Neurological examination

Neurological examination

Neurological examination is the most important part of the clinical evaluation of the neurological patient. It is performed on awake animal and with present owner. The neurological examination is consisting of examination of the mental status, behaviour, posture, gait, postural reactions, head nerves, spinal reflexes and pain perception. The neurological examination should be always performed slowly and playfully without causing unnecessary stress to the animal. It is preferred not to use muzzle during the examination. The aims of the neurological examination are as follows:

1. define if the animals problem is neurological or not
2. define which part of the nervous system is affected
3. make the list of possible diseases able to cause the condition
4. make the diagnostic work-up plan in order to confirm the diagnosis  

Examination of mental status

Consciousness (mental status) is the state of being conscious. It can be described as a state of responsiveness of the brain to impressions made by the senses. Consciousness is maintained by the permanent impulses from the reticular formation (brainstem) to the cerebral cortex. The decrease in consciousness is usually caused by disruption of connections between the reticular formation and cerebral cortex and therefore is always related to abnormal brain function. Nevertheless, the cause of such a disorder can be intra- and extra-cranially. Mental status can be normal, depressed (lethargic, sleepy), stuporous (sleepy, but can be aroused by strong stimulation) and comatose (sleepy, can not be aroused by strong stimulation).

Examination of behaviour

Behaviour is the way the animal behaves or performs. Assessment of beahviour is used clinically as a measure of cerebral activity. In small animals it is hugely influenced by environment the animal is living in and training therefore should be always judged very carefully. The physiology of behaviour is complex and involve interaction of various parts of brain, but can be grossly localized to the limbic system (localized in forebrain and the rostral brainstem). Nevertheless, the complexity of animal behaviour is in integration of inherited patterns of behaviour, sensory input from outside and the regulatory centers (limbic system and cerebral cortex). Abnormal behaviours might include aggression, fear, withdrawal, disorientation, yawning, head pressing, compulsive walking, circling and “stargazing”. Pure behavioural changes without additional neurological deficits are rarely caused by a brain disease. 

Examination of posture

The normal posture of the animal is the result of the interaction of different functional systems of the nervous tissue: motor neurons in the brain and spinal cord, balance system, visual system, proprioceptive system and the muscles. The disease of any of them can cause abnormal posture. When evaluating the posture of the dog or cat it is important to notice the position of the head, back, limbs and tail. The most frequent abnormalities in the posture of the head is the head tilt, head turn and ventroflexion (downwards) or dorsoflexion (upwards) of the head. The abnormal postures of the back include kyphosis (upwards arched back), lordosis (downwards arched back) and scoliosis (deviation of the back to the side). The abnormal postures of the head frequently indicate balance problems or brain disease and the diseases of the spine are usually associated with abnormal posture of the back.  

Examination of gait 

Gait examination is probably the most important but also the most difficult part of the neurological evaluation of the dogs and cats. The normal gait in dogs and cats is the diagonal gait, that means that at the same time one front and one diagonal hind limb is bearing the weight and the other two limbs are in the swing phase. Some animals will have also pacing (front and hind limb on the same side are bearing weight and the both limbs on the opposite side are in swing phase) as a normal gait pattern. Most of the neurological diseases will cause gait abnormalities, but so will be also with orthopedical and even internal medicine conditions. Three abnormalities can be distinguished in evaluation of gait: lameness, weakness (paresis) and lack of coordination (ataxia). Very frequently the neurological diseases cause mixture of paresis and ataxia or mixture of lameness and paresis. On the other hand the diseases of the balance system and diseases of cerebellum will cause just pure disturbance of coordination. The aim of the examination of gait is to define which limbs are affected and what kind of gait abnormality is present.

Examination of postural reactions

Examination of postural reactions is performed after gait examination and is helping the examiner to visualize better the deficits which have gone unnoticed or were not so clear during the gait examination. There are numerous postural reactions but the common idea in most of them is to make the animal stand, walk or jump just on one or a pair of limbs: hemistanding, hemiwalking, hopping, wheelbarrowing, extensor postural thrust and other reactions. The other important postural reaction which should be tested in every neurological patient is the proprioceptive positioning. This reaction provides information about the proprioceptive system (the system which informs the brain about the position of the body parts in the three dimensional space) of the patient.

Examination of cranial nerves

Cranial nerves are 12 pairs of nerves (12 on each side) which have the origin in the brain. These nerves innervate the structures in the head such as muscles of mastication, tongue, facial expression, muscles of the ears and the eyes as well as provide the important sensory impulse for the olfactory, visual, acoustic, balance and gustatory systems. By examining cranial nerves also the function of the brain and it’s most important parts (cerebrum, brainstem and cerebellum) can be evaluated. Very frequently the diseases of the brain will cause abnormalities in the cranial nerves, mostly it can be said about the lesions in the brainstem in dogs and cats.

Examination of spinal reflexes

Examination of the spinal reflexes is usually performed at the end of the neurological examination. The patient is positioned on the side and the reflexes of the hind limbs are usually examined first followed by the reflexes of the front limbs. The reflexes in the hind limbs are patellar, tibial cranial and the flexor reflex. The most reliable two reflexes in the front limbs include extensor carpi radialis reflex and the flexor reflex. The reflexes might be normal, decreased, absent or exaggerated. The main aim of examination of spinal reflexes is the precise lesion localization within the peripheral nervous system or the spinal cord.

Examination of pain perception

This is definitely the very last part of the neurological examination as the painful impulse is applied and the reaction of the patient is observed. The superficial pain perception is tested when the skin is gently pinched and the deep pain perception is tested when the toe is strongly and shortly pressed. The pain perception provides information about the integrity of the sensory system and in some cases it is an important prognostic sign in patients with signs of paralysis.

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