Chapter 51 - Diagnostic neuro disease Flashcards
1
Q
What basic equipment is required for a neurologic examination in horses?
A
A transilluminator, a hemostat, and a pleximeter or patella hammer (for neonates).
2
Q
hat are the four states of consciousness, and how is each characterized?
A
Normal (alert and responsive), obtunded (reduced alertness but responsive), stuporous (minimal responsiveness, needs painful stimuli), and comatose (unresponsive to all stimuli).
3
Q
What are typical abnormal behaviors associated with CNS disease in horses?
A
Self-mutilation, head-pressing, compulsive walking, hyperresponsiveness, aggression, and loss of learned behaviors.
4
Q
What does a head tilt indicate, and which structures are likely involved?
A
A head tilt often suggests vestibular labyrinth, vestibular nerve, or medulla oblongata/cerebellum involvement.
5
Q
How does head turning without tilting differ in neurologic implications?
A
It usually points to forebrain involvement, not vestibular dysfunction.
6
Q
What is the clinical significance of nystagmus direction in vestibular disease?
A
Horizontal or arc-shaped nystagmus with the fast phase directed away from the lesion indicates peripheral vestibular disease.
7
Q
How does proprioceptive deficit manifest in brainstem disease?
A
Deficits are typically ipsilateral due to affected tracts within the brainstem.
8
Q
Which cranial nerves are commonly associated with vestibular disease signs?
A
Cranial nerves VII (facial) and VIII (vestibulocochlear).
9
Q
What conditions are commonly associated with obtundation and ataxia in horses?
A
Equine protozoal myeloencephalitis (EPM), West Nile virus, trauma, and neoplasia.
10
Q
What behavior might indicate cerebellar cortical disease in horses?
A
Coarse or fine intentional head bobbing and a lack of menace response despite normal vision.
11
Q
How can examining head orientation provide clues to lesion location?
A
Head tilt suggests vestibular or cerebellar issues, while horizontal positioning or extended neck may suggest muscular or upper cervical problems.
12
Q
Describe an abnormal jaw response indicating masticatory muscle paresis.
A
A dropped jaw with tongue protrusion and easy separation of jaws indicates bilateral paresis.
12
Q
How is symmetry in temporalis muscle assessed?
A
How is symmetry in temporalis muscle assessed?
13
Q
What signs indicate pterygoid muscle atrophy?
A
Deepness of the supraorbital fossa on the atrophied side.
14
Q
What is the significance of a blank facial expression with drooping ears and eyelids?
A
It may indicate obtunded consciousness due to neurologic dysfunction, not systemic disease.
15
Q
Which signs suggest involvement of the thalamus in neurologic disease?
A
Behavioral changes, contralateral sensory deficits, and possibly central blindness.
16
Q
What role does video recording play in a neurologic examination?
A
It provides a medical record, assists with progressive conditions, and helps with intermittent events like seizures or gait deficits.
16
Q
A
Figure 51-2. Atrophy of the muscles of mastication in a horse with equine protozoal myeloencephalitis. Beginning about a month after foaling, this 11-year-old Thoroughbred mare had an insidious onset of ataxia and limb weakness. (A) Six weeks later, ataxia and weakness were worse, especially in the left limbs, and there was obvious atrophy of the masseter and temporalis muscles on the right side. (B) The lower jaw was deviated away from the affected side.
16
Q
A
Figure 51-3. Facial paralysis in a horse with polyneuritis equi (neuritis of the cauda equina). Over the previous 2 weeks, this 13-year-old Quarter Horse mare had several exacerbations and remissions of right-sided facial paralysis. Beginning 3 days ago, there were also signs of cauda equina syndrome, including a weak tail and paralysis of the anus.
17
Q
How does brainstem disease typically affect cranial nerve function?
A
It can cause multiple cranial nerve deficits, often affecting consciousness, proprioception, and vestibular function.
18
Q
What sensory condition may occur with injury to the proximal trigeminal nerve?
A
Hypalgesia, or reduced facial sensation, over one side of the face.
19
Q
What does weakness or atrophy of the muscles of mastication indicate?
A
It indicates involvement of the motor division of the trigeminal nerve, its roots, or the trigeminal motor nucleus in the pons.
20
Q
What additional signs may be observed with trigeminal damage at the level of the pons?
A
Signs of hindbrain disease, such as obtundation, cranial nerve dysfunction, and proprioceptive deficits.
21
Q
What are the physical signs of complete unilateral facial paralysis?
A
Drooping of the ear, upper eyelid (ptosis), lower lip, and asymmetry of external nares.
22
What reflexes are tested to evaluate facial nerve function?
"Flick" reflexes on the lips, eyes, and ears.
23
What anatomical structures are implicated if abnormalities of facial tone are present?
The facial nucleus in the medulla oblongata, facial nerve root, or its motor branches.
24
What does a reduced tear production on the affected side during the Schirmer tear test suggest?
A lesion affecting secretomotor fibers proximal (central) to the middle eaf
25
What common clinical sign is associated with facial paralysis involving the vestibular system?
Spontaneous nystagmus and head tilt.
26
What is indicated by reduced or absent responses to a noxious stimulus during sensory testing?
Involvement of the contralateral forebrain.
27
How is the menace response tested?
By making a threatening gesture toward the eye and observing the blinking response.
28
What clinical signs may accompany hemifacial hypalgesia due to forebrain disease?
Blindness, obtundation, and abnormal behaviors.
29
What role does the cerebellum play in the menace response pathway?
It provides essential input to the facial nucleus involved in the response.
30
What might a decreased menace response indicate regarding the lesion's location?
It can indicate a contralateral, central lesion in the forebrain.
31
What is a key sign of long-term facial paralysis affecting the parotidoauricularis muscle?
An obvious subcutaneous depression along the back of the mandible.
32
How can facial nerve dysfunction affect the cervicofacial reflex?
Its interpretation is influenced by the dysfunction, even though it is not a primary test for facial nerve function.
33
What are potential nonneurologic signs associated with facial paralysis?
Exposure keratitis or keratoconjunctivitis sicca, and inspiratory stridor during exercise.
34
What should be observed in normal neonates regarding menace response?
There is typically no menace response, but the horse can still see.
35
What abnormal behaviors might be observed in a horse with forebrain disease?
Compulsive walking in circles, seizures, and head and neck turn.
36
How can eyelid paralysis influence the menace response?
It can prevent the response, leading to an abnormal palpebral (eyelid flick) reflex.
37
What is the primary purpose of examining the pupils in subdued or dim light?
To allow easier appreciation of reflex constriction.
38
Define anisocoria.
Anisocoria refers to unequal pupillary size.
39
What does a constricted pupil indicate in veterinary terms?
A constricted pupil is termed miotic.
40
What is the significance of the dazzle reflex in equine eye examinations?
The dazzle reflex indicates eyelid closure in response to bright light, reflecting functional vision pathways.
41
Explain the pupillary light reflex (PLR).
The PLR is the immediate constriction of both pupils in response to light directed into one eye.
42
How does a lesion in the optic nerve affect the direct PLR and menace response?
A lesion in the optic nerve affects both the direct PLR and menace response on the same side.
43
What clinical signs are associated with mydriasis?
Mydriasis can result from increased sympathetic tone or damage to the oculomotor nerve, leading to fixed and dilated pupils.
44
Describe Horner syndrome and its association with miosis.
Horner syndrome involves miosis due to loss of sympathetic influence, typically accompanied by other signs like ptosis and enophthalmos.
45
What does vestibular strabismus indicate in horses?
Vestibular strabismus indicates abnormal eye position, often reflecting vestibular disease.
46
What is the expected response of the eyeball to a modified corneal reflex test?
The normal response is retraction (adduction) of the eyeball.
47
Differentiate between physiological nystagmus and spontaneous nystagmus.
Physiological nystagmus occurs with head movement, while spontaneous nystagmus occurs when the head is stationary.
48
What clinical signs might indicate involvement of the nucleus ambiguus?
Dysphagia, coughing, and signs of aspiration pneumonia may indicate nucleus ambiguus involvement.
49
Describe the method for assessing swallowing competency in horses.
Assess swallowing competency by noting feed or water returning through the nose and using a nasogastric tube to evaluate swallowing movements.
50
What are the implications of a horse demonstrating tongue curling towards the normal side?
It indicates unilateral weakness in the tongue muscles.
51
How can the position of the eyeballs help in diagnosing vestibular disease?
Abnormal positions, like ventral deviation on the side of the lesion, can indicate vestibular disease.
52
What is the role of the oculomotor nerve in the pupillary light reflex?
The oculomotor nerve mediates the efferent response for pupil constriction in the PLR.
53
Describe how mydriasis is diagnosed in a horse.
Mydriasis is diagnosed through observation of fixed, dilated pupils and the response to light stimulation.
53
What is the significance of the slap test in equine examinations?
The slap test assesses for laryngeal paralysis, indicating potential nerve damage
54
What could cause absent physiologic nystagmus in a horse?
Absent physiologic nystagmus can occur in horses with bilateral vestibular disease.
54
How does involvement of the hypoglossal nerve affect tongue retraction?
Damage to the hypoglossal nerve can lead to delayed or absent retraction of the tongue, indicating upper motor neuron involvement.
55
What is the first step in examining a horse's neck?
Assess muscle mass and look for asymmetries while the horse stands squarely.
56
What does a firm press on the cranial edge of the cervical transverse processes from C3 to C6 test for?
It tests for a pain response.
57
What might indicate cervical and/or thoracic pain during the examination?
Inability to lower the neck or the horse advancing one thoracic limb to reach food on the ground.
58
What condition is often indicated by severe or rapidly developing muscle atrophy?
Denervation, which is a localizing sign.
59
How is neurogenic muscle atrophy caused?
By damage to the lower motor neuron in the ventral column of the gray matter or associated nerve roots.
60
Which spinal cord segments are associated with neurogenic atrophy of the thoracic limb musculature?
C6 to T2 spinal cord segments.
61
What response is expected during the slap test?
slight palpable movement (adduction) of the left arytenoid in response to each slap.
62
hich reflex provides sensory input to the slap test?
: Sensory nerves and roots from approximately T7 to T11.
63
What does a diminished cervicofacial reflex indicate?
Interruption of reflex components in the facial nerve, cervical nerves or roots, or local cervical spinal cord segments.
64
What is tested by the cutaneus trunci reflex?
The responsiveness of the skin to stimulation along the sensory field.
65
Where does the reflex pathway for the cutaneus trunci reflex lead?
From sensory thoracic nerves to the ipsilateral spinal cord, then rostrally to segments C8 and T1.
66
What is the expected reaction when the back reflexes are tested?
A brisk extension of the back and pelvis followed quickly by a return to normal posture.
67
What abnormal reactions might occur during the back reflex test?
Partial collapse in the pelvic limbs, wobbling of the pelvis, or no response.
68
How can limb strength be assessed in horses?
By observing responses to passive pressure, hopping tests, and resistance to pressure over the pelvis and tail.
69
What does a horse's inability to resist sideways pressure during the tail pull indicate?
Possible interruption of the antigravity myotatic reflex pathway.
70
Which areas of the spinal cord are implicated when cutaneous sensation over the saphenous vein is absent?
The ventral aspect of the shaft of the ilium where the sensory saphenous nerve joins the femoral nerve.
71
How can spinal cord disease be identified during the examination?
By observing ataxia, weakness in limbs, and changes in gait.
72
73
why might the cutaneus trunci reflex not be elicited in some horses?
Due to variations in neck anatomy that affect palpation.
74
What may be observed in a horse with cervical spinal cord disease during the slap test?
Abnormal adductor responses or bilateral effects if the disease is severe.
75
What are some associated clinical signs of cervical spinal cord disease beyond ataxia and weakness?
Dysphagia, aspiration pneumonia, and Horner syndrome.
76
Figure 51-5. Unilateral tongue atrophy in a horse with possible equine protozoal myeloencephalitis. Note the characteristic longitudinal folds on the atrophied (right) side. The tongue intermittently deviated toward the left side when the mouth was held open.
76
Figure 51-7. Testing for strength: walk backward and pull the horse in counterclockwise circles, then repeat in mirror-image fashion in clockwise circles.
76
Figure 51-6. Force the horse to hop on each front limb to evaluate limb strength.
77
Figure 51-8. Gait analysis: pull the horse sideways and backward in tight circles so that it pivots around a point midway between the thoracic and pelvic limbs. Repeat on the right side.
78
Figure 51-9. Testing the patella reflex in a recumbent horse. The limb is held in a flexed and slightly abducted position, and the skin over the middle patella ligament is struck with a twitch handle.
79
80
Figure 51-11. Lumbosacral cerebrospinal fluid collection. The caudal border of the tuber coxae (large dark arrows), the cranial edge of the tuber sacrale (small dark arrows), and the spine of L6 (open arrow) are used as landmarks.
81
82
Figure 51-12. Survey radiographs of the neck of a standing normal horse. (A) Fifth cervical vertebra. a, Caudal articular process of C4; b, cranial articular process; c, transverse process (cranial part or ventral tubercle); d, vertebral body; e, dorsal lamina; f, intervertebral disc space; g, vertebral canal. The line shows the sagittal diameter of the vertebral foramen.
83
Figure 51-12. Survey radiographs of the neck of a standing normal horse. (A) Fifth cervical vertebra. a, Caudal articular process of C4; b, cranial articular process; c, transverse process (cranial part or ventral tubercle); d, vertebral body; e, dorsal lamina; f, intervertebral disc space; g, vertebral canal. The line shows the sagittal diameter of the vertebral foramen. (B) to (F), Five overlapping views of a complete cervical series. Note for this figure: the transverse processes of C6 differ from those of C3 to C5 by presenting an additional ventral process. The caudal part (also called dorsal tubercle) of the transverse processes (most often of C6 but occasionally of other cervical vertebrae as well) can have a separate center of ossification that should not be confused with a fracture. C7 is a relatively short vertebra with usually a small dorsal spinous process and short transverse process that lacks the ventral, cranially facing tubercle that is present in C3 to C6. (
84
What are common abnormal movements noted from the side view of the gait?
Toe-dragging, knuckling, stride asymmetry, hyperflexion, hypometria, and hypermetria.
85
What might tight circle gait examination reveal about an ataxic horse?
Weak, inconsistent limb placement, or a tendency to pivot on pelvic limbs.
86
What indicates a spinal cord lesion between C1 and T2?
Ataxia and weakness in both thoracic and pelvic limbs
87
How does thoracic limb ataxia relate to cervical spinal cord compression?
It often accompanies more severe signs in the pelvic limbs.
88
What suggests a lesion located between T2 and S3?
Severe ataxia and weakness in the pelvic limbs, with normal thoracic limbs.
89
What does asymmetry in gait abnormalities indicate?
A spinal cord lesion that is more severe on the affected side
90
How can ataxia without weakness differ in cause from weakness without ataxia?
How can ataxia without weakness differ in cause from weakness without ataxia?
91
What clinical sign might aid in spinal lesion localization?
Abnormal reflexes, such as cervicofacial, slap, or cutaneus trunci reflexes.
91
How can ataxia without weakness differ in cause from weakness without ataxia?
Abnormal reflexes, such as cervicofacial, slap, or cutaneus trunci reflexes.
92
What differentiates reflexive from voluntary movement in nociception testing?
What clinical sign might aid in spinal lesion localization?
93
What clinical sign might aid in spinal lesion localization?
Limb flexion with a visible reaction to the pinch.
94
What is indicated by an absent patellar reflex?
Potential damage to the spinal cord or reflex arc affecting that limb.
95
How can the patellar reflex aid in assessing limb health?
A brisk extension response is normal, while absence or exaggeration may indicate spinal issues.
96
What might be indicated by the inability to dog-sit in a horse?
Lesions likely located cranial to the T2 spinal cord segment.
97
What reflex abnormality may result from trauma to the upper motor neurons?
What reflex abnormality may result from trauma to the upper motor neurons?
98
What reflex abnormality may result from trauma to the upper motor neurons?
What reflex abnormality may result from trauma to the upper motor neurons?
99
What reflex abnormality may result from trauma to the upper motor neurons?
Possible cauda equina syndrome involving S2 or more caudal spinal segments.
100
What are signs of cauda equina syndrome in horses?
Analgesia, tail and rectal paralysis, urinary incontinence, and bladder paralysis.
101
What advantages does the AO site offer for CSF collection?
Lower risk of blood contamination and simple collection.
102
When might the lumbosacral space be preferred for CSF collection?
For its proximity to potential caudal spinal cord lesions.
103
What is required to perform a C1-C2 CSF collection safely?
Ultrasonographic guidance to avoid injury to nerves or vasculature.
104
What might make lumbosacral CSF collection more technically challenging?
Higher risk of blood contamination and the procedure’s complexity.
105
What indicates successful AO needle placement during CSF collection?
A free flow of CSF following a “pop” as the needle pierces the dura mater.
106
What precaution is taken to avoid needle injury during C1-C2 CSF collection?
Ultrasonography to accurately place the needle near the spinal cord.
107
108
Figure 51-16. Lumbosacral epiduroscopy in the standing horse, looking cranially. Top of the picture is dorsal. A right spinal nerve root (black arrow) passes through the epidural space. Note the epidural fat (white asterisk) and the surface of the dura mater (black asterisk).
109
Figure 51-14. Cervical myelography: dorsal myelographic column (left of figure), dural diameter (right of figure).
110
Figure 51-13. Cervical myelographic series in a normal horse. (A) to (C) The neck is in a neutral position. Note that the transverse processes of C6 in this horse do not have the typical ventral extension. (D) Now centered caudally, the neck is in extended position. (E) to (F) Cranial and middle views of the neck in flexed position.
111
Why is it recommended to start with lower doses of sedation for LS fluid collection?
To avoid oversedation, which can cause the horse to sway, making the procedure harder.
111
Why might a horse hold its head stiffly after AO CSF collection?
Possibly from transient irritation similar to a human headache post-aspiration.
112
How does spinal cord damage affect thoracic limb reflexes?
Reduced or absent reflexes if motor or sensory nerves are affected.
113
What might an absence of response to deep pain stimulus indicate?
Potentially catastrophic spinal cord damage cranial to the tested region
114
Where is the tap site for LS fluid collection located?
On the midline within or slightly in front of the V-shaped landmark formed by the tubera sacrale.
115
What volume of local anesthetic is used at the tap site of CSF?
0.5 to 1 mL.
116
What is a typical CSF total nucleated cell count in horses?
Approximately 3 cells/μL.
116
What precaution is taken with the CSF sample if it will not be analyzed immediately and appears cloudy?
Place it in an EDTA tube to prevent coagulation.
117
Why might cytology slides be prepared soon after CSF collection?
To preserve cell morphology for accurate cytological evaluation.
118
What are the expected normal protein values in CSF for adult horses and foals?
Up to 80 mg/dL in adults and 100 mg/dL in foals.
119
What types of analysis can be performed on CSF samples?
Cytology, biochemical analysis, DNA for pathogens, serology, biomarkers, and microbial cultures.
120
What imaging views are useful for evaluating a horse's head?
Lateral, oblique, and dorsoventral (or ventrodorsal in anesthetized animals) views.
121
What anatomical feature appears on lateral radiographs of the head in young foals?
The fontanel in foals under 3 months.
122
Which suture disappears by 5 years of age in horses?
The parietal-occipital suture.
123
The parietal-occipital suture.
Fractures in the frontal, parietal, basilar bones, petrous temporal bone, and stylohyoid fractures.
124
When is cervical spine radiography indicated in horses?
For deformities, palpable abnormalities, ataxia, limb weakness, neck trauma, stiffness, or pain.
125
What equipment requirements are generally needed to image C7 to T1 in horses?
75–100 kV and 75–100 mAs.
126
What common anatomical abnormality is detected with sagittal diameter measurements in cervical vertebrae?
Cervical vertebral stenotic myelopathy.
127
What are typical sagittal ratios indicating stenotic myelopathy in horses?
Ratios below 0.5 for intervertebral and less than 0.52 for C3-C6, and 0.56 for C6-C7.
128
Which horse breeds are more prone to cervical vertebral compressive myelopathy?
Thoroughbreds, Tennessee Walking Horses, and Warmbloods.
129
What vertebra has a large dorsal spinous process and a cranial projection, or dens?
The axis, or C2.
130
At what age does the dens typically fuse with the head of C2?
Around 7 months of age.
131
What degenerative condition in cervical vertebrae might be visible on radiographs?
Degenerative joint disease.
132
What distinguishes the C6 vertebra on radiographs?
An additional ventral process on the transverse processes.
133
What signs may prompt thoracolumbar radiography?
Trauma, deformity, chronic or acute back pain, and weakness or ataxia.
134
Why are two lateral exposures needed for optimal thoracolumbar imaging with film-screen systems?
To capture images optimized separately for vertebral bodies and dorsal spinous processes.
135
What vertebral range is typically viewable in lateral projections of thoracolumbar vertebrae?
T1 to L3.
136
How does the orientation of thoracic dorsal spinous processes change along the spine?
They slope caudally to T7, then become vertical (T15), then slope cranially.
136
What anatomic changes are visible on radiographs for horses overrepresented in back pain studies?
Radiographic alterations in the caudal thoracic spinous processes.
136
What vertebral abnormality is often associated with degenerative joint disease in horses?
Osteoarthritis in thoracic spine articulations.
137
What spinal imaging projection is important for full assessment of the cervical spine?
True lateral projections to avoid interpretive complications.
138
Which joint disease is common in the thoracolumbar spine and is visible on radiographs?
Degenerative joint disease and ossifying spondylosis.
139
What is the typical shape of a horse's cervical spine when viewed from the left?
A reverse-S shape.
140
How does breed or age potentially affect vertebral sagittal ratios in horses?
Sensitivity and specificity of ratios can vary with breed and age.
141
What condition might be indicated by the appearance of myelopathy in a young foal on radiographs?
Occipitoatlantoaxial malformation, among other congenital conditions.
142
What are common indications for sacrococcygeal radiography?
Signs of cauda equina syndrome, pain, or deformity over the sacrum or tail.
143
What is often confused with the first coccygeal vertebra on radiographs?
The last sacral segment (usually S5).
143
What initial preparation is recommended before a myelography procedure?
Administering an NSAID such as flunixin meglumine or ketoprofen.
144
* What type of contrast medium is used in equine myelography?
Iohexol (300 mg/mL).
145
How much CSF is typically withdrawn per 100 kg body weight in a myelography procedure?
10 mL per 100 kg (e.g., 50 mL for a 500-kg horse).
146
Where is the contrast medium injected during a myelography?
Into the subarachnoid space.
147
What does a reduction of 20% in dural diameter indicate in myelography?
It is indicative of compressive or stenotic myelopathy.
148
Which views reveal dynamic compression in the middle and cranial neck?
Flexion views.
149
What is the sensitivity of a 20% dural diameter reduction at C6 to C7?
Highly sensitive and specific in neutral or flexed neck positions.
150
What adverse effects are associated with myelography in horses?
Hyperthermia, seizures, and transient worsening of ataxia.
151
What medication is used to control seizures post-myelography?
Diazepam (0.05–0.1 mg/kg IV).
152
Which joints are commonly assessed with ultrasound in horses?
Cervical dorsal intervertebral joints and sacroiliac joints.
153
Which condition is CT particularly useful for in the skull?
Temporohyoid osteoarthropathy.
154
What role does MRI play in diagnosing equine trigeminal neuritis?
Provides detailed images to assess nerve inflammation or damage.
155
What percentage of horses in a study had complications from myelography?
34% experience complications
156
What does vertebral canal endoscopy (VCE) allow clinicians to visualize directly?
The anatomical structures within the vertebral canal.
157
Which meninge serves as the de facto border between the subarachnoid and epidural spaces?
The dura mater
157
What are the two types of spaces that can be endoscopically examined in VCE?
The subarachnoid space (myeloscopy) and the epidural space (epiduroscopy).
157
What are the three meninges surrounding the spinal cord?
The dura mater, arachnoidea, and pia mater.
158
What contents are found in the epidural space?
Fat, lymphatic tissue, and blood vessels, including the ventral internal vertebral venous plexus.
159
What structure contains clear and colorless cerebrospinal fluid (CSF)?
The subarachnoid space.
160
Where do spinal nerve roots pass through after emerging from the spinal cord?
The epidural space and then the intervertebral foramina.
161
What ligaments are located within the subarachnoid space?
The denticulate ligaments.
162
Which approach allows access to both the epidural and subarachnoid spaces in the cervical vertebral canal?
The atlantooccipital space.
163
Where does the subarachnoid space taper off in horses?
Midsacrum.
164
Why is ketamine avoided as an anesthetic in VCE?
It increases intracranial pressure and lowers the seizure threshold.
165
Which anesthetic combination is recommended for VCE in horses?
Thiopental (4 mg/kg IV) and guaifenesin (50 mg/kg bwt IV).
166
What anesthetic gas is used to maintain anesthesia during VCE?
Isoflurane in oxygen.
167
Why is positive-pressure ventilation recommended during VCE?
To prevent hypercapnia and subsequent increase in intracranial pressure.
168
How is the surgery table positioned to reduce cerebrospinal fluid pressure during VCE?
Tilted in a reverse Trendelenburg position, raising the head by 20 degrees.
168
What position is the horse placed in during cervical vertebral canal endoscopy?
Lateral recumbency with the head flexed at 90 degrees.
169
Which muscles are separated to expose the nuchal ligament during VCE
The splenius capitis and semispinalis capitis muscles.
169
Where is the 15-cm skin incision made for cervical vertebral canal endoscopy?
On the dorsal midline, over the cranial edge of the atlas wings.
170
What ligament is retracted to access the atlantooccipital membrane?
The nuchal ligament.
171
Which membrane is incised to enter the epidural space for epiduroscopy?
The dorsal atlantooccipital membrane.
172
What is required to access the subarachnoid space after opening the epidural space?
An incision through the dura mater and arachnoidea.
173
How long is the incision made on the dura mater for accessing the subarachnoid space?
1.5 cm on the dorsal midline.
173
What structure becomes visible upon entering the epidural space?
The white surface of the dura mater.
174
How is a seal created around the endoscope to limit CSF loss during myeloscopy?
By gently tightening the sutures around the endoscope
174
What is the purpose of endoscopically accessing the atlantooccipital space?
To explore both the epidural and subarachnoid spaces in the cervical canal.
175
Why are two simple interrupted sutures placed after the dura mater incision?
To divide the incision into three sections for controlled endoscope insertion.
176
What anatomical function does the pia mater serve in relation to the spinal cord?
It attaches closely to the surface of the spinal cord.
176
What procedure term is used when the subarachnoid space is viewed endoscopically?
Myeloscopy.
177
What is epiduroscopy specifically used to examine?
The epidural space of the vertebral canal.
178
Why is general anesthesia typically required for repetitive nerve stimulation in horses?
The nerve stimulation can be painful.
178
Which nerve's external branch is located within the subarachnoid space?
The accessory nerve
178
Why is the atlantooccipital membrane incised during VCE?
To open the epidural space.
178
What function do the denticulate ligaments serve in the vertebral canal?
They connect the arachnoidea to the pia mater.
178
What is the main diagnostic application of repetitive nerve stimulation?
To diagnose neuromuscular junction disorders.
178
What is the main risk associated with the loss of CSF during myeloscopy?
Potential for decreased intracranial pressure and CSF leakage complications.
179
In which condition in foals has repetitive nerve stimulation shown diagnostic value?
Botulism.
180
What does single-fiber EMG primarily study?
Neuromuscular transmission at single end plates.
181
How does single-fiber EMG differ from traditional EMG?
It focuses on motor unit action potentials over a small area with a concentric electrode.
182
What is the primary purpose of muscle and nerve biopsy in neuromuscular diagnostics?
To assess the integrity of muscle and intramuscular nerve branches.
183
What types of muscle atrophy can muscle biopsy help differentiate?
Neurogenic muscle atrophy and disuse atrophy
184
Which muscle is recommended for biopsy in cases of suspected EMND?
The sacrocaudalis dorsalis medialis, due to its high type I fiber content.
185
For diagnosing diseases affecting type 2 fiber-rich muscles, which muscles are preferred for biopsy?
The gluteus and semitendinosus muscles.
186
Why are nerve biopsies uncommon in horses?
Due to collection challenges, safety concerns, and risk of complications.
187
Which nerve is commonly sampled in horses if a nerve biopsy is performed?
The ventral branch of the spinal accessory nerve.
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What is the diagnostic use of transcranial magnetic stimulation (TMS)?
To assess motor tract function of the spinal cord.
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Which factors can contribute to deafness in neonatal foals?
Sepsis, hypoxia, bilirubin toxicity, and prematurity
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Figure 51-17. Cervical vertebral canal endoscopy. Myeloscopy during withdrawal of the endoscope. Subarachnoid space dorsal to the spinal cord, looking caudally. Top of the picture is dorsal. The arachnoid/dura mater is dorsal (white arrow), partially covered by broken down arachnoid trabeculations (white arrowheads). Ventral, the spinal cord (large black arrow) with blood vessels that are partially enclosed in the delicate pia mater can be seen. A left dorsal nerve root (black arrowheads) is visible.
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Figure 51-18. Instruments for the collection of muscle samples. (A) Top: scalpel blade; center: 8-mm skin punch biopsy; bottom: Bergstrom biopsy needle with its components. (B) Double Kelly forceps to be used with one hand to clamp a piece of muscle between the jaws of the forceps. This technique provides a 1.5- by 1.5-cm muscle specimen.
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Figure 51-19. (A) The shaved areas depict the region for gluteus medius muscle biopsy, and the black line indicates the site for biopsy of the semimembranosus muscle. The surgical incision required is smaller than the one shown here. (B) Bergstrom biopsy needle for gluteus medius muscle biopsy. The biopsy is performed at about one-half to two-thirds of the distance between the base of the tail and the tuber coxale. Needle is directed 45 to 65 degrees perpendicular to the ground and directed medially to the horse. (C) Area of the sacrocaudalis dorsalis lateralis muscle at the base of the tail.
