Neurological examination Flashcards
What are the specific regions of the nervous system
Attempts should be made to explain all the abnormal findings of the neurological exam by a single lesion within one of the following specific regions of the nervous system:
- focal forebrain, brainstem, cerebellum - C1-C5 spinal cord segments - C6-T2 spinal cord segments - T3-L3 spinal cord segments - L4-L6 spinal cord segments - L7-S3 spinal cord segments - peripheral nerve, neuromuscular junction, muscle
When a single lesion cannot explain all the abnormal findings identified, what can you conclude
If a single lesion cannot explain all the abnormal findings identified, the lesion localisation is considered as being multifocal or diffuse
What are the different state of consciousness that can be observed during the hands-off examination
Disturbances in the state of consciouness are classified in order of severity as:
- depression (mentally dull but still conscious)
- lethargy
- obtundation
- stupor (semi-coma) (mostly unconscious but can be aroused with external stimuli, but quickly lapses back into a state of unconsciousness)
- coma (cannot be aroused from a state of unconsciousness by external stimuli)
When you observe an alteration of the state of consciousness, what can you conclude
As a rule, altered states of consciousness relate either to:
- a diffuse lesion or widespread multifocal lesions of both central hemispheres
- or a focal lesion affecting the ascending reticular activating system (ARAS) of the brainstem
What is associated with a head tilt
vestibular disorder
What is associated with a head turn
An ipsilateral forbrain lesion
What is associated with ventroflexion of the neck
A neuromuscular disorder or severe cervical spinal cord grey matter lesion
What is the position of the tail in cats suffering a significant loss of balance
Cats often carry their tail elevated straight dorsally when they are suffering a significant loss of balance
Give a definition of ataxia
Ataxia is an uncoordinated gait arising from:
- a peripheral nerve or spinal cord lesion (general proprioceptive ataxia)
- a vestibular lesion (vestibular ataxia) - a cerebellar lesion (cerebellar ataxia)
What is the definition of paresis
Paresis is defined as:
- a loss of ability to support weight (lower motor neuron disease)
- or inability to generate a gait (upper motor neuron disease)
What are the two postural reactions pathways
Afferent arm components:
- joint proprioceptor
- peripheral sensory nerve
- spinal cord and brainstem ascending pathway
- contralateral forebrain
Efferent arm components:
- contralateral forebrain
- descending motor pathways within the brainstem and spinal cord
- peripheral motor nerve and skeletal muscle
What are the three postural reactions tests used in cats
Hopping
Wheelbarrowing
Tactile placing
Paw position testing can be very difficult to assess in cats
What is evaluated by the thoracic limb withdrawal reflex
In the thoracic limb, the withdrawal reflex evaluates:
- the integrity of the C6-T2 spinal cord segments (and associated nerve roots)
- brachial plexus - peripheral nerves (radial, axillary, musculocutaneous, median and ulnar) - the muscles innervated
What is evaluated by the pelvic withdrawal reflex
In the pelvic limb, the withdrawal reflex evaluates:
- the integrity of the L4-S1 spinal cord segments (and associated nerve roots)
- the femoral and sciatic nerves - the muscles innervated
When does the patellar reflex appear exaggerated
A lesion cranial to the L4 spinal cord segment can cause a normal or exaggerated reflex
- in the absence of other neurological deficits, it has little clinical signification
The patellar reflex can also appear hyperreflexic in a cat with a sciatic nerve or L6-S1 spinal cord segment lesion
- this pseudohyperreflexia is a result of decreased tone in the muscles that flex the stiffle and normally counteract stifle extension
What are the afferent and efferent arms of the menace response
Afferent arm:
- the retina
- optic nerve (CN II)
- contralateral optic tract
- contralateral forebrain
Efferent arm:
- contralateral forebrain
- ipsilateral cerebellum
- ipsilateral facial nerve (CN VII)
Explain the pathways of the pupillary light reflex
The size of the pupils represents a balance between the parasympathetic system, which is responsive to the amount of light entering the eye, and the sympathetic system, which is responsive to the emotional state of the cat
- the parasympathetic component of the oculomotor nerve (CN III) is involved in the control of pupillary constriction
- the sympathetic system dilates the pupil during periods of stress and fear, and in response to painful stimuli
- it will also keep the eyeball protruded, the palpebral fissure widened and the third eyelid retracted
When you notice a modification in the cat’s behavior despite normal blood test results, where can you localize the problem
Neurological causes for alterations in behavior (e.g., head-pressing into corners, howling uncontrollably) include lesions within the limbic system and extrapyramidal nuclei
Whar are the main categories of problems leading to an anomaly in the cat’s posture
Alterations in the cat’s posture may be due to:
- neurological disease
- weakness
- musculoskeletal pain
What are the particular posture adopted by weak cats
Weak cats will often adopt particular postural abnormalities:
- passive neck ventroflexion (presumed to be due to the lack of a nuchal ligament)
- upright posture with limbs tucked under the body - frequent adoption of sternal recumbency with head placed on forelimbs or table - inability to retract claws passively
What is opisthotonos
This body position is characterized by adoption of lateral recumbency with extension of the head and neck and rigid extension of the forelimbs
This posture often occurs with lesions of:
- the rostral cerebellum
- caudal midbrain
- other structures within the caudal fossa
What is decerebrate rigidity
Decerebrate rigidity is characterized by all four limbs held in rigid extension generally resulting from a lesion of the flexor motor tracts that traverse midbrain and pons
- usually coma or stupor are also present
What is decerebellate rigidity
Decerebellate rigidity occurs when there is an isolated rostral cerebellar lesion
This position differs from decerebrate rigidity in that the hind limbs are mostly flexed and the level of consciousness is not impaired (if this is the only lesion present)
What is Schiff-Sherrington posture
Schiff-Sherrington posture is characterized by increased extensor tone of the thoracic limbs and flaccid paralysis of the pelvic limbs
- head and neck are not altered
This posture is seen after acute thoracolumbar (T3-L3) spinal coord lesions
- it is rarely seen in cats
If the cat has gait abnormalities but is not ataxic, what can you conclude
If the cat has gait abnormalities but is not ataxic, we can consider the presence of musculoskeletal disease or disorders of the peripheral nervous system
What are the characteristics of proprioceptive (sensory) ataxia
This is the most common form of ataxia seen in small animal practice
The proprioceptive pathways lie at the peripheral aspects of the spinal cord, and are thus easily damaged by external compressive lesions such as tumors or ruptured intervertebral discs
Hallmarks of proprioceptive ataxia are:
- a wide-based stance
- prolongation of stride length
- stumbling or knuckling whilst walking or performong postural reactions
The most common cause of proproceptive ataxia is spinal cord disease
- brainstem disease may produce marked proprioceptive ataxia, however disease in this location is usually accompanied by an altered level of consciousness and/or cranial nerve deficits
What are the characteristics of vestibular ataxia
Hallmarks of vestibular ataxia are:
- presence of a head tilt towards the side of the lesion
- the animal will often lean, fall or roll towards the side of the lesion
What are the characteristics of cerebellar ataxia
Unilateral cerebellar disease produces ipsilateral hyper-metric ataxia with no proprioceptive deficits or loss of strength
What is the objective of postural reaction tests (hemi-walking, wheelbarrowing and hopping)
Postural reactions are tests used to detect subtle problems with limb strength and coordination
Poor initiation of the movement indicates proprioceptive problems
Poor follow-through indicate motor deficits (paresis)
What are the clinical signs associated with a lesion of CN I
CN I is olfactory CN
The owner may note that the cat cannot detect the presence of food
The most common causes of anosmia are nasal cavity diseases
- Brain disease is rare with head trauma the most frequent cause
What are the clinical signs associated with a lesion of CN II
CN II is optic CN
Clinical signs include:
- blindness
- absence of PLR
- absence of menace response
What are the clinical signs associated with a lesion of CN III
CN III is oculomotor CN
Clinical signs of oculomotor nerve dysfunction include:
- lateral and ventral strabismus due to paralysis of the extra-ocular muscles
- ptosis due to paralysis of the levator palpebri muscle
- dilated pupil that is unresponsive to a light stimulus
What are the clinical signs associated with CN IV
CN IV is trochlear CN
Clinical signs with trochlear nerve dysfunction include:
- presence of a dorsomedial strabismus
What are the clinical signs associated with CN V
CN V is trigeminal CN
Clinical signs of trigeminal nerve dysfunction include:
- loss of ipsilateral facial sensation
- corneal and palpebral reflexes may be diminished
- bilateral loss of motor function of CN V may result in mandibular paralysis (dropped jaw)
- atrophy of masseters and temporalis muscles
What are the clinical signs associated with a lesion of CN VI
CN VI is abducens CN
Clinical signs of dysfunction of the abducens nerve include:
- paralysis of the lateral rectus resulting in a medial strabismus
- the affected eye cannot be abducted fully in response to the corneal reflex
What are the clinical signs associated with a lesion of CN VII
CN VII is facial CN
Clinical signs of facial nerve dysfunction include:
- ipsilateral facial paresis or paralysis
- the palpebral fissure on the affected side may be slightly wider and fails to close in response to stimulation via the corneal or palpebral reflexes
- exposure keratitis on affected side
- because of the close anatomical loccation of the facial and the vestibulococlear nerves at their brainstem and also their course through the petrosal bone they are often affected simultaneously by the same lesion (e.g., otitis interna)
What are the clinical signs associated with a lesion of CN VIII
CN VIII is the vestibulocochlear CN
Dysfunction of the CN VIII include:
- loss of hearing
- presence of spontaneous nystagmus
- lack of normal physiological nystagmus
- positional strabismus
What are the clinical signs associated with a lesion of CN IX, X XI
CN IX is the glossopharyngeal CN
CN X is the vagus CN
CN XI is the accessory CN
Clinical signs of glossopharyngeal, vagus and accessory nerve dysfunction include:
- varying degrees of dysphagia and difficulty with swallowing
- the gag reflex is reduced or absent
- paralysis of the laryngeal muscles
- regurgitations may occur due to megaoesophagus
What are the clinical signs associated with a lesion of CN XII
CN XII is hypoglossal CN
Clinical signs of hypoglossal nerve dysfunction include:
- paresis or paralysis of the tongue that may be ipsilateral in unilateral lesions
-affected animals are unable to prehend food or water
- unilateral lesion results in deviation of the tongue towards the side of the lesion
What is the upper motor neuron and what is its function
The upper motor neuron is the motor system confined to the central nervous system
It is responsible for:
- the initiation of voluntary movements
- the maintenance of postural tone against gravity and to establish the posture upon which voluntary activity can be performed
- the control of muscular activity associated with visceral functions (i.e., respiratory, cardiovascular, …)
It can be divided into pyramidal and extra-pyramidal components
Where are located the cell bodies of the pyramidal system
The cell bodies of the pyramidal system are located in the motor area of the frontal and parietal lobes of the cerebral cortex
What is the extrapyramidal system
The extrapyramidal system consists of diverse groups of interconnected and functionally related neurological structures
They work in conjunction with the pyramidal system and provide muscular tone to support the body against gravity and to recruit the spinal reflexes for the initiation of voluntary movement, by influencing the activity of the alpha and gamma motor neurons in the ventral column of the spinal cord
Where are located the cell bodies of the extrapyramidal system
The cell bodies of the extrapyramidal system are located in nuclei dispersed throughout all the areas of the brain
What is the site of the lesion for an UMN disease
Lesions that occur cranial to the reflex arc disconnect the reflex from inhibition that is normally supplied by the higher brain centers
- signs are observed on the contralateral side of the body if the lesion is rostral to the junction between the midbrain and pons (tend to be less profound)
- signs are observed ipsilateral if located caudal to the junction between midbrain and pons (tend to be more obvious and debilatating)
What are the signs of UMN disease
Signs of UMN disease consist of:
- exaggeration of myotatic reflexes or muscular clonus
- paresis
- spasticity
- crossed extensor reflex
- a distended bladder that is difficult to express (“upper motor neuron bladder”)
What is the lower motor neuron
The lower motor neuron is the efferent neuron of the peripheral nervous system that connects the CNS with a group of muscle cells or a gland
The lower motor neuron is divided into three components:
- the general somatic efferent system, which innervates striated voluntary skeletal muscle
- the general visceral efferent system, which innervates the smooth muscle associated with blood vessels, visceral structures, glands and cardiac muscle (this is an involuntary system and represents the nerves of the autonomic nervous system)
- the special visceral efferent system, which innervates striated muscles of visceral structures of the respiratory and digestive systems derived from branchial arch mesoderm
Where are located the general somatic efferent neurones
These neurons are located throughout the entire spinal cord in the ventral column
The axons of the general somatic efferent neurons leave the spinal cord in the ventral root
Where are located the three sacral segments of the spinal cord in the cat
In the cat the three sacral segments are usually located over the body of L6 and the spinal cord ends at around L7 (the remainder of the spinal canal being occupied by the spinal nerves that make up the cauda equina)
What are the clinical signs of LMN signs
Lesions within the lower motor neuron itself lead to loss of muscular function
Signs of lower motor neuron disease consist of:
- decreased or absent reflexes
- paresis or paralysis
- hypotonia or atonia of muscles
- neurogenic atrophy
- loss of anal tone
- a distended bladder that is easy to express or has overflow incontinence (“lower motor neuron bladder)
