Page 780 - Clinical Small Animal Internal Medicine

748 Section 8 Neurologic Disease

Prognosis for Animals with Spinal Trauma frequent assessment of both systemic and neurologic
VetBooks.ir Prognosis associated with SCI is influenced by the severity injuries can allow for a successful outcome. Additionally,
treatment strategies should remain flexible, adjusting to
of cord injury and the presence of injuries to other organs
(e.g., lungs, heart, and bladder). The form of treatment the patient’s needs and changes in neurologic status.
A complete understanding of intracranial physiology and
(surgical versus conservative) does not appear to influence the effects of injury will aid in the management of dogs
outcome, although in published case series, the more and cats with head trauma.
severely affected patients tend to be treated surgically, and
so a true comparison is difficult. Prognostic indicators
based on the neurologic examination are somewhat differ- Injury‐Related Intracranial Physiology
ent for different regions of the spine.
Following injury, cerebral blood flow is often significantly
Thoracolumbar injuries carry a guarded to grave prog- reduced due to associated elevations of intracranial pres-
●
nosis for recovery of pelvic limb function and fecal and sure (ICP) (>/= (greater than or = to)12–20 mmHg). Specific
urinary continence if the animal is paraplegic with factors that decrease cerebral blood flow (CBF) include the
loss of nociception to its pelvic limbs. If nociception is presence of edema, hematomas, compression of vessels
still present, these animals do have a good chance of from mass effect, and vasospasm. Additionally, trauma
recovery. significant enough to cause brain injury likely causes some
Cervical injuries are associated with a guarded to grave degree of systemic shock and hypotension. The presence of
●
prognosis if the animal is tetraplegic and unable to hypotension further reduces cerebral blood flow.
ventilate adequately. If treated surgically, the risk of Reduction of CBF due to elevation of ICP can lead to
perioperative death can be as high as 36% in cervical brain ischemia. A series of physiologic responses are in
injuries. Note that it is extremely unusual to see tetra- place to try to prevent this when CBF declines. Reduced
plegic animals that lack nociception because cervical blood flow to the vasomotor centers in the brainstem
spinal cord transection usually causes death by respir- leads to reduced carbon dioxide removal. A subsequent
atory failure and bradyarrhythmias. Delaying referral, elevation in local carbon dioxide concentrations stimu-
diagnosis, and treatment does worsen the prognosis. lates the sympathetic nervous system to increase mean
Less severe injuries carry a much better prognosis, arterial pressure. The result is systemic hypertension in
with the majority of cases making a recovery if man- an effort to maintain blood flow to the brain. However, as
aged appropriately. the baroreceptors located in the aorta and carotid sinus
The prognosis for recovery of fecal and urinary conti- both detect systemic hypertension, a signal is sent to the
●
nence in lumbosacral and sacrocaudal fractures is vagal centers of the brainstem. A reflex bradycardia
approximately 50% if there is absent anal tone and no occurs as a consequence. This phenomenon is referred
nociception in the perineal region or the tail at the to as the Cushing reflex. Therefore, concurrent systemic
time of presentation. Positive tail base sensation is hypertension and bradycardia can indicate elevated ICP
useful to identify cases that will recover within 30 days in head trauma patients.
of the injury, but it is not very useful to discriminate Additionally, an elevation in ICP and the subsequent
the cases that will recover despite not having tail base reduction of cerebral perfusion pressure (CPP) stimulates
sensation. Because the cauda equina is largely com- the release of catecholamines. This catecholamine surge
posed of peripheral nerves, displacement of fracture can lead to the brain–heart syndrome, which causes
fragments is less likely to cause complete transection arrhythmias and myocardial ischemia.
but severe pain due to nerve root entrapment is com-
mon and can be a reason for euthanasia.
Pathophysiology of Brain Injury
After trauma, the brain parenchyma is susceptible to two
Head Trauma types of injury: primary injury and secondary injury.

Traumatic brain injury in veterinary patients occurs Primary or Biomechanical Injury
most commonly secondary to automobile accidents. This is injury to the brain tissue from direct trauma and
Other common causes of traumatic brain injury include the forces applied to the brain at impact. An impact to
kicks to the head, falls, gunshot wounds, and animal the skull exerts the following forces on the brain: accel-
bites. Immediate and appropriate treatment is critical to eration, deceleration, and rotational forces. The brain is
potentiate an acceptable recovery. Although treatment unable to tolerate these forces because of its composition
recommendations remain controversial, there are several and lack of internal support. The superficial gray matter
guidelines for head trauma management. Accurate and is most susceptible to the forces of acceleration, leading