Craniovertebral Junction (CVJ) Anomalies

What structures compose the craniovertebral junction (CVJ) according to the summary?

The occiput, the foramen magnum, and the first two cervical vertebrae. Summary 1

What parts of the central nervous system are encompassed by the CVJ?

The medulla oblongata and the upper cervical spinal cord. Summary / Anatomy 2

How can anomalies of the CVJ be broadly categorized based on onset?

They may be congenital or acquired. Summary / Etiology 3

What condition can CVJ anomalies that decrease posterior cranial fossa volume (e.g., platybasia) cause?

Chiari malformations. Summary 4

What condition is caused by erosion of cervical vertebrae leading to cranial migration of the odontoid process?

Basilar invagination. Summary 5

What condition results from anomalous fusion of the cervical vertebrae?

Klippel-Feil syndrome. Summary 6

What causes the clinical features of CVJ anomalies?

Compression of the brain stem and the spinal cord. Summary 7

List three common clinical features of CVJ anomalies mentioned in the summary.

Recurrent occipital headaches, neck aches, bulbar palsy, and upper/lower motor neuron palsy. (Any 3) Summary 8

What complications can arise if CVJ anomalies obstruct CSF flow?

Syringomyelia and/or hydrocephalus. Summary 9

What diagnostic imaging is used for CVJ anomalies?

Neck x-ray and CT/MRI of the head and neck. Summary / Diagnosis 10

What is the typical treatment approach for CVJ anomalies when neurological symptoms are present or anticipated?

Surgery is often indicated to prevent or treat neurological symptoms. Summary / Treatment 11

Name two congenital anomalies of the occiput that can affect the CVJ.

Condylar hypoplasia, fusion of the atlas to the occiput (atlantooccipital assimilation), or platybasia (abnormal flattening of the base skull). (Any 2) Overview (Etiology) 12

Name one congenital anomaly of the atlas and one of the axis that can affect the CVJ.

Atlas: atlantooccipital assimilation, atlantoaxial fusion, aplasia of arches. Axis: hypoplasia of the odontoid process (dens). Overview (Etiology) 13

List three categories of acquired anomalies of the CVJ.

Trauma (bones/ligaments), Inflammatory (rheumatoid arthritis, ankylosing spondylitis), Genetic syndromes (Down, achondroplasia, osteogenesis imperfecta), Malignancies (chondrosarcoma, MM, mets). (Any 3) Overview (Etiology) 14

What is the definition of Chiari malformations?

Caudal displacement of the cerebellum with/without the medulla oblongata, through the foramen magnum, due to CVJ anomalies. Chiari Malformations 15

Which type of Chiari malformation is the most common?

Type I Chiari malformation. Chiari Malformations 16

List three conditions commonly associated with Chiari malformations.

Neural tube defects (esp. meningomyelocele), syringomyelia, hydrocephalus, Klippel-Feil syndrome, or basilar invagination. (Any 3) Chiari Malformations 17

Briefly describe the "fluid theory" for Chiari malformation pathophysiology.

Neural tube defect → CSF leakage → decreased posterior cranial fossa volume → compression and downward displacement of cerebellum +/- medulla through foramen magnum. Chiari Malformations 18

Briefly describe the "crowding theory" for Chiari malformation pathophysiology.

Small posterior cranial fossa leads to crowding of neural tissue at the foramen magnum. Chiari Malformations 19

What defines Type I Chiari malformation (CM)?

Ectopic extension of cerebellar tonsils through the foramen magnum. Chiari Malformations 20

What are common symptoms of Type I Chiari malformation, and when do they usually appear?

Occipital headache (worse with Valsalva/activity), neck pain, radicular arm pain, lower cranial nerve disorders, cerebellar symptoms (dysarthria, ataxia), downbeat nystagmus. Usually symptomatic in adolescence/young adulthood. Chiari Malformations 21

What defines Type II Chiari malformation (Arnold-Chiari malformation)?

Protrusion of cerebellar tonsils, vermis, and medulla oblongata into the foramen magnum. Chiari Malformations 22

What are common symptoms of Type II Chiari malformation, and when do they usually appear?

Obstructive hydrocephalus, breathing difficulties (apnea), feeding difficulties, muscle weakness/numbness. Always associated with myelomeningocele. Usually symptomatic in infancy. Chiari Malformations 23

What defines Type III Chiari malformation?

Herniation of parts of the cerebellum and brain stem through an abnormal opening in the back of the skull (encephalocele). Chiari Malformations 24

What is the prognosis for Type III Chiari malformation?

Mostly fatal in early infancy. Survivors have severe neurological deficits (motor palsies, cranial nerve disorders, cerebellar symptoms, epilepsy, intellectual disability). Chiari Malformations 25

What are CT/MRI findings in Type I Chiari malformation?

Caudal displacement of cerebellar tonsils and a small posterior cranial fossa. Chiari Malformations 26

What additional CT/MRI findings characterize Type II Chiari malformation beyond Type I features?

Caudal displacement of a beaked dorsal midbrain, and (possibly) the fourth ventricle. Chiari Malformations 27

When is surgery indicated for Chiari malformations?

In all patients with Type II and Type III CM, and in symptomatic Type I CM. Chiari Malformations 28

What is the management for asymptomatic Type I Chiari malformation?

Surveillance with annual MRI of the brain to look for development of syringomyelia and/or hydrocephalus. Chiari Malformations 29

What is basilar invagination?

Abnormal protrusion of the odontoid process (dens) of the axis into the foramen magnum. Basilar Invagination 30

What is the most common etiology of basilar invagination?

Acquired CVJ abnormalities. Basilar Invagination 31

List three clinical features of basilar invagination.

Recurrent occipital headache, neck pain, breathing difficulties (sleep apnea), bulbar palsy, downbeat nystagmus. (Commonly associated with Chiari, hydrocephalus, syringomyelia). (Any 3) Basilar Invagination 32

How is basilar invagination diagnosed on a lateral neck x-ray?

Protrusion of the odontoid process by ≥ 3 mm above Chamberlain line. Basilar Invagination 33

What is Klippel-Feil syndrome?

Congenital fusion of ≥ 2 cervical vertebrae. Klippel-Feil Syndrome 34

What are common associated conditions with Klippel-Feil syndrome?

Chiari malformations, scoliosis, spina bifida occulta, or Sprengel deformity (congenitally elevated scapula). Klippel-Feil Syndrome 35

What is the classic triad of clinical features in Klippel-Feil syndrome?

Short neck, restricted cervical mobility, and low posterior hair line. Klippel-Feil Syndrome 36

Besides the classic triad, what other system abnormalities are common in Klippel-Feil syndrome?

Hearing loss, genitourinary abnormalities, and cardiovascular abnormalities. Klippel-Feil Syndrome 37

What imaging is used to diagnose Klippel-Feil syndrome and assess associated issues?

Cervical spine x-ray (AP/lateral: fusion, scoliosis, Sprengel, spina bifida). CT (surgery planning). MRI (if neuro symptoms: cord compression, Chiari). Klippel-Feil Syndrome 38

When is conservative management indicated for Klippel-Feil syndrome?

In mildly symptomatic patients without cervical spine instability (using cervical collars/braces/traction). Klippel-Feil Syndrome 39

When is surgery indicated for Klippel-Feil syndrome?

In patients with cervical spine instability or neurological symptoms. Klippel-Feil Syndrome 40