The muscles of the neck play an important role in human physiology. The neck has several muscles that help support the head and others that facilitate speaking and swallowing. Some of these muscles are innervated by cranial nerves, whereas others receive their nerve supply from spinal nerves. Weakness and atrophy of neck muscles threaten survival; an inability to support the head can cause life-threatening injuries to the spinal cord.
Details: Head Support Muscles
The following muscles in the neck support the head:
- Sternocleidomastoid (SCM): This prominent muscle on either side of the neck helps with head rotation and flexion. When one side contracts, it turns the head to the opposite side; when both sides contract together, they flex the neck forward.
- Nerve: Accessory nerve (Cranial Nerve XI) and branches of the cervical plexus (C2-C3).
- Trapezius: This large muscle extends from the base of the skull down the spine and across the shoulder blades. It helps stabilize and move the shoulder blades and supports the head by assisting in extending and rotating the neck.
- Nerve: Accessory nerve (Cranial Nerve XI) and branches from the cervical plexus (C3-C4).
- Splenius Capitis: This muscle extends from the upper thoracic vertebrae to the base of the skull at the rear. It helps in extending and rotating the head.
- Nerve: Dorsal rami of the cervical spinal nerves (C3-C4).
- Splenius Cervicis: This muscle extends from the upper thoracic vertebrae to the cervical vertebrae. It aids in the extension and rotation of the neck.
- Nerve: Dorsal rami of the cervical spinal nerves (C5-C6).
- Semispinalis Capitis: This muscle runs from the upper thoracic and lower cervical vertebrae to the base of the skull. It assists in extending and rotating the head.
- Nerve: Dorsal rami of the cervical spinal nerves (C1-C6).
- Longus Colli: This deep muscle runs from the cervical and upper thoracic vertebrae to the cervical vertebrae and assists in flexing and rotating the neck.
- Nerve: Anterior rami of the cervical spinal nerves (C2-C6).
- Longus Capitis: This muscle extends from the cervical vertebrae to the base of the skull, and helps with flexing and rotating the head.
- Nerve: Anterior rami of the cervical spinal nerves (C1-C3).
- Rectus Capitis Posterior Major and Minor: These small muscles are located at the back of the neck and help with extension and rotation of the head.
- Nerve: Suboccipital nerve (dorsal ramus of C1).
- Obliquus Capitis Superior and Inferior: These muscles are part of the suboccipital region and help with extension and rotation of the head.
- Nerve: Suboccipital nerve (dorsal ramus of C1).
Neck muscles involved in supporting the head will weaken in the same manner as any other muscle affected by ALS; once the disease has set in to a given nerve, the muscles innervated by that nerve will begin to weaken.
The pattern of neck weakness progression as it pertains to supporting the head varies from person to person, however, "drop head", where the head tends to drop forward is the most common early sign of neck weakness.
¶ Head and Neck Support
Bracing becomes necessary to ensure safety and comfort when neck muscles can no longer adequately support the head. Proper head and neck support is crucial to prevent injury, especially during transfers.
Head support is also important while riding in a vehicle. Large bumps, heavy acceleration, braking, or abrupt direction changes can put significant stress on the head and neck. In extreme cases, the head may hit parts of the interior.