. 2019 Feb;27(1):85-94. [PubMed: 30420075]

28.

Shin A, Yoo L, Chaudhuri Z, Demer JL. Independent passive mechanical behavior of bovine extraocular muscle compartments. Invest Ophthalmol Vis Sci. 2012 Dec 19;53(13):8414-23. [PMC free article: PMC4113332] [PubMed: 23188730]

29.

Pauzenberger R, Pikula R, Berchtold V, Mühlbacher J, Rieger UM. Anatomy of the supratrochlear nerve: implications for the surgical treatment of migraine headaches. Plast Reconstr Surg. 2014 May;133(5):723e-724e. [PubMed: 24776587]

30.

Turhan-Haktanir N, Ayçiçek A, Haktanir A, Demir Y. Variations of supraorbital foramina in living subjects evaluated with multidetector computed tomography. Head Neck. 2008 Sep;30(9):1211-5. [PubMed: 18642294]

31.

Domeshek LF, Hunter DA, Santosa K, Couch SM, Ali A, Borschel GH, Zuker RM, Snyder-Warwick AK. Anatomic characteristics of supraorbital and supratrochlear nerves relevant to their use in corneal neurotization. Eye (Lond). 2019 Mar;33(3):398-403. [PMC free article: PMC6460700] [PubMed: 30262895]

32.

Konofaos P, Soto-Miranda MA, Ver Halen J, Fleming JC. Supratrochlear and supraorbital nerves: an anatomical study and applications in the head and neck area. Ophthalmic Plast Reconstr Surg. 2013 Sep-Oct;29(5):403-8. [PubMed: 23928468]

33.

Erdogmus S, Govsa F. Anatomy of the supraorbital region and the evaluation of it for the reconstruction of facial defects. J Craniofac Surg. 2007 Jan;18(1):104-12. [PubMed: 17251847]

34.

Sertel S, Pasche P. Pericranial Flap for Inner Lining in Nasal Reconstruction. Ann Plast Surg. 2016 Oct;77(4):425-32. [PubMed: 26418782]

35.

Park SS. Reconstruction of nasal defects larger than 1.5 centimeters in diameter. Laryngoscope. 2000 Aug;110(8):1241-50. [PubMed: 10942120]

36.

Sadashivam S. Isolated Orbital Roof Fracture: Can It Be Catastrophic? Asian J Neurosurg. 2018 Jul-Sep;13(3):935-937. [PMC free article: PMC6159092] [PubMed: 30283587]

37.

Liu H, Hu S, Qin W. Traumatic prolapse of the globe into the anterior cranial fossa: a case report. BMC Ophthalmol. 2020 Apr 03;20(1):128. [PMC free article: PMC7119161] [PubMed: 32245433]

38.

Lopez J, Pineault K, Pradeep T, Khavanin N, Kachniarz B, Faateh M, Grant MP, Redett RJ, Manson PN, Dorafshar AH. Pediatric Frontal Bone and Sinus Fractures: Cause, Characteristics, and a Treatment Algorithm. Plast Reconstr Surg. 2020 Apr;145(4):1012-1023. [PubMed: 32221225]

39.

Lofrese G, Mongardi L, De Bonis P, Scerrati A, Nicassio N, Cultrera F. Spontaneous Repositioning of Isolated Blow-In Orbital Roof Fracture: Could Wait and See Be a Strategy in Asymptomatic Cases? J Craniofac Surg. 2020 May/Jun;31(3):e263-e266. [PubMed: 32049903]

40.

Gómez Roselló E, Quiles Granado AM, Artajona Garcia M, Juanpere Martí S, Laguillo Sala G, Beltrán Mármol B, Pedraza Gutiérrez S. Facial fractures: classification and highlights for a useful report. Insights Imaging. 2020 Mar 19;11(1):49. [PMC free article: PMC7082488] [PubMed: 32193796]

41.

Salam GA. Regional anesthesia for office procedures: part I. Head and neck surgeries. Am Fam Physician. 2004 Feb 01;69(3):585-90. [PubMed: 14971840]

42.

Herlich A. Focused local anesthesia and analgesia for head and neck surgery. Int Anesthesiol Clin. 2012 Winter;50(1):13-25. [PubMed: 22227420]

43.

Novitch M, Hyatali FS, Jeha G, Motejunas M, Bonneval L, Pankaj T, Cornett EM, Jones MR, Kaye RJ, Urman RD, Kaye AD. Regional techniques for head and neck surgical procedures. Best Pract Res Clin Anaesthesiol. 2019 Dec;33(4):377-386. [PubMed: 31791557]

44.

Lee HJ, Choi KS, Won SY, Apinuntrum P, Hu KS, Kim ST, Tansatit T, Kim HJ. Topographic Relationship between the Supratrochlear Nerve and Corrugator Supercilii Muscle--Can This Anatomical Knowledge Improve the Response to Botulinum Toxin Injections in Chronic Migraine? Toxins (Basel). 2015 Jul 17;7(7):2629-38. [PMC free article: PMC4516933] [PubMed: 26193317]

45.

Filipović B, de Ru JA, van de Langenberg R, Borggreven PA, Lacković Z, Lohuis PJFM. Decompression endoscopic surgery for frontal secondary headache attributed to supraorbital and supratrochlear nerve entrapment: a comprehensive review. Eur Arch Otorhinolaryngol. 2017 May;274(5):2093-2106. [PubMed: 28124109]

46.

Gfrerer L, Guyuron B. Surgical treatment of migraine headaches. Acta Neurol Belg. 2017 Mar;117(1):27-32. [PubMed: 28013487]

47.

Khan TT, Colon-Acevedo B, Mettu P, DeLorenzi C, Woodward JA. An Anatomical Analysis of the Supratrochlear Artery: Considerations in Facial Filler Injections and Preventing Vision Loss. Aesthet Surg J. 2017 Feb;37(2):203-208. [PubMed: 27530765]

48.

Cho KH, Dalla Pozza E, Toth G, Bassiri Gharb B, Zins JE. Pathophysiology Study of Filler-Induced Blindness. Aesthet Surg J. 2019 Jan 01;39(1):96-106. [PubMed: 29873688]

49.

Li X, Du L, Lu JJ. A Novel Hypothesis of Visual Loss Secondary to Cosmetic Facial Filler Injection. Ann Plast Surg. 2015 Sep;75(3):258-60. [PMC free article: PMC4612148] [PubMed: 26207560]

50.

Allali J, Bernard A, Assaraf E, Bourges JL, Renard G. [Multiple embolizations of the branches of the ophthalmic artery: an unknown serious complication of facial surgeries]. J Fr Ophtalmol. 2006 Jan;29(1):51-7. [PubMed: 16465125]

51.

Wu S, Pan L, Wu H, Shi H, Zhao Y, Ji Y, Zeng H. Anatomic Study of Ophthalmic Artery Embolism Following Cosmetic Injection. J Craniofac Surg. 2017 Sep;28(6):1578-1581. [PubMed: 28749836]

Disclosure: Patrick Zito declares no relevant financial relationships with ineligible companies.

Disclosure: Pradip Chauhan declares no relevant financial relationships with ineligible companies.