Difference between revisions of "Neuro Exam of The Horse - Pathology"
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− | + | [[Neurological Examination of Horses Overview]] | |
+ | |||
+ | |||
+ | [[Neurological Examination Initial Observation - Horse]] | ||
+ | |||
+ | ==[[Cranial Nerve Examination - Horse]]== | ||
+ | |||
+ | |||
+ | ==[[Body, Spinal Cord and Limb Neurological Examination - Horse]]== | ||
+ | |||
+ | |||
+ | |||
+ | ==[[Site of Spinal Lesions Determination - Horse]]== | ||
+ | |||
+ | * If there are no brain or brainstem signs, an animal with ataxia or weakness is most likely to have a lesion in the spinal cord. | ||
+ | * The spinal reflexes used in small animals to assess specific segments are not very useful in adult horses. | ||
+ | ** However, withdrawal reflexes are useful in recumbent horses with severe lesions. | ||
+ | *** A stimulus is applied to the distal limb and the reflex results in limb withdrawal. | ||
+ | |||
+ | ===Cervical Lesions=== | ||
+ | |||
+ | * Cervical lesions occur from C1 to C5 | ||
+ | ** C6 and C7 may also be included. | ||
+ | * Horses with defects in all four legs are most likely to have a cervical lesion. | ||
+ | * The pelvic limbs tend to be more severely affected than the thoracic limbs. | ||
+ | ** This is due to the topographical arrangement of the white matter tracts in the spinal cord. | ||
+ | |||
+ | ====Effects on Reflexes==== | ||
+ | |||
+ | * Cervicofacial reflex | ||
+ | ** The cervicofacial reflex is tested by lightly stimulating the skin of the lateral neck. | ||
+ | *** In an intact reflex movement of the lips should be observed. | ||
+ | *** This reflex varies widely between individual horses. | ||
+ | *** This is not intact in cervical lesions. | ||
+ | * Withdrawal reflexes | ||
+ | ** Only of use in recumbent horses. | ||
+ | ** In cervical lesions, reflexes in both thoracic and pelvic limbs may be exaggerated. | ||
+ | *** This is due to a loss of upper motor neuron inhibition. | ||
+ | |||
+ | ===Brachial Lesions=== | ||
+ | |||
+ | * Brachial lesions occur from C6 to T2. | ||
+ | * Signs of a spinal lesion at this level differ in the thoracic and pelvic limbs. | ||
+ | ** Thoracic limbs | ||
+ | *** Lower motor neuron signs | ||
+ | **** Weakness | ||
+ | ***** May be mild | ||
+ | ***** May manifest unwillingness to take the weight on the other thoracic limb when one is picked up. | ||
+ | **** Muscle atrophy | ||
+ | *** Withdrawal reflex in recumbent animals may be reduced. | ||
+ | ** Pelvic limbs | ||
+ | *** Ataxia | ||
+ | *** Upper motor neuon weakness | ||
+ | **** For example, swaying and stumbling. | ||
+ | *** Withdrawal reflex in recumbent animals may be exaggerated. | ||
+ | |||
+ | ===Thoraco-lumbar Lesions=== | ||
+ | |||
+ | * Thoraco-lumbar lesions occur in the segments T3 to L3 of the spinal cord. | ||
+ | * In an animal that has pelvic limb ataxia and weakness but no thoracic limb involvement, the lesion will be between T2 and L3. | ||
+ | ** I.e. caudal to the brachial plexus. | ||
+ | ** The animal should be closely examined for symmetry over the gluteals and pelvic limbs. | ||
+ | *** If there is symmetry, the lesion is likely to be at this level. | ||
+ | *** If there is no symmetry, the lesion is likely to be more caudal, and involve the pelvic outflow. | ||
+ | * Asymmetry may be detected in the cutaneous trunic reflex. | ||
+ | ** This is tested by lightly stimulating the skin of the lateral thorax. | ||
+ | * The withdrawal reflex in the pelvic limb may be exaggerated. | ||
+ | * Flexibility of the thoracolumbar spine may be assessed. | ||
+ | ** The skin of the longissimus musculature is firmly stimulated, and observed for: | ||
+ | *** A lordotic movement over the thorax and cranial lumbar region, and | ||
+ | *** A kyphotic movement over the caudal lumbar region and gluteals. | ||
+ | |||
+ | ===Lumbosacral Lesions=== | ||
+ | |||
+ | * Lumbosacral lesions occur between the segments L4 and S3. | ||
+ | * Horses with such lesions may: | ||
+ | ** Exhibit atrophy of one or more muscles of the pelvic region, and so | ||
+ | ** Be easy to pull over when standing, and | ||
+ | ** Be unwilling or unable to take weight on the affected side when the other limb is lifted. | ||
+ | * More caudal lesions may: | ||
+ | ** Affect the anal and perineal reflexes. | ||
+ | *** These are tested by lightly stimulating the skin surrounding the anus and observing for a reflex contraction of the anal sphincter. | ||
+ | ** Cause paresis of the tail. | ||
+ | * The withdrawal reflex may be reduced or absent in the pelvic limb. | ||
+ | |||
+ | ===Sacral Lesions=== | ||
+ | |||
+ | * Damage to the savral spinal cord can affect bladder function and control of defaecation. | ||
+ | |||
+ | ====Bladder Incontinence==== | ||
+ | |||
+ | * The bladder is reflexely controlled, via higher order neurones in the caudal brainstem and cerebrum, by the: | ||
+ | ** Pelvic nerve | ||
+ | *** Parasympathetic fibres leave the spinal cord in the sacral segments and combine to form the pelvic nerve. | ||
+ | **** These fibres innervate the smooth detrusor muscle of the bladder wall. | ||
+ | ** Pudendal nerve | ||
+ | *** The pudendal nerve innervates the striated muscle of the bladder neck. | ||
+ | * During micturition, the bladder is evacuated as: | ||
+ | ** The striated muscle is relaxed. | ||
+ | ** Stimulation of the pelvic nerve causes the detrusor smooth muscle to contract. | ||
+ | |||
+ | ====Faecal Incompetence==== | ||
+ | |||
+ | * Lesions in the sacral region may also be manifest as faecal incompetence. | ||
+ | ** In horses, problems are usually caused by defects in the lower motor neurons in the pelvic nerve. | ||
+ | *** Faeces is retained. | ||
+ | |||
+ | |||
+ | [[Category:Neurological Examination - Horse]] |
Revision as of 12:51, 10 March 2011
Neurological Examination of Horses Overview
Neurological Examination Initial Observation - Horse
Cranial Nerve Examination - Horse
Body, Spinal Cord and Limb Neurological Examination - Horse
Site of Spinal Lesions Determination - Horse
- If there are no brain or brainstem signs, an animal with ataxia or weakness is most likely to have a lesion in the spinal cord.
- The spinal reflexes used in small animals to assess specific segments are not very useful in adult horses.
- However, withdrawal reflexes are useful in recumbent horses with severe lesions.
- A stimulus is applied to the distal limb and the reflex results in limb withdrawal.
- However, withdrawal reflexes are useful in recumbent horses with severe lesions.
Cervical Lesions
- Cervical lesions occur from C1 to C5
- C6 and C7 may also be included.
- Horses with defects in all four legs are most likely to have a cervical lesion.
- The pelvic limbs tend to be more severely affected than the thoracic limbs.
- This is due to the topographical arrangement of the white matter tracts in the spinal cord.
Effects on Reflexes
- Cervicofacial reflex
- The cervicofacial reflex is tested by lightly stimulating the skin of the lateral neck.
- In an intact reflex movement of the lips should be observed.
- This reflex varies widely between individual horses.
- This is not intact in cervical lesions.
- The cervicofacial reflex is tested by lightly stimulating the skin of the lateral neck.
- Withdrawal reflexes
- Only of use in recumbent horses.
- In cervical lesions, reflexes in both thoracic and pelvic limbs may be exaggerated.
- This is due to a loss of upper motor neuron inhibition.
Brachial Lesions
- Brachial lesions occur from C6 to T2.
- Signs of a spinal lesion at this level differ in the thoracic and pelvic limbs.
- Thoracic limbs
- Lower motor neuron signs
- Weakness
- May be mild
- May manifest unwillingness to take the weight on the other thoracic limb when one is picked up.
- Muscle atrophy
- Weakness
- Withdrawal reflex in recumbent animals may be reduced.
- Lower motor neuron signs
- Pelvic limbs
- Ataxia
- Upper motor neuon weakness
- For example, swaying and stumbling.
- Withdrawal reflex in recumbent animals may be exaggerated.
- Thoracic limbs
Thoraco-lumbar Lesions
- Thoraco-lumbar lesions occur in the segments T3 to L3 of the spinal cord.
- In an animal that has pelvic limb ataxia and weakness but no thoracic limb involvement, the lesion will be between T2 and L3.
- I.e. caudal to the brachial plexus.
- The animal should be closely examined for symmetry over the gluteals and pelvic limbs.
- If there is symmetry, the lesion is likely to be at this level.
- If there is no symmetry, the lesion is likely to be more caudal, and involve the pelvic outflow.
- Asymmetry may be detected in the cutaneous trunic reflex.
- This is tested by lightly stimulating the skin of the lateral thorax.
- The withdrawal reflex in the pelvic limb may be exaggerated.
- Flexibility of the thoracolumbar spine may be assessed.
- The skin of the longissimus musculature is firmly stimulated, and observed for:
- A lordotic movement over the thorax and cranial lumbar region, and
- A kyphotic movement over the caudal lumbar region and gluteals.
- The skin of the longissimus musculature is firmly stimulated, and observed for:
Lumbosacral Lesions
- Lumbosacral lesions occur between the segments L4 and S3.
- Horses with such lesions may:
- Exhibit atrophy of one or more muscles of the pelvic region, and so
- Be easy to pull over when standing, and
- Be unwilling or unable to take weight on the affected side when the other limb is lifted.
- More caudal lesions may:
- Affect the anal and perineal reflexes.
- These are tested by lightly stimulating the skin surrounding the anus and observing for a reflex contraction of the anal sphincter.
- Cause paresis of the tail.
- Affect the anal and perineal reflexes.
- The withdrawal reflex may be reduced or absent in the pelvic limb.
Sacral Lesions
- Damage to the savral spinal cord can affect bladder function and control of defaecation.
Bladder Incontinence
- The bladder is reflexely controlled, via higher order neurones in the caudal brainstem and cerebrum, by the:
- Pelvic nerve
- Parasympathetic fibres leave the spinal cord in the sacral segments and combine to form the pelvic nerve.
- These fibres innervate the smooth detrusor muscle of the bladder wall.
- Parasympathetic fibres leave the spinal cord in the sacral segments and combine to form the pelvic nerve.
- Pudendal nerve
- The pudendal nerve innervates the striated muscle of the bladder neck.
- Pelvic nerve
- During micturition, the bladder is evacuated as:
- The striated muscle is relaxed.
- Stimulation of the pelvic nerve causes the detrusor smooth muscle to contract.
Faecal Incompetence
- Lesions in the sacral region may also be manifest as faecal incompetence.
- In horses, problems are usually caused by defects in the lower motor neurons in the pelvic nerve.
- Faeces is retained.
- In horses, problems are usually caused by defects in the lower motor neurons in the pelvic nerve.