Where is C4 and C5 on Your Spine? Your Cervical Anatomy

C4 and C5 are two vertebrae sitting right in the middle of your cervical spine, the seven-bone column that forms your neck. They land roughly at throat level, with C4 aligning near the upper edge of the thyroid cartilage (the bump you can feel at the front of your neck) and C5 just below it. These two bones and the disc between them form one of the most mobile and clinically significant segments in your entire spine, playing a central role in everything from turning your head to keeping your diaphragm working.

Counting Down from the Skull

Your cervical spine starts at the base of your skull with C1 (the atlas) and C2 (the axis), which are specialized vertebrae responsible for most of your head’s nodding and rotation. Below them, C3 through C7 are called the “typical” cervical vertebrae because they share a more uniform shape. C4 is the fourth bone down, and C5 is directly beneath it. Together they sit in the middle third of your neck, roughly behind the Adam’s apple region in men or the corresponding area of the throat in women.

The cervical spine ends at C7, which is the bony knob most people can feel at the base of the neck when they tilt their head forward. From C7, count four vertebrae upward and you arrive at C4, with C5 one step below. In practice, though, counting by touch is unreliable. Doctors and surgeons more often use external throat landmarks or imaging to pin down the exact level.

Finding C4 and C5 by Touch

Clinicians have long used structures in the front of the throat as rough signposts for cervical levels. The thyroid cartilage, the hyoid bone, and the cricoid cartilage each supposedly line up with a specific vertebra. But research shows these landmarks are far less precise than anatomy textbooks suggest.

One imaging study found that the thyroid cartilage correctly identified the expected cervical level only about 42% of the time, and the cricoid cartilage was accurate roughly 43% of the time.¹ Traditional teaching places the thyroid cartilage at the C4-C5 disc space and the cricoid cartilage at the C6 body.² But actual alignment varies considerably depending on sex, age, and height. A separate study found that the thyroid cartilage could correspond to anything from the C3-C4 disc all the way down to C7, with an average landing point around C5.³

The practical takeaway: if you place your finger on the front of your throat at the level of the thyroid cartilage, you are in the neighborhood of C4 and C5, but you could easily be off by a full vertebral level in either direction. Surgeons do not rely on surface landmarks alone for procedures at this level. They use intraoperative imaging to confirm exactly which vertebra they are working on.

What C4 and C5 Look Like

Each typical cervical vertebra has a small, wide body at the front and a bony arch at the back that forms a protective ring around the spinal cord. Sticking out from each side are the transverse processes, and each of these contains a hole called the transverse foramen. The vertebral arteries thread through these openings on their way to the brain. A study of dried cervical vertebrae from C3 through C6 found the average diameter of the transverse foramen was about 5.5 mm, and roughly a quarter of the specimens had an extra or duplicated foramen on one side.⁴ That kind of anatomical variation matters during surgery because an unexpected extra opening could mean the artery takes a slightly different path than expected.

Between C4 and C5 sits an intervertebral disc, a flexible pad of cartilage that acts as both a shock absorber and a spacer. Behind the disc, two small facet joints connect the vertebrae on each side. The disc handles compressive loads while the facet joints guide and limit motion. Together, the disc and the paired facets form what spine specialists call a “motion segment,” and the C4-C5 segment is one of the busiest in the neck.

How Much C4-C5 Moves

Your neck’s total range of motion is the sum of small contributions from each cervical segment. C4-C5 and C5-C6 contribute more to forward-and-backward bending than any other levels. Research on flexion-extension motion found that C4-C5 handles the greatest share of movement when your total neck range is moderate (under about 50 degrees), while C5-C6 takes over during larger movements.⁵ In other words, everyday small motions like checking your phone or glancing at a monitor lean heavily on C4-C5.

Biomechanical studies of the C4-C5 segment show that how the load distributes among the disc, the ligaments, and the facet joints depends on the direction of movement. The structure bearing the most force tends to match the structure most often injured in that type of motion.⁶ During side-bending in particular, the C4-C5 facet joints carry a disproportionately large share of the translation compared to the disc.⁷ All of this high-demand movement helps explain why C4-C5 is so prone to wear and injury over a lifetime.

Why C4 and C5 Matter for Breathing

Perhaps the most critical function linked to this part of the spine is breathing. The phrenic nerve, which controls the diaphragm, originates primarily from spinal cord levels C3, C4, and C5. An old clinical mnemonic captures it: “C3, 4, 5 keeps the diaphragm alive.” Within that range, the C4 segment appears to be the most influential. Animal research on high cervical spinal cord injury found that the C4 segment was the most responsive to electrical stimulation and required the lowest current to activate the phrenic nerve and produce a breathing response.⁸

Damage to C4 and C5 together can be devastating for diaphragm function. In a mouse model of mid-cervical spinal cord contusion targeting both levels, researchers documented loss of phrenic motor neurons, degeneration of the phrenic nerve itself, and persistent weakness in the diaphragm on the injured side that lasted throughout the six-week study period.⁹ In humans, injuries at or above C4 often require mechanical ventilation because the diaphragm loses its nerve supply. Injuries at C5 and below typically spare enough phrenic function for independent breathing, though capacity may be reduced.

Muscles and Sensation Controlled by C4 and C5 Nerves

Each cervical nerve root exits the spine above the vertebra of the same number (C4 exits above C4, C5 exits above C5). These nerve roots carry signals to specific muscles and receive sensation from specific skin areas.

The C5 nerve root is classically linked to the deltoid muscle at the shoulder and the biceps in the upper arm. However, the picture is more complicated than textbooks often show. One study that electrically stimulated individual nerve roots found that both C5 and C6 contribute to the deltoid and biceps, with the balance varying from person to person. In patients with spinal cord compression at C4-C5, the C5 root tended to dominate deltoid innervation.¹⁰ But a cadaver study found the opposite pattern in healthy specimens: C6 nerve fibers more often contributed the largest share of fibers to the deltoid.¹¹ The apparent contradiction likely reflects both natural variation and the fact that disease can shift which root becomes dominant when one is compromised.

The C4 nerve root primarily supplies the upper trapezius and parts of the diaphragm. It also carries sensation from the skin over the top of the shoulders and the lower neck. The C5 dermatome, the skin patch served by C5, covers the outer surface of the upper arm near the deltoid. If you experience numbness in a band across the top of your shoulder or down the outer arm, it could point to involvement at one of these levels.

Why Disc Problems Love This Neighborhood

C4-C5 and C5-C6 are two of the most common sites for cervical disc herniation and degeneration. The reason is mechanical: these segments handle the most movement, bear the weight of the head, and sit at the transition point where the relatively mobile upper neck meets the stiffer lower segments. In a study of over 1,000 symptomatic patients, C5-C6 was the most commonly degenerated single level, followed by C4-C5.¹² A similar pattern appeared in a study of 1,300 symptomatic patients, where C5-C6 consistently showed the highest rates of degeneration across multiple age groups.¹³

In a Hispanic population in Puerto Rico, C5-C6 accounted for about 35% of surgically treated cervical herniations and C4-C5 for about 28%.¹⁴ The pattern is consistent across studies and populations: C5-C6 leads, C4-C5 follows, and together these two levels account for the majority of cervical disc disease requiring medical attention.

Age plays a role too. Hospital-based imaging data show that the rate of disc bulging or herniation at C4-C5 and C5-C6 tends to increase with age up to about 50 years, then actually decreases after 60.¹⁵ That counterintuitive finding may reflect the fact that the discs lose water content and become stiffer with advanced age, making them less prone to the kind of bulging that shows up on MRI, even as overall spinal degeneration continues.

What C4-C5 Problems Feel Like

When a disc herniates or bone spurs develop at C4-C5, the C5 nerve root is the one most often compressed as it exits the spinal canal. The hallmark symptom is shoulder weakness, specifically difficulty raising the arm out to the side. A clinical analysis of patients with cervical radiculopathy causing deltoid paralysis confirmed this pattern: the problem typically traces to disc herniation or spondylotic narrowing at C4-C5, pinching the C5 root.¹⁶

Other common symptoms from C5 nerve root compression include pain that radiates from the neck into the shoulder and upper arm, numbness or tingling along the outer arm, and weakness when trying to bend the elbow. In more severe cases where the disc bulge compresses the spinal cord itself rather than just the nerve root, the consequences can include coordination problems in the hands, difficulty walking, and changes in bladder function. A case report described a large spondylotic disc bulge at C4-C5 that caused spinal cord compression severe enough to produce myelomalacia, actual damage to the spinal cord tissue.¹⁷

Not all C5 radiculopathy causes pain. Some patients present with isolated shoulder weakness and no significant pain, a pattern sometimes called painless motor radiculopathy. These cases can be tricky to diagnose because the absence of pain makes people less likely to think “neck problem” when their shoulder feels weak.

How Doctors See C4 and C5

MRI is the go-to imaging tool for evaluating problems at C4-C5. It gives the clearest picture of soft tissue: the discs, the spinal cord, the nerve roots, and any swelling or damage. A comparison study between CT and MRI for cervical disc herniations found that both methods agreed well on the location and severity of herniations, but CT tended to underestimate how far a disc was bulging compared to MRI.¹⁸ CT scans remain useful for evaluating bone detail, such as the size of bone spurs or the width of the spinal canal, but MRI is generally preferred when the concern is a disc pressing on a nerve or the cord.

In rare cases, a disc fragment can migrate through the tough outer membrane (the dura) and end up inside the spinal canal. A systematic review of these intradural herniations found that MRI is the most commonly used diagnostic tool, and specific signs on the images, such as a “halo” around the fragment, help radiologists identify the problem.¹⁹ These cases are uncommon but worth knowing about because they can mimic tumors on imaging and are easily missed if the radiologist is not looking for them.

Treatment Options at C4-C5

Most C4-C5 disc problems improve without surgery. Conservative treatment typically includes physical therapy to strengthen the neck muscles, anti-inflammatory medications, and activity modifications. For more acute or stubborn symptoms, cervical epidural steroid injections can help. In one reported case of painless motor radiculopathy at C4-C5, a single cervical epidural steroid injection led to progressive improvement starting the next day, with full recovery of shoulder strength within two weeks.²⁰

When conservative measures fail or when there is significant spinal cord compression, surgery becomes an option. The two main surgical approaches at C4-C5 are anterior cervical discectomy and fusion (ACDF), where the disc is removed and the two vertebrae are fused together, and total disc replacement, where an artificial disc preserves motion at the segment. A five-year randomized trial comparing the two approaches found that patients who received a disc replacement had a significantly lower chance of needing a second surgery at the treated or neighboring levels compared to those who had fusion. The reoperation-free rate was about 97% for disc replacement versus roughly 86% for fusion over five years.²¹ The most common reason for reoperation after fusion was incomplete bone healing at the fusion site, while for both groups, surgery at an adjacent level was typically driven by recurring neck or arm pain.

Posture, Screen Time, and the C4-C5 Segment

The rise of smartphones and desk-bound work has drawn increasing attention to what happens at the mid-cervical spine during prolonged forward head posture. When you tilt your head down to look at a phone, the load on your cervical joints increases substantially. Research on cervical spine loading during neck flexion confirmed that bending the neck forward increases joint forces in a way that supports the “text neck” hypothesis, reinforcing the case for proper workstation and monitor setup.²²

Because C4-C5 handles a large proportion of small-range flexion movements, as described earlier, the segment bears a disproportionate share of the stress from habitual forward head posture. This does not mean looking at your phone will herniate a disc, but it does mean that hours of daily neck flexion accelerate the wear on the discs and facet joints at C4-C5 and C5-C6. Adjusting your screen to eye level, taking breaks, and strengthening the deep neck flexor muscles are simple steps that reduce cumulative loading on these segments. None of this is a guarantee against disc disease, but given that C4-C5 is already the second most vulnerable level in the cervical spine, it makes sense to avoid piling on extra mechanical stress.

How Age Changes the C4-C5 Region

Cervical disc degeneration is not just a disease of old age. The discs at C4-C5 and C5-C6 start losing water content and developing small tears as early as the third decade of life. Imaging data show that the rate of disc bulging and herniation at these levels climbs steadily through middle age, peaking around 50.¹⁵ After 60, the discs have often dehydrated and stiffened to the point where they are less likely to bulge outward, even though the overall degeneration of the spine continues through bone spur formation and facet joint arthritis.

This means the nature of C4-C5 problems shifts with age. In younger adults, a soft disc herniation pressing on the C5 nerve root is the more common scenario. In older adults, the problem is more often bony narrowing of the spinal canal or the nerve exit holes (foraminal stenosis), caused by bone spurs and thickened ligaments rather than a discrete disc bulge. Both can produce similar symptoms, but the treatment approach and surgical considerations differ. A younger patient with a single-level soft herniation is often a good candidate for disc replacement, while an older patient with multilevel bony stenosis may need a different strategy entirely.