Craniovertebral Congenital Anomalies & Variants Flashcards
What line is used to diagnose basilar impression with occipitalization?
McGregor’s line
(Dens >8-10mm above)
Name 4 possible causes of primary basilar impression
- occipitalization of atlas
- agenesis/hypoplasia of atlas
- Klippel Feil syndrome
- chiari malformation
Name 4 possible causes of secondary basilar impression
- pagets
- osteomalacia
- fibrous dysplasia
- osteogenesis imperfecta
What is occipitalization?
Congenital fusion of C0/C1
What are the radiographic findings of occipitalization?
- may appear as no C1, but C1 agenesis doesn’t exist
- lat: decreased jt space, no spinolaminar line
- APOM: no visible jt between C0/C1
What is the clinical significance of occipitalization?
Concern for atlantoaxial instability
What is occipitalization frequently associated with?
- C2/C3 fusion
- skull base morphology (basilar impression)
What are your next steps for a patient who is occipitalized?
- flexion/extension radiographs to check for instability (can have acquired or congenital problem w/ transverse lig)
- thorough neuro exam
- advanced imaging
What is a chiari malformation?
Herniation of the cerebellum more than 5mm beyond the margin of the foramen magnum
What is the clinical significance of a chiari malformation?
Can cause hydrocephalus if foramen of magendie and Luschka (4th ventricle drainage sites) are clogged
What other anomaly is associated with chiari malformations?
syrinx/syringomyelia
What is a syrinx?
Fluid-filled cyst in central aqueduct/spinal cord
What is syringomyelia?
When a syrinx causes neurological symptoms
What anatomical region is most commonly affected by syringomyelia?
Upper extremity
What are the radiographic findings of a chiari malformation?
Plain radiographs are typically not helpful with diagnosis, but may show associated skeletal malformations (eg. Occipitalization)
How is a chiari malformation diagnosed?
MRI
- herniation of cerebellum >5mm beyond foramen magnum
- cerebellar tonsils appear peg-shaped, elongated, and low-lying
What are your next steps if a chiari malformation is found?
- neuro consult to R/o other findings (may need surgery)
- brain MRI
What are the symptoms of a chiari malformation?
May be clinically silent with no symptoms
- headache (MC)
- cervical/facial pain
Your patient who is occipitalized shows positive results on neurological examination. After obtaining flexion/extension radiographs, what are your next steps?
order MRI to check for Chiari malformation
How is a syrinx diagnosed?
T/S MRI
Appears as bright streak
What are the possible symptoms of syringomyelia?
Neuropathic arthritis
- cloak-like pain (neck & shoulder area)
- loss of pain and temperature sensation
What is the most common anomaly of the craniovertebral junction?
Occipitalization
What is an epitransverse process?
A variation of congenital bone bar that extends from the atlas TP, superiorly toward the adjacent occiput
(may form a joint or fuse)
What is the diagnosis?
Epitransverse process
What is a paracondylar process?
A variation of congenital bone bar that extends more medial and anterior to the paracondylar area of the occiput
(may form a joint or fuse)
What is the diagnosis?
Paracondylar process (arrow)
(Arrowhead = styloid process)
What is the most common form of an occipital vertebrae?
third condyle
What is a third condyle?
midline bony process located between the 2 occipital condyles and continuous with the anterior foramen magnum
What is the diagnosis?
Third condyle
(Not visible on APOM)
