A disc herniation occurs when the soft, gel-like center of an intervertebral disc pushes through a tear in the outer layer. This frequently occurs in the cervical spine (the seven neck vertebrae) which supports the head and facilitates motion. When the disc material is displaced, it can press on nearby spinal nerves or the spinal cord. A herniation between the fourth and fifth cervical vertebrae (C4-C5) causes symptoms related to the specific nerve root affected at that location.
The Role of the C4 and C5 Vertebrae
A disc herniation between the C4 and C5 vertebrae typically irritates or compresses the C5 nerve root, which exits beneath the C5 vertebra. The C5 nerve root is a mixed nerve, containing both motor fibers (controlling movement) and sensory fibers (transmitting feeling). This nerve plays a primary role in the function of the shoulder and upper arm, which become the focus of symptoms.
The motor fibers of the C5 root innervate the deltoid muscle (covering the shoulder joint) and contribute to the biceps muscle, which bends the elbow. The sensory fibers supply sensation to the C5 dermatome, covering the lateral side of the shoulder and the upper outer arm. In rare cases, the C4 and C5 nerve roots contribute to the phrenic nerve, meaning a severe disc issue could potentially impact breathing function.
Specific Neurological Symptoms
The most common complaint resulting from C5 nerve root compression is pain, often starting in the neck and radiating into the shoulder blade area. This radiating pain (cervical radiculopathy) travels down the arm, focusing on the outer shoulder and upper arm. The pain is typically described as a deep ache, a sharp sensation, or a burning discomfort, often worsened by specific neck movements.
Motor weakness involves a noticeable reduction in strength in C5-supplied muscles. Patients may have difficulty raising the arm due to impaired deltoid function. Biceps weakness makes it challenging to bend the elbow against resistance. Physicians may observe a diminished or absent biceps tendon reflex, as the C5 nerve root mediates this reflex arc.
Sensory changes include numbness, tingling, or a “pins-and-needles” sensation (paresthesia). These altered sensations are felt in the C5 dermatome, covering the lateral shoulder and upper arm. Coughing or sneezing can momentarily increase pressure inside the spinal canal, often causing a brief, sharp flare-up of the arm pain.
Confirming the Diagnosis
Diagnosis begins with a thorough physical examination to pinpoint the source of nerve irritation. This includes assessing the neck’s range of motion and identifying movements that intensify the pain. The doctor tests the strength of C5-innervated muscles, such as the deltoid and biceps, looking for weakness.
The physician checks the biceps reflex using a reflex hammer, comparing the response to the opposite side to detect C5 nerve root compromise. A sensory examination involves lightly touching the skin over the C5 dermatome to determine if feeling is decreased or altered. If the clinical exam suggests cervical radiculopathy, imaging studies are ordered to confirm the diagnosis.
Standard X-rays are often the first step to rule out issues like fractures or bony spurs, but they cannot show soft disc material. Magnetic Resonance Imaging (MRI) is the most definitive tool, providing detailed pictures of soft tissues and clearly showing the disc herniation and nerve root compression. A Computed Tomography (CT) scan, sometimes with an injected dye (myelogram), is used when MRI is contraindicated, such as due to medical implants.
Initial Conservative Management
Initial management for a C4-C5 disc herniation is typically conservative, as many herniations improve naturally over time. The first step involves rest and activity modification, avoiding positions or activities that aggravate arm or neck pain. This reduces mechanical stress on the injured disc and irritated nerve root.
Pharmacological treatment focuses on controlling pain and reducing inflammation. Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) decrease swelling and alleviate mild pain. Prescription options include muscle relaxers to ease neck spasms, and sometimes neuropathic pain medications to calm the irritated nerve.
Physical therapy is a structured component of care, focusing on exercises to improve posture and strengthen cervical spine support muscles. A therapist uses gentle stretching and specific strengthening routines to stabilize the neck and reduce disc strain. For persistent symptoms, an epidural steroid injection may be recommended to deliver anti-inflammatory medication directly to the compressed nerve root for targeted pain relief.