Type:
Educational Exhibit
Keywords:
Foetal imaging, Musculoskeletal spine, Ultrasound, Education, Foetus
Authors:
M. Kapanigowda1, U. Gunakala1, A. Makam2, P. Jhawar1, R. S1, P. Wadhwani1, S. K L1; 1Bengaluru/IN, 2Bangalore/IN
DOI:
10.26044/ecr2019/C-3417
Findings and procedure details
Normal spine:
- The spine should be always evaluated in three planes because few abnormalities are better seen in one particular plane.
- High-frequency probe is very useful in the evaluation of spinal cord and fluid column around the cord.
- Axial plane shows the ossification centers of vertebral bodies and posterior elements.
- Sagittal plane helps in better assessment of sacrum,
cord termination (Fig 1).
- Newer techniques: Omni view and VCI (Fig 2) helps in better assessment.
Tips:
- Quality of images can be improved by getting a good amount of amniotic fluid above the skin by releasing the probe pressure.
- Presence of fluid column anterior and posterior to the spinal cord rules out most of the anomalies (Video clip 1).
- Termination and an upward curving of sacrum should be assessed always.
Classification:
Spinal abnormalities can be broadly classified into
- Spina bifida
- Bony abnormalities
Spina bifida:
- Most common CNS anomaly competent with life.
- Incidence is about 1 in 1000/2000 births.
Causes: Multifactorial
- Single gene disorders: Various syndromic conditions
- Chromosomal: Trisomy 13 & 18 and triploidy
- Hereditary: Mode of transfer is unknown
- Maternal diabetes
- Teratogens: Valproic acid and hypervitaminosis A.
Pathogenesis:
Two theories were proposed:
1. Failure of closure.
2. Normal closure and re-opening following the insult.
- Nerve roots get damaged because of exposure to amniotic fluid.
- CSF leak in open spina bifida leads to herniation of posterior fossa.
Subtypes:
- Occulta: Tethered cord,
Subcutaneous or intra-spinal lipoma,
dermoid/ epidermoid,
diastematomyelia,
myelocystocele.
- Intact overlying skin (Fig 3)
- Sacral dimple or hair tuft may be seen
- Spinal cord and nerves are usually normal.
- Cystica (Open type): Myelocele and Myelomeningocele.
- Loss of skin covering.
- Exposure of nerve roots to amniotic fluid.
- Leakage of CSF leads to downward herniation of posterior fossa contents leads to the development of Arnold Chiari malformation.
- These classifications are confusing,
so simple way to remember is closed and open type depends on intactness of the skin; whether nerve roots (myelo) component is present or not.
- Spina bifida is associated with paralysis,
orthopedic deformities,
loss of bowel & urinary bladder control depends on the level of the spinal abnormality.
Bony abnormalities:
- Abnormal shape – Hemi-vertebrae,
butterfly vertebrae
- Absent/ dysplastic vertebrae – Irregular ossification center (costochondral dysplasia,
sacral dysgenesis)
- Kyphosis/ scoliosis - >40-45 degree forward angulation; usually due to block vertebrae.
Associated with an open neural tube defect.
CASES:
- Close spina bifida (Fig 4) - spina bifida with herniation of meningeal sac and spinal cord fibers.
- Open spina bifida (fig 5 & 6) - Loss of posterior elements and skin covering over lumbar vertebrae leads to AC II malformation.
- Anterior spinal meningocele (Fig 7)
- Abnormalities associated with spina bifida (Fig 8)
- Kyphosis and scoliosis (Fig 9)
- Hemivertebrae (Fig 10)