Page 784 - Clinical Small Animal Internal Medicine

752 Section 8 Neurologic Disease

Table 69.4 Modified Glasgow Coma Scale Tone is evaluated by placing the limbs through passive
VetBooks.ir Score range of motion. Increased tone can be seen following
cranial trauma, as CNS inhibitory modulation to the

leading to coma will be associated with decreased tone in
Motor activity lower motor neurons is lost. However, severe brain injury
Normal gait, normal spinal reflexes 6 all limbs. Spinal reflexes are evaluated to primarily assess
Hemiparesis, tetraparesis 5 nerve function, but may provide some information
Recumbent, intermittent extensor rigidity 4 regarding cerebral activity. Animals may have exagger-
Recumbent, constant extensor rigidity 3 ated reflexes following cerebral injury and absent reflexes
when comatose.
Recumbent, constant extensor rigidity with 2 An animal’s posture after head trauma can also provide
opisthotonus information about location and degree of brain injury.
Recumbent, hypotonia of muscles, depressed or absent 1 Decerebrate rigidity can occur following cerebral trauma
spinal reflexes
and suggests severe brain injury and a poor prognosis as
Brainstem reflexes this posture reflects loss of communication between the
Normal pupillary light reflexes and oculocephalic reflexes 6 cerebrum and the brainstem. Animals with decerebrate
Slow pupillary light reflexes and normal to reduced 5 rigidity have opisthotonus with hyperextension of all
oculocephalic reflexes four limbs and are stuporous or comatose, with abnor-
Bilateral unresponsive miosis with normal to reduced 4 mal pupillary light reactions (Figure 69.10). Decerebellate
oculocephalic reflexes rigidity suggests acute cerebellar damage and may cause
Pinpoint pupils with reduced to absent oculocephalic 3 either flexion or extension of the pelvic limbs; however,
reflexes consciousness may be normal.
Unilateral, unresponsive mydriasis with reduced to 2
absent oculocephalic reflexes Assessment of Brainstem Reflexes Pupil size, the pupillary
Bilateral, unresponsive mydriasis with reduced to absent 1 light reflex, and the oculocephalic reflex should all be
oculocephalic reflexes immediately evaluated in all head trauma patients. Pupil
size, symmetry, and reactivity can provide valuable infor-
Level of consciousness mation about severity of brain injury and prognosis.
Occasional periods of alertness and responsive to 6 These parameters should be frequently assessed as they
environment can signal a deteriorating neurologic status. Response of
Depression or delirium, capable of responding but 5 the pupils to a bright light indicates sufficient function of
response may be inappropriate
Semicomatose, responsive to visual stimuli 4
Semicomatose, responsive to auditory stimuli 3
Semicomatose, responsive only to repeated noxious 2
stimuli
Comatose, unresponsive to repeated noxious stimuli 1

more severe clinical signs (Table 69.4). The score from
each category is added together to determine a patient’s
coma score ranging from 3 to 18, which may be used to
guide treatment decisions and prognosis.

Assessment of Limb Function The first category of the
MGCS describes a patient’s motor activity, limb tone,
and posture. Voluntary motor activity is characterized
as normal, paretic, or recumbent. Patients typically
maintain some degree of voluntary motor activity even
in altered states of consciousness unless they are coma-
tose. Abnormal motor function usually reflects either
brainstem injury or spinal cord injury; the latter may Figure 69.10 Extensor rigidity of the limbs as seen in this cat can
complicate the assessment of head trauma be compatible with severe brain injury following trauma.