Chapter 31 Cervical Vertebral Column and Spinal Cord Flashcards
Why might animals with cervical spinal cord disease present with more pronounced pelvic limb dysfunction vs thoracic limb
Because descending UMN tracts to pelvic limbs are more peripherally located than those responsible for thoracic limb motor function.
In what scenario might thoracic limb motor dysfunction be more profound than in the PLs
Lesion affecting central aspect of SC = “central spinal cord syndrome”
What spinal cord segement does lateral thoracic nerve come from?
C8-T1
Which nerve is responsible for each area?
From what spinal cord segements does phrenic nerve come?
C5-C7
SC lesion affectign which segments can –> horners?
T1-T3
(likely to be accompanies by ipsilateral reduction in reflexes helps to localise horners to SC segment vs a more peripheral issue)
N.B. leisons cranial to T1-T3 can sometimes cause horners
What area of Sc damage typically causes incontinence?
Dorsal portion
Damnit v ddx for C1-C5 myelopathy
Damnit v ddx for C6-T2 myelopathy
Name 3 approaches to cervical vertebral column
- Ventral approach (+ modified between sternohyoideus and sternocephalicus)
- Lateral approach
- Dorsal approach
List 3 benefits to modified ventral approach to cervical vertebral column
- Protection of tracheal, recurrent laryngeal and vagosympathetic trunk
- Increased exposure
- Less likely to cause haemorrhage from caudal thyroid artery
List two ventral approaches to AA joint
- Ventral apprach
- Modified ventral approach (between sternocephalicus and sternothyroid)
Name anatomical landmark for ventral C1
Ventral tubercle on caudal aspect of C1
Describe the lateral approach to cervical vertebral column
See figures in the book - helpful. Approaches book makes most sense!
- Skin incision from C2 to cranial margin of the scapula at the level of the cervical zygapophyseal
- Incise platysma to expose underlying brachiocephalicus and trapezius muscles.
- In the cranial cervical region, the splenius and serratus ventralis are exposed by bluntly dividing and retracting the brachiocephalicus muscle in a direction parallel to its individual fibers, using a grid technique (Figure 31.5).
- Superficial fibers of the serratus ventralis muscle are bluntly divided and retracted, facilitating exposure to the medial fibers of the serratus ventralis muscle, which are subsequently bluntly dissected from the underlying muscles of the longissimus system.
- To approach the C5-C7 vertebral segments, the splenius and serratus ventralis muscles are exposed by separating the brachiocephalicus muscle craniolaterally and the trapezius muscle in a caudodorsolateral direction after insertion of a self-retaining retractor in the fascial plane that naturally divides these muscles (Figure 31.6).
- The superficial cervical artery and vein, which are located between the brachiocephalicus and trapezius muscles, are then isolated, ligated, and divided.
- Exposure to the C6-C7 vertebral segment is further facilitated by simultaneous abduction and caudal retraction of the scapula. Retraction of the scapula is performed to expose the articulation of the C6-C7 vertebrae without the need to incise the muscular attachments on the cranial border of the scapula.
Name anatomical landmark of c6
Prominent transverse processed of c6
Describe approach to brachial plexus
- Curvilinear incision 3 to 4 cm cranially from midpoint ofcranial border of scapula to slightly distal to the greater tubercle.
- Inscise platysma muscle and cervicsl fascia cervical fascia, exposing brachiocephalicus, omotransversarius, and trapezius muscles.
- The superficial cervical artery and vein, which emerge between the brachiocephalicus and trapezius muscles, is ligated. The superficial cervical lymph node, lying medially to these vessels, is retracted caudally.
- Inscise omotransversarius muscle near insertion on spine of the scapula and retracted cranially.
- Continue dissection medially along the dorsal border of the brachiocephalicus, which is withdrawn ventrally. A Gelpi retractor is positioned between brachiocephalicus and trapezius muscles.
- The scapula is withdrawn caudally with a Farabeuf retractor. The extrathoracic part of the brachial plexus can now be exposed and palpated ventrally.
- The ventral branches of C5-T1 spinal nerves are exposed by transecting the superficial and deep portions of scalenus muscle. The spinal nerves can be found deep to the scalenus muscle.
whch direction does AO joint move? and AA joint?
AO joint = yes joint
AA joint = no joint (primarily moves by rotation)
How many foramina are there in the atlas and what runs through each?
3 foramina (2 paired): vertebral foramen, transverse foraminae, lateral vertebral foraminae
Vertebral foramen: SC
Transverse foramina: Vertebral artery on its way to lateral vertebral foramen
Lateral vertebral foramen: Vertebral artery + vein and first cervical spinal nerve
Label the diagram
How many centres of ossification does the atlas have?
And the axis?
When do the fuse?
Atlas 3 centres of ossification (dorsal arch fused 106d, ventral 115d)
Axis 7 centres of ossification (up to a year for full fusion)
Name the ligamentous structures of the aa joint
- AA ligament
- Transverse ligament
- Apical ligement (–> basioccipital bone)
- Alar ligament (paired) (–> occipital condyles)
Name 6 possible anomalies of the AA joint (that may predispose to aa sublux)
- Dysplasia
- Hypoplasia/Aplasia
- Dorsal angulation/separation of the dens
- Absence of transverse liagement
- Incomplete atlas ossification
- Block vertebrae
Anatomical reason mini breeds are prone to aa sublux
Dens prone to maldevelopment due to aberrant physeal growth plate closure in miniature breeds
What is most common cs of aa sublux?
Gait dysfunction (94%)
How is aa lux dx on rads?
- Increased space between dorsal lamina of atlas and spinous process of axis (should rest on dorsal lamina of atlas)
- (AA angle <162º more predictive of aa instability than decreased aa overlap)
A, Lateral radiograph of the cervical vertebral column in a slightly extended position, which does not normally reveal such obvious separation between the cranial aspect of the spinous process of C2 (arrow) and the laminae of the atlas (arrowhead).
B, Ventrodorsal radiograph of the occipitoatlantoaxial articulation of the same dog as in A, revealing a markedly hypoplastic dens (odontoid process) (arrow).
C, A flexed lateral radiograph of the cervical vertebral column demonstrates marked subluxation of C1 (arrowhead) and C2 (arrow) vertebrae. Such a view is not uniformly recommended because it can be associated with a high risk for further neurologic compromise.
Comment on use of extrenal coaptationin AA lux (3 points)
- Aim to stabilise AA while ligamentous structures heal
- Must extend from rostral to ears to include thorax
- External coaptation likely to lead to recurrent/progressive signs
List 9 complications associated with external copatation for AA
- Recurrence of disease
- Corneal ulcers
- Splint migration –> ineffective
- moist dermatitis/ulcers
- Hyperthermia
- respiratory compromise
- anorexia
- OE
- Accumulation of food in splint
In what situations might exteral coaptation for AA be considered (sugery generally advised)
- Financial limitations
- Poor systemic health
- younf patient (wait for growth before sx)
- Severe neuro dysfunction so assess poss prognosis before committing to sx.
Name a contraindication for dorsal AA stabilisation
In which scenario might dorsal technique be preferable?
Dorsal deviation of the dens
Animals <2kg or if ventral stabilisation has failed
Which technique (dorsal vs ventral) is preferred for AA stabilisation and why?
What is complication rate of dorsal AA stabilisation techniques vs ventral?
What % of dorsal technique cases had good/excellent outcome?
And with ventral technique?
What is overall reported failure rate with dorsal vs ventral technique
- Ventral preferred as possibility of bony ankylosis
Complication rate:
- Dorsal 71%
- Ventral 53%
Good/excellent outcome:
- Dorsal 62% g
- Ventral 47-92%
Overall failure rate:
- Dorsal 48%
- Ventral 44%
Name 4 techniques for dorsal AA stabilisation
And 4 for ventral
Dorsal:
- Kishigami AA tension band
- Nuchal ligament technique
- Dorsal crosspinning + PMMA
- Dorsal AA wiring (also reported suture between muscles in X-fashion)
Ventral:
- Transarticular screws/pins
- Pins + PMMA (i.e transarticular pins AND perpendicular pins + PMMA)
- Screws + PMMA
- Ventral plating
Name a benefit of kishigami AA tension band over other dorsal techniques
Reduced risk of SC damage
List 4 technique for reduction/temporary stabilisation of AA lux, from ventral approach
- Bone screw in caudal C2 vertebral body
- Halsted forceps over vertebral body
- Instrument in C1-C2 IVD space
- Gelpi with an armi in AO space and other in C2-C3 space
At what angle should transarticular screws for AA lux be placed, from medial to lateral and from ventral to dorsal
What screw size?
- 40º from medial to lateral (aim to come out medial to alar notch)
- 20º from ventral to doral
3-5mm corridor
1.5mm screw
What are the two described screw placement configurations in axis for ventral AA stabilisation
Atlas:
- (same for both): Medial aspect of each atlas wing (caudal to transverse foramen) +- a third midline (not penetrating vertebral canal)
Axis:
- Four screws in body (one screw is placed in the middle of the caudal aspect of each of the cranial articular surfaces of the axis at the insertion point of the longus colli muscle. The screws are directed craniolaterally at 30 to 40 degrees. The second pair of screws is placed at the base of the transverse processes of the axis or in the C3 vertebra and is directed laterally at 30 to 40 degrees to the midline. With this technique, Steinmann pins or Kirschner wires can be used to bridge the screws; the pins or wires are positioned parallel to midline and are secured by orthopedic wire to the screws)
- Two in body, along midline (one can be used initially for reduction.
Encased in PMMA
Name 2 plate types used for ventral aa plating
- H-plate (2.0mm)
- Five hole butterfly plate (1.5mm)
List 5 possible complications following AA stabilisation sx
- Neurological deterioratioon
- Respiratory compromise (lar par, racheal necrosis from PMMA, aspiration)
- Implant failure
- Fracture
- Recurrent pain
What factor was associated with good outcome following conservative management?
What factors were associated with good outcome following surgical management?
Conservative management:
- Affected for <30d
Surgical management:
- Age of onset <24 months
- Affected for <10 months
- Lower severity of clinical signs
Which method of surgical management for AA lux reported to have least success?
Transarticular pins alone (cf multpile pins/scres and PMMA)
Which spinal cord segments contribute to brachial plexus?
C6-T2
(and C5 in 24% of dogs)
Partial brachial plexus injuries most commonly affect the spinal nerve roots that contribute to the whih (cranial or caudal) portion of the brachial plexus
Caudal
Describe the crossectional anatomy of peripheral nerve
Endoneurium surrounds each axon
Groups of axons are surrounded by perineurium
The connective tissue around the entire nerve, called the epineurium
What are the 13 named nerves of the brachial plexus/direct continuations of formative spinal nerves?
- Brachiocephalic
- Suprascapular
- Subscapular
- Musculocutaneous
- Axillary
- Radial
- Medial
- Ulnar
- Dorsal thoracic
- Lateral thoracic
- Long thoracic
- Pectoral
- Muscular
When do spinal nerves forming brachial plexus become named nerves?
As they exit plexus
Where along the nerve anatomy does brachial plexus injury most commonly occur?
Intradurally where nerve root arises from SC. Lack epineurium here so weak
If damage is severe may lead to SC injury to –> PL ataxia/UMN paresis/plegia
Describe the classes of traumatic nerve injury.
Class 1:
Class 2
Brachial plexus injury is divided into 3 types, what are they and what are the associated exam findings?
- Injury to cranial portion (C6-C7 = Suprascapular, subscapular, musculocutaneous, axillary).
- Rare.
- Few c/s. Loss of shoulder movement and elbow flexion
- Injury to caudal portion (C8-T2 = radial, median, ulnar nerves)
- More common, radial nerve involved in 92% of brachial plexus injuries.
- Limb may be flexed as musculocutaneous, axillary and suprscapular nerves intact. No elbow or carpal extension. High proportion have Horner’s or loss of cuteneou strunci reflex (C8-T1)
- Injury to all spinal nerve roots (C6-T2)
- Drag limb, knuckled.
Describe the sensory loss associated with cranial- , caudal- and complete brachial plexus injury
What is the acronym for remebering order of brachial plexus nerves? And their spinacl cord segment they originate from?
SSMARMU!!
What re 3 types of surgical nerve repair
Eepineural, fascicular, and graft repair.
Direct end-to-end neurorrhaphy is carried out using an epineurial repair approach (upper panel), which entails placing sutures through the epifascicular epineurium and bringing the nerve stumps into approximation.
Fascicular repair (upper panel) involves placing sutures through the perineurium.
Graft repairs (lower panel) are performed when direct end-to-end neurorrhaphy would cause excessive tension on the repair site. The graft material is harvested from a “nonessential” nerve and is then sutured between fascicles.
How can lateralized/formainal disc material be better assessed using myelography?
Oblique view
A: A lateral myelogram of the cervical vertebral column demonstrating compression of the spinal cord at the C3-C4 intervertebral disc space. Note the attenuation of the contrast medium in the dorsal subarachnoid space at dorsal articulation of C3-C4. Ventrally, the subarachnoid space also is attenuated (arrow). Additionally, there is “splitting” of the ventral contrast column suggestive of a lateralized or ventral midline extradural lesion.
B: A ventral oblique view reveals attenuation of the contrast medium in the subarachnoid space along the right side of the spinal cord (arrow), which suggests a lateralized extradural lesion.
What is the classical sign of HNPE on MRI
How does the extruded material look on T2, STIR and T2 FLAIR?
“Seagull sign”
T2: Isointense to CSF
STIR: Isointense to CSF
T2 FLAIR: Supressed
A sagittal (A) and transverse plane (B) T2-weighted magnetic resonance image of the cervical vertebral column of a dog with hydrated nucleus pulposus extrusion at the C4-C5 intervertebral disc space (arrow) and consequent compression of the spinal cord.
List the three main radiographic changes in disc associated CSM
- Changes in shape of vertebral body
- Narrowed IV disc space
- Vertebral canal stenosis
N.B. 25% of clinically normal Dobermans have similar rad changes.
Lateral (A) and ventrodorsal (B) radiographic images of a 5-year-old Great Dane with osseous-associated cervical spondylomyelopathy. Note severe, osteoarthritic proliferative changes (arrows) throughout his cervical vertebral column in the radiographs.
C, Dorsal T2-weighted magnetic resonance imaging shows bilateral spinal cord compression (arrows) in the caudal cervical region.
List 4 indirect decompression techniques for management of CSM
- Distraction-stabilization with metal implants + PMMA (+ ventral slot)
- Screw bar - PMMA
- Distraction using PMMA plug
- Locking plate (w partial ventral slot or discectomy + bone graft)
- Alternative techniques e.g. titanium cage, intervertebral spacer, intervertebral cage of carbon fibre reinforced polmyer (PEEK), intervertebral traction screw + plate.
Lateral radiograph of polyetheretherketone (PEEK) cage and locking plates in a 7-year-old Doberman Pinscher with cervical spondylomyelopathy.
Name a motion preserving technique for management of CSM .
How many spaces can it be used for?
Supposed advantage?
Outome?
- Disc arthroplasty
- 2-3 spaces
- Advantage = allows decompression by dorsal annulectomy
- 91% positive outcome (100% subsidence though)
Name a motion preserving technique for management of CSM .
How many spaces can it be used for?
Supposed advantage?
Outome?
- Disc arthroplasty
- 2-3 spaces
- Advantage = allows decompression by dorsal annulectomy
- 91% positive outcome (100% subsidence though)
What is shown in images?
Synovial cyst in the cervical region of a Rottweiler Dog with cervical spondylomyelopathy. Sagittal (A) and transverse (B) T2-weighted MR images showing the synovial cyst at C5-C6 (arrows). Note the enlarged articular process associated with the cyst in B.
Sagittal plane T2-weighted magnetic resonance image of the lumbar vertebral column and sacrum of a 1.5-year-old German Shepherd Dog, exhibiting multiple extradural synovial cysts (arrows).
