Monthly Archives: ธันวาคม 2021

Spinal Dysraphism

Spinal dysraphism, splaying of the posterior ossification centers of the spine, usually indicates spina bifida resulting from failure of closure of the posterior neuropore. However, spinal dysraphism can be due to other abnormalities as follows:

Fig 1, Fig 2, Fig 3

Major differential diagnoses

• Spina bifida
  • meningocele
  • meningomyelocele
  • myeolochisis
• Arnold-Chiari malformation type II
• Pseudodysraphism: technical pitfalls (described previously)

Minor differential diagnoses

• Diastematomyelia: a splitting of the spinal cord
• Lipomyelomeningocele: asymmetric lesion of lipoma originating in the spinal cord or cauda equina
• etc.

Fig 1:  Spina bifida   Cross-sectional scan of the lumbar and thoracic spine: separation of posterior ossification centers at the lumbar region with small protrusion of the overlying tissue

Fig 2:  Spina bifida   Coronal scan of the lumbosacral spine: separation of the ossification centers of the spine (arrow)

Fig 3:  Spina bifida  Cross-sectional scan of the lumbar and thoracic spine: separation of posterior ossification centers at the lumbar region with small protrusion of the overlying tissue (arrow)

Masses on the Back

Lumbosacral masses can be caused by a number of specific anomalies, especially meningomyelocele, which is the most common cause. The differential diagnosis for lumbosacral mass can be summarized as follows:

Fig 1, Fig 2, Fig 3

Major differential diagnoses

Meningomyelocele (most common)

• spinal dysraphism
• solid-cystic mass located at the lumbosacral spine in most cases
• associated cranial signs of spina bifida, such as lemon sign, banana sign, and ventriculomegaly

Sacrococcygeal teratoma (SCT) (uncommon)

• solid-cystic, solid predominantly in most cases but entirely cystic in 15% of cases
• high vascularization
• intra-abdominal components in most cases with a displacement effect on internal structures
•  usually located in the sacrococcygeal area

Limb-body wall complex (uncommon)

• solid-cystic asymmetric mass
• abnormal spinal curvature
• no specific location
• severe abdominal wall defects
•  limb defects
• no or very short umbilical cord

Amniotic band syndrome (uncommon)

• solid-cystic asymmetric mass
• no specific location
• associated limb reduction/constriction defects
• amniotic band in the amniotic cavity.

Minor differential diagnoses

• Artifacts: extrafetal mass, such as chorioangioma attached to the fetal back
• Rare tumors: lipomas, lipomyelomeningocele, and large hemangioma.

Fig 1:  Sacrococcygeal teratoma   Sagittal scan of the spine: abnormal complex solid mass (*) beneath the sacral spine

Fig 2:  Large meningomyelocele   Scan of lower spine: large solid mass with heterogeneous echodensity (solid circle) (arrow = sacrum)

Fig 3:  Lumbar meningocele   Sagittal scan of the spine: small solid mass protruding from lumbar region

Abnormal Spinal Curvature

These abnormalities include kyphoscoliosis, hemivertebrae, angulations or disorganized vertebral structures. Scoliosis, an abnormal lateral deflection of the spinal column, is the most common in this category.

Fig 1, Fig 2, Fig 3, Fig 4

Sonographic differential diagnosis:

• Normal
• Meningomyelocele (common)
• LBWC (uncommon)
• Amniotic band syndrome (uncommon)
• Skeletal dysplasia
• VATER or VACTERL associations (rare)
• Isolated hemivertebrae
• Iniencephaly (very rare)
• Caudal regression syndrome

Note:

• Hemivertebrae are an example of congenital scoliosis resulting from failure of segmentation, which is mostly associated with other anomalies.
• The normal flexible skeleton can be subject to strong deformation forces in utero resulting in transient scoliosis.
• Gross skeletal defects, including absent ribs or hemivertebrae, associated with lateral spinal deflection probably represent truly pathologic scoliosis.

Fig 1:  Scoliosis   Coronal scan of the spine: scoliosis of spine at the thoracic region (arrow)

Fig 2:  Angulation of spine   Coronal scan of the spine: angulation of spine at the thoraco-lumbar region (arrow)

Fig 3:  VATER associations   Coronal scan of the spine: scoliosis

Fig 4:  Disorganized spine :   Coronal scan of the spine: scoliosis and disorganized

Abnormal Hands and Feet

Hands and feet should be examined to exclude polydactyly, brachydactyly, abnormal hand posture, sandal gap, clinodactyly, Rocker-bottom foot, clubfoot, etc. These abnormalities are commonly part of several syndromes.

Polydactyly Fig 1

Polydactyly is the presence of an additional digit, which can be postaxial (on the ulnar or fibular side) or preaxial (on the radial or tibial side) and with a central form. This extra digit may range from a fleshy nubbin to a complete digit. Postaxial polydactyly is the most common form and is inherited autosomal dominantly as an isolated finding in most cases. However, it is significantly related to some syndromes, especially trisomy 13 or short-rib polydactyly syndrome. Preaxial polydactyly, especially a triphalangeal thumb, is most likely to be part of a syndrome.

The major differential diagnoses for polydactyly include

• Isolated polydactyly
• Chromosome abnormalities, especially trisomy 13
• Meckel Gruber syndrome
• Asphyxiating thoracic dystrophy
• Short-rib polydactyly syndrome
• Achondroectodermal dysplasia (Ellis-Van Creveld syndrome)
• Smith-Lemli-Opitz syndrome.

Fig 1:  Polydactyly

Clubfoot Fig 2

A clubfoot is one of the most common congenital anomalies, occurring in 1:250 to 1 in 1000 births. In 95% of cases, the sole is turned medially (talipes equinovarus). This can be caused by external compression in the case of oligohydramnios or by internal factors including abnormal bone formation, spina bifida, muscular defects or genetic causes (15% have a family history of clubfoot). Most clubfeet are found in otherwise normal infants. However, about 10% of cases are associated with several syndromes including Pena-Shokier phenotype, trisomy 18 and 13, etc.

Rocker bottom foot Fig 3

Vertical talus, or eversion of the planar arch, produces a rocker-bottom (convex outward) appearance of the bottom of the foot. This is most often associated with chromosomal abnormalities, particularly trisomy 13 and 18, although it may also be seen as an isolated anomaly, with caudal dysplasia sequence, neural tube defects, and neuromuscular disorders, and as part of the Potter sequence

Fig 2:  Clubfoot  Longitudinal scan of the lower leg: plantar view of the foot seen in the same plane of longitudinal view of tibia and fibula

Fig 3:  Rocker bottom foot   Prominent calcaneous bone (arrow) associated with trisomy 13

Abnormal hand posture Fig 4, Fig 5, Fig 6

Fetal hand malformation may be isolated or associated with chromosomal abnormalities, limb reduction defect, a neuromuscular disorder, or skeletal dysplasia. Ultrasound evaluation of the fetal hand requires assessment of the number and configuration of the fingers, the presence and position of the thumb, and the relationship of the thumb and fingers to each other and to the hand and wrist. The phalanges should be evaluated in the long-axis rather than the short-axis view. Short-axis views may represent the metacarpals rather than the phalanges. The normal fetal hand is most often in a resting position with loosely curled fingers, which the fetus periodically opens. Sonographic assessment requires skill on the part of the examiner in following the movement of the hand and documenting the extended fingers and thumb should the hand open during the examination.

Clenched hands Fig 7, Fig 8

Clenched hands or abnormal hand postures are often related to other abnormalities and more than half of cases have aneuploidy, predominantly trisomy 18 (88% of aneuploid fetuses).

Fig 4:  Pena-Shokier phenotype  Fixed flexion of both elbow and wrist joint (arrow) as well as persistent mouth opening (*)

Fig 5:  VATER associations  Longitudinal scan of forearm: absent radius with abnormal hand posture

Fig 6:  Hitchhiker thumbs   Abnormal posture and wide separation of the thumb (arrow) in the fetus with diastrophic dysplasia (25 weeks)

Fig 7:  Clenched hand   Overlapping fingers of the fetus with trisomy 18

Fig 8: Clenched hand   Overlapping fingers of the fetus with trisomy 18

Clinodactyly Fig 9, Fig 10

Clinodactyly is the permanent curvature or deflection of one or more fingers. It is frequently associated with abnormal chromosomes especially trisomy 21.

Syndactyly

Syndactyly is the fusion of digits and may consist of bony or soft tissue fusion. This may also be difficult to detect sonographically, especially those cases consisting of soft tissue fusion. Syndactyly is associated with a number of syndromes. It may be seen in the SRPD syndromes with the characteristics of polydactyly, and it may be seen in triploidy or Down’s syndrome.

Fig 9: Clinodactyly   Curved-in position of the fifth finger (arrow) of the fetus with trisomy 21

Fig 10:  Clinodactyly  Scan of the hand: disproportionately small middle phalange of the fifth finger (arrow)

Limb Reduction Defects

Limb reduction deformities, presenting alone or as part of a specific syndrome, occur in approximately 0.5 per 10,000 births. Half of them are simple transverse reduction deficiencies of one forearm or hand without associated anomalies and the remaining half have additional anomalies.

Fig 1, Fig 2, Fig 3

Isolated limb reduction:

• isolated limb deficiency more commonly occurs in the upper extremities rather than the leg, which generally occurs within the context of a syndrome, as do bilateral amputations or reduction of all limbs
• sporadic occurrence in most cases with negligible risk of recurrence

Limb reduction associated amniotic band:

• secondary to entanglement with mesodermic bands derived from the chorionic surface of the amnion after the latter has separated from the chorion
• isolated or multiple limb reductions, with or without other defects

Phocomelia:

• typically hands and feet are present, but the intervening arms and legs are absent
• main differential diagnoses include Robert’s syndrome, variants of TAR syndrome, and Grebe’s syndrome
• can be caused by exposure to thalidomide but this is only of historical interest

Radial ray defects: radial clubhand may be part of

• TAR syndrome (thrombocytopenia with absent radius)
• Fanconi’s syndrome: an autosomal recessive disorder consisting of pancytopenia anemia, leukopenia and thrombocytopenia and skeletal anomalies, especially radial clubhand
• Aase’s syndrome: an autosomal recessive disorder characterized by hypoplastic anemia and radial clubhand with bilateral triphalangeal thumb and a hypoplastic radius
• Holt-Oram syndrome: an autosomal dominant disorder characterized by congenital heart defects, radial hypoplasia and triphalangeal or absent thumb
• VATER association: a sporadic disorder resulting from defective mesodermal development during embryogenesis consisting of vertebral segmentation (70%), anal atresia (80%), tracheoesophageal fistula (70%), esophageal atresia, and radial (65%) and renal defects (53%)
• Goldenhar’s syndrome: characterized by hemifacial microsomia, hypoplasia of the malar and maxillary or mandibular region, vertebral anomalies, and radial defects
• Klipple-Feil syndrome
• Chromosomal abnormalities, particularly trisomy 18 and 21.

Fig 1:  Transverse limb reduction  Scan of the foot: absent distal end of foot

Fig 2:  Absent radius syndrome  Longitudinal scan of upper limb (15 weeks): short ulna (arrow) without radius with fixed flexion of wrist joint (arrowhead)

Fig 1:  Limb reduction   Longitudinal scan of lower limb: absent tibia and fibula, abnormal foot (*) arising from femur (arrow) in the fetus with VATER association

Long Bone Bowing

The degree of long-bone curvature should be examined. Campomelic (bent-bow) dysplasia is characterized by ventral bowing of the long bones. Thanatophoric dysplasia and osteogenesis imperfecta also have bowed extremities.

Fig 1, Fig  2

The major differential diagnoses are as follows:

• Campomelic dysplasia (bowing but no shortening)
• Osteogenesis imperfecta type II (related to fracture and callus formation)
• Thanatophoric dysplasia (severe shortened long bones)
• Achondrogenesis
• Hypophosphatasia

Fig 1:  Campomelic dysplasia   Longitudinal scan of tibia: anterior bowing of well ossified tibia

Fig 2:  Osteogenesis imperfecta type IIB  Irregular and angular fracture of long bones (arrow) but rather well-ossified

Fracture In Utero

The detection of rib or long bone fractures in association with severe micromelia suggests a diagnosis of osteogenesis imperfecta. Fractures may be subtle or may lead to angulation.

Fig 1, Fig2, Fig 3

The major differential diagnoses for fractures in utero are as follows:

• Osteogenesis imperfecta type II (most common)
• Hypophosphatasia (rare)
• Campomelic dysplasia (not a true fracture but bowing).

Fig 1:  Fracture in utero  Longitudinal scan of upper extremity: poorly ossified and fracture in osteogenesis imperfecta type IIA

Fig 2:  Callus formation of long bone  Longitudinal scan of humerus and femur: irregularity due to callus (arrowhead) in osteogenesis imperfecta type IIA

Fig 3:  Rib fractures  Multiple rib fractures with poor ossification in the fetus with osteogenesis imperfecta type IIA

Sonolucent Bones

Diffuse demineralization of the skull and long bones almost always occurs with fetal skeletal dysplasia syndromes. In the case of severe demineralization of the bony calvarium, the cranium is thin without an acoustic shadow and so poorly ossified that the intracranial structure can easily be seen. This increased visualization of the intracranial structures may be confused with such abnormalities as exencephaly due to acrania or acalvaria. Unlike exencephaly, however, there is an intact but poorly ossified skull. Careful scanning reveals concomitant limb anomalies.

Fig 1, Fig 2, Fig 3, Fig 4

The main differential diagnoses of the sonolucent skull are as follows:

• Osteogenesis imperfecta (most common)
• Hypophosphatasia (rare)
• Achondrogenesis type I (rare).

Fig 1:  Hypophosphatasia  Longitudinal scan of long bones: shortened and poorly ossified bones

Fig 2:  Poorly ossified and compressible skull   Cross-sectional scan of skull: deformable skull with sonolucency in osteogenesis imperfecta type IIA

Fig 3:  Micromelia in Thanatophoric dysplasia   Severe shortenings of long bones (arrow) but normal ossification

Fig 4:  Sonolucent and shortened arm   Longitudinal scan of the arm: Sonolucent and shortened humerus (*) in case of achondrogenesis

Bone Shortening

All long bones should be measured in each extremity, although subjective evaluation may be sufficient in most cases. The severity of bone shortening varies from extreme to mild.

Fig 1, Fig 2, Fig 3

The major differential diagnoses of bone shortenings are as follows:

Severe shortening

• thanatophoric dysplasia (micromelia) (common)
• osteogenesis imperfecta type II (micromelia) (common)
• achondrogenesis (micromelia) (common)
• short-rib polydactyly syndrome (uncommon)
• diastrophic dysplasia (uncommon)
• homozygous achondroplasia (uncommon)
• mesomelic dysplasia (uncommon)
• chondrodysplasia punctata, rhizomelic type

Mild-to-moderate shortening

• osteogenesis imperfecta type II (common)
• heterozygous achondroplasia (common)
• asphyxiating thoracic dysplasia (common)
• campomelic dysplasia (uncommon)
• hypophosphatasia (uncommon)
• chondroectodermal dysplasia (uncommon).

Fig 1:  Long bone shortening   Longitudinal scan of the thigh and leg: shortening of thigh and leg, compared with foot (achondrogenesis)

Fig 2:  Short humerus  Longitudinal scan of long bones: shortened but well ossified humerus of the fetus with Juene syndrome

Fig 3:  Micromelia in Thanatophoric dysplasia   Severe shortenings of long bones (arrow) but normal ossification

Normal Examination

Normal Spine

Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6

–     Mineralization of the spine begins at 8 weeks of gestation. The three ossification centers of individual vertebrae include a single ventral center for the vertebral body (centrum) and two paired dorsal centers that will become the lateral masses and the posterior arch. They are well visualized from 15 to 16 weeks onwards. However, spina bifida can be detected much earlier. The posterior ossification centers begin at the base of the transverse processes. As ossification progresses, the laminae become visible, usually after 19 weeks. The inward angulation of the normal laminae is the opposite of the outward splaying of the laminae seen in spina bifida, an optimal situation for detecting this anomaly. The arch of the upper sacral region is not consistently recognizable until after 25 weeks.

• Technique of examination: The spine can be systematically examined during the second and third trimesters as follows:
  • Adjust the transducer on the maternal abdomen to achieve a cross-section image of the fetal abdomen or thorax.
  • Identify the location of the fetal spine, noting the acoustic shadow behind the spine, and carefully adjust the transducer to demonstrate all three ossification centers.
  • To obtain the sagittal view, from the previous image, make an attempt to bring both posterior centers to the middle of the image, lying horizontally or perpendicular to the ultrasound beam, and then rotate the transducer 90 degrees and meticulously adjust it to obtain the best image of the coronal view.
  • To obtain the coronal view, from the cross-section image, make an attempt to bring both posterior centers to the middle of the image, lying vertically or parallel to the ultrasound beam, and then rotate the transducer 90 degrees and meticulously adjust it to obtain the best image of the coronal view.
• Evaluation of the three views of the spine:
  • On the transverse (axial) view, the anterior ossification center (vertebral body) and posterior ossification centers (pedicles, transverse processes, laminae, and spinous processes) may all be identified as echogenic structures. This view may be superior to longitudinal views in demonstrating small spinal defects, since all three ossification centers can be imaged simultaneously.
  • On the sagittal view, many vertebrae can be visualized on a single image. The curvature can be best evaluated<?is this sentence complete enough?>. The normal spine appears as two parallel lines formed by the vertebral bodies anteriorly and the ossification centers of the lateral processes converging in the sacrum. The lines correspond to the posterior elements of the vertebrae and the vertebral body. This view can optimally demonstrate interruption of the overlying integument when myelomeningocele is present.
  • On the coronal view, many vertebrae can be visualized on a single image. Hence, scoliosis, hemivertebrae, and disorganized vertebrae are optimally visualized on this view. <?can you check the following sentence>The images oriented through the dorsal ossification centers can demonstrate the two parallel rows of echogenicity in these centers and also the extent of a dysraphic defect compared to adjacent vertebrae in the case of spina bifida.

Fig 1:  Normal spine   Cross-sectional scan of the abdomen: posterior ossification centers of spine align vertically

Fig 2:  Normal thoracic spine  Coronal scan of the thoracic spine: normal echodensity and alignment

Fig 3:  Normal spine :   Cross-sectional scan of the abdomen posterior ossification centers of spine align horizontally (arrow = anterior ossification center)

Fig 4:  Normal spinal curvature  Sagittal view of the spine: normal curvature (arrow) with complete overlying skin

Fig 5:  Normal lumbar spine  Coronal scan of the lumbar spine (arrowhead) (arrow = iliac bone)

Potential pitfalls:

• • Incomplete ossification: Scanning in early pregnancy reveals incomplete ossification of the lateral centers. Hence, on the transverse view, the posterior centers may appear to be parallel to one another rather than converging to the midline. This may be misinterpreted as spinal dysraphism.
  • Pseudodyspharism: On the coronal plane of the cervical and lumbar spine, the two parallel lines of posterior centers normally diverge. This divergence should not be mistaken for a spinal dysraphism.
  • Pseudodyspharism: <?please check the following sentence>On the transverse scan of the lumbosacral spine, if the ultrasound beam angled obliquely across the vertebral body of one vertebra but missed the posterior element or the posterior centers of another, this could simulate dyspharism. A normal appearance is restored when the ultrasound beam is reoriented perpendicular to the spinal axis.
• High-quality sonograms can also show the spinal cord within the spinal canal. The central canal is readily detectable within the cord. The more echogenic cauda equina (nerve roots) can be seen distal to the conus medullaris (distal spinal cord). With growth of the spine, the position of the conus medullaris ascends with gestational age.
• The spinal cord neural tissue, like that of most brain tissue, is echopenic. The conus medullaris and the craniocervical junction can be seen, albeit inconsistently, in nearly all fetuses by 18-20 weeks. The tissues surrounding the cord (leptomeninges) are brightly echogenic, as are those that surround the brain, and the dura is usually also seen discretely as a linear bright reflector. In fetuses with myelomeningoceles, determination of the most cephalic spinal level lesion is an important factor in prognosis. This level can be determined by counting up from the last ossified vertebral segment.