Axis Anomalies

1.   Persistent ossiculum terminale = Bergman ossicle

√  unfused odontoid process > 12 years of age

DDx:   type 1 odontoid fracture

2.   Odontoid aplasia (extremely rare)

3.   Os odontoideum

=  independent os cephalad to axis body in location of odontoid process

√  absence of odontoid process

√  anterior arch of atlas hypertrophic + situated too far posterior in relation to axis body

Cx:   atlantoaxial instability

DDx:   type 2 odontoid fracture (uncorticated margin)

Odontoid Erosion

mnemonic:   P LARD

Psoriasis

Lupus erythematosus

Ankylosing spondylitis

Rheumatoid arthritis

Down syndrome

Atlantoaxial Subluxation

=  displacement of atlas with respect to axis

(1)  Posterior atlantoaxial subluxation (rare)

(2)  Anterior atlantoaxial subluxation (common)

=  distance between dens + anterior arch of C1 (measurement along midplane of atlas on lateral view):

Causes of subluxation:

A.  Congenital

1.   Occipitalization of atlas

0.75% of population; fusion of basion + anterior arch of atlas

2.   Congenital insufficiency of transverse ligament

3.   Os odontoideum / aplasia of dens

4.   Down syndrome (20%)

5.   Morquio syndrome

6.   Bone dysplasia

B.  Arthritis

due to laxity of transverse ligament or erosion of dens

1.   Rheumatoid arthritis

2.   Psoriatic arthritis

3.   Reiter syndrome

4.   Ankylosing spondylitis

5.   SLE

rare:  in gout + CPPD

C.  Inflammatory process

pharyngeal infection in childhood, retropharyngeal abscess, coryza, otitis media, mastoiditis, cervical adenitis, parotitis, alveolar abscess

√  dislocation 8–10 days after onset of symptoms

D.  Trauma (very rare without odontoid fracture)

E.  Marfan disease

mnemonic:   JAP LARD

Juvenile rheumatoid arthritis

Ankylosing spondylitis

Psoriatic arthritis

Lupus erythematosus

Accident (trauma)

Retropharyngeal abscess, Rheumatoid arthritis

Down syndrome

Pseudosubluxation of Cervical Spine

=  ligamentous laxity in infants allows for movement of the vertebral bodies on each other, esp. C2 on C3

SPINAL DYSRAPHISM

=  abnormal / incomplete fusion of midline embryologic mesenchymal, neurologic, bony structures

External signs (in 50%):

•  subcutaneous lipoma

•  hypertrichosis

•  pigmented nevi

•  pathologic plantar response

•  bladder + bowel dysfunction

•  spastic gait disturbance

•  foot deformities

•  absent tendon reflexes

•  sinus tract

•  skin dimple

Spina Bifida

=  incomplete closure of bony elements of the spine (lamina + spinous processes) posteriorly

Spina Bifida Occulta

=   OCCULT SPINAL DYSRAPHISM

=  cleft / tethered cord WITH skin cover

Frequency:   15% of spinal dysraphism

•  rarely leads to neurologic deficit in itself

Associated with:

(a)  vertebral defect (85 – 90%)

(b)  lumbosacral dermal lesion (80%):

•  hairy tuft (= hypertrichosis), dimple, sinus tract, nevus, hyperpigmentation, hemangioma, subcutaneous mass

1.   Diastematomyelia

2.   Lipomeningocele

3.   Tethered cord syndrome

4.   Filum terminale lipoma

5.   Intraspinal dermoid

6.   Epidermoid cyst

7.   Myelocystocele

8.   Split notochord syndrome

9.   Meningocele

10.   Dorsal dermal sinus

11.   Tight filum terminale syndrome

Spina Bifida Aperta

=  SPINA BIFIDA CYSTICA

=  posterior protrusion of all / parts of the contents of the spinal canal through a bony spinal defect

Frequency:   85% of spinal dysraphism

Associated with:   hydrocephalus, Arnold-Chiari II malformation

◊  Most severe form of midline fusion defect

•  neural placode WITHOUT skin cover

Associated with:   neurologic deficit in > 90%

1.   Simple meningocele

=  herniation of CSF-filled sac without neural elements

2.   Myelocele

=  midline plaque of neural tissue lying exposed at the skin surface

3.   Myelomeningocele

=  a myelocele elevated above skin surface by expansion of subarachnoid space ventral to neural plaque

4.   Myeloschisis

=  surface presentation of neural elements completely uncovered by meninges

Caudal Spinal Anomalies

=  malformation of distal spine and cord

Associated with:   hindgut, renal, genitourinary anomalies

1.   Terminal myelocystocele

2.   Lateral meningocele

3.   Caudal regression

Segmentation Anomalies of Vertebral Bodies

during 9^th–12^th week of gestation two ossification centers form for the ventral + dorsal half of vertebral body

1.   Asomia = agenesis of vertebral body

√  complete absence of vertebral body

√  hypoplastic posterior elements may be present

2.   Hemivertebra

(a)  Unilateral wedge vertebra

√  right / left hemivertebra

√  scoliosis at birth

(b)  Dorsal hemivertebra

√  rapidly progressive kyphoscoliosis

(c)  Ventral hemivertebra (extremely rare)

3.   Coronal cleft

=  failure of fusion of anterior + posterior ossification centers

May be associated with:   premature male infant, Chondrodystrophia calcificans congenita

Location:   usually in lower thoracic + lumbar spine

√  vertical radiolucent band just behind midportion of vertebral body; disappears mostly by 6 months of life

4.   Butterfly vertebra

=  failure of fusion of lateral halves ← persistence of notochordal tissue

May be associated with:   anterior spina bifida ± anterior meningocele

√  widened vertebral body with butterfly configuration (AP view)

√  adaptation of vertebral endplates of adjacent vertebral bodies

5.   Block vertebra

=  congenital vertebral fusion

Location:   lumbar / cervical

√  height of fused vertebral bodies equals the sum of heights of involved bodies + intervertebral disk

√  “waist” at level of intervertebral disk space

6.   Hypoplastic vertebra

7.   Klippel-Feil syndrome

VERTEBRAL BODY

Increased T1 Signal Intensity of Spinal Bone Marrow

=  mostly benign

A.  FOCAL

1.   Hemangioma (11%)

2.   Modic type 2 endplate changes

3.   Lipoma

4.   Paget disease (later stage)

5.   Hemorrhage (with fracture)

6.   Melanoma

B.  DIFFUSE / multifocal

1.   Normal variant

2.   S/P radiation treatment

3.   Osteoporosis

4.   Multiple hemangiomas

5.   Spondyloarthritis

6.   Anorexia nervosa

Decreased T1 Signal Intensity of Spinal Bone Marrow

=  equal to / lower than SI of muscle

A.  CENTERED ON ENDPLATE

1.   Modic type 1 + 3 endplate changes

2.   Osteomyelitis

3.   Amyloid

B.  CENTERED IN VERTEBRAL BODY

1.   Malignancy (metastasis, lymphoma, plasma cell dyscrasia, solitary plasmacytoma, multiple myeloma)

2.   Fracture

3.   Hemangioma (rare presentation)

4.   Fibrous dysplasia

C.  CENTERED IN POSTERIOR ELEMENTS METASTASES, MYELOMA, LYMPHOMA, FRACTURE, PRIMARY BONE TUMOR

D.  DIFFUSE / MULTIFOCAL

1.   Hematopoietic hyperplasia

(a)  chronic anemia: sickle cell disease, thalassemia, hereditary spherocytosis

(b)  chronic illness: HIV

(c)  heavy smoking

(d)  obesity

(e)  drugs: granulocyte-colony-stimulating factor, erythropoietin

2.   Neoplasm

√  avid enhancement

3.   Renal osteodystrophy

4.   Systemic inflammation: sarcoidosis, gout, spondyloarthropathy

4.   Hematologic malignancy: myelofibrosis. mastocytosis

Destruction of Vertebral Body

A.  NEOPLASM

1.   Metastasis

2.   Primary neoplasm: chordoma, chondrosarcoma, lymphoma, multiple myeloma

B.  INFECTION

1.   Pyogenic vertebral osteomyelitis

2.   Tuberculous spondylitis

3.   Brucellosis

4.   Fungal disease

5.   Echinococcosis

6.   Sarcoidosis

Granulomatous Spondylitis

1.   TB

2.   Brucellosis

3.   Sarcoidosis

Gas in Vertebral Body

1.   Osteonecrosis = Kümmell disease

√  linear collection

2.   Osteomyelitis

√  small gas bubbles ± extension into adjacent soft-tissues

3.   Intraosseous displacement of cartilaginous / Schmorl node

√  branching gas pattern

4.   Malignancy

Small Vertebral Body

1.   Radiation therapy

during early childhood in excess of 1,000 rad

2.   Juvenile rheumatoid arthritis

Location:   cervical spine

√  atlantoaxial subluxation may be present

√  vertebral fusion may occur

3.   Eosinophilic granuloma

Location:   lumbar / lower thoracic spine

√  compression deformity / vertebra plana

4.   Gaucher disease

=  deposits of glucocerebrosides within RES

√  compression deformity

5.   Platyspondyly generalisata

=  flattened vertebral bodies associated with many hereditary systemic disorders: achondroplasia, spondyloepiphyseal dysplasia tarda, mucopolysaccharidosis, osteopetrosis, neurofibromatosis, osteogenesis imperfecta, thanatophoric dwarfism

√  disk spaces of normal height

Vertebra Plana

mnemonic:   FETISH

Fracture (trauma, osteogenesis imperfecta)

Eosinophilic granuloma (Langerhans cell histiocytosis)

Tumor (metastatic neuroblastoma, myeloma, leukemia, aneurysmal bone cyst, Ewing sarcoma)

Infection

Steroids (avascular necrosis)

Hemangioma

mnemonic:   MELT

Metastasis / Myeloma

Eosinophilic granuloma

Lymphoma

Trauma / TB

SIGNS OF ACUTE VERTEBRAL COLLAPSE ON MR

1.   Osteoporosis

√  retropulsion of posterior bone fragment

2.   Malignancy

√  epidural soft-tissue mass

√  no residual normal marrow signal intensity

√  abnormal enhancement

Enlarged Vertebral Body

1.   Paget disease

√  “picture framing”; bone sclerosis

2.   Gigantism

√  increase in height of body + disk

3.   Myositis ossificans progressiva

√  bodies greater in height than width

√  osteoporosis

√  ossification of ligamentum nuchae

Enlarged Intervertebral Foramen

=  NEUROFORAMINAL WIDENING = DUMBBELL-SHAPED / HOURGLASS LESION

A.  SOLID BENIGN

1.   Benign peripheral nerve sheath tumor (PNST):

›  Neurofibroma

›  Neurilemmoma = schwannoma

2.   Meningioma

3.   Extradural cavernous hemangioma

4.   Congenital absence / hypoplasia of pedicle

B.  SOLID MALIGNANT

1.   Metastatic destruction of pedicle: neuroblastoma

2.   Malignant PNST

3.   Ewing sarcoma / primitive neuroectodermal tumor

4.   Solitary bone plasmacytoma

5.   Chondrosarcoma

C.  CYSTIC

1.   Dural ectasia (Marfan syndrome, Ehlers-Danlos syndrome)

2.   Synovial cyst

3.   Traumatic pseudomeningocele

4.   Arachnoid cyst

5.   Hydatid cyst

Cervical Spine Fusion

mnemonic:   SPAR BIT

Senile hypertrophic ankylosis (DISH)

Psoriasis, Progressive myositis ossificans

Ankylosing spondylitis

Reiter disease, Rheumatoid arthritis (juvenile)

Block vertebra (Klippel-Feil)

Infection (TB)

Trauma

Vertebral Border Abnormality

Straightening of Anterior Border

1.   Ankylosing spondylitis

2.   Paget disease

3.   Psoriatic arthritis

4.   Reiter disease

5.   Rheumatoid arthritis

6.   Normal variant

Anterior Scalloping of Vertebrae

1.   Aortic aneurysm

2.   Lymphadenopathy

3.   Tuberculosis

4.   Multiple myeloma (paravertebral soft-tissue mass)

Posterior Scalloping of Vertebrae

in conditions associated with dural ectasia

A.  INCREASED INTRASPINAL PRESSURE

1.   Communicating hydrocephalus

2.   Ependymoma

B.  MESENCHYMAL TISSUE LAXITY (dural ectasia)

1.   Neurofibromatosis

2.   Marfan syndrome

3.   Ehlers-Danlos syndrome

4.   Posterior meningocele

C.  BONE SOFTENING

1.   Mucopolysaccharidoses: Hurler, Morquio, Sanfilippo

2.   Achondroplasia

3.   Acromegaly (lumbar vertebrae)

4.   Ankylosing spondylitis (lax dura acting on osteoporotic vertebrae)

mnemonic:   SALMON

Spinal cord tumor

AchondroPlasia

Mucopolysaccharidosis

Osteogenesis imperfecta

Neurofibromatosis

mnemonic:   DAMN MALE SHAME

Dermoid

Ankylosing spondylitis

Meningioma

Neurofibromatosis

Marfan syndrome

Acromegaly

Lipoma

Ependymoma

Syringohydromyelia

Hydrocephalus

Achondroplasia

Mucopolysaccharidoses

Ehlers-Danlos syndrome

Bony Outgrowths from Vertebra

A.  CHILDHOOD

1.   Hurler syndrome = gargoylism

√  rounded appearance of vertebral bodies

√  mild kyphotic curve with smaller vertebral body at apex of kyphosis displaying tonguelike beak at anterior half (usually at T12 / L1)

√  “step-off” deformities along anterior margins

2.   Hunter syndrome

less severe changes than in Hurler syndrome

3.   Morquio disease

√  flattened + widened vertebral bodies

√  anterior “tonguelike” elongation of central portion of vertebral bodies

4.   Hypothyroidism = cretinism

√  small flat vertebral bodies

√  anterior “tonguelike” deformity (in children only)

√  widened disk spaces + irregular endplates

B.  ADULTS

1.   Spondylosis deformans

√  osteophytosis along anterior + lateral aspects of endplates with horizontal + vertical course ← shearing of outer annular fibers (Sharpey fibers connecting annulus fibrosus to adjacent vertebral body)

2.   Diffuse idiopathic skeletal hyperostosis (DISH)

√  flowing calcifications + ossifications along anterolateral aspect of > 4 contiguous thoracic vertebral bodies ± osteophytosis

3.   Ankylosing spondylitis

√  bilateral symmetric syndesmophytes (= ossification of annulus fibrosus)

√  “bamboo spine”

√  “diskal ballooning” = biconvex intervertebral disks ← osteoporotic deformity of endplates

√  straightening of anterior margins of vertebral bodies ← erosions

√  ossification of paraspinal ligaments

4.   Fluorosis

√  vertebral osteophytosis + hyperostosis

√  sclerotic vertebral bodies + kyphoscoliosis

√  calcification of paraspinal ligaments

5.   Acromegaly

√  increase in anteroposterior diameter of vertebrae + concavity on posterior portion

√  enlargement of intervertebral disk

6.   Hypoparathyroidism

7.   Neuropathic arthropathy

8.   Sternoclavicular hyperostosis

Spine Ossification

1.   Syndesmophyte = ossification of annulus fibrosus

√  thin slender vertical outgrowth extending from margin of one vertebral body to next

Associated with:   ankylosing spondylitis, ochronosis

2.   Osteophyte

=  ossification of anterior longitudinal ligament

√  initially triangular outgrowth several millimeters from edge of vertebral body

Associated with:   osteoarthritis

3.   Flowing anterior ossification

=  ossification of disk, anterior longitudinal ligament, paravertebral soft tissues

Associated with:   DISH

4.   Paravertebral ossification

√  initially irregular / poorly defined paravertebral ossification eventually merging with vertebral body

Associated with:   psoriatic arthritis, Reiter syndrome

Vertebral Endplate Abnormality

1.   Cupid’s bow vertebra

Cause:   ? (normal variant)

Location:   3^rd–5^th lumbar vertebra

√  two parasagittal posterior concavities on inferior aspect of vertebral body (best viewed on AP)

2.   Osteoporosis (senile / steroid-induced)

(a)  “fish vertebra / fish-mouth vertebra”

Cause:   osteoporosis, osteomalacia, Paget disease, osteogenesis imperfecta, multiple myeloma, hyperparathyroidism, Gaucher disease

√  biconcave vertebra

√  bone sclerosis along endplates

(b)  wedge-shaped vertebra

√  anterior border height reduced by > 4 mm compared to posterior border height

(c)  “pancake” vertebra

√  overall flattening of vertebra

3.   “H-vertebra”

=  compression of central portions ← subchondral infarcts

Cause:   sickle cell + other anemias, Gaucher disease

4.   Schmorl / cartilaginous node

=  intraosseous herniation of nucleus pulposus at center of weakened endplate

Cause:   Scheuermann disease, trauma, hyperparathyroidism, osteochondrosis

5.   Butterfly vertebra

Cause:   congenital defect

6.   Limbus vertebrae

=  intraosseous herniation of disk material at junction of vertebral bony rim of centra + endplate (anterosuperior corner)

7.   “Rugger-jersey spine”

Cause:   hyperparathyroidism, myelofibrosis

√  horizontal sclerosis subjacent to vertebral endplates with intervening normal osseous density (resembling the stripes on rugby jerseys)

8.   “Sandwich” / “Hamburger” vertebra

Cause:   osteopetrosis, myelofibrosis

√  sclerotic endplates alternate with radiolucent midportions of vertebral bodies

9.   “Ring” epiphysis

Ring Epiphysis

=  normal small steplike recess at corner of anterior edge of developing vertebral body that calcifies ~ 6 years of age, ossifies ~ 13 years of age, and fuses with vertebral body ~ 17 years of age

1.   Severe osteoporosis

2.   Healing rickets

3.   Scurvy

Bullet-shaped Vertebral Body

mnemonic:   HAM

Hypothyroidism

Achondroplasia

Morquio syndrome

Bone-within-bone Vertebra

=  “ghost vertebra” following stressful event during vertebral growth phase in childhood

1.   Stress line of unknown cause

2.   Leukemia

3.   Heavy metal poisoning

4.   Thorotrast injection, TB

5.   Rickets

6.   Scurvy

7.   Hypothyroidism

8.   Hypoparathyroidism

Ivory Vertebra

=  increase in opacity of vertebral body retaining its size and contours

Cause:  stimulation of osteoblasts, coarsening of trabeculae, reactive bone formation

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