Page 29 - VetCPD Jnl Volume 7, Issue 4

Postural reactions
Postural reactions are the complex responses that allow a rabbit to maintain its normal upright position and bring the limb into an appropriate position to bear weight.These reactions involve all levels
of the nervous system (from the cerebral cortex to brainstem and spinal cord) as intact sensory and motor pathways are required throughout the nervous system
as well as unimpaired processing and integration in the brain, to obtain normal postural reactions.The examination should be performed on a nonslip surface or mat (avoid the use of metal or other surfaces that would cause sliding or slipping), while carefully supporting the rabbit’s body to avoid trauma.A conscious proprioceptive abnormality indicates a neurological lesion (as opposed to an orthopedic one), but it does not allow a precise localization of the lesion within the nervous system. Multiple postural reactions can be performed
to evaluate the same neuro-anatomic pathways. However, additional testing will be required to localise the lesion further within the pathway of the deficit.
VETcpd - Exotics Table 3: Assessment and usefulness
of cranial nerve function in rabbits (modified from Keeble 2006b and Warnefors et al. 2018)
CRANIAL NERVE
CN I (Olfactory)
CN II (Optic)
CN III (Oculomotor)
FUNCTION TEST
Response to noxious odour
Menace Response
Pupillary light reflexes (PLR) Visual placing reactions
Pupillary size and symmetry
Pupillary light reflex (PLR) (direct)
Consensual
USEFULNESS IN RABBITS
Difficult to evaluate, not routinely performed
Often rabbits do not blink in response to a menace gesture
PLR may be slow Obstacles may be used
Evaluation of pupillary size may be difficult for physical barriers (e.g. cataracts) or animal’s temperament
The PLR may be slower and not as complete as in dogs
The consensual PLR may be difficult to evaluate
hemiwalking, placing and righting Motor Function masticatory muscles common with dental disease Subscribers
Conscious propioceptive positioning
As for CN III
CN IV (Trochlear) (strabism, resting nystagmus,
The physiological nystagmus is seen with head movements
corneal reflex, pupillary size)
reactions (e.g., wheelbarrow, hopping, CN V (Trigeminal): Atrophy of Atrophy and facial swelling are
reactions) can be performed in a similar (mandibular nerve) Jaw tone It may be difficult to assess the manner to those performed in more Only jaw tone
common companion animals (Figures.
3 - 4). However, a normal rabbit may
freeze and display apparent conscious
CN V (Trigeminal): Corneal reflex
Sensory Function Palpebral reflex Can be evaluated in rabbits
Facial skin and lip pinching
CN VI (Abducent) Examine for strabism, resting As for CN (III) nystagmus, corneal reflex
3
4
CN VII (Facial)
CN VIII (vestibulocochlear)
CN IX (glossopharyngeal), X (Vagus) and
XI (accessory)
CN X (vagus)
CN XII (hypoglossal)
Facial symmetry
Palpebral reflex
Blinking and ear movement
Response to sudden noise
Nystagmus induced by head movement, head tilt, ataxia, strabism
Observation of swallowing Gag reflex
Swallowing reflex Oculo-cardiac reflex
Tongue movement and strength
Can be evaluated in rabbits
Hearing loss may be difficult to evaluate clinically
Difficult in nervous rabbits
Gag reflex not done in rabbits because of the anatomy of their oral cavity
Assessment of XI is difficult
Difficult in nervous rabbits
Accurate assessment difficult with rapid heart rate
Difficult to grasp the tongue but it can be examined with an otoscope
Figure 3 and 4: Postural reaction: visual placing. Move the animal towards the edge of a table while supporting the weight of its body. The normal response is to place the paws on the table as it is approached, before the paw gets contact with the table. The neuroanatomy is as for conscious proprioception but the visual placing also allows evaluation of both peripheral and central vision. This rabbit shows a normal postural reaction.
VETcpd - Vol 7 Issue 4 - Page 27