The Splenius Capitis is a significant postural muscle located in the back of the neck, forming part of the deeper layer of muscles that support the neck and head.
Location
The Splenius Capitis is situated at the upper back and neck region. It lies beneath the trapezius muscle and is part of the superficial layer of the intrinsic muscles of the back, which are involved in the movements of the vertebral column and head.
Structure
The muscle is broad and band-like, characterized by its oblique orientation on the back of the neck. It is one of the larger muscles in the neck area, contributing to the bulk and shape of the neck. The muscle fibers run upward and laterally, from the vertebrae in the neck and upper thorax to the skull.
Origin
The Splenius Capitis originates from the lower half of the nuchal ligament (a ligament that extends from the base of the skull to the vertebrae in the neck) and the spinous processes of the upper three or four thoracic vertebrae (T1 to T4 or T5).
Insertion
The muscle inserts onto the mastoid process of the temporal bone (a part of the skull behind the ear) and the lateral portion of the superior nuchal line (a ridge on the occipital bone at the back of the skull).
Nerve Supply
The Splenius Capitis is innervated by the dorsal rami (posterior branches) of the lower cervical nerves (usually C3 and C4). These nerves supply the muscle with the necessary signals to facilitate its actions.
Action
The actions of the Splenius Capitis include:
- Extension of the Neck: When both sides of the muscle work together (bilaterally), they extend the head and neck backward. This is a critical action for looking upwards or returning the head to an upright position from a bowed stance.
- Lateral Flexion of the Neck: When one side of the muscle acts independently (unilaterally), it bends the neck to the same side, aiding in movements such as tilting the head to the shoulder.
- Rotation of the Head: The unilateral action of the Splenius Capitis also contributes to the rotation of the head to the same side. This movement is essential for looking over one’s shoulder.
Function
The Splenius Capitis plays several critical roles in head and neck movement and stability.
- Extension of the Head and Neck: One of the primary functions of the Splenius Capitis is to assist in extending the head and neck. When the muscles on both sides of the neck contract simultaneously (bilaterally), they pull the head backward, helping to maintain an upright posture or to look upwards. This action is crucial for counterbalancing the forward bending (flexion) of the neck and head, which occurs during activities such as reading or typing, thereby helping to prevent neck strain and maintaining a balanced posture.
- Lateral Flexion of the Neck: The Splenius Capitis also facilitates lateral flexion, or side-bending, of the neck. This action occurs when the muscle contracts unilaterally (on one side). For example, when the left Splenius Capitis contracts, it will draw the head and neck to the left side. This movement is essential for various daily activities, such as driving, where looking over the shoulder or checking blind spots requires lateral flexion of the neck.
- Rotation of the Head: Another significant function of the Splenius Capitis is contributing to the rotation of the head. This occurs when the muscle contracts on one side, rotating the head towards the same side. For instance, when the right Splenius Capitis contracts, it helps turn the head to the right. This action is vital for many everyday movements, such as looking to the sides while walking, driving, or engaging in conversation.
- Postural Support and Stability: Beyond movement, the Splenius Capitis provides essential postural support for the head and neck. By maintaining a state of mild contraction, it helps keep the head aligned over the spine, which is crucial for a balanced and ergonomic posture. This support is especially important when standing or sitting for extended periods, helping to prevent neck pain and fatigue.
- Protective Role: The muscle also plays a protective role for the cervical spine. By controlling the speed and range of neck movements, it helps prevent sudden, uncontrolled motions that could result in injury. This is particularly important during high-impact activities or if one experiences a jolt or sudden movement, as the muscle’s contraction can help stabilize the head and neck.
- Contribution to the Venous and Arterial Circulation: Although not a primary function, the muscle’s movements can influence the venous and arterial circulation within the neck, assisting in blood flow to and from the brain. This indirect role can affect overall comfort and health, especially during prolonged periods of stationary posture.
Clinical Significance
Neck Pain and Stiffness: The Splenius Capitis is often involved in cases of neck pain and stiffness, conditions commonly seen in clinical practice. Tension or strain in this muscle can result from poor posture, especially in individuals who sit for prolonged periods or habitually maintain an improper neck position (such as looking down at a smartphone). Muscle tension can lead to discomfort, reduced mobility, and headaches.
Whiplash Injuries: This muscle can be particularly affected by whiplash injuries, which occur when the head is suddenly jerked forward and backward, such as in a car accident. Such rapid movements can stretch or tear the muscle fibers, leading to pain, swelling, and decreased neck movement. Rehabilitation for whiplash often involves treatments targeting the Splenius Capitis, among other muscles.
Myofascial Pain Syndrome: The Splenius Capitis can develop trigger points – tight, tender areas within the muscle – contributing to myofascial pain syndrome. These trigger points can cause referred pain, meaning pain felt in other areas of the body, such as the head, shoulders, or upper back. Identifying and treating these points are essential aspects of managing chronic neck pain.
Cervicogenic Headaches: Since the Splenius Capitis has attachments near the base of the skull, tension in this muscle can contribute to cervicogenic headaches – headaches originating from cervical spine issues. These headaches are typically felt at the back of the head, and treatment may involve addressing dysfunction in the Splenius Capitis and other neck muscles.
Rehabilitation and Physical Therapy: Understanding the anatomy and function of the Splenius Capitis is crucial for physical therapists and other healthcare professionals when designing rehabilitation programs for the neck. Therapeutic exercises, stretching, and manual therapy techniques focusing on this muscle can help restore neck mobility, alleviate pain, and improve quality of life for patients with various neck-related issues.
Diagnostic Consideration: In the clinical assessment of neck pain and dysfunction, the Splenius Capitis should be considered, especially if symptoms include restricted neck movement or pain exacerbated by specific head positions. Accurate diagnosis can guide effective treatment strategies, including manual therapy, heat therapy, and targeted exercises.
