2 - Congenital Anomalies Flashcards
What is nonsegmentation of C0 from C1
Occipitalization
Four examples of occipital vertebrae
Third condyle
Epitransverse process
Paracondylar process
Paramastoid process
What is a third condyle?
Occipitalization vertebrae from the front of forament magnum to anterior tubercle
What is epitransverse process?
Occipitalization vertebrae off TP of C1 that articulates with C0.
What is paracondylar process?
Occipital vertebrae off C0 next to condyle to TP of C1
What is paramastoid process?
Occipital vertebrae adjacent to mastoid to TP of C1
Basilar impression
When dens is pushed up into foremen magnum
What 2 measurements are used to see if there is basilar impression?
McGregor’s line: palate to inferior occiput
Chamberlain’s line: palate to posterior foramen magnum
What is abnormal measurement for McGregors Line
If dens is >8-10 mm above line it means there is occipitalization
If dens is >4.5 mm above line it means there is basilar invagination
What is abnormal measurement for Chamberlain Line
If dens is >3 mm above the line, basilar invagination
What are primary and secondary reasons for basilar impression?
1˚ : occipitalization, C1 posterior arch agenesis - spina bifida occulta
2˚ : bone softening d/t Pagets, osteomalacia, fibrous dysplasia
What is Arnold-Chiari malformation
Downward displacement and elongation of brain stem and cerebellar tonsils
Sx of Arnold-Chiari malformation
Mild HA, neck pain, stridor, apnea, nystagmus, CN palsies
Many are asymptomatic
stridor
High-pitched breath sound resulting from turbulent air flow in larynx or lower in bronchial tree
Other findings associated with Arnold-Chiari malformation
Syringomyelia and hydrocephalus
Arnold-Chiari malformations greater than ____ are concerning
3mm
<3mm is not concerning
In an MRI how can you tell the difference between T1 and T2 weighted
T1 CSF is dark
T2 CSF is bright
What is syringomyelia
Spinal cord cavity (syrinx)
Etiology of syringomyelia
Pressure, tumor, congenital, Arnold-Chiari malformation (2˚ to pathologically CSF dynamics)
What is spina bifida occulta, is it significant?
Failure of fusion of 2 posterior arch ossification centers that produce midline defect
Usually NOT significant. Though some authors disagree and say increased posterior disc herniation and isthmic spondy
How does spina bifida appear on xray?
No spinolaminar junction
What are the things you need for stability between C1-C2? (4)
Intact dens,
Anterior arch,
Lateral masses,
Transverse ligaments
What are signs seen on xray of posterior arch agenesis?
Hypertrophy and sclerosis of anterior arch, megaspinous of C2
Etiology of posterior arch agenesis
Congenital
SOL
Infection (e.g. osteomyelitis) though unlikely because there is no vertebral body (vertebral bodies contain blood vessels, desirable to infection to spread more easily)
What is posterior ponticle of C1?
Partial or complete ossification of oblique portion of atlanto-occipital membrane
So it looks like a bony arch from posterior arch to lateral masses
What is characteristic of Trisomy 21 (Down Syndrome) ?
Atlanta-axial instability due to lax transverse ligament and therefore that can cause increased ADI (atlanto-dental interspace)
Prone to cervical spondylitis and myelopathy
What is ossiculum terminale and what does it look like?
Non-fusion of 2˚ growth center of the dens
Looks like a little bone at the tip of the dens.
Also called Persistens of Bergman
How do you DDX ossiculum terminale/persistens of Bergman from acute fracture?
Congenital ossiculum terminale would be sclerotic and not have a clean line
What is os odontoideum?
2 halves of odontoid unite and do not fuse to C2
Is os odontoideum considered stable or unstable?
Unstable. The transverse ligament is intact but unstable because dens is unattached to C2 body
What is a hypoplastic/agenesis odontoid
Odontoid halves do not develop fully or at all
Should you manipulate hypoplastic/agenesis odontoid?
Not if its unstable. Obviously.
Do flexion/extension films.
What is block vertebra/synostosis?
Non segmentation of 2 adjacent segments.
What are the radiographic findings for block vertebra/synostosis? (triad)
Wasp waist appearance
Rudimentary disc
Fused posterior elements
Surgical vs congenital block vertebra/synostosis
SPs separated
Most common vertebral levels for congenital block vertebra?
C2/3
C5/6
L4/5
What is klippel-feil syndrome?
Multiple block vertebra, Spina bifida occulta, Scoliosis, Sprengel’s deformity (1 scap undescended), and Platybasia
Rule #3 applies here: look for soft tissue anomalies. May have GU anomalies especially kidneys (e.g. horseshoe kidney, 2 ureters from 1 kidney, etc)
What is the classic triad for klippel-feil syndrome?
Short, webbed neck (pterygium colli)
Lowered hairline
Reduced cervical ROM
What is sprengel’s deformity?
Congenitally undescended scapula
What chunk of bone may be present in Sprengel’s deformity?
Omovertebral bone: a chuck of bone that fixes scapula to spine
What is cervical spondylolisthesis?
Congenital form caused by bilateral agenesis of pedicles and dysplasia of articulation processes
What cervical level is most commonly involve in spondylolisthesis? What sex is more common?
C6
M>F
Spina Bifida Occulta (SBO) is commonly at this level too
What level is a cervical rib most common at?
C7, 6, 5.
If rib is at C5 pt will have ribs at C6, C7 too.
