Page 30 - VetCPD Jnl Volume 7, Issue 4

VETcpd - Exotics
proprioceptive deficits in response to stress, but in absence of any neurologic impairment.Therefore, when interpreting postural reaction findings one should consider the possibility that a delayed or altered response may be the result of a nervous system lesion or simply normal behaviour in a nervous rabbit.
Reflexes
Attention should be paid to a rabbit’s positioning while performing these manipulations.The patient, if possible, is kept lying comfortably on its side.This allows assessment of the sensory and motor components of the reflex arches being examined and the descending motor pathways of the same reflexes (Vernau et al 2007). The response should be noted as absent (0), depressed (+1), normal (+2), exaggerated (+3), and exaggerated with clonus (+4).
Rostral
perception is usually a poor prognostic sign as it results from severe damage to the spinal cord. Many diseases can cause
Figure 5: Intraoperative image during left lateral ear canal resection and lateral bulla osteotomy in a lop rabbit. The patient is in right lateral recumbency with the rabbit's nose to the left of the picture and the left ear is lifted to expose the proximal tract of the ear canal (horizontal portion in a lop rabbit). The tip of the pinna is at the top of the photo. The image shows the purulent material accumulated within a dilation
of the proximal tract of the surgically
open external ear canal (green arrow) which clinically presented as an ear base swelling. This rabbit also showed head tilt. A CT scan confirmed left-sided material accumulation within the external ear canal, middle and inner ear. The Encephalitozoon cuniculi serology was negative. Bacterial culture in this case yielded a pure growth of Staphylococcus aureus. The rabbit also presented respiratory symptoms.
from lesions in the cerebellum and brainstem. Rabbits with central vestibular disease may show changes in mentation
Cranial nerves
Subscribers
Especially when a brain lesion is spinal pain, including neurological diseases (mental dullness), abnormal cranial nerve
suspected, examination of the cranial as well non-neurological ones. Lesion responses, gait abnormalities, ataxia, and
nerves is fundamental as it can help to localization is very important when spinal head tilt or head turn (chin to shoulder,
more precisely localize neurological pain is present in order to ensure that the nose to side) and often exhibit loss of
lesions. Cranial nerves dysfunction may correct diagnostic tests are performed. appetite. Nystagmus may be present
indicate a CNS lesion (brainstem disease) Furthermore, interpretation of test results (horizontal, rotatory or vertical). In these
or a peripheral lesion (affecting the will only be possible with the knowledge cases, the prognosis becomes guarded to
cranial nerves after they have exited the of the results of the neurological poor for complete recovery. brainstem and course through the skull). examination.The treatment of spinal Peripheral vestibular disease may
Eye movement, head movement, blinking, jaw and tongue movement and general symmetry of the head should be carefully assessed. Cranial nerves I to XII can be evaluated in a similar manner as in dogs and cats, although reliability of some of these tests in rabbits may be questionable (Table 3). An ophthalmologic examination should also be performed as this would assist with the evaluation of CN II (optic), III (oculo-motor), IV (trochlear), and VI (abducens).
Pain perception
Examination of cranial nerves, spinal reflexes and propioceptive reactions allows evaluation of some sensory pathways but perception of superficial and deep pain needs to be further assessed. However, accurate evaluation and interpretation of pain perception may be extremely difficult in rabbits as they can freeze without showing any response even to a noxious stimulus (Keeble 2006). In addition,
simple withdrawal of the limb, following application of a noxious stimulus, may simply be indication of a segmental spinal reflex and not of a conscious pain response, which is instead indicated by turning of the head towards the painful stimulus (Vernau et al. 2007). Loss of deep pain
Page 28 - VETcpd - Vol 7 - Issue 4
pain must be addressed both by treating the underlying disease as well as the pharmacological alleviation of discomfort.
be due to lesions in the cochlea and vestibular apparatus of the inner ear
or along the vestibular nerve. Signs of peripheral vestibular disease may include head tilt (ear towards the shoulder, nose forward, towards the lesion), torticollis (twisted neck), nystagmus (fast phase away from affected side), circling (towards the lesion), rolling and loss of balance.
If the middle ear is involved, there may also be facial nerve paralysis affecting
the lip, eye, nictitans and facial muscles. Bacterial infections (e.g. caused by Pasteurella multocida, Bordetella bronchiseptica, Pseudomonas aeruginosa, Staphylococcus aureus) causing peripheral vestibular disease can also spread from the nasal cavity through the Eustachian tube to
the middle, inner ear and vestibular tract causing concurrent respiratory symptoms. Many rabbits may still have a normal attitude and appetite. However, it is not uncommon for secondary gastrointestinal symptoms to arise including reduced appetite to anorexia, altered faecal output, and lethargy. Otitis interna is defined by the presence of an empyema of the tympanic bulla, associated with neurological signs (vestibular syndrome; such as heat tilt, horizontal nystagmus,
Only
Central versus peripheral
vestibular disease
Vestibular disease is commonly seen
in rabbits and may be caused by Encephalitozoon cuniculi and/or bacterial infections (e.g. Pasteurella multocida)
but other differential diagnosis may include toxoplasmosis, listeriosis, herpes virus encephalitis, trauma, abscess, cerebrovascular accident, degenerative disease, toxins and neoplasia (Keeble 2006; Fisher et al. 2020).
Central vestibular disease may result
Further neuro-anatomical lesion localisation
Once the rabbit’s details and a complete
history have been taken, and complete physical and neurological examinations have been performed determining that the patient has indeed a neurological problem, the next step is to try and localise the problem further to a specific area within the nervous system (Vernau et al. 2007). General principles used in dogs and cats may apply.