31. Cervical Spine Flashcards
why are more severe neurologic signs seen in the pelvic limbs vs the cervical limbs in patients with cervical spinal cord dz?
motor pathways to pelvic limbs are more peripherally locations than those responsible for thoracic limb motor function
thoracic limb gait with C1-C5 lesion vs C6-T2 lesions
THORACIC limbC1-C5 long strides, increased limb stride lengthC6-T2 short stilted choppy (often accompanied by long strides pelvic limbs–two engine gait)
percentage of single level cervical disc lesions incorrectly localized based on reflex examination
34% of dogs with single level cervical disc lesion were incorrectly localized based on spinal reflex examex. dogs with C1-C5 lesion may have decreased withdrawal and incorrectly localize dz
how long does it take for neurogenic or den nervation atrophy to be seen in front limbs
7 dayswhereas disuse atrophy may take up to several weeks
Horners may be seen with C1-C5 lesions or C6-T2 lesions?
C6-T2 lesions esp if affecting T1-T3 nerve roots and loss of SNS in this area
phrenic nerve spinal cord segments
C5-6-7
structures involved in cervical pain
meningesannulus fibrosisperiosteumjoint capsule of zygapophyseal jointepaxial musculatureligamentous structures
nerve “root signature” signs may accompany what cervical lesion localization
C6-T2
surgical approaches to the cervical spine
- ventral–routine ventral, modified ventral with paramedian dissection btwn R sternocephalicus and sternohyoideus m2. lateral–bunt dissection through brachiocephalicus m (superficial cervical artery/vein); , splenius is medial (deep)3. dorsal
approach to the brachial plexus
- lateral platysma, cleidocervicalis, omotransversarius (inserts on spine of scapula–is transected), trapeziussuperficial cervical artery/vein
benefit of modified ventral approach to cervical spine
paramedian dissection btwn R sternocephalicus and sternohyoideus musclesprotects trachea, right recurrent laryngeal n, vagosympathetic n, right carotid sheathprovides increase exposure to caudal cervical vertebradecreases likelihood of hemorrhage from right caudal thyroid artery
paired muscle group on floor of cervical vertebra
paired longus colli muscle
anatomy of AA joint
atlas (C1) lacks a spinous process; wing like transverse processes—develops from 3 boney elementsaxis (C2) large spinous process–develops from 7 boney elements; dens (odontoid process) held down by transverse ligament”no joint”
ligamentous attachments of C1-2 (7)
dens is held down by TRANSVERSE ligamentdens attaches to foramen magnum via APICAL ligamentdens attaches to occipital condyles via ALAR ligamentsC1-C2 dorsal AA ligamentC1-C2 AA joint capsuleC1-C2 AA lateral ligamentsC1 to occipital bone AO joint capsule
developmental malformations of the dens
young small breed dogshypoplasia/aplasia 46%dysplasia 34%dorsal angulationseparation of densabsent transverse ligament
T/F24% of dogs with AA instability will have a normal dens
TRUE24% of dogs with AA instability will have a normal dens
1 clinical sign of AA instability
1 NECK PAIN (30-60%)(aymmetric, mild postural rxn abN, rarely tetraplegic, worse pelvic than thoracic limbs, torticollis due to concurrent syringohydromyelia)
radiographic signs of AA instability
increased space btwn dorsal lamina of atlas and spinous process C2malalignment of C1 and C2 vertebral bodies (sublux/lux)angle btwn C and C2 of < 162 degrees is more predictive of instability presence/size of dens (VD film or oblique)
complications with splinting/conservative tx of AA instability
- recurrence2. corneal ulcers3. splint movement4. moist dermatitis/ulceration5. hyperthermia6. respiratory compromise7. anorexia8. otitis
SURGICAL techniques for AA repair
- DORSAL (decompress, reduce and stabilize)–AA wiring +/- PMMA, Braided suture, nuchal ligament technique, dorsal cross pinning +/- PMMA, Kishigami AA tension bandDOES NOT RESIST MOVEMENT IN DIRECTIONS OTHER THAN FLEXION (minimal osseous fusion occurs)2. VENTRAL (–bone plating, transarticular screws/pins, pins +/-PMMA, screw +/-PMMA, combo pins/screws +/- PMMAMay require odontoidectomy, cancellous bone graft and removal of cartilageADVANTAGE OF JOINT FUSION TO OCCUR With VENTRAL TECHNIQUES
what is a contraindication for dorsal stabilization for AA instability
compression of spinal cord due to dorsal deviation of dens
drill position for transarticular screw placement to tx AA instability
Ventral approach1.5 mm screw 1.1 drill bitdrill is directed craniolaterally 30 degrees from midlineaim for medial border of alar notch
complication rates btwn ventral and dorsal stabilization of AA instability
dorsal 71% complications; failure 48%ventral 53% complications; failure 44%
types of complications following surgery for AA instability
- neurologic deterioration (concussive injury)2. Respiratory system compromise (recurrent laryngeal n damage, compression of trachea from implants/PMMA, CNS trauma, aspiration pneumonia3. implant failure (improper bone purchase 25% dorsal, 18% ventral)4. fracture of C1, C25. recurrent pain
prognosis with conservative mgmt AA instability
38%dogs affected < 30 days were more likely to hav a better outcome compared to affected dogs > 30 days
perioperative mortality for AA instability
10-30%age < 24 months and clinical signs < 10 months had better outcome
long term success with dorsal stabilization of AA instability
good to excellent 61%dorsal wire 52%dorsal suture 50%dorsal nuchal 75% (only 4 dogs evaluated)Kishigami AATB 75% (only 8 dogs evaluated)
long term success with ventral stabilization of AA instability
good to excellent 47-92%transarticular pin alone 47% (least success)transarticular screws 90%
T/Fpartial injuries of brachial plexus most often affect the caudal plexus
TRUEpartial injuries of brachial plexus most often affect the caudal plexus
brachial plexusSSMARMU
(CRANIAL)1. suprascapular2. subscapular3. musculocutaneous (C6-C8)4. axillary5. radial (C7-T2)6. median7. ulnar
weakest part of nerve and area of injury most often present with brachial plexus injury
site of root avulsion = intraduralweakest part = intradural bc lacks epineuriummotor (ventral) roots appear to be more susceptible
6 classifications of nerve injury
- neuropraxia–reversible, interruption in fx and conduction WITHOUT structural changes2. axonotmesis–reversible, crush/percussion injury, wallerian degeneration distally, but internal structure preserved3. neurotmesis–disruption of axons/endoneurium but intact perineurium4. neurotmesis–disruption includes perineurium5. neurotmesis–entire nerve is severed6. COMBINATION injury of whole fascicle
clinical signs with CRANIAL brachial plexus avulsion
C(5)6-C7SSMA affectedRAREelbow extensors are NOT affected (radial nerve)animal can bear weightmay see atrophy of supraspinatus/infraspinatus
clinical signs with CAUDAL brachial plexus avulsion
C8-T2RMUMORE COMMONHorners (T1-T3); loss of CTRinvolvement of radial nerve to triceps dictates how much animal can bear weight (distally can be more weight)because musculocutaneous n intact can flex arm
clinical signs with COMPLETE brachial plexus avulsion
C6-T2 SSMARMUseverelimb knuckled over, atrophy, hypotonic
surgical techniques for repair brachial plexus
- neurotization (nerve transfer/graft)–cats did well2. reimplantation of nerve roots to spinal cord3. end to end neurorrhaphy4. carpal arthrodesis5. tendon transposition techniques6. limb amputationrarely need sx bc not usually neurotmesis injurystill need some radial nerve function to bear weight
surgical complications to brachial plexus avulsion repair
- neurological deterioration2. cutaneous trauma/self mutilation
type of joint for intervertebral disc
amphiarthrodial
T/Fmost dogs with cervical disc disease have extrusions rather than protrusions
TRUE most dogs with cervical disc disease have extrusions rather than protrusionsEXCEPTION: large breed dogs with CAUDAL cervical lesions (wobbler’s) are more likely to be protrusions
overall accuracy for radiographic correct site ID in dogs with cervical IVDD
only 35% accurate on rads at predicting correct site
surgical approaches for cervical disc disease
- ventral slot (length and width 1/3–avoid internal vertebral venous plexus)2. Slanted V slot (caudal aspect of cranial vertebral body removed without removing much annulus in attempt to maintain some stability)3. hemilaminectomy (removes articular facets, avoid vertebral artery)4. dorsal laminectomy (rare–multifidus muscle elevation, spinous process and yellow ligament removed)+/- fenestration as an adjunct treatment–NOT by itself
advantages and disadvantages of cervical Vslot approach
advantages: minimal muscle dissection, prophy fenestrationdisadvantages: hemorrhage from sinus, small field of vision, inadequate exposure for lateralized discs
surgical complications for cervical disc surgery
- respiratory compromise–phrenic nerve C5-7, CNS disease, aspiration pneumonia, hypovent2. Cardiac arrhythmias3. blood loss (internal vertebral venous plexus)4. neurological deterioration (horners, lar par)5. Vertebral instability/sublux/lux6. seroma (esp with dorsal approaches)
key static factor in wobblers pathogenesis
vertebral canal stenosis
difference btwn osseous and disc associated CSM/wobblers
disc–older, Dobies, stenosis–>torsion–>disc protrusion more so in caudal vertebra; most commonosseous–>younger, Great Danes, stenosis congenital malformation–>osseous proliferation
T/Fwith spinal cord stretch, a ventrally positioned extradural lesion will worsen spinal cord compression
TRUE
single site vs multiple site CSM/wobblers in large vs giant breeds
large 50:50 giant breeds 20 (single site):80 (multiple sites)
radiographic signs of CSM
changes in shape of vertebral bodynarrowing of disc spacevertebral canal stenosisosteoarthritic, sclerotic changes in zygapophyseal jt
myelographic views for CSM
ventral flexion, dorsal extension, linear tractionMRI is still gold standard for diagnosis and spinal parenchymal changes at the most affected site
other diagnostics to consider for Wobblers patients
–COMPLETE ORTHO/NEURO EXAM–thyroid testing–vWF–BMBT–echo
improvement seen in medically treated dogs vs surgically treated dogs
medical tx 54% improved surgical tx 81% improvedregardless of therapy MST was identical 36 months
direct decompression methods to tx CSM
- dorsal laminectomy (mostly for osseous associate CSM)2. dorsal laminoplasty3. V slot4. inverted cone slot5. hemilaminectomy
INdirect decompression methods to tx CSM
distract (gelpis, caspar distractors) and stabilize1. bone grafts2. pins/screws PMMA3. metallic spacers4. plastic plates, metallic plates (locking)5. K wire spacers6. harrington rods7. interbody PMMA plugs8. fusion cages+/- disectomy, V slots, fenestration
long term success rate for CSM treated with v-slot direct decompression
72%
morbidity associated with dorsal laminectomy technique to treat direct compression of CSM patients
70%most improve over time (~3.6 months)
long term success rate for CSM treated with indirect decompression and stabilization ( pin/screws w PMMA or PMMA plug, or locking plate)
pins/screws PMMA 73%PMMA plug 82%locking plate 73%
motion preserving technique under investigation for treatment of CSM
cervical disc arthroplastytitanium artificial disc placement to reestablish disc width/height and preserve motion of disc spacehopes are to decrease risk of domino effect
complications with surgical treatment of CSM
~ 15 % overall complications–neurological deterioration–vertebral canal and foramina penetration (aim 30-35 degrees and 45 degrees if C7)–Domino effect (20%)–laminectomy membrane–implant failure (7.5-30%)–collapse of intervertebral foramina–insufficient decompression
recurrence rate for CSM patients
24% regardless of surgical technique
where do extradural synovial cysts arise from
originate from zygapophyseal jointlocated EXTRA rurallydivided into synovial cysts (have epith lining) and ganglion cysts (no lining)degeneration changes in joint appear to be main predisposing factor
