Page 782 - Clinical Small Animal Internal Medicine

750 Section 8 Neurologic Disease

compliance is exhausted, small increases in volume will continued decline in the head trauma patient. Therefore,
VetBooks.ir result in dramatic elevations in ICP, which will be accom- a complete systemic evaluation and stabilization is
required in addition to a thorough neurologic assess-
panied by a rapid decline in the patient’s neurologic
status.
This ability to compensate is more effective if the ment (Table 69.3).
increase in volume occurs slowly. With continued eleva- Systemic Assessment
tion of ICP, brain herniation can result. There are four Initial assessment should involve evaluation of the
types of brain herniation. patient’s respiratory and cardiovascular system. An air-
way must be established, if necessary through endotra-
Falcine herniation: herniation of one cerebral hemi-
● cheal intubation. Breathing patterns may be affected by
sphere ventral to the falx cerebri.
Transtentorial herniation: herniation of the parahip- thoracic trauma, but may also be secondary to brain
● injury. Auscultation of the thorax may detect pulmonary
pocampal gyrus below the tentorium cerebelli which pathology or cardiac arrhythmias. Oxygen support
causes compression of the midbrain, leading to should be given as necessary and mechanical or manual
mydriatic, unresponsive pupils, loss of consciousness, ventilation may be required with severe pulmonary inju-
and subsequent failure of the cardiorespiratory cent- ries. Traumatic pneumothorax may require thoracocen-
ers. A sign of developing transtentorial herniation is tesis or chest tube placement to allow proper ventilation.
asymmetric mydriasis followed by symmetric mydria- The cardiovascular system should be evaluated by moni-
sis as the parasympathetic portion of the cranial nerve toring heart rate, blood pressure, and electrocardiogra-
III nucleus is compressed. Transtentorial herniation phy. An electrocardiogram may demonstrate cardiac
can be life‐threatening, leading to sudden cardiopul- arrhythmias secondary to traumatic myocarditis, sys-
monary arrest.
Foramenal herniation: cerebellar herniation into the temic shock, or brain injury. Arterial blood analysis and
● lactate concentrations may provide additional informa-
foramen magnum (see Figure 69.9). This is frequently tion regarding systemic perfusion and respiratory
fatal, causing respiratory arrest by compressing the function.
respiratory centers of the medulla.
Calvarial herniation: the brain can also herniate Temperature assessment on a frequent basis is impor-
● tant in all patients. Cerebral metabolic rate is propor-
through a defect in the skull.
tional to body temperature and increases 5–7% per
degree centigrade. Hyperthermia should be avoided in
Clinical Assessment all patients and cooling techniques should be considered
if this is noted. Hypothermia reduces the cerebral
The ability to recognize signs consistent with elevated metabolic rate and although this may be advantageous to
ICP or a declining neurologic status is critical in the the injured brain, it also increases the risk of cardiac
management of dogs and cats following head trauma. abnormalities.
Trauma significant enough to cause brain injury will Once the patient is stable, CT or radiographs of the chest
have systemic effects, which may be life‐threatening. and abdomen are recommended to evaluate for pulmonary
Additionally, systemic injuries and shock will cause

Figure 69.9 A sagittal T2‐weighted MRI
confirms cerebellar vermal herniation
through the foramen (arrow).