Deck 5 Flashcards
(100 cards)
1
Q
How many laminae are present in the spinal cord grey matter?
What are their broad functions?
Which lamina are Renshaw cells located in?
A
Ten
1-4 are the dorsal grey horn and deal with exteroceptive processing
5-6 are at the base of the dorsal horn and deal with proprioceptive processing
7 is the intermediate substance associated with autonomic function - this contains Renshaw cells
8-9 represent the ventral horn / associated motor neurons
10 is the central grey substance
2
Q
At approximately what level is each of these cross sections from?
What are the arrows at each image?
A
3
Q
Where is the lateral cervical nucleus located?
A
C1-2, laterally in the dorsal grey horn
4
Q
What type of sensory neurons innervate neuromuscular spindles versus Golgi tendon organs?
A
Neuromuscular spindles — 1a
Gogli tendon organs — 1b
5
Q
Label these tracts. Which sensory tract is missing?
A
The missing tract is the dorsal column post-synaptic that runs with the fasciculi gracilis and cuneatus
6
Q
Per Uemura, which sensory receptors are involved in conscious proprioception and which are involved in subconscious proprioception?
A
Conscious — neuromuscular spindle, Golgi tendon organ, Pacinian corpuscle and Ruffini’s corpuscle
Subconscious — neuromuscular spindle and Golgi tendon organ
7
Q
List 5 places that the nucleus of the solitary tract projects axons to.
A
- Thalamus (via solitarothalamic tract)
- Reticular formation for coordination of respiratory, cardiac, etc… centers
- Nucleus ambiguus to control swallowing
- Parasympathetic nucleus of IX (innervation of palate / pharynx)
- Parasympathetic nucleus of X (innervation of viscera)
8
Q
What are the four trigeminal associated brainstem nuclei and what are their functions?
A
- Nucleus of the mesencephalic tract - proprioception
- Pontine sensory nucleus - touch
- Nucleus of the spinal tract - pain & temperature
- Motor nucleus
9
Q
True or false — bone wax is resorbable
A
False — it is not (or minimally) resorbable, and if left in large quantities can cause poor bone healing or infection
10
Q
What is the difference between iris and tenotomy scissors?
What are Pott’s scissors?
A
Iris scissors have a sharp tip, while tenotomy scissors do not.
Pott’s scissors have the tips angled at 45 degrees
11
Q
What is the name for the tips on these Steinmann pins?
What is the main clinical difference between them?
A
Trocar (left) and chisel (right)
Chisel tips generate less heat during placement
12
Q
Describe the differences in thread type in positive profile pins in regards to holding cortical v cancellous bone.
A
Cortical bone — smaller pitch, smaller diameter threads
Cancellous bone — larger pitch, larger thread diameter
13
Q
What is the weakest link of any neurosurgical construct?
A
Pin-bone interface
14
Q
Is high speed or low speed superior at placing pins with power? Why?
A
Low speed is better — high speed can lead to hot bone, and subsequent bone necrosis allowing the bone-pin interface to become weaker
15
Q
What are 2 ways to increase the pin / cement interlock?
A
Notch the ends of the pin protruding from the bone, or bend the end of the pin to a right angle
16
Q
What determines the pull-out strength of a screw? Bending strength? Which diameter is the size of the pre-drilled hole for a screw?
A
Thread diameter (aka major diameter) determines pull-out strength
Core diameter (aka minor diameter) determines bending strength; core diameter represents the diameter of the pre-drill hole.
17
Q
True or false: measuring the depth of the drill hole should be done prior to tapping the drill hole.
A
True — measuring the depth following tapping could damage the tap threads
18
Q
How much does stripping the thread of screw reduce the holding strength by, and what are two possible ways to address this?
A
> 80% reduction
Can either use a larger screw (limited value) or can fill the hole with PMMA and try again (preferred)
19
Q
What type of screw — cancellous or cortical — is likely to have a stronger bending strength? Why?
A
Cortical — generally have larger core diameters compared to cancellous
20
Q
When using a self-tapping screw, what is important to remember regarding the length of the screw?
A
The self-tapping tip portion of the screw does NOT contribute to holding purchase within the bone, and thus, these screws should be advanced 1-2 mm more to engage the cortex with the holding part of the screw.
21
Q
Which screw is self-drilling? Which is self-tapping?
A
Left is self-drilling and right is self-tapping
22
Q
What types of screws are pictured here?
A
Left — self- tapping locking screw
Middle — non-tapping cortical screw
Right — non-tapping cancellous screw
23
Q
What is the main difference between the composition of vertebrae and long bones?
A
Long bones have thicker cortical bone and less cancellous bone compared to vertebrae.
24
Q
What is a unique advantage of the SOP plating system compared to other locking systems?
A
You can use regular cortical screws and achieve locking properties from them with this system, although they will still be weaker than if you had used locking screws.
25
How long does Shores’ text recommend to be NPO following craniectomy?
24 hours
26
What is the range in which cerebral auto-regulatory properties are active? What can impact this?
50-150 mmHg (MAP)
Inhalant anesthetics can compromise this system
27
What percent of patients with primary intracranial neoplasms have primary neoplasms somewhere else?
23%
28
What two anti-convulsants are proposed to have neuroprotective effects in patients undergoing craniotomy that have NOT had seizures previously?
Phenobarbital and levetiracetam
29
True or false: CKCS getting surgery for COMS are less likely to have clinically relevant mitral valve disease than other CKCS
True — in breeding attempts to lessen mitral valve disease, inadvertent selection for CKCS with COMS occurred; the vice versa is also true!
30
What is the preferred anti-septic use in surgical patient preparation in patients with open skull fractures?
Betadine — this is because chlorhexidine may be neurotoxic
31
Which location of intracranial hemorrhage is characterized by a “biconvex” appearance?
Epidural
32
What artifact compromises the ability of CT to image the caudal cranial fossa?
Explain why this artifact happens.
Beam hardening artifact — results in streaks of dark areas within the region of the associated neuroparenchyma
The petrous temporal bone in this area is the densest bone in the body. Most of the photons that hit this bone are absorbed — only the highest energy photons make it through this bone, and when these photons hit the detector plate, the plate assumes that all this energy got through because there was nothing / low-attenuating tissue there — this, black streaks occur
33
What are some brain MRI features of metastatic neoplasia?
Multiple
Small
Located between junction of white / gray matter (watershed zone)
Marked edema
34
What is the amount of CSF that can be safely removed from a patient?
1 mL/5 kg (0.2 mL/kg)
35
Fill in the blanks.
36
What tract carries sensory information up to the pontine micturition center?
Spinothalamic (GSA and GVA)
37
Via what tract does sensory information from the head / face make its way to the cerebrum for conscious perception?
Axons from the pontine sensory nucleus and nucleus of the spinal tract cross over in the “quintothalamic” tract to form the trigeminal lemniscus. This joins with the medial lemniscus and runs to the thalamus. These trigeminal fibers then synapse on the ventral caudal medial nucleus of the thalamus, and from there go to the cerebrum.
Note that the axons mediating GP info from the mesencephalic sensory nucleus will first make a synapse in the pontine sensory nucleus prior to joining the quintothalamic tract.
38
What are the restiform and juxtarestiform body, respectively?
Restiform — caudal cerebellar peduncle
Juxtarestiform — portion of the caudal cerebellar peduncle carrying reciprocal connections between flocculonodular lobe and vestibular nuclei
39
What nerves innervate the orbicularis oculi muscle?
- palpebral branch of auriculopalpebral (dorsal half)
- ventral buccal nerve (ventral half)
40
Fill in the blanks
41
What are the fibers carried by the deep petrosal nerve?
What does this nerve ultimately form?
Post-ganglionic sympathetic fibers running from the cranial cervical ganglion
Nerve of the petrosal canal when it meets the major petrosal nerve
42
Per Uemura, what is the motor arm for the corneal reflex?
Abducens nerve
43
What two cranial nerves leave the cranial vault within a common dural sheath?
Facial and vestibulocochlear
44
What tract provides voluntary ocular movement control? What tract provides in-voluntary / reflex ocular movement control?
Voluntary — corticonuclear
Involuntary — medial longitudinal fasciculus
45
What innervates the carotid body?
What innervates the carotid sinus and related receptor (which is called what)?
Explain the firing pattern of these systems.
Glossopharyngeal innervates the carotid body. Carotid body monitors PaO2 and PaCO2. When O2 decreases or CO2 increases, the glossopharyngeal firing rate increases, which puts more activity into the solitary nucleus, which then tells the medullary respiratory center to fire more.
The glossopharyngeal nerve innervates the carotid sinus and the vagus nerve innervates the aortic arch, which monitor blood pressure. The firing rate is dependent to the pressure (high pressure = high firing rate). Via the vagus nerve feeding into the solitary nucleus, we get activation of various brainstem pathways to include the medullary reticular formation, PSN of CN X, and hypothalamus.
46
Through what nuclei do the fibers of the hypoglossal nerve run through?
Olivary nuclei
47
Where are the hypoglossal motor nuclei located? What other nuclei are also immediately adjacent to this nuclei?
Dorsal midline in caudal medulla just ventral to fourth ventricle
Parasympathetic nuclei of X is just lateral — solitary nuclei is lateral to that — lateral cuneate nuclei is lateral to that
48
True or false — in acute cases of hypoglossal nerve dysfunction, the tongue deviates towards the side of the lesion when licking
True — unopposed protrusion action of the genioglossus muscle causes tongue deviation towards the lesioned side
49
What are the name of the nuclei associated with the reticular formation? What neurotransmitter do they release? What is the name and function of one of these nuclei in particular?
Raphe nuclei
Serotonin
Nucleus raphe magnus — projects to dorsal horn of spinal cord to modulate / inhibit ascending pain signals
50
What is a good rule of thumb for which motor tracts are excitatory for flexors and which motor tracts are excitatory to extensors?
Tracts in the lateral funiculus of spinal cord are facilitatory for flexors (rubrospinal, medullary reticulospinal), while tracts in the ventral funiculus are facilitatory to extensors (vestibulospinal, pontine reticulospinal).
51
Describe the reflex pathway for swallowing.
GVA fibers supplying the pharynx via CNN IX and X are stimulated when there is food in the pharynx. They project this information to the nucleus of the solitary tract, who sends information to the nucleus ambiguus to coordinate the motor part of swallowing.
52
What is the external medullary lamina? What separates this layer from the internal capsule?
External medullary lamina is a thin layer of white matter covering the lateral aspect of the thalamus. It is covered by a narrow nuclear area called the thalamic reticular nucleus.
53
What is the internal medullary lamina?
This is a layer of white matter that projects into the thalamus, and helps divide it into various sections.
54
What are the three functional groups of neurons in the thalamus, and what are their roles?
- direct cortical projection system — relays specific information regarding specific sensory modalities to the cerebrum
- diffuse cortical projection system — not a super well defined function on its own, but receives afferents from the cerebrum and thalamus
- thalamic reticular system — the most rostral portion of ARAS, and via projections to the diffuse projection system, awakes the entire cerebrum
55
What clinical signs will lesions at these specific thalamic nuclei induce?
Lateral geniculate —
Medial geniculate —
Ventral caudal lateral —
Ventral caudal medial —
Ventral lateral —
Ventral rostral —
Lateral geniculate — contralateral vision loss (hemianopsia)
Medial geniculate — potentially vestibular signs; unable to detect the hearing deficits associated with such lesions in dogs
Ventral caudal lateral — contralateral hypalgesia & proprioceptive deficits
Ventral caudal medial — contralateral hypalgesia of the head / face
Ventral lateral — possibly cerebellar ataxia
Ventral rostral — contralateral proprioceptive deficits
56
Two reasons for absent oculocephalic reflex
Severe brainstem lesion - likely interrupting ascending MLF neurons
Bilateral otitis interna / other internal ear disease
57
What is the floor of the hypothalamus called? What extends from this floor?
Tuber cinerum
Infundibulum
58
What type of hypothalamic neurons are dysfunctional in cases of equine Cushing disease? Treatment option?
Dysfunction of hypothalamic dopaminergic neurons, allowing the pars intermedia of the pituitary to function excessively.
Treatment with pergolide, a dopaminergic agonist may be helpful.
59
What is the dose for contrast for myelography? What is the maximum recommended dose?
0.3-0.45 mL/kg
8 mL
60
What is the paradoxical contrast obstruction sign, and when is it used?
What is another technique that could be performed in conjunction with looking for this sign?
This is used when there is no deviation of the contrast columns on the VD (remember, deviation is normally what helps us determine lateralization of an extra-dural lesion).
This sign refers to a larger length of attenuation of the contrast column on the opposite side of the compressive lesion due to squishing of the spinal cord against the rigid bone of the vertebral canal.
Oblique views
61
What size dog has less epidural fat around their spinal cords? What is the clinical significance of this?
Small dogs have less epidural fat than big dogs. This might make non-contrast enhanced CT less sensitive in small dogs for detecting extra-dural compression because you can’t rely as much on detecting the displacement of epidural fat.
62
Specifically for cervical spondylomyelopathy, what does the combination of T2W hyper and T1W isointensity indicate? The combination of T2W hyper and T1W hypointensity?
T2W hyper / T1W iso = mild loss of neurons, gliosis, edema, demyelination, Wallerian degeneration
T2W hyper / T1W hypo = necrosis / malacia
63
How much more sensitive is CT than radiographs at detecting bone density change?
CT can detect a 0.5% change, while radiographs can only detect a greater than 10% change
64
What are the three ligaments penetrated during a lumbar CSF tap?
Supraspinous, interspinous, and ligamentum flavum (interarcuate)
65
True or false: per Shores, there is no additional safety of collecting CSF via lumbar puncture when there is concern for elevated ICP
True
66
Where should muscle biopsies be taken in acute disease? Chronic disease?
Acute — severely affected muscles
Chronic — less severely affected muscles (to avoid just getting fibrosis)
In both cases, consider getting biopsies on the opposite side from the side you did EMG on.
67
For the pelvic limb, which combination of nerve / muscle can be biopsied via a single incision? Thoracic limb?
PL: Common peroneal, gastrocnemius and biceps femoris
TL: ulnar nerve, medial head of triceps, and superficial digital flexor
68
Describe what is marked in this photo
Top line / solid arrow — incision for biopsy of the common peroneal nerve, gastrocnemius and biceps femoris mm
Middle line / dashed arrow — biopsy site of cranial tibial muscle
Bottom line / double arrow — tibial nerve
Blue dashed line represents the lateral saphenous vein
69
What percentage of the nerve diameter can you take with a biopsy?
30-50%
70
Describe what this photo is demonstrating.
This is picture, centered at the medial aspect of the elbow. The top arrow is pointing to the triceps muscle biopsy, the middle arrow is showing the ulnar nerve biopsy site, and the bottom arrow is showing the superficial digital flexor biopsy site.
71
What are the anatomic landmarks for a transfrontal craniectomy, specifically in regards to drilling the outer table? What is the angle they recommend drilling at?
1. Rostral — junction of the nasal bones
2. Lateral — medial aspect of zygomatic process of frontal bone
3. Caudal — junction of the frontal-parietal sutures
30 degree angle
72
True or false: Shores recommends post-operative antibiotics for all post-op transfrontal craniectomies
True
73
Explain why supplemental oxygen therapy may be an effective medical management strategy for symptomatic pneumocephalus.
By supplementing oxygen, you increase the amount of oxygen in the lungs — simultaneously you are decreasing the amount of nitrogen in the lungs and therefore in the bloodstream. Remember that nitrogen is the majority of what is in room air. This creates a concentration gradient that favors the movement of nitrogen into the bloodstream, and hopefully out of the skull / brain.
74
What is an alternative means of closure if you break your outer table transfrontal bone flap?
Cover the defect in PMMA
75
What nerve is located at the rostral aspect of the incision made for a rostrotentorial craniectomy? What does this nerve supply?
Auriculopalpebral n
The dorsal half of the orbicularis oculi m.
76
Label these bones
77
What artery is prone to bleeding when removing the flap of bone from a rostrotentorial craniectomy?
Middle meningeal artery
78
When accessing intraparenchymal brain neoplasms, where should the incision be made? Why?
Should be made in the overlying gyri as sulcar incisions can be associated with more hemorrhage.
79
When does Shores recommend drilling the suture holes in a transfrontal craniectomy?
Prior to using the sagittal saw to remove the outer table
80
Per Shores, what are the four indications to perform a FMD?
1. Neosplasms
2. Quadrigeminal diverticula
3. COMS
4. Cerebellar biopsy
81
What is the main artery encountered during the approach to the occipital bone? What is an alternative name for this artery?
Caudal auricular artery, also termed great auricular artery
82
In what common domestic animal is there no nuchal ligament?
Cat
83
True or false — when doing a duraplasty for COMS correction, a water tight seal must be obtained when suturing on the synthetic dura.
False
84
How much adjacent bone is recommended to be removed when removing a skull tumor?
1-2 cm
85
Where does peri-ventricular edema usually first appear? What does this look like on CT?
Dorsolateral aspect of the lateral ventricles
Blurred edges to the normally crisp margins of the ventricles
86
How much of the VP shunt should be placed within the abdominal cavity?
1/3 to 1/2 the length of the shunt
87
What percent of VP shunt patients require revision surgery?
15%
88
What breed of dog is over-represented for quadrigeminal diverticula?
Shih Tzus
89
What increases the likelihood that a quadrigeminal diverticula is clinically relevant?
Compression of the occipital lobes by greater than 14%, or dual compression of the occipital lobes and cerebellum.
90
What two spinal structures are notochord remnants?
Nucleus pulposus
Apical ligament of the dens
91
Why may a patient (dog primarily) with a cranial cervical injury present with signs of brainstem dysfunction?
Compression / damage to the basilar artery, resulting in brainstem ischemia. Theoretically possible in cats as well, although this artery flows cranial to caudal in cats.
92
What is the size of the gap between the dorsal arch of the atlas and the cranial aspect of the C2 spinous process needed to call something an AA subluxation?
4-5mm
93
What is the ideal angle for placement of transarticular implants when stabilizing the AA joint?
30 degree
94
What is a means of reducing iatrogenic surgical complications associated with the ventral approach to the AA joint?
Paramedian approach between the right sternocephalicus and sternohyoideus mm
95
What are four factors associated with a better outcome for surgical management of AA subluxation?
- less than 2 yo
- duration of clinical signs less than 10 mo
- duration of clinical signs greater than 30 days
- ambulatory pre-op status
96
Which portions of the cerebral cortex do not have 6 laminae? What are they referred to as?
Entorhinal cortex
Cortex of lateral olfactory gyrus
(AKA together these make up the piriform lobe cortex)
Referred to as paleocortex
97
Which nucleus is actually just a portion of the caudate nucleus that was split from it by the internal capsule? Together, what are these two nuclei referred to as?
Putamen
Striatum / neostriatum
98
Describe (as best possible) the direct and indirect pathways associated with the motor system.
Direct pathway:
- neostriatum influences the medial GP
- medial GP influences the thalamus
Indirect pathway:
- neostriatum influences the lateral GP
- lateral GP influences the subthalamic nuclei
- subthalamic nuclei influences the medial GP
- medial GP influences thalamus
The neostriatum can be activated via cerebral cortex.
The D1 dopamine receptors from substantia nigra specifically excite the neostriatal neurons that inhibit the medial GP. The D2 dopamine receptors from substantia nigra specifically inhibit the neostriatal fibers that inhibit the lateral GP.
The neostriatum can also inhibit the substantia nigra itself.
Neostriatum also inhibits both the medial and lateral GP.
The lateral GP inhibits the subthalamic nucleus. The subthalamic nucleus activates the
medial GP. The medial GP inhibits the thalamus. The thalamus activates the motor cortex.
All of this can be used to create varying feedback loops on motor control.
99
Which tract — lateral or ventral corticospinal — extends all the way down the SC? What is the distribution of axons splitting off in this tract? How far down the SC does the other tract continue?
Lateral corticospinal tract extends all the way down the SC.
50% of axons leave in neck, 30% in thoracic, and 20% in the LS region
The ventral corticospinal tract only extends to the mid-thoracic region
100
Which descending motor tract is an exception to the rule that tracts in the ventral funiculus are excitatory to extensors / inhibitory to flexors?
Ventral corticospinal tract — does the same thing as the lateral one
