Craniovertebral anomalies

Craniovertebral anomalies

1. Craniovertebral Junction Anomalies Guide : Dr. Ashish Patel Sir Candidate : Dr. Sagar Dagdiya

2. Craniovertebral Junction Is a transition zone between mobile cranium and vertebral column & collectively constitutes the Occiput (posterior skull base), Atlas, Axis and Supporting ligaments. It encloses soft tissue and neural structures of the cervicomedullary junction (medulla, spinal cord & lower cranial nerves)

3. ANATOMY

4. Embryology Starts during 2 nd to 3 rd weeks of gestation. Mesodermal Cells in the midline condense to form Notochordal Process that forms Notochord. Paraxial Mesoderm forms the Somites (total 42 at 4 th week) Somites then form the Sclerotomes that eventually will give rise to Vertebral Bodies.

5. Each Sclerotome differentiates b/t rostral part forming the vertebral body & caudal part forming the IVD. 1 st two-three sclerotomes forms the Basiocciput . 4 th Sclerotome forms the Proatlas . Proatlas gives rise to Occipital Condyles , FM, Atlas, Dens of Axis and Alar , Cruciate & Apical Ligaments.

6. CVJ - LANDMARKS A: Nasion B: Post.pole of Hard Palate C: Ant.arch of atlas D: Dens E: Post.arch of Atlas F: Ophisthion G: Basion H: Tuberculum Sellae A: Tip of Mastoid B: Occipital Condyles C: Dens D: Axis Body E: Lateral masses of Atlas

7. A- nasion B-posterior pole of hard palate C-anterior arch C1 D- odontoid process E-posterior arch C1 F- opisthion G- basion H- tuberculum sellae A B C D E F G H A B C D E A- tip of mastoid process B-occipital condyle C- odontoid process D-axis body E-lateral mass of atlas CVJ - LANDMARKS

8. CRANIOMETRY Craniometry of the CVJ uses a series of lines, planes and angles to determine the normal anatomical relationship of the CVJ. These measurements can be taken on Plain X-Rays, 3D-CT or on MRI. Neither single measurement is helpful nor these are very much specific due to variations in normal anatomical structures and planes within normal range.

9. CRANIOMETRY - LINES CHAMBERLAIN’S LINE Posterior margin of hard palate to opisthion ( ) Normal- tip of dens is less than 7mm below this line Line from basion to opisthion ( ) Normal – tip of dens below this line McRAE’s LINE

10. CRANIOMETRY - LINES WACKENHEIM’S LINE Posterior margin of hard palate to lowest part of occipital bone Normal- tip of dens is less than 5mm below this line Line extrapolated along dorsal surface of clivus Normal – dens should be tangential or anterior to this line Mc GREGOR’S LINE

11. DIGASTRIC LINE BIMASTOID LINE Line between incisurae mastoidae ( ) Normal- 10mm above atlanto -occipital joint Line between tips of mastoid processes ( ) Normal – intersects atlanto -occipital joint CRANIOMETRY - LINES

12. CRANIOMETRY - ANGLES WELCHER BASAL ANGLE CLIVUS CANAL ANGLE Angle at junction of nasion-tuberculum and tuberculum-basion lines Normal- 132-140 degree Abnormal->143 degree in platybasia Angle at junction of Wackenheim’s line and posterior vertebral body line Normal – 150-180degree Abnormal-<150 degree in platybasia

13. ATLANTOOCCIPITAL JOINT AXIS ANGLE KLAUS INDEX Angle formed at junction of lines along atlanto -occipital joints ( ) Normal -124-127 degree Obtuse in condyle hypoplasia Distance between dens and tuberculum cruciate line ( ) Normal-40-41mm Basilar invagination -<30mm CRANIOMETRY Tuberculum C ruciate Line Klaus Height Index IOP

14. Classification Of CVJ Anomalies Congenital : Malformations of Occipital Bone: Hypoplastic Basiocciput Condylar Hypoplasia Remnants Around Foramen Magnum Malformations of Atlas: Occipitalization of Atlas(Assimilation) Atlantoaxial Fusion Aplasia / Hypoplasia of Atlas Arches

15. Malformation of Axis: Blocked C2-C3 Odontoid Anomalies: -- Os Odontoideum -- Ossiculum Terminale (Bergman Ossicle ) -- Agenesis of Odontoid Developmental & Acquired : Abnormalities of FM: Foraminal Stenosis (e.g. Achondroplasia ) 2° Basilar Invagination (e.g. Pagets , Osteomalacia , Hyperparathyroidism)

16. Atlantoaxial Instability: Inflammatory (e.g. RA, AS) Traumatic Infections Degenerative Tumors Down’s Syndrome Errors of Metabolism Neuraxial Anomalies : Klippel Feil Syndrome Arnold Chairi Malformation Dandy Walker Syndrome Occipito Cervical Myelomeningocele

17. Symptoms And Signs 1. MECHANICAL FEATURES (d/t local irritation) Neck pain, Stiffness, Torticollis , Pain in Occiput or Shoulders. 2. NEUROLOGICAL FEATURES Transient episodes of paresis following trauma may be a Monoparesis , Paraparesis , Hemiparesis , or Quadriparesis . Progressive d/t atlanto -axial dislocation and cord compression are Weakness, Spasticity, Ataxia, Exaggerated DTRs, Clonus , Loss of Proprioception , Sphincter Disturbances and Frank Paralysis. 3. VASCULAR FEATURES (d/t vertebral artery insufficiency) Syncopal Attacks, Vertigo, Diplopia , Mental Deterioration and Seizures. 4. COMBINATIONS Combinations of these features are usually present.

18. Examination Abnormal General Physical Appearance: Short neck [10+(0.035×Ht in cm)] , Short Stature [<140cm] , Low Hair Line [posterior hairline below the normal level] , Torticollis , Scoliosis. Neurological Symptoms: Posterior Occipital Headache That Worsens with Flexion/Extension Lower Cranial Nerves Deficit Exaggerated Deep Tendon Reflexes

19. Failure of segmentation of C1 and skull base Association – C2-C3 fusion, atlantoaxial subluxation CT coronal section showing complete atlanto -occipital assimilation on right side and incomplete atlanto -occipital assimilation on left side( ) ATLANTOOCCIPITAL ASSIMILATION CT sagittal section showing complete atlanto -occipital assimilation( ),short clivus ( ),violation of Chamberlain’s line( )-basilar invagination and atlantoaxial dislocation( )

20. Skull base flattening Increased basal angle(>140) Decreased clivus canal angle(<150) Increased welcher basal angle Association – basilar invagination 32 year old gentleman with decreased clivus canal angle( ) , violation of Chamberlain’s line( , ) acute angulation , compression of cervicomedullary juncion ( ) PLATYBASIA N

21. Abnormally high vertebral column Prolapse into skull base Secondary- basilar impression Chamberlain’s line McRae’s line Digastric line 24 year old gentleman with violation of Chamberlain’s line( ) and digastric line( ), atlantoaxial dislocation( atlantodens interval-3.8mm) BASILAR INVAGINATION

22. CONGENITAL ANOMALIES-OCCIPITAL BASIOCCIPUT HYPOPLASIA Flattened condyles Shortening of clivus Violation of Chamberlain’s line Decreased clivus canal angle Widening of atlanto -occipital joint axis angle(>127°) Causes basilar invagination CT sagittal section showing short clivus ( ), atlantooccipital assimilation ( ) and violation of Chamberlain’s line ( ) CT coronal section showing flattened occipital condyles ( ) and widening of atlanto -occipital joint axis angle ( )

23. Anterior and posterior arch anomalies Total or partial aplasia Isolated anterior arch anomalies –rare Split atlas CT axial section showing posterior atlas arch rachischisis CT a xial section showing partial anterior arch( ) and os odontoideum ( ) Hypertrophic anterior arch( ) Jefferson’s # (Irregular margins) CONGENITAL ANOMALIES-ATLAS

24. OS ODONTOIDEUM OSSICULUM TERMINALE Separate odontoid process Failure of fusion of base with body of axis Bergmann ossicle Failure of fusion of apical segment with base of dens CONGENITAL ANOMALIES-AXIS T1W MRI sagittal section showing os odnotoideum ( CT sagittal section showing os odnotoideum ( ) with ossiculum terminale ( )

25. KLIPPEL FIEL SYNDROME CHIARI MALFORMATION Complex entity causing cervicovertebral fusion Associations- occipito-atlantoid fusion Low lying tonsils Associations- basiocciput hypoplasia , atlanto -occipital assimilation, platybasia CONGENITAL SYNDROMES 16 year old lady with herniated tonsils( ) Acute clivocanal angle( ),short clivus ( ) and cervical cord compression CT sagittal section showing violation of Chamberlain’s line ( ), atlantooccipital fusion( ), atlantodens interval ( ),fused C5-C8( )

26. Klippel Feil Syndrome Type 1: Elements of more than 2 cervical vertebrae are incorporated into single block. Type 2: Failure of complete segmentation at only 1 or 2 Cervical levels. Type 3: Type 1&2 with failure of segmentation in lower dorsal & lumbar spine. Associated conditions: Scoliosis(60%), Genitourinary(65%), Sprengel’s Deformity(35%), Cardiopulmonary(15%), Deafness(30%). 20% cases may show facial asymmetry with Torticollis & Pterygium Colli .

27. Chiari Malformation Type 1: Caudal descent of cerebellar tonsils in cervical region. Presents in early adulthood. A/W Syrengomyelia in 50-70% of cases. Type 2: Caudal descent of cerebellar vermis & brain stem in cervical region. Type 3: Craniocervical Encephalocele containing portions of cerebellum & brain stem. Type 4: Caudal descent of cerebellum & brain stem upto mid cervical region.

28. Congenital Acquired Traumatic Atlantodens interval 3mm - adults 5mm - children ATLANTOAXIAL DISLOCATION 20 year old man with dens fracture(irregular margins( ) and atlantoaxial dislocation( ) 47 year old lady with rheumatoid arthritis with basilar impression, sclerosis of atlantoaxial joint( ) and atlantoaxial dislocation( ) 18 year old lady with TB, retropharyngeal collection( ), lytic area in dens( ) and atlantoaxial dislocation( ) 38 year old lady with increased atlantodens interval( ) SPONTANEOUS INFECTIVE RHEUMATOID ARTHRITIS TRAUMA

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