CRANIO-VERTEBRAL ANOMALIES- OVERVIEW

CRANIO-VERTEBRAL ANOMALIES- OVERVIEWDR. SUMIT KAMBLESENIOR RESIDENTDEPT. OF NEUROLOGYGMC, KOTA

ANATOMY OF CVJ (ARTICULAR) Occiput & atlas Upper surfaces of C1 lateral masses is cup-like or concave which fit into the ball & socket configuration with occipital condyle.( flexion 10*, extension 25*).

Atlas & axis 4 synovial joints 2 median front & back of dens (Pivot variety)2 lateral b/w opposing articular facets (Plane variety)Each joint has its own capsule & synovial cavity.Rotation is upto 90* & approx occurs at the A-A joint.

ANATOMY OF CVJ(LIGAMENTOUS)

Principal stabilizing ligaments of C1 --Transverse atlantal ligament-Alar ligaments

Secondary stabilizing ligaments of CVJ are more elastic & weaker than the primary ligaments.-Apical ligament-Anterior & posterior A-O membranes-Tectorial membrane-Ligamentum flavum-Capsular ligaments

NEURALStructures related are Caudal brainstem (Medulla)Fourth ventricleRostral part of spinal cordLower cranial (9,10,11 ,12) & upper cervical nerves (C1,C2, and C3 nerves with both rami).In cerebellum, only the tonsils, biventral lobules & the lower part of the vermis (nodule, uvula & pyramid)

Classification of CV AnomaliesBony AnomaliesMajor Anomalies1. Platybasia2. Occipitalization of atlas3. Basilar Invagination4. Dens Dysplasia5. Atlanto- axial dislocationB. Minor AnomaliesDysplasia of AtlasDysplasia of occipital condyles, clivus, etc.

II. Soft Tissue anomaliesArnold-Chiari MalformationSyringomyelia/ Syringobulbia

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Classification of CV Anomalies

Congenital-Malformation of occipital sclerotomes Clivus segmentation anomalies Condylar hypoplasia Assimilation of atlasMalformation of atlas Assimilation of atlas Atlantoaxial fusion. Aplasia of atlas arches.Malformation of axis. Irregular Atlantoaxial segmentations. Dens dysplasiaSegmentations failure of c2-c3

Developmental and acquiredAt foraman magnum- stenosisSec.basilar invagination- OI, Pagets ds, osteomalacia, rickets, RA.Atlantoaxial instability down syndrome Ehlers danlos syndrome MPS Trauma Infection TB Tumors- Mets, chordom,osteoblastoma, NFSpontaneous rotatory subluxation- Grisel syndrome

Clinical featuresCervical symptoms and signs- pain suboccipital region radiating vertex, stiffness in 85%Myelopathic Features- long tract involvement and wastingCN involvement- IX, X,XI,XI in 20%Vascular - in 15% Transient Attack of V-B insufficiencySensory symptom of post. column involvement.Cerebellar symptoms/signs- Nystagmus, Ataxia, intention tremor, dysarthriaFeatures of Raised ICT- usually seen in Pateints Having basilar impresssion and/or ACM

INVESTIGATIONS X Rays -Antero-posterior view -Lateral view -Open mouth view for dens Stress X-Rays (neutral, flexion, extention) CT Scan and 3D reconstructionMRI conventional and dynamicMyelogram & VentriculogramAngiography

CRANIOMETRY:

Craniometry of the CVJ uses a series of lines, planes & angles to define the normal anatomic relationships of the CVJ.These measurements can be taken on plain X rays,3D CT or on MRI.No single measurement is helpful. disadvantage --anatomic structures and planes vary within a normal range.

Lines and angles used in radiologic diagnosis of C.V anomalies.

Parameter Normal range limits

PLATYBASIA

BASILAR INVAGINATION

ATLANTO-AXIAL DISLOCATION * Basal angle < 150 degreeBoogards angle < 136 degreeBulls angle < 13 degree Chamberlains line < one third of odontoid above this lineMcgregors line < 5 mmMcrae line odontoid lies below thisKlaus height index > 35 mmAtlanto-temporo > 22mm. mandibular indexAtlanto-odontoid space upto 3 mm in adults upto 5 mm in children

Chamberlains line

From tip of hard palate to posterior tip of Foramen Magnum (opisthion).It helps to recognisebasilar invagination which is said to be present if the tip of the dens is >3 mm above this line

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Mc Gregors line (basal line)

Line drawn from posterior tip of Hard palate to lowest part of OcciputOdontoid tip >5mm above = Basilar InvaginationPosition changed with flexion and extension so not used.Should be used when lowest part of occipital bone is not Foramen Magnum.

Wackenheims clivus canal line

Line drawn along clivus into cervical spinal canalOdontoid is ventral and tangential to this lineIf not suggest AAD or BI

Mc raes line ( foramen magnum line)

Joins anterior and posterior edges of Foramen magnumTip of odontoid is below this line.When sagittal diameter of canal 8 yr of age neurological symptoms occur Foramen Magnum Stenosis

Welchers Basal Angle

Nasion to tuberculum sellaTuberculum sellae to the basion along plane of the clivusNormal 1240 - 142> 1400 = platybasia< 1300 is seen in achondroplasia

Bulls angle

Line representing prolongation of hard palate and line joining the midpoints of the ant & post arches of C1.Normal : 130

Boogard s Angle

1st line between Dorsum sellae to Basion & Mc Raes line. Average - 1220> 1350Basillar impression

Atlantooccipital joint Axis Angle (Schmidt Fischer angle)

Range between 124- 127.Wider in occipital condyle hypoplasia.

OC2AA JTAO JTC1C1

FISHGOLDS DIGASTRIC LINE( Biventer line)

Connects the digastric grooves ( fossae for digastric muscles on undersurface of skull just medial to mastoid process)

Tip of the odontoid process and atlanto-occipital joint normally project11 mmand12 mmbelow this line respectively.Basilar invagination is present when atlanto-occipital joint projects at or above this line.

FISHGOLDS BIMASTOID LINE

Line connecting tip of mastoid process.Odontoid process should be less than 10 mm above this line- BI

HEIGHT INDEX OF KLAUS

Distance between tip of dens and tuberculum cruciate line( line drawn from tuberculum sella to internal occipital protruberence)40-41mm normalIn basilar invagination 140 basal angle.

Occipitalization of atlas/assimilation

50% of all cvj anomaly in india.Failure of segmentation btw last occipital and first spinal sclerotome. Gradual or sudden onset by traumaNo movement btw OA leads increases stress at AA joint get instabilityAssociated with basilar invagination, occipital vertebra, KF syndrome

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Coronal polytomogram demonstrates complete fusion of the lateral C-i masses (1) to the occipital condyles (0).

Incidence - 1.4 to 2.5 per 1000 children. It affects both sexes equally.Neurological symptoms usually occur in third and fourth decades and vary depending on the area of spinal cord impingement.

Clinical Findings

Low hairlinesTorticollisShort necksRestricted neck movement.Dull, aching pain in the posterior occiput and the neckEpisodic neck stiffness

TOPOGRAPHIC FORMS (WACKENHEIM):

Type I: Occipitalization (subtotal) with BI.Type II: Occipitalization(subtotal) with BI & fusion of 2nd & 3rd cervical vertebrae.Type III: occipitalization (Total or subtotal) with BI & maldevelopment of the transverse ligament. may be associated with various malformations like C2-C3 fusion, hemivertebra, dens aplasia, tertiary condyle, etc

Symptoms are due to-absence of a free atlas- TL fails to develop which causes posterior displacement of axis & compression of the spinal cord

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BASILAR INVAGINATION

Basilar invagination implies that the floor of the skull is indented by the upper cervical spine, & hence the tip of odontoidis more cephalad protruding into the FM.Two types : primary invagination, which is developmental and more common, and secondary invagination, which is acquired. Primary invagination can be associated with occipito atlantal fusion, hypoplasia of the atlas, a bifid posterior arch of the atlas, odontoid anomalies.

SECONDARY BASILAR INVAGINATION

Hyperparathyroidism Hurler's syndromeRickets/OM/Scurvy Hajdu-Cheney Syndrome.Paget's disease.Cleidocranial dysostosis Osteogenesis Imperfecta

BI is associated with high incidence of vertebral artery anomalies.

Topographic types of BI :Anterior BI : hypoplasia of the basilar process of the occipital bone.BI of the occipital condyles (Paramedian BI)Condylar hypoplasiaBI in the lateral condylararea.Posterior BI: posterior margin of the FM is invaginated.Unilateral BI.Generalised BI

SIGNS / SYMPTOMS

Usually occur in 2nd or 3rd decade.Short neck(78%),torticollis (68%)Associated ACM & syringomyelia(25 to 35%).Motor & sensory disturbances (85%).Lower cranial nerves involvementHeadache & pain in the nape of neck (greater occipital N) Raised ICP due to posterior encroachment which causes blockage of aqueduct of sylvius.Compression of cerebellum & vestibular apparatus leading to vertical or lateral nystagmus(65%) .Vertebral artery insufficiency s/s.

Atlantoaxial InstabilityAtlantoaxial instability (AAI) is characterized by excessive movement at the junction between the atlas (C1) and axis (C2) as a result of either a bony or ligamentous abnormality. Neurologic symptoms can occur when the spinal cord or adjacent nerve roots are involved.

Incidence of AAD 57% of all CVJ anomalies.8.3% of all causes of cervical compression

GREENBERGS CLASSIFICATION :Incompetence of the odontoid process CongenitalTraumatic -# of odontoid InfectionsTumor 1o/ 2o

Incompetence of the TAL CongenitalTraumaticInflammatory Children (pharynx nasopharynx) Adults (RA & ankylosing spondylitis)

WADIA CLASSIFICATION :Group I: AAD with occipitalization of atlas & fusion of C2 & C3.Group II: odontoid incompetence due to its maldevelopment with no occipitalization of atlas.Group III: odontoid dislocation but no maldevelopment of dens or occipitalization of atlas.

Non-traumatic conditions associated with increase in the atlantoaxial distance:Down syndrome -Due to laxity of the transverse ligament Grisel syndrome Atlantoaxial subluxation associated with inflammation of adjacent soft tissues of the neck Rheumatoid arthritis-From laxity of the ligaments and destruction of the articular cartilage Osteogenesis imperfectaNeurofibromatosis Morquio syndrome -Secondary to odontoid hypoplasiaor aplasiaOther arthridities (Psoriasis, Lupus)

Anterior Atlanto-Dental Interval (AADI)

AAS is + when >3 mm in adults & >5mm in childrenMeasured from posteroinferior margin of ant arch of C1 to the ant surface of odontoidAADI 3-6 mm trans lig. damageAADI >6mm alar lig. damage also

Posterior Atlanto-Dental Interval (PADI) :

Distance b/w posterior surface of odontoid & anterior margin of post ring of C1Considered better method as it directly measures the spinal canalNormal : 17-29 mm at C1PADI 9 mmPADI < 14 mmBasilar Invagination, especially if associatedwith AAS of any degree

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ATLANTO-AXIAL SUBLUXATION (AAS)

Fielding and Hawkins classification:Type I- is simple rotatory displacement with an intact transverse ligament.Type II- injuries involve anterior displacement of C1 on C2 of 3-5 mm with one lateral mass serving as a pivot point and a deficiency of the transverse ligament.Type III -injuries involve greater than 5 mm of anterior displacement.Type IV-injuries involve the posterior displacement of C1 on C2.

Both Type III and IV are highly unstable injuries.

TREATMENT-Type I injuries (stable subluxations) Collar. Type II injuries may be potentially unstable.Type III and IV rotatory displacements that are unstable are treated surgically with a reduction and C1-2 fusion.

Techniques of fusion vary from sublaminar wiring techniques like Brooks or Gallie, Halifax clamp, or transarticular screw of Magerl.

DENS DYSPLASIAType 1 (Os odontoideum) separate odontoid process Type 2 (Ossiculum terminale) failure of fusion of apical segment with its baseType 3 Agenesis of odontoid base & apical segment lies separately.Type 4 Agenesis of odontoid apical segmentType 5 Total agenesis of odontoid process.

OS ODONTOIDEUM

At birth odontoid base is separate from the body of axis by a cartilage which persists until the age of 8, later -ossified,or may remain separate as Os-odontoidium.Independent osseous structure lying cephalad to the axis body in the location of the odontoid process.Anterior arch of the atlas is rounded and hypertrophic but the posterior arch is hypoplastic.Cruciate ligament incompetence and A-A instability are common

Persistent ossiculum terminale: Bergman ossicle

Failure of fusion of the terminal ossicle to the remainder of the odontoid-normally by 12 years of age.Confused with a type 1 odontoid fracture.Stable when isolated and of relatively little clinical significance. Odontoid process is usually normal in height.

Condylar Hypoplasia:

Occipital condyles are underdeveloped and have a flattened -- and widening of the AO joint axis angle --leading to BI.Lateral masses of the atlas may be fused to the hypoplastic condyles, further accentuating the BI.Limits movements at the A-O joint. Violation of the Chamberlain line and widening of atlantooccipital joint axis angle

Basiocciput Hypoplasia:

Hypoplasia of the basiocciput may be mild or severe, depending on the number of occipital sclerotomes affected.Lead-basilar invagination. Clivus-canal angle is typically decreased

Posterior Arch Anomalies

Posterior rachischisis > aplasias and hypoplasia Total or partial aplasia of the posterior atlas arch.Isolated, is usually asymptomatic, but may be associated with anterior AA subluxation.Simulating Jefferson fracture.

SPLIT ATLAS

Anterior +posterior arch rachischisisis =split atlas.Usually asymptomatic but wide clefts with only a fibrous covering may lead to atlas instability

Klippel- Feil Syndrome

TriadDecreased range of motion in the cervical spine m/cShort, webbed neckLow hairline.

Type1- Massive fusion of cervical and upper thoracic vertebra2 Fusion of 2 cervical vertebra ,hemivertebra, scoliosis, OA fusion3-Lower thoracic and upper lumber spine anomaly.4-Sacral agenesis

ASSOCIATED CONDITIONS:

Scoliosis- 60%. Genito-urinary- 65%. m/c is absence of kidney. Sprengel's deformity- 35% Cardio-pulmonary-5-15%, m/c V.S.D. Deafness-30%, all types, MC mixed. Sykinesis-Mirror motions 20%. Cranio-cervical abnormalities- (25%)- Includes C1-C2 hypermobility and instability, BI, Chiari I malformation, diastematomyelia, & syringomyelia.

20% of patients may show facial asymmetry, torticollis and neck webbing (pterygium colli).Ptosis of the eye, Duane's eye contracture, lateral rectus palsy, facial nerve palsy and cleft palate. Upper extremity abnormalities, ie. syndactyly, hypoplastic thumb, supernumary digits and hypoplasia of the upper extremity.

SYMPTOMS: Due to the hypermobility occurring at the open segments, can lead to either frank instability or osteoarthritis. Mechanical symptoms due to joint irritation. Neurologic symptoms due to root irritation or spinal cord compression

Arnold-Chiari Malformation

Type 1- m/c -caudal displacement of peglike cerebellar tonsils below the level of the foramen magnum, -congenital tonsillar herniation, tonsillar ectopia, or tonsillar descent. Syringomyelia in 50 to 70%. Type II -less common and more severe, almost invariably associated with myelomeningocele. Symptomatic in infancy or early childhood. -caudal displacement of lower brainstem (vermis, medulla, pons, 4th ventricle) through the foramen magnum. Type III -herniation of cerebellum into a high cervical myelomeningocele.Type IV -cerebellar agenesis.type III and IV -exceedingly rare and incompatible with life .

Chiari type I malformation.(white line) down to the level of C1 posterior arch.

TREATMENT:No role for prophylactic treatment in an asymptomatic patient with an incidental CMI.All symptomatic patients require surgical treatment.In patients with CMI and hydrocephalus, the primary treatment must be shunting the ventricular system.In presence of symptomatic ventral compression from BI or retroflexion of the odontoid, the treatment is ventral decompression. In patients with a CMI,syrinx with scoliosis, the initial treatment is posterior cervicomedullary decompression.

OUTCOMES:Patients presenting with pain (mainly headache and neck pain) & weakness without associated atrophy best results.Cranial nerve dysfunction moderate recoverySensory recovery poor.Presence of central cord syndrome due to a syrinx-indicative of poor recovery.

Three factors most prognostic of poor outcome are atrophy, ataxia, and scoliosis.

Brain stem and cerebellar syndromes -good recovery

TUBERCULOUS AAD