Page 541 - ONLINE PROCEEDING BOOK WSAVA 2017
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WSVA7-0409
DSAVA: NEUROLOGY
NEUROLOGICAL EXAMINATION MADE EASY. BRAIN AND CRANIAL NERVE LESIONS
M. Berendtm1
1Department of Veterinary Clinical Sciences, Dyrlaegevej 16, 1870 Frb. C, Denmark
The neurological examination is the most fundamental tool that neurologists use to identify and isolate problems in the central and peripheral nervous system (CNS & PNS). A thorough clinical examination should however also be performed, as many non-neurological diseases can provoke signs that are very similar to the presentation of neurological diseases.
First of all, the neurological examination serve to detect malfunctions of the CNS and PNS and to determine if the problem presented is of a neurological nature or not. The individual tests performed in the neurological examination targets speci c structures of the CNS and PNS and
thus abnormal  ndings indicate which neuro-anatomical structures are affected (neuro-anatomical lesion localization). Advanced neuro-diagnostic tests such
as Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and cerebrospinal  uid (CSF) examination are commonly used to advance the diagnostic procedures to a level where a suspected lesion can be precisely localized and the disease process identi ed.
The present abstract highlights the components of the neurological examination concerned with the patient history, mental status and cranial nerve functions.
History
Always listen to the owner! Owners’ certainly know
their animals’ normal behavior and reactions better
than veterinarians, which are only observing the animal through a limited time-window. The bene t of taking up a detailed history can never be emphasized enough!
The history should include the animals breed, sex, age and medical history including information of the events which have motivated the owner to seek veterinary advice.
Some clues to the disease process might already
be indicated by the history, breed or age. Certain neurological diseases are for example more prevalent in certain breeds and at a certain age, e.g. disc disease in middle aged dachshunds or syringomyelia in Cavalier King Charles Spaniels. The debut of neurological signs at a very young age should alert the clinician to consider a congenital malformation. In the case of seizures it is of importance to question the owner about any possible events which preceded seizures and to remember
that seizures can be of intracranial origin as in epilepsy (idiopathic or symptomatic) or of extracranial origin (non- epileptic seizures), where the seizure activity is a reaction of the brain to external factors such as e.g. intoxication or generalized metabolic disease.
It is equally important to retrieve information regarding the nature of the problems observed. Did they come
on acutely or did they develop slowly? Are they of a stationary or progressive nature? Some diseases like e.g. an ischaemic stroke will present with sudden and rather dramatic neurological signs which will not develop further after 48 hours. Other diseases such as e.g. aseptic cerebral meningoencephalitis might initially present
with subtle and unspeci c signs including moderately decreased appetite and retraction, which however, if not recognized, can progress to a stage causing fulminant neurological de cits with changes of mental status, seizures, blindness and paralyses. Other diseases like e.g. degenerative myelopathy (a degenerative disease in middle-aged to older dogs with diffuse axonal necrosis, primarily affecting the thoracolumbar spinal cord lateral and ventral funiculi) will progress slowly over months or even years. A neuromuscular disease such as Myastenia Gravis will be episodic in nature.
Mental status
The normal animal is alert, responsive and attentive and reacts promptly to stimuli to vision, hearing and touch. In the normal brain the Ascending Reticular Activating System (ARAS), consisting of a complex of neuronal circuits situated in the brainstem and projecting to
the brain, is a regulator of such responses. The main function of the ARAS is to regulate arousal and sleep- wake transitions by keeping the brain alerted. The ARAS responds to incoming input by sending stimulating impulses to nuclei in the thalamus, which then projects diffusely to activate higher cerebral cortical centers. Thus the ARAS acts as a “pacemaker” for the brain. Sleep is associated with decreased activity of the ARAS.
If the ARAS is compromised (as can be the case if
e.g. a tumor, ischaemic stroke or hemorrhage affects
the brain stem) the animal will not be able to respond suf ciently to the environment. In that case, the owner might, if questioned thoroughly, report that the animal’s behavior is altered. Very commonly the owner have observed that the animal is no longer coming to the door to greet the family members, sleeps more than before
or do not respond to the mailman’s visit; events which would previously have alerted the animal or triggered a defensive reaction. Animals with lesions compromising the ARAS will show signs of affected consciousness. Such dysfunction is graded after severity into depressed (decreased responsiveness to the environment),
An Urban Experience
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