CERVICAL SPINE USG

The bony framework of the cervical spine is made up of seven cervical vertebra C1 to C7.

C1 cervical vertebra also known as atlas which joins with the occipital bone by atlantooccipital joint. Atlas do not have a spinous process rather it has a posterior tubercle.

C2 vertebra also known as axis is having a bifid transverse process and an odontoid process. It is used as the pivot for the rotation of the head. The Spinous process of C7 is easily identified as it is the largest is size and also known as vertebra prominence.

Foramen transversarium are the foramens at the transverse process of the cervical vertebra. Vertebral artery passes through the foramen transversarium. It enters from the C6 transverse process. There are anterior and posterior tubercles in the transverse process. C6 is having a large anterior tubercle, where as C7 is having a small anterior tubercle and a larger posterior tubercle.

Unlike the lumbar vertebra the vertebral bodies of cervical vertebra are smaller. Superior and inferior articular processes join to form the facet joints. They collectively form the cervical pillars. The collective pillars are wider than the vertebral bodies.

Muscles of Cervical area and back can be divided into two groups

1, The Superficial Group of Muscles

2. The Deep Muscles

The Superficial group of muscles are connected with the upper limb and associated with movements of the shoulder. Deep muscles are associated with movement of the vertebral column and maintains the posture. superficial muscles are supplied by the anterior division of the nerves whereas the deep muscles or intrinsic muscles of the back are supplied by the posterior division of spinal nerves.

Trapezius Muscle - Superficial muscle at the back. Covered within the investing layer (Most superficial) of deep cervical fascia along sternocleidomastoid muscle. It originates from the occipital bone, the nuchal ligament, and the spinous processes of T1–T12. The muscles inserts into the scapular spine, the acromion and the lateral third portion of the clavicle. It is supplied by the accessory nerve.

Levator Scapulae Muscle - The muscle originates from the transverse processes of first to fourth vertebrae (C1-C4) and inserts into the medial border of scapula. It is supplied by anterior division C3, C4 spinal nerves and dorsal scapular nerve (branch of the C5)

Splenius Capitis Muscle - The ward splenius means "bandage". the muscle along with splenius cervicis lies in the back of the neck in a 'V' shaped pattern. This forms the superficial layer of the deep back muscles of the neck. The muscle originates from the spinous processes of the lower cervical and upper thoracic vertebrae (C7-T3) and the nuchal ligament. It inserts into the lateral superior nuchal line of occipital bone and the mastoid process of the temporal bone. Other deep back muscles lies deep to this muscle. It is supplied by the lateral branches of posterior division of C2 and C3 spinal nerves.

Semispinalis capitis Muscle - The Muscle originates from the articular processes of vertebrae C4-C7 and the transverse processes of the vertebrae T1-T6. It is inserted in the occipital bone between the superior and inferior nuchal lines. Nerve supply is from the descending branches from the greater occipital nerve (C2) and spinal nerve C3.

Obliquus Capitis Inferior Muscle - Originates from the spinous process of axis(C2) and inserts into the transverse process of atlas (C1). The bifid spinous process along with this muscle helps to determine the level under ultrasound in cervical spine. This muscle also forms the inferolateral border of sub-occipital triangle. This muscle is supplied by the posterior division of the spinal nerve C1, which is also known as sub-occipital nerve.

Greater occipital Nerve

Greater occipital nerve is a component of the cervical plexus. The Medial branch of the posterior primary ramus of the C2 cervical nerve continues as Greater Occipital Nerve. The nerve emerges between the first two cervical vertebrae along with the lesser occipital nerve. Then the nerve curves below the lower border of the obliquus capitis inferior then lies superficial to it, in between the Semispinalis capitis Muscle and Obliquus Capitis Inferior Muscle and usually blocked at this place. Finally the nerve pierces the trapezius muscle, and becomes subcutaneous. It innervates the skin of the posterior scalp, over the ear and parotid glands.

Lesser Occipital Nerve

This nerve arises from Ventral Ramus of C2, although it often receives fibers from C3

Third Occipital Nerve (TON)

The third occipital nerve is the branch of the Posterior Root of C3 Spinal nerve, It provides cutaneous sensation to a small portion of scalp near occipital area. The C2/3 Facet Joints are solely supplied by Third Occipital Nerve unlike other Facet joints,

It is important to know the nerve supply of the cervical facet joints as pain originating from cervical facet joints can be treated with the RF ablation of the respective branches.

C0- C1 - Atlantooccipital Joint - Supplied by the Anterior Rami C1 Spinal Nerve

C1- C2 - Atlantoaxial Joint - Supplied by the branches of the ventral ramus of the

C2 spinal nerve

C2- C3 Facer Joint - Supplied by the Third Occipital Nerve (TON), which originates from the Posterior Root of C3 spinal nerve.

C3- C4 & below Facet Joints - Medial Branches of Posterior Rami Respective Spinal Nerves (Example - C5-6 facet joint is supplied by the medial branch of dorsal/posterior rami of C5 & C6 spinal nerve. )

C7- T1 Facet Joint - Supplied by the medial branch of dorsal/posterior rami of C7 and C8 Spinal nerve.

Vertebral Artery - Originates from the subclavian artery, enters the foramen transversarium of the 6th cervical vertebrae (occasionally at C7 - 7.5% of cases). The artery passes above through the foramen transversarium of each cervical vertebra. After passing through foramen transversarium of C1, it travels across the posterior arch of C1 through the sub-occipital triangle, and finally enters the foramen magnum.

Occipital artery - Branch from the external carotid, it accompanies the greater occipital nerve. At the superior nuchal line, lateral to the occipital protuberance the greater occipital nerve lies medial to the occipital artery nearly at the junction of medial 1/3 and lateral 2/3 of the line joining occipital protuberance to mastoid.