Spine Flashcards
Hemivertebra
Prevalence: 1 in 200 births.
More common in females than males: 3 to 1.
Ultrasound: After 12 weeks’ gestation: the spine is distorted in the sagittal or coronal view resulting in scoliosis.
The hemivertebra appears as a triangular bony structure, smaller than a regular vertebra, acting like a wedge against the adjacent normal vertebras.
Assoc abnorm: The incidence of chromosomal abnormalities is not increased.
Associated syndromes are common: Jarcho-Levin (autosomal recessive; fused vertebrae, scoliosis, abnormal rib alignment) Klippel-Feil (autosomal recessive or dominant; fusion of cervical vertebrae), VACTERL association (sporadic; vertebral and ventricular septal defects, anal atresia, tracheoesophageal fistula, renal anomalies, radial dysplasia and single umbilical artery), OEIS complex (sporadic; omphalocele, exstrophy of the cloaca, imperforate anus, and spinal defects).
Structural abnormalities, mainly musculoskeletal, genitourinary and cardiac are found in >70% of cases.
Follow up: Ultrasound scans every 4-6 weeks to monitor the evolution of scoliosis.
Prognosis: Isolated: good. In 75% of cases there is no or slow progression of scoliosis, but in 25% there is rapid progression at 2-3 years of age.
Associated with other structural defects: poor with increased risk of perinatal death.
Recurrence: Single vertebra, isolated: no increased risk.
Multiple vertebras isolated: 5-10%.
Part of an autosomal recessive condition: 25%.
Open Spina Bifida
Prevalence: 1 in 1,000 fetuses at 12 weeks’ gestation.
Ultrasound: Diagnosis of spina bifida requires the systematic examination of each neural arch, from the cervical to the sacral region, both transversely and longitudinally. In the transverse scan, the normal neural arch appears as a closed circle with an intact skin covering, whereas in spina bifida the arch is ‘U’-shaped and there is an associated bulging meningocele (thin-walled cyst) or myelomeningocele. The extent of the defect and any associated kyphoscoliosis are best assessed in the sagittal scan.
Site of open spina bifida: lumbosacral (65%), sacral (24%), thoracolumbar (10%), cervical (1%).
Open spina bifida is associated with the Arnold-Chiari II malformation with caudal displacement of the brain stem and obliteration of the cisterna magna.
At 11-13 weeks’ gestation, in the mid-sagittal view of the head the lower part of the brain between the sphenoid bone anteriorly and the occipital bone posteriorly can be divided into the brain stem in the front and a combination of the fourth ventricle and cisterna magna in the back. In most cases of open spina bifida the diameter of the brain stem is increased, the distance between the brain stem and the occipital bone (BSOB) is decreased and the ratio of the brain stem to BSOB is >1.0.
In the second-trimester, more than 95% of fetuses have frontal bone scalloping (lemon sign), and obliteration of the cisterna magna with either an ‘absent’ cerebellum or abnormal anterior curvature of the cerebellar hemispheres (banana sign). A variable degree of ventricular enlargement is present in virtually all cases of open spina bifida at birth, but in only about 70% of cases in the mid-trimester.
Assoc abnorm: Chromosomal abnormalities (mainly trisomy 18), single mutant genes, and maternal diabetes mellitus or ingestion of antiepileptic drugs, are implicated in about 10% of the cases.
Risk of non-chromosomal syndromes is low.
Follow up: Follow-up scans every 4 weeks to monitor evolution of ventriculomegaly, possible kyphoscoliosis and development of talipes.
Prognosis: The 5-year mortality rate is about 35%, with 20% dying during the first 12 months of life. About 25% of fetuses with spina bifida are stillborn
The surviving infants usually have paralysis in the lower limbs and double incontinence; despite the associated hydrocephalus requiring surgery, intelligence is often normal.
Recurrence: Affected parent or one sibling: 5%.
Two affected siblings: 10%.
Supplementation of the maternal diet with folate (5 mg/day) for 3 months before and 2 months after conception reduces the risk of recurrence by about 75%.
Sacrococcygeal Teratoma
Prevalence: 1 in 20,000 births.
It is the most frequent fetal teratoma.
Ultrasound: Usually mixed solid and cystic (multiple cysts irregular in shape and size).
The tumors may be entirely external, partially internal and partly external, or mainly internal.
Most teratomas are extremely vascular, which is easily shown using color Doppler ultrasound.
Assoc abnorm: The incidence of chromosomal defects or genetic syndromes is not increased.
Hydronephrosis due to ureteric compression in the case of internal tumors.
Large tumours may result in fetal anemia and thrombocytopenia (due to sequestration of red blood cells and platelets by the tumor), fetal heart failure, hydrops and placentomegaly (due to a hyperdynamic circulation as a result of arteriovenous shunting), polyhydramnios (due to direct transudation into the amniotic fluid and due to fetal polyuria, secondary to the hyperdynamic circulation) and maternal mirror syndrome (generalized fluid overload and preeclampsia).
Follow up: Follow-up scans every 2 to 3 weeks to monitor growth of the tumor, heart function, MCA PSV and amniotic fluid volume.
Ultrasound guided laser coagulation of vessels within the tumor, fetal blood transfusions and amniodrainage may become necessary.
Prognosis: Perinatal mortality: about 50%, mainly due to the preterm birth (the consequence of polyhydramnios) of a hydropic infant requiring major neonatal surgery.
Difficult surgery, especially with tumors that extend into the pelvis and abdomen, can result in nerve injury and incontinence.
The tumor is invariably benign in the neonatal period but delayed surgery or incomplete excision can result in malignant transformation (about 10% before 2 months of age to about 80% by 4 months).
Recurrence: No increased risk of recurrence.
