Atlas of pathophysiology, 2 Edition

Part II - Disorders

Neurologic disorders

Acceleration-deceleration injuries

Acceleration-deceleration cervical injuries (commonly known as whiplash) result from sharp hyperextension and flexion of the neck that damages muscles, ligaments, disks, and nerve tissue. The prognosis for this type of injury is usually excellent; symptoms usually subside with treatment of symptoms.

Causes

·         Motor vehicle and other transportation accidents

·         Falls

·         Sports-related accidents

·         Crimes and assaults

Pathophysiology

The brain is shielded by the cranial vault (hair, skin, bone, meninges, and cerebrospinal fluid), which intercepts the force of a physical blow. Below a certain level of force (the absorption capacity), the cranial vault prevents energy from affecting the brain. The degree of traumatic head injury usually is proportional to the amount of force reaching the cranial tissues. Furthermore, unless ruled out, neck injuries should be presumed present in patients with traumatic head injury.

In acceleration-deceleration cervical injuries, the head is propelled in a forward and downward motion in hyperflexion. A wedge-shaped deformity of the bone may be created if the anterior portions of the vertebrae are crushed. Intervertebral disks may be damaged; they may bulge or rupture, irritating spinal nerves. Then the head is forced backward. A tear in the anterior ligament may pull pieces of bone from cervical vertebrae. Spinous processes of the vertebrae may be fractured. Intervertebral disks may be compressed posteriorly and torn anteriorly. Vertebral arteries may be stretched, pinched, or torn, causing reduced blood flow to the brain. Nerves of the cervical sympathetic chain may also be injured.

A complex arrangement of ligaments holds the vertebrae in place. Some of the ligaments are barely a centimeter long, and all are only a few millimeters thick. In a whiplash injury, ligaments may be badly stretched, partially torn, or completely ruptured (arrows). Injuries of neck muscles may range from minor strains and microhemorrhages to severe tears. The anterior longitudinal ligament, running vertically along the anterior surface of the vertebrae, may be injured during hyperextension. The posterior longitudinal ligament, running on the posterior surface of the vertebral bodies, may be injured in hyperflexion. The broad ligamentum nuchae may also be stretched or torn.

Closed trauma is typically caused by a sudden acceleration-deceleration or coup/contrecoup injury. In coup/contrecoup, the head hits a relatively stationary object, injuring cranial tissues near the point of impact (coup); then the remaining force pushes the brain against the opposite side of the skull, causing a second impact and injury (contrecoup). Contusions and lacerations may also occur during contrecoup as the brain's soft tissues slide over the rough bone of the cranial cavity. In addition, rotational shear forces on the cerebrum may damage the upper midbrain and areas of the frontal, temporal, and occipital lobes.

Signs and symptoms

Although symptoms may develop immediately, they're commonly delayed 12 to 24 hours if the injury is mild. Whiplash produces moderate to severe anterior and posterior neck pain. Within several days, the anterior pain diminishes, but the posterior pain persists or even intensifies, causing patients to seek medical attention if they didn't do so before. Whiplash may also cause:

·         dizziness and gait disturbances

·         vomiting

·         headache, nuchal rigidity, and neck muscle asymmetry

·         rigidity or numbness in the arms.

Diagnostic test results

·         X-ray of the cervical spine will determine that vertebral injury hasn't occurred.

Clinical Tip

In all suspected spinal injuries, assume that the spine is injured until proven otherwise. Any patient with suspected whiplash or other injuries requires careful transportation from the accident scene. To do this, place him in a supine position on a spine board and immobilize his neck with tape and a hard cervical collar or sandbags.

Until an X-ray rules out a cervical fracture, move the patient as little as possible. Before the X-ray is taken, carefully remove any ear and neck jewelry. Don't undress the patient; cut clothes away, if necessary. Warn him against movements that could injure his spine.

Treatment

·         Immobilization with a soft, padded cervical collar for several days or weeks

·         Ice or cool compresses to the neck for the first 24 hours, followed by moist, warm heat thereafter

·         Over-the-counter analgesics, such as aspirin, acetaminophen, or ibuprofen

·         Muscle relaxants

·         In severe muscle spasms, short-term cervical traction

P.119

WHIPLASH INJURIES OF THE HEAD AND NECK

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