Where Is C4 C5 Located and What Nerves Does It Affect?

C4 and C5 refer to the fourth and fifth cervical vertebrae, located in the middle portion of your neck. They sit roughly at the level of your Adam’s apple, stacked between the base of the skull and the top of the upper back. The nerves that exit between and around these vertebrae affect everything from shoulder movement to the ability to breathe, which is why injuries or disc problems at this level can produce symptoms that seem surprisingly far from the neck itself.

Exactly Where C4 and C5 Sit

Your cervical spine has seven vertebrae, numbered C1 through C7 from top to bottom. C1 and C2 are specialized bones that let you nod and rotate your head. By the time you reach C4 and C5, the vertebrae look more like the rest of the spine: cylindrical bodies cushioned by a disc between them, with bony arches that form a protective canal for the spinal cord. If you run your fingers down the back of your neck, C4 and C5 are roughly in the middle, sitting behind the throat at about the height of the thyroid cartilage.

Between each pair of vertebrae, small openings called foramina allow nerve roots to exit the spinal canal and branch out into the body. The C4-C5 disc sits between those two vertebrae, and the C5 nerve root exits through the foramen just above that disc. This is a clinically busy intersection: the foramen at C4-C5 tends to be smaller than the one at C6-C7 lower in the neck, and age-related joint changes narrow it further. Research on cadaveric specimens found that arthritic changes at C4-C5 significantly shrank the foramen, while the same degree of arthritis at lower levels did not have the same effect. That anatomical bottleneck helps explain why the C5 nerve root is particularly vulnerable to compression.

What the C4 and C5 Nerve Roots Control

Each cervical nerve root carries motor fibers (telling muscles to contract) and sensory fibers (relaying touch, pain, and temperature back to the brain). C4 and C5 contribute to overlapping but distinct territories.

Shoulder muscles: The C5 root is a major driver of the deltoid muscle, which lifts your arm out to the side and forward. It also feeds the biceps, which bends the elbow. Electrical studies show that C5 predominantly powers both the deltoid and biceps, though C6 contributes as well, and the balance between the two varies from person to person.
Rotator cuff: The supraspinatus and infraspinatus muscles, which stabilize the shoulder joint and help rotate the arm, receive innervation through the suprascapular nerve. That nerve draws fibers from C5 and C6.
Diaphragm: The phrenic nerve, which controls the diaphragm and therefore your ability to breathe, classically originates from C3, C4, and C5. An anatomical study of phrenic nerve origins found considerable variation: in some specimens the nerve arose mainly from C3, in others from C4-C5, and in a small percentage from as high as C1-C3.
Skin sensation: The C4 dermatome covers the upper shoulder and the area around the base of the neck. The C5 dermatome runs along the outer shoulder and the lateral upper arm down toward the elbow.

The phrenic nerve connection is worth pausing on. The phrase “C3, 4, 5 keeps the diaphragm alive” is drilled into every medical student for good reason. A spinal cord injury at C4 or above can knock out the phrenic nerve’s input entirely, making it impossible to breathe without a ventilator. Injuries at C5 generally spare enough phrenic nerve function for independent breathing, but the margin is thin. The variability in phrenic nerve origins from person to person makes this boundary even less predictable than textbooks suggest.¹

Why C4-C5 Problems Feel Like Shoulder Problems

One of the most confusing things about C4-C5 nerve issues is that they often masquerade as shoulder injuries. You might feel a deep ache in the shoulder, weakness when trying to lift your arm, or pain that shoots down toward the elbow. A comprehensive review noted that all muscles around the shoulder are innervated by nerves originating from the cervical spine, with the deltoid and rotator cuff specifically receiving fibers from C5 and C6.² Because a pinched C5 nerve root and a torn rotator cuff can both cause shoulder pain and weakness, the overlap trips up patients and clinicians alike.

Research looking at patients with confirmed C5 or C6 nerve compression found that a substantial proportion also had rotator cuff tears visible on MRI, making it harder to determine which problem was actually causing the symptoms.³ The two conditions can and do coexist in the same person. If you have been treated for a “shoulder problem” that does not improve, the culprit may be further up the chain in your neck.

How Doctors Tell the Difference

Sorting out neck-origin pain from shoulder-origin pain relies on a combination of physical examination maneuvers and imaging. A few tests are especially useful.

The Spurling test involves turning your head toward the painful side and pressing gently down on the top of your skull. If this reproduces the radiating arm pain, it strongly suggests a cervical nerve root is being pinched. The test is highly specific, meaning a positive result is a reliable indicator of radiculopathy, but it is not very sensitive, so a negative result does not rule it out.⁴ A meta-analysis of physical examination tests for cervical radiculopathy confirmed that Spurling’s test consistently shows high specificity (ranging from about 0.84 to 1.00 across studies) with more variable sensitivity.⁵

A simpler test that has gained attention is the arm squeeze test: the examiner firmly squeezes the middle third of your upper arm. If this reproduces your pain, it points toward a nerve root problem rather than a local shoulder issue. In one study, about 97% of patients with a positive arm squeeze test turned out to have radiculopathy on imaging, while fewer than 4% of patients with rotator cuff tears tested positive.⁶ It is a quick bedside check that can save you from unnecessary shoulder surgery.

Upper limb neurodynamic tests, which involve stretching the arm in specific positions to tension the nerves, tend to be very sensitive but less specific. They catch most cases of nerve irritation but can also flag problems that turn out to be something else.⁵ In practice, doctors combine several tests and then confirm with imaging, usually MRI, to see exactly which nerve root is being compressed and why.

Common Causes of C4-C5 Nerve Compression

The most frequent culprit is a herniated disc. The disc between C4 and C5 can bulge or rupture, pushing material into the foramen and squeezing the C5 nerve root. This often happens in middle age when the disc begins to lose water content and becomes more prone to tearing under stress.

Degenerative changes are the other major cause. Over decades, the joints alongside the vertebrae (called facet joints and uncovertebral joints) develop bony overgrowths that encroach on the foramen. As noted earlier, the foramen at C4-C5 is already smaller than at lower cervical levels, and arthritis shrinks it further. In elderly individuals, higher grades of arthritic change at C4-C5 were strongly associated with narrower foramina, creating a setup where even mild additional swelling or a small disc bulge can pinch the nerve.⁷

Less common causes include spinal stenosis (narrowing of the central canal rather than the foramen), tumors, infections, and trauma. In any of these scenarios, the resulting symptoms trace back to which nerve root is being affected and how severely.

Treatment Without Surgery

The good news is that most cases of cervical radiculopathy from a C4-C5 disc problem improve without an operation. The nerve root inflammation settles over weeks to months, and the body can partially reabsorb herniated disc material.

A multimodal conservative approach, combining manual therapy, specific exercises, and guided movement, has shown strong results. A case series of older adults with degenerative cervical radiculopathy found that a combined program of hands-on treatment and exercise brought pain scores down from a mean of roughly 6 out of 10 to less than 1 out of 10 at discharge, with patients maintaining those gains at six months.⁸ This is encouraging because it suggests that even in people whose spines have significant wear and tear, the nerve irritation can calm down with the right rehabilitation.

Not all conservative approaches perform equally. A study comparing different types of treatment found that cervical mobilization techniques produced the greatest ongoing pain reduction over the follow-up period, while traction therapy actually worsened symptoms in a few patients and showed a slight regression in pain scores over time.⁹ This is worth knowing if you have been prescribed cervical traction and are not improving: the evidence for traction in cervical radiculopathy is mixed, and switching to manual therapy or exercise-based rehabilitation may work better.

When Surgery Becomes the Conversation

Surgery enters the picture when conservative treatment fails after several months, when there is progressive weakness (especially in the deltoid or biceps), or when the spinal cord itself is being compressed and not just a single nerve root. The most common procedures at C4-C5 are anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (artificial disc replacement).

ACDF involves removing the damaged disc through a small incision at the front of the neck, taking the pressure off the nerve root, and fusing the two vertebrae together with a spacer. It has a long track record and high success rates for pain relief, but fusing a segment does shift extra stress to the discs above and below it over time. Cervical disc arthroplasty replaces the disc with an artificial one that preserves motion at the treated level. C4-C5 and C5-C6 are the most commonly treated levels, accounting for about 85% of disc replacement cases in large series. Disc replacement has been shown to preserve movement at the operated segment and reduce the rate of surgery needed at adjacent levels compared to fusion.¹⁰

One complication that surgeons watch for specifically at this level is C5 palsy: sudden weakness of the deltoid muscle after cervical spine surgery. It occurs because the C5 nerve root has a short course and limited slack, so when the spinal cord shifts backward after decompression, the C5 root can get stretched. Patients who already have a narrow C4-C5 foramen before surgery are at higher risk.⁷ The palsy is usually temporary, resolving over weeks to months, but it can be alarming when it happens.

How Neck Posture Affects Disc Pressure at C4-C5

Your daily habits influence how much stress falls on the C4-C5 disc. A cadaveric study measuring intradiscal pressure at different cervical levels found that bringing the chin all the way down to the chest generated significantly more pressure at C4-C5, C5-C6, and C6-C7 than either traction or a retraction-extension position.¹¹ In practical terms, sustained forward head posture, the kind you adopt when staring down at a phone or hunching over a laptop, loads the mid-cervical discs more heavily than a neutral or slightly extended position.

This does not mean that every person who looks at a phone will herniate a disc, but it does mean that for someone already dealing with a degenerative or bulging disc at C4-C5, posture modifications can be a meaningful part of management. Keeping screens at eye level, taking breaks from sustained flexion, and gently retracting the chin (the “chin tuck” exercise) all reduce the sustained loading on these discs.

Anatomical Variations That Change the Picture

Textbook diagrams make the brachial plexus look standardized, but real human anatomy varies more than most people expect. A prefixed brachial plexus, where C4 contributes fibers to the nerve network that normally begins at C5, has been documented in cadaveric studies. In one case report, the plexus received a contribution from C4 alongside unusual branching of the dorsal scapular and long thoracic nerves.¹² When C4 feeds into the brachial plexus, it means that pathology at the C3-C4 level can produce symptoms typically associated with C5 problems, potentially confusing the diagnosis.

The balance of innervation between C5 and C6 also varies. Electrophysiological testing has shown that in some people, C5 overwhelmingly drives the deltoid, while in others, C6 carries a larger share of the load.¹³ This individual variation means that two people with the same disc herniation at C4-C5 can experience different degrees of shoulder weakness, depending on how much their deltoid relies on C5 versus C6.

C4-C5 Injuries in Children

Cervical spine injuries in children are relatively rare but disproportionately dangerous at certain levels. Younger children tend to injure the upper cervical spine (C1-C2) because their heads are proportionally larger and the ligaments are more lax. Older children and adolescents are more likely to injure the lower cervical spine, including C4 and C5, in a pattern closer to adult injuries. A review of pediatric cervical spine injuries at a level-one trauma center found that complete spinal cord lesions involving C4 through C7 were strongly associated with motor vehicle crashes, and the outcomes were devastating: four out of five children with complete lower cervical cord injuries died.¹⁴

The stakes at C4-C5 in trauma are high precisely because of the phrenic nerve. A cord injury at this level can compromise breathing, and in a child whose body has fewer compensatory reserves, the consequences escalate quickly. This is why emergency responders are trained to immobilize the cervical spine in any child with a significant mechanism of injury, even when the child appears alert and conversational. The absence of obvious bone fracture does not rule out cord damage, particularly in young children whose cartilaginous vertebrae can allow the cord to be injured without a visible break on X-ray, a phenomenon sometimes called SCIWORA (spinal cord injury without radiographic abnormality).

Living With a C4-C5 Disc Problem

If you have been told you have a disc bulge or herniation at C4-C5, the diagnosis can sound scarier than it needs to be. Disc bulges at this level are common incidental findings on MRI in people who have no symptoms at all. The presence of a structural abnormality on a scan does not automatically mean it is the source of your pain. Correlation with your symptoms, physical exam findings, and sometimes nerve conduction studies is what determines whether that disc finding matters clinically.

For the majority of people who do have symptomatic C4-C5 radiculopathy, the trajectory is favorable. Most improve within a few months with activity modification, physical therapy emphasizing cervical mobilization and strengthening, and short-term anti-inflammatory medication if needed. Knowing which nerve root is involved helps guide rehabilitation: if C5 is the issue, targeted exercises for the deltoid and biceps make sense. If numbness is the dominant symptom, the focus shifts to nerve gliding techniques and postural correction. Surgery remains a reliable backup when conservative care does not work, but the need for it is the exception rather than the rule.

1
East African Orthopaedic Journal. Phrenic nerve roots and terminal branches variations: an anatomical study
2
JSES Reviews, Reports, and Techniques. Untwining the intertwined: a comprehensive review on differentiating pathologies of the shoulder and spine
3
PubMed Central. Investigation of C5-C6 radiculopathy and shoulder rotator cuff lesions coexistence frequency
4
PubMed. The Spurling test and cervical radiculopathy
5
PubMed Central. Diagnostic accuracy of physical examination tests for painful cervical radiculopathy: update of a systematic review and meta-analysis
6
The American Journal of Medicine. An Evidence-Based Approach to Differentiating the Cause of Shoulder and Cervical Spine Pain
7
PubMed. Relationship Between Foraminal Area and Degenerative Changes in the Lower Cervical Spine With Implications for C5 Nerve Root Palsy
8
PubMed. Treatment of patients with degenerative cervical radiculopathy using a multimodal conservative approach in a geriatric population: a case series
9
PubMed. Biological, Mechanical or Physical? Conservative Treatment of Cervical Radiculopathy
10
IP Journal of Surgery and Allied Sciences. Paper on role of cervical disc replacement surgery in cervical pivd patients in both elderly and young population and it’s comparison with anterior cervical dissectomy and fusion
11
BMC Musculoskeletal Disorders. Cervical intradiscal pressure responses to end-range supine postures: a cadaveric investigation
12
PubMed Central. Aberrant Dual Origin of the Dorsal Scapular Nerve and Its Communication with Long Thoracic Nerve: An Unusual Variation of the Brachial Plexus
13
PubMed. Nerve root distribution of deltoid and biceps brachii muscle in cervical spondylotic myelopathy: a potential risk factor for postoperative shoulder muscle weakness after posterior decompression
14
PubMed. Cervical spine injuries in children: a review of 103 patients treated consecutively at a level 1 pediatric trauma center