INTRODUCTION

Being hit by a car, human, large animal, falling tree or furniture, being shot at or in a dog fight are all reported causes of head trauma in small animals. The dog that knocks its head against a door frame and carries on walking will not have sustained clinically significant head trauma.

SIGNALMENT

A 6-year-old male crossbred dog.

CASE PRESENTING SIGNS

Presented in a mentally unresponsive state.

CASE HISTORY

A sudden onset of stupor or coma (Table 5.1) should not automatically be blamed on external trauma, unless, of course, the event is witnessed or has produced other physical evidence. The owner must always be questioned, however briefly, on the animal’s recent health status.

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

In this case, the dog had been exercising off the lead and out of view. A train was heard to pass nearby. The dog was called but failed to return. The animal was found soon after, in lateral recumbancy in an unresponsive mental state. The owners presented the dog, saying it had been hit by a train.

CLINICAL EXAMINATION

Initial assessment of a traumatized animal is done quickly and is repeated at frequent intervals. Mental state, pupil size and pupil light reflex (PLR), eye movement (resting position, spontaneous movement, and vestibulo-ocular reflex, VOR) should be noted. Approximately 10% of traumatic brain-injured humans also have a cervical spine injury. Avoid rotating or hyperextending the neck.

The Glasgow Coma Scale was modified by Dr Andy Shores for use in small animals and this helps monitor progression of signs (Table 5.2). One study found that there was a 50% probability of survival during the first 48 hours after head trauma in dogs with a score of 8. Contrary to humans, the age of the animal did not predict survival. The study was not able to suggest a long-term prognosis based on either survival or functional capacity.

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:

• Coma

• Lateral recumbency

• Bilaterally symmetrical pinpoint pupils

• VOR was present

• Regular respiration with good thoracic excursions

• Absence of external signs of trauma

• Heart rate and pulse rate were 126 bpm

• Temperature was 37.7°C.