Suboccipital triangle

anatomy of suboccipital triangle

1. Suboccipital triangle Lecture by: Dr Chitransha Dhakarey

2. Neck extention The back of the neck is limited above by external occipital protuberance and superior nuchal lines. below by spine of C7 vertebra .

3. The important structures on the back of the neck include L igamentum nuchae . E xtensor muscles of the neck S uboccipital triangle A rterial anastomosis around the semispinalis capitis .

4. Soft Tissues on the Back of the Neck The soft tissues on the back of the neck are divided into four layers. From superficial to deep these are: Skin (cutaneous innervation ) Superficial fascia Deep fascia Muscles

5. SKIN The skin on the back of the neck is supplied by dorsal rami of C2, C3, and C4 spinal nerves. Greater occipital nerve (C2) Third occipital nerve (C3) Cutaneous branches of C4 and C5

6. Greater occipital nerve (C2) It pierces the deep fascia at the level of superior nuchal line, 2.5 cm lateral to the external occipital protuberance

7. Supply the posterior part of the scalp as far as the vertex . It is the thickest cutaneous nerve in the body.

8. Third occipital nerve (C3) It pierces the deep fascia medial to the greater occipital nerve, a little below the superior nuchal line & supplies the skin of the nape of the neck up to the external occipital protuberance .

9. Cutaneous branches of C4 and C5 These branches pierce the deep fascia close to the midline in series with the 3rd occipital nerve. They supply the adjacent skin .

10. superficial fascia The superficial fascia of the back is thick and in spite of its fat content, it is very tough. It contains cutaneous nerves and vessels. The cutaneous nerves : greater occipital, 3 rd occipital, and cutaneous branch of C4 and C5.

11. The cutaneous vessels: Occipital artery Twigs derived from 2 nd part of the vertebral artery.

12. Greater occipital nerve (C2) Third occipital nerve (C3) Cutaneous branches of C4 and C5 Occipital artery Twigs of the vertebral artery . Cutaneous nerves Cutaneous vessels

13. deep fascia The deep fascia of the back is called nuchal fascia. It is attached in the median plane to the spines, supraspinous ligaments, and ligamentum nuchae .

14. LIGAMENTUM NUCHAE It is a triangular sheet of fibroelastic tissue that forms the median fibrous septum between the muscles of the two sides. The ligamentum nuchae presents three borders:

15. Superior border attached to the external occipital crest. Anterior border attached to the posterior tubercle of atlas and the spines of the cervical vertebrae (C2 to C7). Free posterior border , which extends from the external occipital protuberance to the spine of the 7th cervical vertebrae.

16. muscles The muscles of the back of the neck on either side are arranged into Superficial: Group: ventral rami Deep Group: dorsal rami

17. SUPERFICIAL GROUP TRAPEZIUS LEVATOR SCAPULAE Rhomboideus major & minor

18. TRAPEZIUS It is a large, flat and triangular muscle which is placed superficially on the back of the neck and thorax. ORIGIN : Arises from the medial third of superior nuchal line, external occipital protuberance, ligamentum nuchae & spinous processes of C7 to T12.

19. INSERTION : Upper surface of lateral third of clavicle, superior crest of spine of scapula, Med . Border of Acromion process, Tubercle of Spine of Scapula .

20. NERVE SUPPLY Motor : Spinal Accessory Nerve Sensory : Ventral Rami of C3 & C4 ACTION : » Helps in the elevation and shrugging of shoulders. » Also helps in retracting and steadying the scapula.

21. Levator scapulae ORIGIN : Arise from post. Tubercles of the transverse processes of the first four cervical vertebrae. INSERTION : Into the med. border of the scapula below the superior angle. NERVE SUPPLY : Branches from ventral. Rami of C3 & C4 ACTION : Elevates the Scapula

22. DEEP GROUP Muscles of this group form the intrinsic musculature & arranged in 4 layers : External : Consisting of SPLENIUS CAPITIS & S. CERVICES Intermediate : Consisting of LONGISSIMUS CAPITIS & L. CERVICES Deep : Consisting of SEMISPINALIS CAPITIS & S. CERVICIS Deepest layer : Formed by the SUBOCCIPITAL MUSCLES

23. LONGISSIMUS CAPITIS Origin: Arises from transverse processes of the lower four cervical vertebrae. (C4-C8) Insertion: Inserts into the mastoid process, deep to the splenius capitis . Nerve supply: Supplied by posterior rami of cervical nerves. Actions: It extends the head and turns the face to the same side.

24. SPLENIUS CAPITIS Origin: from spines of 7th cervical and T1-T4 thoracic vertebrae and lower part of the ligamentum nuchae . Insertion: Runs upwards and laterally & insert on mastoid process and lateral third of the superior nuchal line.

25. Nerve supply: Supplied by posterior rami of middle cervical nerves. Action: Rotates the head and face to the same side. Lateral flexion of neck.

26. SEMISPINALIS CAPITIS It is long, thick powerful muscle and produces longitudinal bulging of the neck on each side of the median furrow. Origin: Arises from transverse processes of lower four cervical and upper six thoracic vertebrae (C4–T6).

27. Insertion: Runs vertically upwards and inserted into the medial part of the area between the superior and inferior nuchal lines of the occipital bones. Nerve supply: Supplied by posterior rami of spinal nerves. Actions: It extends the head.

28. SUBOCCIPITAL TRIANGLE

29. This is a triangular muscular space situated deep in the suboccipital region of the neck, one on each side of the midline and bounded by four suboccipital muscles.

30. Boundaries Superomedial Superolateral Inferior Roof Floor

31. Rectus capitis posterior major Origin: From spine of axis by a pointed tendon. Insertion: lateral part of the inferior nuchal line and area of bone below it. Action: Extends the head at atlanto -occipital joint

32. Rectus capitis posterior minor Origin: From posterior tubercle of the atlas. Insertion: the medial part of the inferior nuchal line and area of bone below it. Action: Extend the head at the atlanto -occipital joint

33. Obliquus capitis inferior Origin: From spine of the axis Insertion: transverse process of the atlas Action: Rotates the head to the same side at the atlantoaxial joint

34. Obliquus capitis superior Origin: From transverse process of the atlas Insertion: into area between superior and inferior nuchal lines of the occipital bone, lateral to the semispinalis capitis .

35. Action Rotates the head to the same side (lateral flexion) at atlanto - axial joint. Acting along with its counterpart of the opposite side, they extend the head at the atlanto -occipital joint

36. Contents The contents of suboccipital triangle are as follows: Suboccipital plexus of veins. Dorsal ramus of 1st cervical nerve ( suboccipital nerve). Third part of vertebral artery.

37. Suboccipital plexus of the veins It lies in and around the suboccipital triangle. It connects the following veins: Muscular veins from neighboring muscles. Occipital veins, deep cervical vein Internal vertebral venous plexus. Transverse sinus through emissary vein. Plexus of the veins around vertebral artery .

38. Applied The connection between suboccipital venous plexus and internal vertebral venous plexus serves as a path of intracranial infection in carbuncles of the neck.

39. DORSAL RAMUS OF C1-SUBOCCIPITAL NERVE It emerges between the posterior Arch of the atlas and the vertebral artery and soon breaks up into branches which supply the four sub occipital muscles.

40. Third part of the vertebral artery The third part of the vertebral artery appears in the suboccipital triangle through foramen transversarium of the atlas vertebra. The vertebral artery is separated from the posterior arch of the atlas by the 1st cervical nerve.

41. Cisternal puncture It is done when lumbar puncture fails to take out CSF sample for therapeutic and diagnostic purposes. Needle is introduced in the midline just above the spine of the axis vertebra. It pierces the posterior atlanto - occipital membrane at a depth of about 2 inch/5 cm in adults.

42. Utmost care should be taken while introducing the needle as medulla lies only 1 inch anterior to the posterior atlanto -occipital membrane which, if damaged, may be fatal.

43. The neck rigidity occurs in meningitis due to spasm of extensor muscles on the back of the neck. The posterior cranial fossa is approached by neurosurgeons to remove the brain tumour by clearing the sub occipital muscles and removing the exposed bone.