Chapter 50 - Anatomy and physiology of neurologic system Flashcards
1
Q
What is the 2 goals of a neurologic examination in horses?
A
o determine if the horse is neurologically normal or abnormal.
To determine neuroanatomical localization of the abnormality
2
Q
List three factors that help in formulating a list of possible causes of neurologic issues in horses.
A
1) Signalment,
2) onset and duration of signs, 3)
presence or absence of pain and fever.
3
Q
Name three aspects that must be evaluated in a neurologic examination.
A
Behaviour
Cranial nerves
gait evaluation
4
Q
What is the central nervous system (CNS) composed of?
A
The brain and spinal cord.
4
Q
What must be evaluated in horses suspected of lacking voluntary movement?
A
Nociception (pain perception)
5
Q
What does the peripheral nervous system include?
A
Nerve roots, ganglia, cranial and spinal nerves, and neuromuscular junctions.
6
Q
What are the embryologic divisions of the forebrain?
A
Telencephalon and diencephalon.
6
Q
Which structures form the cauda equina?
A
Sacral and caudal nerve roots and nerves.
7
Q
What are the three divisions of the autonomic nervous system?
A
Sympathetic, parasympathetic, and intrinsic enteric plexuses.
7
Q
What brain regions are part of the hindbrain (rhombencephalon)?
A
Metencephalon (pons and cerebellum) and myelencephalon (medulla oblongata).
8
Q
What structure runs ventral to the neural crest?
A
The notochord.
8
Q
What is the primary embryological structure from which the nervous system develops?
A
The neural plate.
9
Q
How is the brain functionally divided?
A
Cerebrothalamus
brain stem
cerebellum
10
Q
How does the midbrain (mesencephalon) affect the neural canal?
A
The development of the midbrain reduces the neural canal to a narrow tube called the mesencephalic aqueduct.
10
Q
What structures are formed from the rostral part of the neural tube?
A
The rostral neural tube forms the cerebrum (telencephalon), thalamus, and hypothalamus (diencephalon).
10
Q
How does the neural tube form from the neural crest?
A
The neural crest folds upward and medially, meeting in the midline to form the neural tube.
11
Q
What does the neural canal eventually form?
A
The neural canal forms the ventricular system, including the third and lateral ventricles.
11
Q
In which directions does the neural tube close, starting from the brain–spinal cord junction?
A
The neural tube closes progressively in both rostral and caudal directions.
12
Q
What parts of the hindbrain are developed from the rostral and caudal regions?
A
The rostral hindbrain forms the pons and cerebellum, while the caudal part forms the medulla oblongata.
13
Q
A
13
Q
How are primitive neurons within the spinal cord organized?
A
They are organized into mantle and marginal layers, which become gray and white matter, respectively.
13
Q
What are the three regions of white matter in the spinal cord, and how are they divided?
A
The regions are called funiculi and are divided into dorsal, lateral, and ventral sections.
14
Q
What bones make up the cranium?
A
parietal,
ethmoid,
interparietal,
frontal
occipital,
sphenoid,
temporal bones PEIFOST
14
Q
A
15
What structure attaches to the internal occipital protuberance?
The tentorium cerebelli, a tent-shaped dura mater extension.
16
What is the approximate volume of the cranial cavity in an adult horse?
Approximately 650 mL.
17
What structure separates the cranial cavity’s rostral and caudal concavities?
The internal occipital protuberance.
18
Which bones encase the cerebellum dorsally and laterally?
The occipital and petrous temporal bones.
19
What can happen to the cerebral lobes due to forebrain swelling?
They may herniate under the falx (subfalcine herniation) or the tentorium (transtentorial herniation).
19
What structure in the cranial cavity supports the frontal and olfactory parts of the cerebrum?
The rostral fossa.
20
What bone forms the majority of the rostral fossa?
The sphenoid bone.
20
What structure is attached to the internal parietal crest?
The falx cerebri.
20
What structure passes through the foramina in the cribriform plate?
Olfactory nerve bundles.
21
What is the role of the cribriform plate of the ethmoid?
It forms the rostral wall of the cranial cavity and separates it from the nasal cavity.
22
What cranial nerves pass through the medial groove in the middle cranial fossa?
Cranial nerves III, IV, V (ophthalmic branch), and VI.
22
Figure 50-2. Simplified diagram of the functional (left) and anatomic (right) organization of the spinal cord at the level of the seventh cervical segment. a, Dorsal funiculus of the white matter; b, dorsal root; c, dorsal column of the gray matter; d, intermediate column of the gray matter; e, lateral funiculus of the white matter; f, ventral column of the gray matter; g, ventral root; h, ventral funiculus of the white matter; i, upper motor neuron (descending) tracts; j, sensory/pain (ascending) tracts; k, proprioceptive (ascending) tracts.
23
Figure 50-3. Sagittal section of cranium. a, Frontal bone; b, parietal bone; c, occipital bone (squamous part); d, paramastoid process; e, basioccipital bone; f, basisphenoid bone; g, hypoglossal foramen; h, foramen lacerum; i, internal acoustic meatus; k, spinous notch; l, oval notch; m, carotid notch; n, groove for maxillary nerve; o, optic foramen; p, sphenoidal sinus; q, central compartment sphenoidal sinus; r, perpendicular plate of ethmoid bone; s, septum between frontal sinuses; t, orbital wing of sphenoid bone; u, temporal wing of sphenoid bone; v, internal occipital protuberance.
24
What is the function of the foramen lacerum?
It provides passage for cranial nerves V (mandibular branch), IX, X, and XI.
25
Where is the hypophyseal fossa located?
In the middle cranial fossa.
26
What cranial nerve passes through the hypoglossal foramen?
Cranial nerve XII.
27
What muscles attach to the ventral tubercles on the basilar bones?
The rectus capitis ventralis and longus capitis muscles.
28
What condition can result from remodeling and fusion of the temporohyoid joint?
Temporohyoid osteoarthropathy.
29
What are the two main parts of the temporal bone?
The squamous and petrous bones.
30
Which cranial nerves pass through the internal acoustic meatus?
Cranial nerves VII and VIII.
31
What is housed within the petrous part of the temporal bone?
The cavities and specialized bones of the auditory and vestibular systems.
32
What happens in a transforamen magnum herniation?
The caudal part of the cerebellum is squeezed through the foramen magnum.
33
When does the sphenooccipital synchondrosis typically fuse in horses?
Around 5 years of age.
33
What type of joints are between the plates of the cranium?
Immobile synarthroses.
34
What are the five regions of the vertebral column?
Cervical, thoracic, lumbar, sacral, and coccygeal.
35
What is the typical formula of the vertebral column in horses?
C7, T18, L6, S5, Cy15-21.
36
What are the components of each vertebra?
A body, an arch, and various processes.
37
What is the function of the vertebral foramen?
It protects the spinal cord, nerve roots, and cauda equina.
38
What structures make up the ventral column of the vertebral column?
The ventral longitudinal ligament and the ventral half of the vertebral bodies and discs.
39
What is the relationship between column injury and prognosis for recovery?
As more columns are impacted, the prognosis for recovery decreases.
40
Where are fractures most commonly reported in racing Thoroughbred and Quarter Horses?
The axis and third cervical vertebra.
41
What are the shapes of the cervical vertebrae’s articular processes?
Cranial articular processes are dorsomedially directed, posterior ones are ventrolaterally directed.
42
What is cervical vertebral stenotic myelopathy commonly called in horses?
"Wobblers."
43
What are the main components of the atlas?
Dorsal and ventral arches, lateral processes, and wings.
44
Where does the dens project from and what supports it?
It projects from the body of the axis and rests on the fovea dentis of the atlas.
45
What type of motion is the cranial cervical area vulnerable to?
Hyperflexion, hyperextension, and axial compressive forces.
46
What structure provides additional stability to the thoracic vertebrae?
The bracing action of the ribs and sternum.
47
How is the sacrum formed?
By the fusion of five sacral vertebrae.
48
What condition can result from injury to the sacral nerves?
Cauda equina syndrome or gait abnormalities in the pelvic limbs.
49
What are the ossification centers in each vertebra?
One body, two arches, and physeal plates at either end of the body.
50
What condition is commonly associated with the facet joints in young horses?
Arthropathy, often due to vertebral malformation.
51
The sphenooccipital synchondrosis fuses at what age?
at 5 years old
52
The sutures of parietal bones ossify when?
The suture between the parietal bones ossifies at 4 years, the parietooccipital suture at 5 years, and the parietotemporal suture at 12 to 15 years.
53
What is the vertebral formula of the horse?
C7, T18, L6, S5, Cy15-21.
54
What structures are formed by the arch of each vertebra?
Two lateral pedicles and a dorsal lamina.
55
What is the purpose of the intervertebral foramina?
Provides passage for spinal nerves and vessels.
56
What forms the vertebral canal?
Successive vertebrae joined by dorsal and ventral longitudinal ligaments.
56
Which column primarily contains the vertebral bodies and discs?
The ventral column.
57
What are the three columns in the biomechanical model of the spine?
Ventral, middle, and dorsal columns.
57
How is the prognosis affected by injury to multiple spinal columns?
The prognosis for recovery decreases as more columns are impacted.
58
Which cervical vertebrae are most commonly fractured in racing horses?
The axis (C2) and the third cervical vertebra.
59
What are the typical curvatures of the vertebral column in the median plane?
Cervical (concave ventrally), cervicothoracic junction (concave dorsally), thoracolumbar (gentle ventral concavity), and lumbosacral (more marked ventral concavity).
59
What happens to vertebral canal diameter along the vertebral column?
It varies, with expansions at the cervicothoracic and lumbosacral regions.
60
What is a characteristic of the cervical vertebrae?
Large and long with a thick, strong arch.
60
What condition results from cervical vertebral malformation in horses?
Cervical vertebral stenotic myelopathy, also known as “wobblers.”
61
What modification helps the first two cervical vertebrae support head movements?
The atlas has dorsal and ventral arches and lateral processes, while the axis has a dens that rests on the atlas.
62
What condition can result from severe cervical compression in young horses?
Cervical vertebral stenotic myelopathy.
63
Which ligament attaches the dens to the atlas and occiput?
Ligamentum longitudinale dentis
64
Which region of the vertebral column is most constrained in movement?
The thoracic region.
65
What adds stability to the thoracic vertebrae?
The ribs and sternum.
66
What type of injury may occur in the thoracolumbar region?
Fractures or dislocations.
67
How is the sacrum formed?
By fusion of five sacral vertebrae.
68
What can result from sacral fractures?
Cauda equina syndrome or gait abnormalities.
68
What are the primary sources of CSF production?
Choroid plexus,
ependymal lining,
pia mater,
leptomeningeal capillaries.
69
What is the estimated CSF formation rate in mammals?
Approximately 0.02 to 0.5 mL/min.
70
What influences CSF formation?
Osmotic pressure in blood, such as hyponatremia or hypernatremia.
71
How does CSF pass from production sites to circulation?
It flows from the ventricles over the cerebrum and down the spinal cord.
72
What determines CSF absorption?
Pressure-dependent flow through arachnoid villi into cerebral veins or venous sinuses.
73
How does CSF composition differ from plasma?
Lower in potassium and calcium, higher in chloride, sodium, and magnesium.
74
What diagnostic value does CSF composition provide?
Changes in CSF composition can indicate CNS diseases.
75
What is the blood-brain barrier composed of?
Basal lamina
Endothelial cells,
Pericytes,
Astrocytes,
76
What junctions contribute to the blood-brain barrier?
Continuous tight junctions between endothelial cells.
77
What role do astrocytes play in the blood-brain barrier?
They support and maintain barrier function with their foot processes.
78
What is the function of monoamine oxidases in the blood-brain barrier?
Degradation of compounds like epinephrine.
79
What is the purpose of the Na/K-ATPase pump in the blood-brain barrier?
Regulates sodium and potassium ion levels.
80
How does lipid solubility affect a molecule's ability to cross the blood-brain barrier?
Higher lipid solubility enhances passive diffusion into the CNS.
81
What is one barrier that prevents immunoglobulins from entering the CNS?
The blood-CNS barrier.
82
What primary cellular mechanism drives the nervous system's function?
Electrical signal propagation through cell membrane potential changes.
83
Which ions primarily establish the resting membrane potential in neurons?
K+ ions flowing through resting channels and the Na+/K+-ATPase pump.
84
Which neurotransmitter is primarily excitatory in relay systems?
L-glutamate.
84
Which ion channel opening causes neuronal depolarization?
Opening of Na+ or Ca2+ channels.
85
What triggers an action potential in neurons?
Local potentials reaching the threshold for voltage-gated Na+ channel opening.
86
What is the effect of opening K+ and Cl- channels on neuron excitability?
It decreases neuronal excitability.
87
What inhibitory neurotransmitters are used in local circuits along relay pathways?
GABA and glycine.
88
Name a medical application being explored involving glutamatergic neurotransmission.
Brain injury therapy using glutamatergic system inhibitors.
89
What enzyme synthesizes GABA from glutamate?
Glutamic acid decarboxylase (GAD).
90
What condition in horses is associated with impaired GABAergic transmission?
Stiff-horse syndrome, associated with GAD autoantibodies.
91
List one neurotransmitter involved in diffuse projection systems.
Dopamine.
92
What is the ARAS and its main function?
The ascending reticular activating system, which activates the cerebral cortex for wakefulness.
93
Where is the ARAS primarily located?
In the rostral half of the brainstem, extending into the medulla.
94
What type of brain lesion is more likely to cause obtundation?
Focal or extensive lesions in the brainstem.
95
What is the main function of the upper motor neuron (UMN) system?
Initiating voluntary movement and regulating posture.
96
What are signs of UMN injury in horses?
Limb spasticity, weakness, and hyperactive reflexes.
96
Which brain region contributes most directly to fine motor control in horses?
The pyramidal system for controlling the muzzle and lips.
97
What movement disorder is linked to the neurotoxin repin in horses?
Nigropallidal encephalomalacia.
98
Which plant toxins cause nigropallidal encephalomalacia in horses?
Yellowstar thistle and Russian knapweed.
99
Name a structure within the limbic system involved in behavior.
Amygdala
99
What brain system primarily influences behavior in the forebrain?
The limbic system.
100
What is a seizure, in terms of neural activity?
A transient paroxysmal event due to abnormal depolarization in the cerebral cortex.
101
Which brain area commonly initiates seizures affecting motor control?
The frontal (motor) cortex.
102
What is one sign of a generalized seizure in horses?
Sudden recumbency with extensor tonus and limb movements.
103
Name an extracranial cause of seizures in horses.
Hyperammonemia or hypernatremia.
104
What characterizes juvenile idiopathic epilepsy in Arabian foals?
Generalized seizures without other brain disease evidence in young foals.
105
What is the neurotransmitter dysfunction linked to fluphenazine reactions in horses?
Cholinergic dysfunction.
106
Which CNS component is mostly responsible for voluntary muscle movements?
The upper motor neuron (UMN) system.
107
Describe the primary difference between pyramidal and extrapyramidal systems in horses.
The pyramidal system provides fine motor control, while the extrapyramidal system controls generalized movement.
108
Which neurotransmitter pathway is frequently targeted in psychiatric treatments?
The dopaminergic pathway.
109
What structural component forms the blood-brain barrier?
Tight junctions between endothelial cells in CNS capillaries.
110
What results from unilateral lesions in the sensory parts of the forebrain?
Contralateral facial hypalgesia (reduced pain perception).
111
What is the main cortical area for conscious pain perception, and where is it located?
The sensory (somesthetic) cortex, located primarily in the parietal lobe.
112
What pathway does smell information take after the olfactory bulb?
It passes to the piriform lobe and through the thalamus to both the limbic system and conscious cerebrum.
113
What percentage of optic nerve fibers cross at the optic chiasm in horses?
80% to 90%.
114
What type of blindness results from lesions caudal to the optic chiasm?
Blindness in the opposite (contralateral) eye.
115
What additional pathway is necessary for the menace response, apart from the visual pathway?
Functional facial nerve and cerebellar cortex integrity.
116
Where do cranial nerves responsbile for eye position (III, IV, VI) have origin?
originate in the midbrain and pons.
116
What occurs if there is damage to the midbrain or oculomotor nerve affecting the pupil?
Mydriasis (dilated pupil) in the ipsilateral eye, unresponsive to light directed into either eye.
116
What serious sign indicates advanced cerebral injury in terms of pupillary response?
pupils often are miotic; progression to bilateral mydriasis, often signaling a poor/grave prognosis
116
Which cranial nerves are responsible for eye position,
Cranial nerves III (oculomotor), IV (trochlear), and VI (abducens) control eye position
116
What are the signs of Horner syndrome due to sympathetic nerve disruption?
Miosis, enophthalmos, ptosis, spontaneous sweating, and vasodilation on the affected side of the face.
117
What type of strabismus persists regardless of head position, and what might it indicate?
Strabismus from lesions in extraocular nerves (III, IV, VI), which persists in any head position.
118
What nerve damage results in mydriasis or defective eyeball retraction, and how can this help localize a lesion?
Damage to CN III can cause mydriasis, while CN VI damage affects eyeball retraction, helping localize lesions.
119
What are the clinical signs of unilateral versus bilateral damage to the trigeminal nerve affecting mastication?
Unilateral damage causes jaw deviation toward the normal side; bilateral damage results in a dropped jaw, weak jaw tone, and inability to chew.
120
How can facial nerve damage near the middle ear affect tear production?
Damage to parasympathetic fibers in the facial nerve may reduce tear production due to its control of lacrimal glands.
121
What is the Schirmer tear test, and what is considered normal in horses?
A test to measure tear production; ≥20 mm/min is normal in horses.
122
Which diseases might commonly affect both the facial and vestibulocochlear nerves?
West Nile virus encephalomyelitis, EEE, EPM, temporohyoid osteoarthropathy, among others.
122
What structures provide sensory input for the facial nerve's “flick” reflexes?
Trigeminal neurons provide sensory input that terminates in the medulla and activates facial nerve motor responses.
123
Describe how unilateral vestibular disease typically affects a horse’s movement and posture.
Causes asymmetric ataxia, head tilt, and leaning/falling toward the lesion, with circling possible.
123
What role does the vestibular system play in body orientation and which structures are involved?
It orients the body relative to gravity, with the bony labyrinth, semicircular ducts, and vestibular nuclei involved.
124
How does nystagmus differ between peripheral and central vestibular disease?
In peripheral disease, nystagmus is conjugate, horizontal, or rotatory; in central disease, it may be vertical and directional.
125
What are typical signs of bilateral vestibular disease in horses?
Severe symmetric ataxia with wide, sweeping head movements.
126
What causes deafness in foals, and how does it differ from causes in adult horses?
Foal deafness may result from sepsis, encephalopathy, or congenital malformations, while adults may suffer from temporohyoid osteoarthropathy or otitis.
127
Which cranial nerves contribute to taste sensation and what areas do they innervate?
CN VII (facial) for the anterior two-thirds of the tongue, CN IX (glossopharyngeal) for the posterior third, and CN X (vagus) for the pharynx and palate.
128
Why are deficiencies in the sense of taste difficult to detect clinically in horses?
Taste perception involves complex forebrain processing and lacks reliable clinical tests for detection.
129
what is the cranial nerve reponsible for pain perception?
Parietal cortex, cranial nerve V
The pathways for pain perception in the head pass through the maxillary, ophthalmic, and mandibular branches of the ipsilateral trigeminal nerve and nuclei
130
what is the cranial nerve responsible for smell?
Olfactory bulbs, cranial nerve I
Receptors for olfaction are located in the olfactory neuroepithelium in the ethmoturbinatesI
131
Nerves responsible for vision
Vision (Occipital Cortex, Thalamus, Cranial Nerve II)
In horses, 80% to 90% of optic nerve fibers from one eye cross at the optic chiasm
132
What are the nerves responsible for pupil light reflex?
Pupillary Light Reflex, Pupil Size (Midbrain,
Cranial Nerves II, III)
133
Nerves responsible for eye position
Eye Position (Midbrain; Pons; Cranial Nerves III, IV, VI, Input From VIII [Vestibular])
Originating from nuclei in the midbrain and pons, the oculomotor, trochlear, and abducens nerves exit the cranial cavity through the orbital fissure and ramify in the periorbital tissues to innervate the rectus and oblique muscles of the eye
134
Nerve responsible for mastigation
Mastication (Pons, Cranial Nerve V)
The LMNs of the trigeminal nerve arise in the pons and pass through the petrous temporal bone and the foramen ovale adjacent to sensory trigeminal neurons and are distributed to the muscles of mastication: masseters, pterygoids, temporalis, and rostral digastricus.
135
Nerves responsbile for facial expressions
Facial Expression and Movement
(Medulla, Cranial Nerve VII)
Normal facial tone, expression, and movements are dependent upon the integrity of the facial nerves. These nerves arise from nuclei in the rostral medulla (hindbrain) and exit the calvarium with cranial nerve VIII via the internal acoustic meatus.
136
Nerves responsible for balance and standing, hearing
Balance and Equilibrium, Hearing (Medulla, Cranial Nerve VIII [Auditory])
The vestibular system is responsible for orientation of the horse relative to gravity. The receptor is in the bony labyrinth of the inner ear.
137
Nerves responsible for taste
Taste (Cranial Nerves VII, IX, X)
Taste buds are found on the surface of the tongue and also in the soft palate, pharynx, lips, and cheeks. Sensory gustatory innervation is provided by the facial nerve (rostral two thirds of the tongue), glossopharyngeal nerve (caudal one third of the tongue), and vagus (pharynx and palate).
138
Nerves responsible for pharynx and larynx complex
Movement of Pharynx and Larynx
(Cranial Nerves IX, X, XI)
Motor innervation of the larynx and pharynx originates in neurons in the nucleus ambiguus, a fusiform structure extending the length of the medulla. This nucleus provides axons for the glossopharyngeal, vagus, and spinal accessory (internal branch) nerve roots. These roots form nerves that innervate the soft palate, pharynx, larynx, and cranial esophagus via the pharyngeal plexus and cranial and recurrent laryngeal nerves.
139
140
Tongue Movement is provided by which nerve?
Tongue Movement (Cranial Nerve XII)
The muscles affecting movement of the tongue are supplied by the hypoglossal nerve
141
What is the normal value for Schirmer test in horses?
Schirmer tear test (normal in the horse ≥20 mm/min)
142
Seizures frequently originate in the frontal (motor) cortex and involve muscle fasciculations and tremors around the head or abnormal movements of the jaws and tongue (“chewing gum fits”).
Examples of intracranial causes include skull trauma, juvenile idiopathic epilepsy, equine neonatal encephalopathy, equine protozoal myeloencephalitis (EPM—rare to cause seizures), EEE, intracranial neoplasia, and aberrant parasite migration. Causes external to the brain include hyperammonemia, hyponatremia, hypernatremia, hyperthermia, and hepatic or renal failure. Juvenile epilepsy of Arabian foals occurs because of transiently increased susceptibility to seizures
143
what caratherizes the convulsions in foals? what is the cause?
Convulsions characteristic of neonatal encephalopathy often are of this type. In their severest (generalized) form, seizures manifest as sudden recumbency, with a brief phase of extensor tonus, followed by clonic (“galloping”) movements of the limbs, loss of consciousness, and a variety of signs of autonomic discharge (e.g., sweating, urination, defecation, pupillary dilation).
144
what can cause blindness in a horse? Vision (Occipital Cortex, Thalamus, Cranial Nerve II)
Any disease that causes diffuse, severe cerebral dysfunction is likely to cause blindness. Examples include EEE, postseizure encephalopathy, hyperammonemia, leukoencephalomalacia, and frontal/parietal trauma.
145
Midbrain Pupillary Light Reflex, Pupil Size (Midbrain,Cranial Nerves II, III) lesions responsible for alteration?
Interruption of pre- or postganglionic sympathetic nerves to the eye causes Horner syndrome characterized by miosis, enophthalmos, ptosis, spontaneous sweating, and vasodilatation (also increased temperature of the skin and ears) over the side of the face
146
Facial Expression and Movement
(Medulla, Cranial Nerve VII)
Normal facial tone, expression, and movements are dependent upon the integrity of the facial nerves. Lesion here can be caused by...
Examples of diseases that often affect both nerves are West Nile virus encephalomyelitis, EEE, EPM, migrating parasite (central), polyneuritis equi, lightning strike, petrous temporal bone fracture, temporohyoid osteoarthropathy, or extramedullary neoplasm (peripheral). To distinguish clinically between central and peripheral causes, it is important to look for other signs of brain disease. For example, a horse with a lesion in the medulla affecting the nuclei of cranial nerves VII and VIII, may also be obtunded with gait and proprioceptive deficits of ipsilateral limbs.
147
Common causes of auditory issues (VIII) deafness
The most common causes of deafness in adult horses include temporohyoid osteoarthropathy, congenital sensorineural deafness in Paint horses, multifocal brain disease because of various etiologies, and otitis media/interna.30 Deafness could be bilateral or unilateral depending on the cause. Deafness in foals has been reported with sepsis, neonatal encephalopathy, neonatal isoerythrolysis, prematurity, and associated with specific coat color patterns such as completely or mostly white with blue irides or lavender with pale yellow irides
148
Diseases that can cause hemiplegia laryngea
In horses with bilateral laryngeal paralysis, inspiratory stridor occurs at rest and aspiration pneumonia may develop. Some or all of these pathways can be affected peripherally in horses with botulism, guttural pouch mycosis, extramedullary neoplasia, or basilar skull fracture. Examples of diseases affecting the hindbrain that may cause laryngeal or pharyngeal dysfunction are EEE, EPM, leukoencephalomalacia, bacterial meningitis, and West Nile viral encephalomyelitis (WNVE).
149
Tongue hemiparesia
The nerve can be damaged by extramedullary neoplasia, upper cervical or caudal skull trauma, or guttural pouch mycosis. Tongue hemiplegia and atrophy has been seen in horses with EPM. The nerve can be damaged by extramedullary neoplasia, upper cervical or caudal skull trauma, or guttural pouch mycosis. Tongue hemiplegia and atrophy has been seen in horses with EPM
150
Horses that seem to float walking and spastic paresis what can be the cause?
Spastic paresis is especially common with focal compression of the cervical spinal cord in horses with cervical stenotic myelopathy (CSM) or spinal cord trauma. Other important causes of UMN disease (in the spinal cord) include EPM, equine neuroaxonal dystrophy/degenerative myeloencephalopathy (NAD/EDM), spinal cord abscess or tumor, and aberrant parasite migration.
151
UMN lesions from C1 to T2 (inclusive) cause neurologic signs in
all four limbs,
152
esions caudal to S2 affect what?
do not directly affect gait.
153
lesions from T3 to S2 only affect
the pelvic limbs,
154
With external compression of the cervical spinal cord (as in CSM), signs typically are worse in the thoracic limbs or pelvic limbs?
pelvic limbs than in the thoracic limbs.
155
Where are LMNs for skeletal muscles located within the spinal cord?
In the ventral columns of the gray matter.
156
What forms the ventral root of the spinal cord, and where does it exit the vertebral canal?
LMNs originating from a spinal cord segment form the ventral root, exiting through the intervertebral foramen.
157
Describe the anatomical difference in nerve root exit points between cervical and caudal spinal segments.
Cervical nerve roots exit at the cranial end of each vertebra, while caudal roots exit at the caudal end.
158
What does the joining of the ventral root with the dorsal sensory root form?
The segmental spinal nerve.
159
What clinical signs are associated with LMN disease in horses?
Flaccid weakness, paresis/paralysis, hypotonia, hyporeflexia, and rapid muscle atrophy.
160
explain how muscle atrophy due to LMN disease develops over time.
Noticeable muscle atrophy occurs within 1-2 weeks and progresses rapidly.
161
List diseases affecting LMN function in horses.
Botulism, trauma, cauda equina syndrome, EPM, postanesthetic myelomalacia, and EMND.
162
What type of receptors are involved in proprioception?
Receptors in muscles, tendons, and joints.
163
Which pathways relay proprioceptive information to the cerebellum?
Spinocerebellar tracts.
164
What signs of proprioceptive deficits might you observe in a horse?
Base-wide/narrow stance, swaying trunk, and limb circumduction or interference.
165
Where do parasympathetic LMNs to the bladder originate?
In the intermediate column of sacral spinal segments S2-S4.
166
How does sympathetic innervation influence bladder function?
Sympathetic LMNs from L1-L4 innervate smooth muscle in the bladder body and neck, controlling storage.
167
What LMN controls the striated muscle of the urethra?
The pudendal nerve.
168
hat neurological conditions can cause urinary dysfunction in horses?
CSM, EPM, vertebral trauma, epidural abscess, EHV-1 myeloencephalopathy.
169
How does a spinal cord lesion cranial to S2 affect bladder function?
It causes a "spinal-reflex bladder," with intermittent voiding and urine retention.
170
What are clinical signs of sacral spinal cord injury affecting urination?
Atonic, distended bladder, overflow incontinence, and possible sabulous cystitis.
171
Which nerve innervates the striated muscle of the anus?
The pudendal nerve.
172
What is the role of spinothalamic pathways in sensory perception?
They carry pain, thermal, and touch information from peripheral receptors to the brain.
173
Which spinal cord segments are involved in the withdrawal reflex of the pelvic limb?
Segments L6 to S2.
