The Fourth Cervical Vertebrae, abbreviated C4, is one of seven vertebral segments to comprise the Cervical Spine . C3 , C4, C5 and C6 Cervical Spine vertebrae are often grouped together because of their similar characteristics. While their bony structures resemble each other, their Nerve Root innervation, Pain presentation and treatment protocols are distinct. This page details the structure of this vertebral segment, its function as an extensive attachment site and the nerves it gives rise to.
The rectangular bodies of C3-6 are wider laterally than they are in an anteroposterior direction with a concavity to their inferior and superior surfaces that is generally flatter in other vertebrae (SOURCE-4). The surfaces are less comparable at their margins where on the superior surface they raise posterior-lateral hooks known asUncinate Processesand on the inferior surface the anterior and posterior margins are exacerbated (SOURCE-5). The Uncinate Processes are congruent with the superior vertebrae (C3- C7 ), forming smallUncovertebral Joints(SOURCE-5). When these joints are damaged, this can be relayed onto the intervening outer rings (annuli) of the Intervertebral Discs (SOURCE-5).
The C3- C6 Pediclesare shorter, typically curved in a posterolateral direction and extend thinLaminaeposteromedially which form the lateral walls of theVertebral Foramen(orVertebral Canal) (SOURCE-5). This triangular canal facilitates the passage of the Spinal Cord which is particualry thick in the Cervical Spine due to the addition of the Cervical Plexus and Brachial Plexus (SOURCE-4). The lateral walls of the canal meet posteriorly at theSpinous Processwhich for C-3-6 are short and bifid (SOURCE-5).
Between C3- C6 corresponding superior and inferior articular processes from adjacent vertebrae meet at Zygapophyseal Joints (orFacet Joints). Collectively the C3-C6 vertebrae and the intervening Facet Joints form theArticular Pillar, a column-like structure whose orientation and architechture provide the Cervical Spine with stability while permitting significant Range of Motion .
TheTransverse Processesin this region are short lateral extensions that give offAnterior and Posterior Tubercleswhich are unique to the Cervical Spine and serve as attachment sites (SOURCE-5).
Compared with other vertebrae of the Cervical Spine , C3-6 have (SOURCE-4+5):
Spinous Process- short and bifid, so short certain muscles such as the Trapezius and Splenius Capitis attach to Nuchal Ligament rather than vertebrae
Body- smallest typical vertebrae in Vertebral Column . Broader side to side, than front to back
Laminae- narrow and thin. Forms a large Lamina Groove
Articular Pillars- the superior and inferior articular processes are fused to form a pillar
Transverse Processes- consist of two parts that are separated by a deep sulcus or canal which provides a passage for the corresponding spinal nerve:
Anterior part - arises from the side of the body and finishes at the Anterior Tubercle
Posterior part - the ‘true’ transverse process, ends at the Posterior Tubercle
Transverse Foramen- passage for neurovascular structures, primarily the Vertebral Artery and its accompanying veins and sympathetic nerves
With the several bony protuberances and landmarks, C4 serves as the attachment site for many soft-tissues (SOURCE-4+6):
Deep Stabilisers - short muscles associated with the Spinous Process and Transverse Process (SOURCE-6):
Multifidus - insert onto the lateral aspects and tips of Spinous Process
Semispinalis Cervicis - insert onto the Spinous Process
Rotatores - Transverse Process to Spinous Process of higher segment
Interspinalis Cervicis - course between each segments Spinous Process
Iliocostalis Cervicis - attaches to Transverse Process
Spinotransverse Group - superficial muscles
Splenius Cervicis - arises from thePosterior Tubercleof Transverse Process
Levator Scapulae - attaches toPosterior Tubercleof the Transverse Process
Trapezius - inserts onto the Spinous Process via the Nuchal Ligament
Prevertebral Group - deep anterior muscles
Longus Colli - the Transverse Process serves as an origin for the Superior Oblique Portion, while the anterior vertebral body recieves a portion of the Vertical Intermediate Portion (SOURCE-4)
Longus Capitis - arises from theAnterior Tubercleof the Transverse Process
Lateral Muscles
Middle Scalene - arises from thePosterior Tubercleof Transverse Process
Anterior Scalene - arises fromAnterior Tubercleof Transverse Process
Intervertebral Discs (above and below)
Ligament s
Region
Deep Back Arm Line - direct attachment through Levator Scapulae
Superficial Back Arm Line - through Trapezius
Deep Front Line - multiple direct attachments
Lateral Line - direct attachement through Sternocleidomastoid / Forward Head Posture
Spiral Line - direct attachement through Splenius Cervicis
Superficial Back Line - through Erector Spinae
Unlike the rest of the Vertebral Column , Nerve Roots of the Cervical Spine exit superior of their corresponding vertebrae. The C4 Nerve Root traverses the inferior surface of C3 and superior surface of C4. There is known variation in the course and formation of these peripheral nerves.
Direct Nerve Root branches:
Longus Capitis - ( C1 - Atlas , C2 - Axis , C3 and sometimes C4 and C5 )
Longus Colli - (ventral rami of C2 - Axis , C3 , C4, C5 and C6 )
Anterior Scalene - (ventral rami of C4, C5 and C6 )
Middle Scalene - (ventral rami of C3 - C8 )
Levator Scapulae - the nerves from the anterior rami of C3 and C4 Nerve Roots primarily innervate this muscle. They course inferolaterally to enter the muscle from its lateral border (SOURCE-1)
Peripheral Nerve - the C4 Nerve Root lends fibres to the following nerves:
Phrenic Nerve - ( C3 , C4, C5 )
Supraclavicular Nerve - ( C3 and C4) (sensory)
The following structures are innervated by the C4 Nerve Root :Motor:
Diaphragm - ( Phrenic Nerve )
Prevertebral Muscle s
Longus Capitis - ( C1 - Atlas , C2 - Axis , C3 and sometimes C4 and C5 )
Longus Colli - (ventral rami of C2 - Axis , C3 , C4, C5 and C6 )
Middle Scalene - (ventral rami of C3 - C8 ) with the most superior attachment of the Scalenes , the Middle Scalene is often the only one to receive innervation this high (SOURCE-7)
Sternocleidomastoid - (ventral rami of C2 - Axis , C3 and C4) thought predominantly to be sensory although may have minor motor function (SOURCE-4+8)
Scapula Stabilisers
Levator Scapulae - (ventral rami of C3 and C4) enter the muscle from its lateral border (SOURCE-1)
Sensory:
Dermatomes - anteriorly, C4 provides cutaneous sensory innervation over the lateral Clavicle , Acromion and skin near Pectoralis Minor . Posteriorly C4 covers an oblique laterally coursing strip over the upper Trapezius to the Acromion (SOURCE-10)
Trapezius - the sensory (proprioceptive) functions of this muscle are performed by C3 and C4 (SOURCE-9)
Sternocleidomastoid - branches of the ventral rami of C2 - Axis , C3 and C4 pierce the muscle and perform predominately sensory/ proprioceptive functions (SOURCE-4+8)
Serratus Anterior - a branch from the C4 Nerve Root was identified to provide motor innervation in ~12% of cases (SOURCE-2).
While C4 is subject to many of the traumatic and degenerative pathologies that affect the Vertebral Column and their associated soft-tissues, the following discusses pathologies that are region specific. Akin to stepping on a running gardenhose, misalignment of C4 affects the exiting Nerve Root , known as a Radiculopathy , which may compromise the sensory or motor functions of the tissues it innervates. A C4 Radiculopathy is more often caused by a C3 /C4 Intervertebral Discs pathology and occurs more frequently than a C3 Radiculopathy (SOURCE-3). Additionally, misalignment of C4 may lead to approximation of its Zygapophyseal Joints and consequent referral.
Cervicogenic Headache - in lieu of variation, C4 is usually the most proximal Cervical Spine segment not to directly refer into the head to be a source of Headaches . The referred Pain pattern for both the C2 - Axis /C3 and C3/ C4 Zygapophyseal Joints extends into the cervical region, with the distal joints referring further inferior towards the Superior Angle of Scapula and more proximal joints referring superiorly over the skull (SOURCE-14)
C4 Radiculopathy has the capacity to alter sensation along any of the Dermatomes of the Peripheral Nerves it lends fibres to, including the Supraclavicular Nerve or sensory branches such as those to the Trapezius or Sternocleidomastoid . Similarly, palsy of any of the C4 motor branches may compromise muscle function to any of the Muscles it directly or indirectly innervates.
Although rare, a Neuropathy of particular concern is Diaphragm atic paralysis that may result from palsy of the Phrenic Nerve which arises from ventral rami of C3 , C4 and C5 (SOURCE-13). As C4 is the predominant contributor of nerve fibres, it is most common segement implicated in this injury, usually in the form of a Radiculopathy (SOURCE-13+14). A C2 - Axis / C3 Myelopathy , where the Spinal Cord itself is compressed, may also compromise the C4 neuromere prior to it exiting as a Nerve Root (SOURCE-13). In either instance, chronic disturbance to the Phrenic Nerve can lead to both trophic and nutritional disturbance which causes weakening and dysfunction of the Diaphragm (SOURCE-14).
The following observations may be related to C4 pathology/dysfunction:
Headaches - worse with Cervical Spine movement - suggests Cervicogenic Headache (SOURCE-11). This type of headache is typically described as a dull Pain or internal pressure and may be bilateral, occipital, frontal or facial (SOURCE-11)
Weakness with movement:
Neck - notably Cervical - Lateral Flexion , Cervical - Extension or Cervical - Flexion
Scapular Dyskinesis - Scapulothoracic Joint - Elevation or Scapulothoracic Joint - Downward Rotation may be dysfunctional
The Nerve Root may be evaluated by virtue of the perfomance of the Muscles that share its innervation, known as Myotomes . For C4, Scapulothoracic Joint - Elevation is produced agaisnt the resistance of the practitioner (SOURCE-11).
The Nerve Root may also be evaluated through its sensory distribution, known as a Dermatomes . For C4, anterior cutaneous sensroy innervation covers the lateral Clavicle , Acromion and skin near Pectoralis Minor , while posteriorly C4 covers an oblique laterally coursing strip over the upper Trapezius to the Acromion (SOURCE-3+10).
The following Special Tests may be relevant in evaluating C4 dysfunction:
Spurling’s Test - reproduction of patients referred Pain suggests Radiculopathy or compression of Zygapophyseal Joints
Cervical Distraction Test - alleviation of patients referred Pain suggests Radiculopathy or compression of Zygapophyseal Joints
Cervical Quadrant - approximates Zygapophyseal Joints
Mobilisations - particular Joint Play techniques may be used to evaluate the relative positon and movement available to the individual vertebral segments. In a similar fashion, the effectiveness of a Mobilisation with Movement technique applied to a particular joint/ motion may serve as a diagnostic finding
For treating symptoms of Pain or restriction in any of the soft-tissues innervated by C4, see the treatment section of their respective pages. The following techniques may be used to improve the Mobility and relative position of C4 with the hopes of reducing radicular symptoms.
Stretching techniques used to improve the relative position of C4 generally aim to restore length in the superficial Cervical - Flexion Muscles to reduce the extent of Forward Head Posture (SOURCE-5). Additionally, restoring length to related fascial continuities has the capacity to improve C4 posture and movement.
Door Frame Neck Stretch - self-guided neck stretch with several variations
Seated Thoracic Rotation with Breathing - large lateral flexion and rotation range coupled with breathing
Swimmers Oblique Extensions - exercise that may be used to lengthen entire Lateral Line through large body-wide lateral-flexion range
Bent Over Lat Stretch - accessible active stretch with large GH Joint - Flexion or Horizontal GH Joint - Adduction range
Jefferson Curl - maximal stretch for posterior chain with emphasis on intersegmental movment of the Vertebral Column and capacity to add load
The Fascia l continuities described below may influence the resting tone of soft-tissues that attach to C4 to remotely impact its resting postion and ability to articulate. In some instances the release of a single structure contained within a fascial continuity forms an effective treatment, while in others the entire Fascial Lines may require attention.
Deep Back Arm Line - direct attachment through Levator Scapulae
Deep Front Line - multiple direct attachments
Lateral Line - direct attachement through Splenius Capitis / Sternocleidomastoid
Spiral Line - direct attachement through Splenius Cervicis
Superficial Back Line - through Erector Spinae
Superficial Front Line - shortened Sternocleidomastoid perpetuates Forward Head Posture
The following Strength techniques emphasise quality movement of the Cervical segmentsInitial Phase:
Quadruped
Mid-Phase:
Late Phase:
Glute Bridge - Neck Bridge variant
The following Mobilisation techniques may be indicated to correct malalignment of the C4 vertebrae or treat C4 Nerve Root pathology:
Joint Play - passive accessory movements performed without active movement Passive Accessory Intervertebral Movements
Cervical - PAVIMs - mid-cervical techniques
Passive Physiological Intervertebral Movements - assess C4 through more global, cervical-wide movements. May provide insight into which physiological movements are most affected.
Mobilisation with Movement - mobilisations applied with active movement
The following tissues have Dry Needling procedures detailed on their respective pages:
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