5 Head trauma
CASE HISTORY
Table 5.1 Causes of stupor and coma
Brainstem | Bilateral cerebrum |
---|---|
Trauma | Metabolic encephalopathies |
Hypoglycaemia | |
Hyperosmolar (DKA; hypernatraemia) | |
Hypo-osmolar (water intoxication) | |
Uraemia | |
Acidosis | |
Anoxia | |
Portosystemic shunt | |
Hyperkalaemia | |
hypocalcaemia | |
Tumour | Toxicity |
Inflammation | Post-ictal |
Vascular | Hydrocephalus |
Hydrocephalus | Herniation with secondary compression of brainstem |
CLINICAL EXAMINATION
Table 5.2 The modified Glasgow Coma Scale for small animals
Small animal coma scale | Score |
---|---|
Motor activity | |
Normal gait, normal spinal reflexes | 6 |
Hemiparesis, tetraparesis, or decerebrate activity | 5 |
Recumbent, intermittent extensor rigidity | 4 |
Recumbent, constant extensor rigidity | 3 |
Recumbent, constant extensor rigidity with opisthotonus | 2 |
Recumbent, hypotonia of muscles, depressed or absent spinal reflexes | 1 |
Brainstem reflexes | |
Normal pupillary light reflexes and oculocephalic reflexes | 6 |
Slow pupillary light reflexes and normal to reduced oculocephalic reflexes | 5 |
Bilateral unresponsive miosis with normal to reduced oculocephalic reflexes | 4 |
Pinpoint pupils with reduced to absent oculocephalic reflexes | 3 |
Unilateral, unresponsive mydriasis with reduced to absent oculocephalic reflexes | 2 |
Bilateral unresponsive mydriasis with reduced to absent oculocephalic reflexes | 1 |
Level of consciousness | |
Occasional periods of alertness and responsive to environment | 6 |
Depression or delirium, capable of responding but response may be inappropriate | 5 |
Semicomatose, responsive to visual stimuli | 4 |
Semicomatose, responsive to auditory stimuli | 3 |
Semicomatose, responsive only to repeated noxious stimuli | 2 |
Comatose, unresponsive to repeated noxious stimuli | 1 |
Note: Asymmetrical abnormalities (e.g. pupil size) are assigned the lower score of the two possible. Score before medication and supportive care administered. Oculocephalic reflex, VOR; Semicomatose-stuporous.
Examination in this case revealed:
Neuroanatomic localization
The lesion was localized to the cerebrum or brainstem ARAS based on the coma.
CASE WORK-UP
1. Assessing oxygenation
• Pulmonary contusions are common post-trauma. Auscultation detects increased lung sounds distributed unevenly over the thorax, or decreased lung sounds with consolidation. There is no specific therapy. Treatment is supportive.
• Neurogenic pulmonary oedema is rare but most often associated with severe head trauma. It progresses within hours or days to resolution or death. Improvement, if it is to occur, is usually seen within 48 hours. It results from a central sympathetic discharge from an increase in ICP. Treatment is aimed at reducing ICP, oxygenation, and diuretics.
2. Assessing ventilation
• Hypoventilation results from brain injury, thoracic trauma and pain, weakness secondary to spinal cord or brainstem injury. In addition, ventilation-perfusion mismatch can follow head trauma without evidence of pulmonary disease on the radiographs.
• Short, shallow respiration with intermittent attempts at deep respiration accompanies pleural space disease (pleural effusions, pneumothorax).
3. Assessing systemic perfusion
• Hypoperfusion manifests as a faster heart rate (dog), weaker pulse, paler mucous membrane colour, slower capillary refill time, and lower rectal temperature. Hypovolaemic animals have a depressed mentation which improves with treatment. The mortality rate in humans with severe traumatic brain injury is doubled with a systolic blood pressure of <90 mmHg.
4. Assessing intracranial pressure (Table 5.3)
• The closed skull gives the traumatized, swelling brain little room for accommodation. Increasing ICP forces blood and CSF out of the brain. As ICP equals or exceeds the systemic arterial pressure, the systemic blood pressure increases and a reflex bradycardia follows. These reflex changes are called the Cushing’s reflex and are more common in end-stage disease.
• Increases in ICP are monitored by neurological examination in veterinary patients. Papilloedema is rarely seen after acute head injury in humans.
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