Chapter 32 Thoracolumbar Vertebral Column Flashcards
Label the diagram
A, T11 vertebra, cranial aspect (top) and lateral aspect (bottom), showing vertebral body, lamina, pedicle, spinous process, vertebral foramen, rib, and articular process. B, L5 vertebra cranial aspect (top) and lateral aspect (bottom), showing vertebral body, lamina, pedicle, spinous process, accessory process, and cranial articular process.
What are A B and C
A - Spinal branch
B - Intercostal artery
C - Azygous vein
Label the diagram
What structures contribute passive stability to the vertebral column?
- Intervertebral discs (greatest contributor)
- Zygapophyseal joints
- Muscle tendon/Ligamentous
- Three long ligaments = supraspinous ligament, dorsal and ventral longitudinal ligaments
- Three short ligaments = yellow ligament, interspinous, intertransverse ligaments.
- Intercapital ligaments also present T2-T11 (lies ventral to dorsal longitudinal ligament. Thought to be one reason why IVDH less common cranial to T11)
Which is usually the anticlinal vertebra?
List 3 specific features of the antclinal vertebra
T11
What attached to the accessory process?
Tendon of longissimus lumborum
(tendon runs caudalaterally from accessory process to muscle)
How can L1 transverse process be distinguished from the other lumbar ones
Shorter
List the 3 anatomic parts to intervertebral disc
- Annulous fibrosis (concentric lamellae of collagen)
- Nucleus pulposus (GAGs and collagen IV matrix)
- Cartilaginous end plate (attaches to bony end plate of vertebral body)
List 3 approached to TL vertebral column
Dorsal
Lateral
Dorsolateral
List the three compartments that provide stability to vertebral column (e.g. during approach)
Which forces does each structure resist?
When should stabilization be considered?
- Vertebral body – resists bending and axial load.
- Zygapophyseal joints – resist all forces
- Intervertebral disc – stabilizing factor against rotation and lateral bending.
Stabilize if:
- >1 compartments compromised (particularly if bilaterally)
- traumatically injured (rather than surgically)
- large dog
What are the landmarks for hemilaminectoy borders?
Ventral border = ventral aspect of accessory process.
Dorsal border = base of spinous process.
Cranial and caudal border = base of articular process.
Describe a Funkqvist A, Funqvist B, modified dorsal laminectomy and deep dorsal laminectomy
- Funkquist A = removal of spinous process, laminae, articular processes and half pedicles.
- Funkquist B = removal of spinous process and laminae.
- Modified dorsal laminectomy = removal of spinous process, laminae and caudal articular process (medial aspect of pedicles is undercut to enhance exposure but cranial articular process intact. i.e. midway between A and B.
- Deep dorsal laminectomy = removal of spinous process, dorsal laminae, articular processes and pedicles to level of ventral spinal cord.
Define sensitivity
and specificity
- Sensitivity* = number of positive animals identified by a test divided by the total number of animals with the disease (true-positives/true-positives + false-negatives). Essentially, higher sensitivity leads to a lesser chance of false-negative results.
- Specificity* = number of animals without disease that test negative divided by the total number of animals without disease (true-negatives/true-negatives + false-positives). In other words, it is the ability of a test to correctly identify those individuals that do not have disease. Or, thought of another way, high specificity implies few false-positives.
List 5 radiographic features of IVDH
Features of IVDH include:
- Narrowed disc space (highest sensitivity)
- Wedging of disc space
- Increased articular process overlap
- Mineralized material superimposed over intervertebral formaen/vertebral canal
- Reduced intervertebral foramen diameter
Vacuum phenomenon = gas radiolucency within intervertebral disc space due to degeneration (uncommonly seen with IVDH, but v specific for this on one report).
What is accuracy of radiography for determining presence of IVD lesion?
50-60%
List the three myelographic patterns?
extradural, intradural-extramedullary or intramedullary.
List possible adverse effects of myelography
seizures (occurs in 10-21.4% of studies, increased risk if large body size or cisternal delivery in one study, although incidence 3%), myelopathy, apnoea, arrhythmia, meningitis, subarachnoid haemorrhage, death.
What is the prognosis for successful outcome in
- Dogs treated surgically with normal nociception?
- Dogs treated surgically with absent nociception?
- Dogs treated surgically with normal nociception = 72 - 100%
- Dogs treated surgically with absent nociception? 50%
- In this population, length of the intramedullary pattern/length of L2 vertebra ratio on a lateral view of ≥5 was a negative prognostic indicator
Dogs with intact nociception: 72-100% success (voluntary ambulation + urinary continence).
Dogs with intact nociception more likely to return to ambulation (86% success) than those without. Another study found 96% return to ambulation after 3 months (mean 12.9 days), dogs with voluntary motor function returned to ambulation sooner (7.9d) than those without (16.4d, but not statistically significant.) No difference in time to ambulation with age, time of onset à decompression, GA duration, surgery duration, steroids.
Paraplegia and absent nociception: 43-62% return to ambulation.
Variable results re time of onset à time of surgery. One study found that progression to non-ambulatory within 1 hour had poorer outcomes. Dogs that recover nociception within 2 weeks more likely to recover and those without nociception within 2 weeks less likely to. Subdural haemorrhage, increased age and BW may be related to prolonged recovery. One study found 58% regained ambulation, mean time 7.5 weeks (some had urinary/faecal incontinence).
List 2 CT findings of IVDh in additionto the usual radiographic findings
- Loss of epidural fat opacity surrounding compressed SC
- Material within epidural space with density consistent with haemorrhage (compressive material is hyperattenuating relative to Sc, likely due to haemorrhage ad mineral dense intervertebral disc material in majority of dogs).
What is typical appearance of intervertebral disc material on MRI?
- Hypointense on T1W and T2W images (unless non-degenerate nucleus pulposus (common in cervical SC) which is T1W isointense and T2W hyperintense).
HOw can haemorrhage be recognized on MRI?
T2* signal void
What are typical CSFfindings indogs with IVDH?
- Rarely pleocytosis, if present then mild, usually neutrophilic (if from cisterna), lymphocytic (if lumbar)
- Elevated protein
When might a partial lateral corpectomy be performed?
For chronic IVDE or IVDP
Partial lateral corpectomy (1/4 length of each vertebra):
A) Chronic intervertebral disc herniations can produce a “wrapping” effect: The spinal cord spreads out on either side of the ventral aspect of the vertebral canal around the margins of the protruded material. The dotted line represents the portion of the intervertebral disc and body of the vertebral that will be removed. B) Craniolateral view of lumbar vertebra following partial corpectomy: A lateral slot has been drilled under the herniated intervertebral disc material through the intervertebral disc and the vertebral epiphysis of two adjacent vertebral bodies. Following excision of the protruded intervertebral disc, the spinal cord returns to its normal position. May provide better exposure to ventral canal but possible instability à increased risk of fracture/luxation. Study assessing outcome found immed. post-op improvement in 18.7%, at discharge 52.8%, 4 weeks post op 64.2% and 6 mo post op 91.4% of dogs were ambulatory. Worse pre-op neuro grade more likely to improve post-op.
Describe the innervation to the bladder:
What type of innervation is provided by each of the following nerves.
What spinal cord segment does each originate from?
Pelvic nerve
Pudendal nerve
Hypogastric nerve
Pelvic nerve:
Parasympathetic innervation (motor and sensory) to the detrusor muscle. The preganglionic neurons are located in the sacral spinal cord segments. Preganglionic axons synapse with ganglionic neurons at the pelvic ganglia and within the wall of the bladder.
Pudendal nerves:
Somatic innervation (motor and sensory) to the external urethral sphincter, perineal musculature, and anal sphincter and skin of the perineum (sensory). The neurons that give rise to the pudendal nerve are derived from the sacral spinal cord segments.
Hypogastric nerve:
Sympathetic innervation to the internal urethral sphincter, the pelvic (parasympathetic) ganglia, and the detrusor muscle. The preganglionic neurons are located in L1 through L4 spinal cord segments. Preganglionic axons course through splanchnic nerves to synapse with their ganglionic neurons in the pelvic plexus. Postganglionic sympathetic axons course in the hypogastric nerve. Sympathetic input to the pelvic ganglia inhibits the ganglionic parasympathetic neurons during urine storage. The hypogastric nerve also contains sensory fibers from the bladder wall and is involved in bladder nociception. Descending motor information includes inhibitory and excitatory upper motor neuron input to the detrusor muscle and urethral sphincters.
Normal urine storage and voiding are accomplished by both reflexive and conscious input.61 Urine storage is accomplished by beta-mediated detrusor muscle relaxation, alpha-mediated internal urethral sphincter tone, and cholinergic (nicotinic)-mediated external urethral tone. To empty the urinary bladder, adrenergic input to the bladder is decreased, allowing increased detrusor muscle activation and decreased internal urethral sphincter tone. Cholinergic stimulation via the pelvic (parasympathetic) and pudendal nerves (skeletal innervation) results in detrusor muscle contraction and external urethral sphincter relaxation, respectively.
What is most common breeds and locations for SAD?
Commonly cranial cervical (young, large breed (Rottweiler)) and caudal thoracic (old, small breed (Pug)) spinal cord regions.
Describe the approach to the dorsal cranial thoracic vertebral colums (T1 - T5)
- Skin
- SC
- Dorsal tendinous raphe (if possible, keep supraspinous/nuchal ligament intact)
- Retract rhomboideus and trapezius
- Longissimus cervicis, thoracic et lumborum exposed - elevate and retract them
- If need to exise T1 will compromise nuchal ligament. 3 options
- cut nuchal ligamnet - clinically fine
- divide nuchal ligament along midline and preseve continuation to supraspinous ligament
- ostectomise most dorsal part of spinous process and leave in situ
Where does nuchal ligament attach?
Originates spine of Axis
Inserts tip of spinous process of T1
(continuous with supraspinous ligament)
Which muscle attached to the articualt processes in T6-L6?
Multifidus muscle
prognostic indicators for ANNPE?
And compared to ischaemic myelopathy?
