Deck 6 Flashcards
1
Q
What is the parent artery for the middle meningeal artery?
A
External carotid artery
2
Q
What is the primary endpoint for the pyramidal system in horses?
A
Facial nuclei — coordinates muscle movement for the lips
3
Q
What gyri constitute the motor cortex (dogs)? Which gyri do what? What cortex does this overlap with?
A
Post-cruciate = appendicular musculature
Rostral suprasylvian = head / neck / face
Somatosensory cortex
4
Q
Which is lateral and which is medial — globus pallidus or putamen
A
Globus pallidus is medial
Putamen is lateral
5
Q
The nucleus accumbens is an extension of which nuclei and participates in the function of what system?
A
Ventral extension of the caudate nucleus
Extrapyramidal motor system
6
Q
Who tells the neurons in the red nucleus what to do?
Who tells the UMNs in the reticular formation what to do?
A
Neurons in the ipsilateral motor cortex of the cerebrum
Neurons in the contralateral cerebral hemisphere (probably from the motor cortex as well?)
7
Q
How might you position a patient for a dorsal approach to the caudal cervical vertebral column?
A
With the thoracic limbs extended cranially and crossed to help abduct the scapulae
8
Q
When performing a C2 laminotomy, which direction is the bone flap rotated and what ligaments are left intact?
A
The bone flap is rotated in a cranial direction. Both the dorsal atlanto-axial and nuchal ligaments are preserved.
9
Q
When is fusion of the ventral slot site expected?
A
8-12 weeks post-op
10
Q
Approximately what percentage of post-op necks (of any type) require post-op ventilatory support?
A
5%
11
Q
Label these muscles
A
T - trapezius
R - rhombodieus
Sp - splenium
BC - biventer cervicalis
SC - spinalis cervicalis
C - complexus
MC - multifidus cervicis
LCp - longissimus capitis
LCv - longissimus cervicis
ITv - intertransversarii
SV - serratus ventralis
O - omotransversarius
B - brachiocephalicus
12
Q
True or false - self-tapping screws are appropriate for use in cervical stabilization.
A
False - remember that the last 1-2 mm of self- tapping screws don’t actually engage the bone / contribute to holding strength. You already don’t have a lot of holding strength here due to the short nature of the screw corridors in the neck. Additionally, self-tapping screws are more likely to penetrate the trans cortex
13
Q
When does Shores recommend obtaining a fat graft during a TL hemi?
A
Start of surgery, just after skin incision
14
Q
What are the names of these procedures?
A
Top - hemilaminectomy
Middle - pediculectomy / mini-hemi (preservation of articulation)
Bottom - partial pediculectomy (preservation of articulation and accessory process)
15
Q
What is the name of this retractor?
A
Weitlaner retractor
16
Q
Describe the motion with which instruments should be inserted / removed from the disc for fenestration.
A
Insert the instrument straight into the disc, then pull down and out. Do not twist or push the instrument up.
17
Q
What are the proposed margins for a corpectomy?
A
25% length of the vertebral body, cranially and caudally
50-66% width of the vertebral body (in a transverse plane)
50% the height of the vertebral body
18
Q
What are two ways that you can avoid laminectomy membrane formation following a dorsal laminectomy?
A
- preserving the supraspinous ligament and suturing it back at the end of surgery
- spanning the gap between the spinous processes with a figure of 8 non-absorbable suture
19
Q
What are the four variations of a dorsal laminectomy?
A
- Funquidst A = removal of the articulations
- Funquidst B = keeping the articulations
- Modified = removing the caudal articular facets
- Deep = removal of the entire dorsal arch to include the pedicles
20
Q
What structures are within the three compartments of the spinal instability model?
A
Dorsal — spinous process, lamina, articular processes, pedicles and associated ligaments
Middle — DLL, dorsal annulus, dorsal vertebral body and associated transverse processes
Ventral — rest of the disc and vertebral body, VLL
21
Q
True or false: bicortical implant placement is preferred for treatment of cervical fractures
A
False — bicortical implant is associated with an unacceptably high degree of iatrogenic spinal cord, nerve or blood vessel injury
22
Q
What is the recommended thickness of PMMA? What anatomic boundary should be respected when using PMMA in the neck and why?
A
1-1.5 cm
The ventral boundary of the longus colli — thicker than this will result in pressure on the trachea and esophagus
23
Q
True or false - contouring of SOP plates should be kept to a minimum when it comes to vertebral stabilization
A
True
24
Q
Hyperflexion injury of the vertebral column leads to what type of fracture/ luxation? Rotational?
A
Hyperflexion = Oblique caudal end plate fracture and subluxation
Rotational = articular process fractures
25
What is the angle for bicortical pedicle screws for the thoracolumbar spine?
The angle progressively increases from T10 onwards until L1.
T10 - 22
T11 - 28
T12 - 30
T13 - 45
L1-6 - 60
26
What is a possible solution to not having enough screws per segment when using locking plates due to their fixed angle construct mechanics?
Placement of a second locking plate
27
What are the requirements to be met in order to consider spinal stapling?
Small dog or cat
Inherently stable fracture
28
How many vertebrae cranial and caudal should be incorporated in a spinal staple?
3 cranial and 3 caudal
29
Where are the dendrites and axons of the Purkinje neurons, respectively?
Are Purkinje neurons excitatory or inhibitory to the cerebellar nuclei?
Dendrites - form a large portion of the molecular layer
Axons - project to cerebellar medullary nuclei (or rarely directly to the vestibular nuclei as is the case for the flocculonodular lobe)
Inhibitory
30
What is the functional difference between mossy and climbing cerebellar fibers? Are these excitatory or inhibitory?
Mossy — do not directly interact with the Purkinje neurons, but instead synapse with granule and Golgi cells, who then influence Purkinje neurons
Climbing — directly synapse onto dendrites of Purkinje cells within the molecular layer
Both mossy and climbing fibers are excitatory to their targets.
31
What are the two cell types that granule cells synapse with? What do they do at these synapses?
Who controls the function of the granule cells?
Granule cells give off parallel fibers that synapse with Purkinje dendrites in the molecular layer. They excite Purkinje neurons, but only in a specific layer given their arrangement.
Granule cells also synapse with basket cells, just in a layer next to the layer of the Purkinje cells they already excited. They active the basket cells. These basket cells then inhibit the Purkinje cells in the layer where they are.
Thus, granule cell activation causes specific Purkinje cell activation (directly) and specific Purkinje cell inactivation (indirectly via basket cells).
Golgi cells inhibit the function of granule cells. They are activated either by mossy fibers, or by the granule cells themselves.
32
Where do climbing fibers arise from?
olivary nucleus
33
What are the three cortical zones of the cerebellum?
Which nuclei does each zone associate with?
What are the alternative names of these zones?
What do they broadly do?
1. Vermis, intermediate and lateral
2. Vermis — fastigial; intermediate — interposital; lateral — lateral
3. Lateral group = cerebrocerebellar; the other two groups form the spinocerebellar group; flocculonodular lobe = vestibulocerebellar
4. Cerebrocerebellar — planning and control of fine movements (typically of extremities); spinocerebellar — control of posture and gait; vestibulocerebellar — control of balance and eye movements
34
There are two components to the spinocerebellar system — what are they, and what does each control?
1. Fastigial nucleus + vermis = control of axial musculature
2. Interposital nucleus + intermediate zone = control of appendicular musculature
35
What are the only cell types to arise in the molecular layer of the cerebellum?
Who activates basket cells? What do basket cells do?
Basket cells
Granular neurons activate basket cells — importantly, these basket cells are not in the same plane as the Purkinje neurons the granular cells activate.
Basket cells inhibit Purkinje neurons in plane with them.
36
Origin of mossy fibers? Climbing fibers?
Mossy fibers — pontine nuclei, vestibular nuclei, lateral cuneate nucleus, nucleus thoracicus
Climbing fibers — olivary nuclei
37
What nuclei do the cerebellar efferents go to (AKA where do axons from the cerebellar nuclei go)?
- ventral lateral thalamic nucleus
- red nucleus
- vestibular nuclei
- olivary nucleus
- reticular formation
38
Purkinje neurons always release this neurotransmitter and are thus always _______.
Cerebellar neurons always release these neurotransmitters and are thus always ______.
GABA, inhibitory
Aspartate / glutamine, excitatory
39
Describe the feedback loop mediated by the cerebrocerebellum.
- corticopotine axons originating in the motor cortex synapse in pontine nuclei
- pontine nuclei axons cross over and form the middle cerebellar peduncle
- these axons (mossy fibers) synapse in the lateral cerebellar nuclei and cortex
- axons from the lateral cerebellar nucleus then travel out the rostral cerebellar peduncle and cross over to the contralateral thalamus
- in the thalamus, they synapse onto the ventral lateral thalamic nucleus, which projects to the cerebrum
40
Besides the thalamus, where are the other two places that the lateral cerebellar nuclei sends fibers to? Via want peduncle?
Red nucleus
Olivary nucleus
41
What are the afferents of the spinocerebellar system?
What are the efferents of this system / per portion of this system?
- all the tracts carrying subconscious proprioception (dorsal and ventral spinocerebellar, and spinocuneocerebellar) and the olivary nuclei
- both portions project to the lateral thalamic nuclei, reticular formation and the olivary nuclei. The fastigial / vermal portion also projects to the vestibular nuclei while then intermediate portion also projects to the red nuclei.
42
What cerebellar layer is formed very early in utero? What layer is formed much later?
Purkinje cell layer
Granule cell layer
43
What does the term ‘altricial’ mean? What is the reason these animals are this way?
Unable to walk on their own at the time of birth — dogs, cats and people are this way. It has to do with the degree of cerebellar development, specifically related to how much of the external germinal layer has yet to migrate into the granular layer.
44
What cells form the parallel fibers in the molecular layer of the cerebellum?
Granule neurons
45
What happens to the efferent cerebellar axons that leave the rostral cerebellar peduncle?
They decussate almost immediately, just caudal to the rubrospinal decussation.
46
True or false - the cerebellum has fibers that project to the spinal cord LMNs
False — the cerebellum influences the LMNs via influence on the various UMN tracts within the brainstem / corticospinal tracts
47
Define these structures:
- Archicerebellum
- Paleocerebellum
- Neocerebellum
Archicerebellum - flocculonodular lobe
Paleocerebellum - rostral vermis / nearby hemispheres
Neocerebellum - caudal vermis / majority of cerebellar hemispheres
48
Describe the differences in UMN quality hypermetria and cerebellar hypermetria.
The difference lies in whether the limb is in extension or flexion when it is reached too far in front of the body.
UMN = extended
Cerebellar = flexed
49
Describe the ocular changes seen with experimental ablation of the fastigial and interposital nuclei.
Fastigial — contralateral mydriasis with abnormal PLR, ipsilateral 3rd eyelid elevation
Interposital — ipsilateral mydriasis with abnormal PLR, contralateral 3rd eyelid elevation AND ipsilateral widened palpebral fissure
50
What viral infection can cause cerebellar dysfunction in young dogs? How is this different than young kittens with cerebellar signs?
Herpesvirus in dogs less than 1 week of age can cause this. This is not necessarily a hypoplasia of the cerebellum as it is in cats that get in utero panleukopenia.
51
Cerebellar cortical abiotrophy involves degeneration of which neurons?
Purkinje
52
What is the percentage of normal brain weight of the cerebellum?
10-12%
53
What breed of horse develops a cerebellar cortical abiotrophy? What is a unique clinical sign in these horses?
Arabians
Head bobbing and swaying, as well as rearing up and extending the thoracic limbs
54
In cattle with BVDV, are the cerebellar changes reflective of hypoplasia or atrophy?
Both — destruction of the external germinal layer prevents formation of the granuar layer (hypoplasia), but destruction of the already formed Purkinje neurons and associated white matter results in atrophy
55
Explain the pathophysiology behind dermoid and epidermoid cysts.
Common location?
Which type will have adnexal features on histopathology?
During the neural tube closure, a small amount of adjacent ectodermal tissue gets stuck with the developing neuroparenchymal tissue, where it will grow slowly over time, eventually causing neurologic deficits when large enough.
Dermoid cysts will have adnexal features.
Caudal cranial fossa
56
There are two acquired storage disorders. What are they?
1. Ingestion of Swainsona, causing alpha-mannosidosis in cattle
2. Ingestion of Solanum species of plant in cattle, causing Purkinje dysfunction
57
What is the pathogenesis of hereditary ataxia? Breeds? Outcomes? What electrodiagnostic test can help diagnose these patients?
This is an axonopathy (w/ secondary demyelination) of the more superficially located tracts of the lateral and ventral funiculi, to include the spinocerebellar tracts — this is what results in a cerebellar quality ataxia.
Jack Russell terriers and smooth fox terriers +/- Ibizan hounds
Usually not a bad outcome as signs often stabilize within a few months of their onset.
BAER test — only waves I and II are present due to dysfunction of the trapezoid body
58
What percentage of spinal tumors are extra-dural, intra-dural extramedullary, and intermedullary?
Extradural — 50%
Intradural extramedullary — 35%
Intermedullary — 15%
59
What is the average amount of time between placement of an indwelling urinary catheter and UTI development?
3 days
60
What are the main electrolyte differences between endolymph and serum?
What is the importance of this?
Endolymph has high K and low Na
The high potassium is important because this is the ion that rushes in through the tip-linked potassium channels of the hair cells.
61
What happens when the hair cells when they bend towards towards the kinocilium? Away?
What happens once potassium enters the hair cells?
Towards - opening of tip-linked potassium channels and depolarization
Away - continued closure of tip-linked potassium channels, resulting in hyper-polarization
Once potassium enters the cells, voltage gated potassium channels open up and allow for neurotransmitter release via vesicles.
62
Are the flocculonodular lobe efferents excitatory or inhibitory? What cell type can help you know this?
Inhibitory to vestibular nuclei
Signals are coming straight from Purkinje neurons in the cortex of the flocculonodular lobe, and Purkinje neurons are always inhibitory.
63
What additional neuronal cell body does the medial vestibulospinal tract synapse on besides the ventral horn motor neurons?
Motor neurons of the accessory nerve within the lateral horn of the cervical spinal cord.
(This should help you remember that the medial vestibulospinal tract only runs to the mid-thoracic region).
64
Explain why changing a patient’s position can induce nystagmus?
Proprioceptors from throughout the body (but maybe more so from the region of the neck thanks to the spinovestibular tract in the cranial cervical spinal cord) feed into the vestibular nuclei. By activating these proprioceptors and thus stimulating the vestibular nuclei, you can cause spontaneous nystagmus in a diseased patient.
65
True or false — you will have paradoxical vestibular signs if you lesion the caudal cerebellar peduncle and ipsilateral vestibular nuclei.
False — any time there is vestibular nuclei damage, you will see non-paradoxical vestibular signs; similar in concept to only seeing LMN signs when there is concurrent UMN and LMN disease
66
What do the efferent neurons from the dorsal nucleus of the trapezoid body do?
They synapse on the hair cells (or their axons) to regulate the activity / sensitivity of these hair cells - thought to help prevent sound over-exposure.
67
Where does the peri-orbital fascia attach, and what does it blend with at this location?
Orbital fissure & optic canal
Dura mater
68
What are the three nuclei involved in the protective middle ear reflex?
Cochlear nuclei
Dorsal nuclei of the trapezoid body
Either the motor nucleus of CN V or VII
69
Which one (rods / cones) are sensitive to light and which are sensitive to color?
Rods — sensitive to light (300x more so than cones), but don’t do color
Cones — insensitive to light (only active with bright lights) but are used for color vision
70
What is the fovea? Where is it located? What are alternative names for it?
It is the area of the retina with the highest proportion of cone cells, and it is located just dorsolateral to the optic disc. It is also called the area centralis or visual streak.
71
What is the most external cell layer of the retina?
What is its job?
What is special about this layer at the tapetum lucidum?
Retinal pigmented epithelium
Prevents scattering of light throughout the eye
At the tapetum lucidum, there is no melanocytes in the RPE, allowing light to reflect — supposedly to help with dark vision
72
What cells do the rod and cone cells synapse on? What do then those cells synapse on?
Rod and cone cells synapse on bipolar cells. Bipolar cells then synapse on ganglion cells, which travel on to make up the optic nerve.
73
What determines visual acuity? Do rods or cones have better visual acuity?
Visual acuity is determined by how many photoreceptor cells feed into a single ganglion cell. The less number of photoreceptors that feed into a ganglion cell, the higher the acuity.
Cones have higher acuity than rods.
74
What are rostral and caudal extents of the hypothalamus?
Rostral - lamina terminalis
Caudal - mammillary bodies
75
What type of tissue / glands are innervated by cholinergic sympathetic fibers?
Merocrine (eccrine) sweat glands
76
The intermediolateral nucleus is under control of what two brainstem centers? Via what tracts?
The reticular formation and the hypothalamus.
Pontine and medullary reticulospinal tracts and hypothalamospinal tract
77
What two ganglia do most sympathetic nerve fibers pass through prior to reaching the cranial cervical ganglion? What connects these two ganglia?
Cervicothoracic ganglion
Middle cervical ganglion
Ansa subclavia
78
What is the origin of sympathetic fibers that reach the cranial cervical ganglion?
Most of them come from T1-3, but can come from as far back as T7
79
What is the function of the vertebral nerve? What supplies C1-2?
Supply post-ganglionic sympathetic fibers to the C3-8 regions.
The cranial cervical ganglion is located at C2-3, and post-ganglionics from there will supply the C1-2 distribution (as well as the head).
80
Where do post-ganglionic sympathetic fibers from the middle and cervicothoracic ganglia go? Where do the pre-ganglionics arise from?
Primarily to the heart and lungs
T1-3 intermediate horn
81
What nerve carries sympathetic input to the pelvic viscera? Where are its pre-ganglionic fibers arising from?
Hypogastric nerve
L1-4 (dog) / L2-5 (cat) intermediate horn
82
What are the four cranial ganglia that have post-ganglionic parasympathetic fibers? What are their parent nerves?
- Ciliary ganglion, oculomotor nerve
- Pterygopalantine ganglion, facial nerve (although its part of V at this point)
- Mandibular/sublingual ganglia, facial nerve (although its part of V at this point)
- Otic ganglion, glossopharyngeal nerve
83
What does sympathetic stimulation do to the detrusor and internal urethral sphincter? What are the receptors at each location?
Results in relaxation of the detrusor via B adrenergic receptors, and construction of the internal urethral sphincter via A adrenergic receptors.
84
Via what descending spinal cord tract is micturition coordinated by the pontine micturition center? What does this tract do?
Pontine reticulospinal tract
It inhibits the intermediolateral (sympathetic) nucleus AND the LMNs of the pudendal nerve, while activating the parasympathetic sacral nucleus. Thus, the detrusor is contracted and the sphincters are relaxed.
85
The sympathetic nervous system can cause vasoconstriction and vasodilation. Where does each happen and via what receptors?
- causes vasoconstriction of skin vessels via alpha 1 receptors
- causes vasodilation of skeletal muscle vessels via beta 2 receptors
86
What type of acetylcholine receptors are present at autonomic ganglia?
Nicotinic
87
Per Dewey, what two cranial nerve deficits may be seen in patients with prosencephalic disease? Why?
Contralateral facial weakness and contralateral miosis
Supposedly, the cerebral cortex may have an inhibitory influence on the GVE motor nucleus of 3, and a facilitatory influence on the GSE motor nucleus of 7.
88
What are the names of the two spinal cord tracts dealing with the eyes that leave the midbrain?
Medial tectospinal tract (visual / auditory reflex)
(Lateral) tectotegmentospinal tract (sympathetics to the eye)
89
What is the UMN center supplying the LMNs of the phrenic and intercostal muscles?
Medullary reticulospinal tract
90
Fill in the blanks.
There are three sensory tracts missing — what are they?
There is one motor tract missing — what is it?
Sensory — spinomedullary, spinocervicothalamic, dorsal column post-synaptic
Motor — ventral corticospinal
91
What unique clinical phenomenon can occur with a C6-8 lesion?
Decreased withdrawal due to LMN dysfunction of the musculocutaneous nerve, with UMN dysfunction of portions of the radial nerve resulting in increased tone.
92
What is the function of the rostral ventrolateral medulla? Caudal ventrolateral medulla?
What is the clinical significance of this?
RVLM — supply constant tonic influence on the cell bodies of the intermediolateral horn to maintain BP
CVLM — inhibit the RVLM
When the solitary nucleus receives evidence of hypoxemia from the carotid body, it will stimulate neurons in the RLVM to increase sympathetic tone.
However, when the solitary nucleus receives evidence of hypertension from the carotid sinus, it will stimulate neurons in the CVLM. This inhibits the RVLM, decreasing sympathetic tone.
93
How long does it take CSF to normalize following myelography?
Cell counts — 3 days
Protein — 7 days
94
Pros and cons of collecting CSF in an EDTA tube?
Pros - better preservation of cellular morphology
Cons - falsely increased protein, falsely decreased cell counts
95
What is the ideal timeframe in which CSF should be processed?
30 minutes
96
True or false — the number of expected white blood cells per red blood cells in CSF is different for dogs and cats.
True per Dewey
Dogs — 500 RBC / 1 WBC
Cats — 100 RBC / 1 WBC
97
What two myelographic patterns can look identical on a VD projection?
Intramedullary and extradural (especially midline lesions)
98
Explain the concept of window leveling and window width in regards to CT.
The human eye can only see 20 shades of grey. Naturally, there are probably more than 20 variations of tissue composition in the body that could be represented by different shades of grey when performing a CT — our eyes just couldn’t detect it.
Window leveling picks the specific HU (shade of grey) for the tissue of interest and focuses the middle of the spectrum of greys on that. Window width refers to the range of the HUs that the rest of available shades of grey will cover.
For example, brain windowing has the window level at 35, and a window width of 150 — anything above 150 will show up the same! Conversely, bone windowing will have a window level of 420, and a window width of 1500 — therefore, we have 1500 HU to split into 20 shades of grey — thus all the soft tissues look very similar, while bone stands out crisply.
99
The Larmor equation states that ________ is proportional to _________.
The precessional frequency of hydrogen protons is proportional to the magnet strength.
100
What is required to generate signal for MRI?
Application of a RF pulse at the same frequency as the precessional frequency of the hydrogen protons —this will cause them to gain energy and “flip” out of the longitudinal plane into the transverse plane
