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Questions and Answers
What does head pressing in an animal with a forebrain lesion indicate?
What does head pressing in an animal with a forebrain lesion indicate?
In an animal with a forebrain lesion, why does circling typically occur towards the side of the lesion?
In an animal with a forebrain lesion, why does circling typically occur towards the side of the lesion?
What is the primary cause of stuporous behavior in a patient?
What is the primary cause of stuporous behavior in a patient?
Which type of ataxia is characterized by drifting towards one side and a head tilt?
Which type of ataxia is characterized by drifting towards one side and a head tilt?
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What is the main difference between paralysis and paresis in neurological terms?
What is the main difference between paralysis and paresis in neurological terms?
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Which type of gait abnormality is most likely to be associated with dysmetria and hypermetria?
Which type of gait abnormality is most likely to be associated with dysmetria and hypermetria?
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Which cranial nerve is responsible for the gag reflex in animals?
Which cranial nerve is responsible for the gag reflex in animals?
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Which cranial nerve innervates the trapezius muscle and can rarely show atrophy?
Which cranial nerve innervates the trapezius muscle and can rarely show atrophy?
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Which nerve originates from the medulla and is the most caudal?
Which nerve originates from the medulla and is the most caudal?
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Which region of the brain is primarily responsible for proprioception and limb placement?
Which region of the brain is primarily responsible for proprioception and limb placement?
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Which reflex involves repetitive flexion and extension of a joint in response to a single stimulus?
Which reflex involves repetitive flexion and extension of a joint in response to a single stimulus?
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In assessing animals, the cutaneous trunci reflex is used to help locate lesions affecting which part of the body?
In assessing animals, the cutaneous trunci reflex is used to help locate lesions affecting which part of the body?
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Which neurological abnormality would likely be associated with animals that keep their limbs in extension and exhibit generalized depression of reflexes?
Which neurological abnormality would likely be associated with animals that keep their limbs in extension and exhibit generalized depression of reflexes?
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What is a possible cause of hamstring atrophy, crouched stance, and flinging forward of limbs in animals?
What is a possible cause of hamstring atrophy, crouched stance, and flinging forward of limbs in animals?
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Which type of lesion would be most likely to cause urinary retention due to increased tone of detrusor muscle and urethral sphincter?
Which type of lesion would be most likely to cause urinary retention due to increased tone of detrusor muscle and urethral sphincter?
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Which type of posture in ataxic animals involves rigidity in thoracic limbs with possible opisthotonus and flexed pelvic limbs, linked to cerebellum or cerebellar peduncle lesions?
Which type of posture in ataxic animals involves rigidity in thoracic limbs with possible opisthotonus and flexed pelvic limbs, linked to cerebellum or cerebellar peduncle lesions?
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What type of posture indicates rigidity in all limbs with opisthotonus, often associated with brainstem (midbrain) lesions in ataxic animals?
What type of posture indicates rigidity in all limbs with opisthotonus, often associated with brainstem (midbrain) lesions in ataxic animals?
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What does a head turn in ataxic animals typically indicate?
What does a head turn in ataxic animals typically indicate?
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Which syndrome is characterized by increased extensor tone in thoracic limbs and paresis to plegia in pelvic limbs, associated with T3-L3 myelopathy?
Which syndrome is characterized by increased extensor tone in thoracic limbs and paresis to plegia in pelvic limbs, associated with T3-L3 myelopathy?
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What does opisthotonus in ataxic animals indicate?
What does opisthotonus in ataxic animals indicate?
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Which condition results in facial muscle contracture and a fixed grimace, as seen in tetanus?
Which condition results in facial muscle contracture and a fixed grimace, as seen in tetanus?
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In ataxic animals, where is spasticity typically a sign of upper motor neuron lesions?
In ataxic animals, where is spasticity typically a sign of upper motor neuron lesions?
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Schiff Sherrington Syndrome is associated with which specific pattern of limb abnormalities?
Schiff Sherrington Syndrome is associated with which specific pattern of limb abnormalities?
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Torticollis in ataxic animals mainly involves:
Torticollis in ataxic animals mainly involves:
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Rigidity in all limbs with opisthotonus is commonly associated with:
Rigidity in all limbs with opisthotonus is commonly associated with:
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Study Notes
Neurologic Exam and Lesion Localization
- Behavioral Changes: pacing, head pressing, circling, aggression, blindness, obsessive behavior, incontinence, and seizures due to forebrain lesions
- Head Pressing: due to disinhibition of the red nucleus in the midbrain, causing the animal to walk into walls
- Circling: towards the side of the lesion due to hemineglect
- Mentation: level of consciousness, including obtunded, stuporous, and comatose states
- Gait: ataxia, proprioceptive, vestibular, cerebellar, and paresis
- Reflexes: rule out systemic disease, assess reflexes in all limbs
- Posture: decerebrate, decerebellate, Schiff-Sherrington, and risus sardonicus
- Lesion Localization: central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS), and specific regions of the brain and spinal cord
Neuroanatomy
- CNS: brain and spinal cord
- PNS: nerves and muscles
- Intumescence: widening of the spinal cord where nerves come out
- Decussation: everything in the forebrain crosses over before going to the rest of the body
- Brainstem and Spinal Cord: ipsilateral, lesion on one side causes signs on the same side
- Encephalopathy: lesion to the brain
- Myelopathy: lesion to the spinal cord
- Lesions to PNS: radiculopathy, neuropathy, myelinopathy, junctionopathy, and myopathy
Upper and Lower Motor Neurons
- Upper Motor Neuron (UMN): cells that arise from the forebrain, brainstem, or cerebellum
- Lower Motor Neuron (LMN): cells that arise from spinal cord segments
- Ventral Nerve Roots: formed by the axons of the LMN
- Nerve Roots: combine to form named nerves
- Spinal Cord Segments vs Vertebrae: 8 cervical spinal cord segments, 7 cervical vertebrae, etc.
Neurologic Deficits
- Hemineglect: animal ignores one side of their world due to decussation
- Nystagmus: involuntary side-to-side or circular motion of the eyes
- Dysmetria: inability to control distance, speed, and range of motion
- Hypermetria: overflexion and overextension of the limb
- Localizing Neurologic Deficits: to specific neuroanatomic regions (CNS vs PNS)
- UMN vs LMN: assess reflexes and tone of limbs, prognosis
Cranial Nerves
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Olfactory Nerve (I): typically not assessed, avoid irritating substances
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Optic Nerve (II): menace response, pupillary light reflex, fundic exam
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Oculomotor Nerve (III): innervates dorsal, ventral, and medial rectus, ventral oblique, and pupillary sphincter
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Trochlear Nerve (IV): innervates dorsal oblique
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Abducent Nerve (VI): innervates lateral rectus and retractor bulbi
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Trigeminal Nerve (V): comes from the pons, 3 branches (ophthalmic, maxillary, and mandibular)
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Facial Nerve (VII): originates from the medulla, motor to muscles of facial expression, sensory to inner ear pinna, parasympathetic for lacrimal/nasal gland secretions
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Vestibulocochlear Nerve (VIII): originates from the medulla, maintains posture and balance, detects acceleration and deceleration, coordinates eye movement### Assessing Cochlear Function
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Deafness in animals can be assessed by testing hearing in both ears, but a crude method is to clap loudly once; a more objective way is to use brainstem auditory evoked response with electrodes.
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The glossopharyngeal (IX), vagus (X), and cranial nerves originate from the caudal medulla and nucleus ambiguus, innervating the oropharynx, larynx, and esophagus.
Assessing Cranial Nerves
- The oropharynx is associated with the gag reflex (sensory: X, motor: IX, X, and XII), and an animal usually licks after (tongue, XII).
- Swallowing involves the sensory nerve X and motor nerves IX, X, and XII.
- The larynx is innervated by the recurrent laryngeal nerve (branch of vagus nerve) and accessory XI (spinal accessory nerve).
- The hypoglossal nerve (XII) is the most caudal cranial nerve, coming from the medulla.
Assessing Proprioception and Motor Function
- Proprioception is the sense of where limbs are in space, graded similarly to cranial nerves.
- Paw placement and hopping tests are used to assess proprioception, requiring minimal strength but some strength.
- Forebrain, brainstem, and spinal cord lesions can cause delayed or absent paw placement and hopping.
- Wheelbarrowing, extensor postural thrust, and hemiwalking/hemistanding tests are also used to assess proprioception and motor function.
Segmental Spinal Cord Reflexes
- Reflexes must be evaluated in conjunction with other neurological abnormalities to be reliable.
- Graded 0-4, reflexes are absent, weak, normal, exaggerated, or display clonus.
- Thoracic limb reflexes include the withdrawal or flexor reflex, which is polysynaptic and involves multiple synapses and interneurons.
- Myotatic reflexes are monosynaptic, involving a direct response to muscle stretch, and include the biceps, triceps, and extensor carpi radialis reflexes.
Pelvic Limb Reflexes
- The withdrawal or flexor reflex is also reliable in the pelvic limb, primarily involving the sciatic nerve.
- Hamstring atrophy, crouched stance, dropped hock, and flinging limb forward when walking are signs of sciatic nerve deficits.
- Other reflexes include the patellar reflex (femoral nerve, L4-L6), hock flexion (tibial nerve), stifle flexion (sciatic nerve), and hip flexion (femoral nerve).
Other Reflexes
- The cutaneous trunci reflex is helpful for narrowing down the location of a lesion but should not be used to change localization.
- The perineal reflex (pudendal nerve) is a reliable test for sacral spinal cord or pudendal nerve lesions.
- The Babinski reflex (extensor toe) is normally absent in adults but present in newborns.
- Crossed extensor reflexes result from lesions in ipsilateral descending pathways, signifying UMN disease, likely chronic.
- Hyperpathia and hyperesthesia are not helpful for localization, but nociception (deep pain) determines prognosis for paralyzed patients.
Bladder Function
- Lesions to S1-S3 (pelvic and pudendal nerve) can cause decreased tone of detrusor muscle and urethral sphincter, leading to incontinence.
- Lesions cranial to S1 (UMN lesion) can cause increased tone of detrusor muscle and urethral sphincter, leading to firm bladder and urinary retention.
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Description
Understand how to perform a neurologic exam and observe behavior changes indicating forebrain lesions. Learn about symptoms like head pressing, circling, blindness, and seizures.
