Variation Of The Vertebral Column Flashcards
What forms the vertebrae?
Sclerotome of somites
When the sclerotome surrounds the Spinal Cord and notochord, when does it fuse with the opposite side?
4th week of development
What is resegmentation in regards to the development of vertebrae?
The caudal half of one somite an the cranial half of the next somite fuse to form the resegmented sclerotome that will become a vertebra
Eg. The caudal half of the 5th somite and the cranial half of the 6th somite forms C1 (Pang and Thompson, 2011)
What genes regulate formation of vertebrae? Where are these genes inherited from?
HOX genes
Maternal mRNA
What cells are found between two vertebrae?
Mesenchymal
What is the reference for vertebral embryology?
Sadler, 2012
What features are fused in complete occipitalisation of the atlas?
Posterior arch
Anterior arch
Lateral masses
What is partial occipitalisation of the atlas?
Any osseous bridge uniting a focal areas of the atlas and occiput
What are the three zones in the classification of occipitalisation of the atlas? (Reference?)
Zone 1 = Anterior arch
Zone 2 = Lateral masses
Zone 3 = Posterior arch
(Gholve et al., 2007)
What is the embryological origin of occipitalisation of the atlas?
Sclerotome fails to differentiate into cranial and caudal parts
Caudal part of occipital sclerotome 4 and cranial part of C1 sclerotome remain fused
Lack of resegmentation between loose and dense zones of cervical sclerotome
What are the sequelae of occipitalisation of the atlas?
Anomalous vertebral arteries
Torticollis
Neck pain and stiffness
Myelopathy
Atrophy of rectum capitis posterior major
Inadequate attachment for obliquus capitis
What is the Thavarajah and McKenna, (2012) case study?
Congenital absence of anterior arch of C1
35 year old female with 4 day history of neck pain
CT showed congenital absence and non fusion of anterior arch of C1
What is the Khanna et al., (2014) case study?
Complete absence of posterior arch of C1
46 year old male with upper cervical and occipital pain
What is the prevalence of congenital absence of anterior arch of atlas?
0.1%
What is the prevalence of congenital absence of the posterior arch of C1?
4-5%
What are the five types of absence of posterior arch of C1? (Reference?)
Type A = Two hemiarches (90%) Type B = Unilateral cleft Type C = Bilateral cleft Type D = Absence of arch with tubercle Type E = Absence of arch and tubercle (Currarino et al., 1994)
What are the sequelae of congenital absence of anterior arch of C1?
Instability Torticollis No articulation site for dens Absence of transverse ligament of atlas Lack of attachment for: - Longus coli and ALL - Atlanto-occipital membrane and anterior atlanto-occipital ligament Subluxation and Cord compression = Quadriparesis
What are the sequelae of congenital absence of the posterior arch of C1?
Usually stable Generally asymptomatic Spinal canal stenosis Myelopathy Neck pain
In what percentage of Down’s syndrome patients is atlantoaxial subluxation seen?
15-20%
What is the prevalence of accurate foramen of the atlas? (Reference?)
16.7%
Elliot and Tanweer, 2014
What environmental factors could contribute to arcane foramen of the atlas?
Carrying heavy objects on head
What is an arcade foramen of the atlas?
A bony bar (ponticulus) arises from the lateral masses and turns the groove for the vertebral artery into a foramen
Describe the pathogenesis of calcification of the posterior atlanto-occipital membrane and how it can result in an arcane foramen of the atlas?
Calcifies from posterior superior articular process to posterior arch of C1
Can be complete/incomplete
Can be unilateral/bilateral
Encloses the V3 portion of the vertebral artery
Why are ossified primitive ligaments an unlikely pathogenesis for arcuate foramen of atlas?
Ossification centres not identified in that location
Apart from calcification of the posterior atlanto-occipital membrane and ossified primitive ligaments, what are the other pathogeneses of arcuate foramen of the atlas?
Bony feature forming a bridge over the vertebral artery
Accessory transverse foramen of atlas
How can an arcuate foramen of C1 affect the vertebral artery?
Increased incidence of dissection as it is tethered:
- Neck movements = Repetitive trauma
Compression
What syndrome can result from periarterial sympathetic plexus disruption in arcuate foramen of C1? How does it present? (Reference?)
Barre-Lieou Syndrome: - Headache - Retro-orbital pain - Facial vasomotor disturbance - Visual disturbance - Difficulty with swallowing and phonation (Limousin, 1980)
How can arcuate foramen of the atlas affect surgery?
Mistaken for broad posterior arch
- Screws inserted into arcuate foramen
Complications posterior approaches
What is hypoplasia of the dens?
Short dens height
What is os odontoideum?
Failed fusion of dens to centrum
What is os terminale persistens?
Failed fusion of ossiculum terminale to body of dens
How does a bifid dens arise?
Failed/Partial fusion of the two parts of the body of the dens
What is pseudosubluxation of C2?
Anterior sliding of C2 on C3
Why is pseudosubluxation of C2 more common in the juvenile skeleton?
Hypermobility Lax ligaments Large head (in relation to weak neck muscles) Shallow, angled facet joints Incomplete ossification of dens
What effects does pseudosubluxation of C2 have on the juvenile skeleton?
None
What effects does pseudosubluxation of C2 have on the adult skeleton?
C2 dislocation
Possible Hangman’s fracture
What syndromes is pseudosubluxation of C2 seen in?
Down’s syndrome
Moquio’s syndrome
What is the reference for pseudosubluxation of C2?
Kim, 2013
What is Klippel-Feil syndrome?
Abnormal congenital fusion of 2 or more cervical vertebrae
What is the epidemiology of Klippel-Feil syndrome?
0.71% prevalence
More common in females
What factors can result in Klippel-Feil syndrome?
Genetics:
- Autosomal recessive or dominant
Environmental:
- Alcohol
What is the pathogenesis of Klippel-Feil syndrome?
Improper segmentation of cervical vertebrae during 3rd-8th weeks of gestation
What is Type 1 Klippel-Feil syndrome?
Cervical spine fusion
Many elements of many vertebrae are incorporated into a single block
What is Type 2 Klippel-Feil syndrome?
Cervical spine fusion
Failure of complete segmentation at only 1 or 2 cervical levels
May include occipito-atlantal fusion
What is Type 3 Klippel-Feil syndrome?
Type 1 or 2 PLUS
Co-existing segmentation errors in:
- Lower thoracic spine OR
- Lumbar spine
What is the reference for types of Klippel-Feil syndrome?
Vaidyanathan et al., 2002
Where is the most common level of fusion in Klippel-Feil syndrome? (Reference?)
C2-C3
Cho et al., 2014
What did the Yadav et al., 2014 case study see in Klippel-Feil syndrome?
C2-C3 Completely fused on both anterior and posterior aspects
Foramen transversarium all present
No IV discs
What did the Leung et al., (2011) study into Klippel-Feil syndrome at C2-C3 find?
All neck movements in a C2-C3 fused KFS spine displayed greater levels of stress compared to normal
Certain movements resulted in significantly higher stress:
- Neck extension
- Neck lateral flexion to the right
What functional change can result from Klippel-Feil syndrome?
Reduced range of movement
What degenerative changes can arise in Klippel-Feil syndrome?
Acquired cervical stenosis -> Myelopathy
Osteoarthritis -> Radiculopathy
Dens fracture
What is the reference for functional and degenerative changes in Klippel-Feil syndrome?
Pizzutillo et al., 1994
In what percentage of young Klippel-Feil syndrome patients is scoliosis present? (Reference?)
53.3%
Samartzis et al. 2011
What results in neural arch variations?
Changes in ossification process
What are retrosomatic clefts?
Vertical defects in the pedicle
What are retroisthmic clefts?
Defects in lamina immediately dorsal to the inferior articular process
What is spinal dysraphism?
Failure of neural arch fusion
What is spinal dysraphism associated with?
Spina bifida:
- Occulta
- Meningocoele
- Myelomeningocoele
What is primary spondylolysis of the axis?
Clef through C2 pars interarticularis
What is the reference for neural arch variations?
Mellado et al. 2011a and 2011b
Where is spinal canal stenosis commonest?
Lumbar or cervical regions
What are the symptoms of cervical spinal stenosis?
Gait disturbance
Partial paralysis of lower limbs
Limited Flexion of neck
What are the symptoms of lumbar spinal stenosis?
Pain in: - Hips - Groin - Buttocks Numbness/Weakness in lower limbs and lower back
What can cause spinal canal stenosis?
Degenerative disc bulging
Hypertrophied ligamentum flavum
Degenerative facet joint changes
Why do symptoms arise in spinal stenosis?
Spinal cord compression
What is the gold standard for classification of (lumbar) canal stenosis?
There is none
What are the references for spinal canal stenosis?
Azimi et al., 2015; ManfrÃ, 2016
What is the incidence of spina bifida?
0.5-0.8/1000 live births
What is the pathogenesis of spina bifida? (Reference?)
Failure of neural tube closure during week 4 of development Vertebral arch is either: - Incomplete - Absent (Copp et al., 2015)
What is spina bifida occulta?
Absence of spinous process
Variable amount of laminae
What is meningiocele?
Herniation of meningeal tissue and CSF
What is myelomeningiocele?
Herniation of meningeal tissue, CSF and CNS tissue
What is the prevalence of spina bifida occulta in the general population?
10-15%
How can meningiocele present?
Usually asymptomatic so incidental finding
Low incidence of hydrocephalus
What is the pathogenesis of the sensory and motor defects in myelomeingiocele?
Prolonged exposure of open neural tube to amniotic fluid
Neuronal differentiation occurs, even below lesion
Toxicity of amniotic fluid causes haemorrhage and neuronal death
What is myelomeningiocele associated with?
Urinary and faecal incontinence
65-85% associated hydrocephalus
Type II Chiari malformation
What is the reference for types of spina bifida?
Copp et al., 2015
How does Butterfly vertebra present?
Usually asymptomatic
When does butterfly vertebra arise?
Between weeks 3-6 of gestation
What is the pathogenesis of butterfly vertebra?
Symmetric fusion defect -> ‘Split’ vertebra
Both chondrification centres fail to develop (related to hemivertebrae)
What can butterfly vertebra be confused with?
Compression fracture if trapezoidal or cuneiform anterior wedging
What does the Ozaras et al., (2015) case study on butterfly vertebra show?
38 year old male with lower back pain: - Worse when standing and walking PMHx of Behçet's disease Coronal CT showed butterfly vertebrae at: - L3 - T9
What syndromes is butterfly vertebra associated with?
Pfeiffer syndrome
Jarcho-Levin syndrome
Crouzon syndrome
Alagille syndrome
What other spinal anomalies is butterfly vertebra associated with?
Kyphoscoliosis
Hemivertebrae
Spina bifida
When does hemivertebrae arise?
During weeks 4-6 of development
What is the pathogenesis of hemivertebrae?
One chondrification centre fails to develop -> Wedge of bone:
- Half of a vertebral body
- 1 pedicle
- Hemilamina
In what region(s) are hemivertebrae most common?
Thoracic
Lumbar
What spinal deformity do hemivertebrae result in?
Congenital scoliosis
What is a fully segmented hemivertebra?
Has no attachment to other vertebrae
What is a semisegmented hemivertebra?
Half is fused with vertebra above or below
No IV disc
What is an incarcerated hemivertebra?
Joined by pedicles to vertebrae above and below
What is a non-segmented hemivertebra?
Connected to vertebrae above and/or below
What is the most concerning type of hemivertebra?
Fully segmented
What conditions are associated with hemivertebrae?
VATER syndrome
VACTERL syndrome
Jarcho-Levin syndrome
Klippel-Feil syndrome
What are the references for hemivertebrae?
Johal et al., 2016
Ozaras et al., 2015
Weerakkody, 2017
In regards to block vertebrae, what does Leviseth et al., (2005) show?
Causally adjacent disk height is significantly less
Discs not affected cranially
In regards to block vertebrae, what did Guille et al., (1995) show?
59% of Klippel-Feil syndrome patients had degeneration adjacent to block vertebrae
In regards to block vertebrae, what did Karuppal et al., (2013) show?
1st rib fracture associated with type 1 cervical block vertebra
What can lumbar block vertebrae be associated with?
Weakness in muscles:
- Abdominals
- Hip flexor
- Quadriceps
