The Neonatal Spine Holdorf PhD, MPA, RDMS, RVT, LRT(AS)

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The Neonatal SpineHoldorf PhD, MPA, RDMS, RVT,
LRT(AS)
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The Neonatal Spine

• Embryology
• Anatomy
• Function
• Indications
• Sonographic Technique
• Sonographic Appearance
• Pathology

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Embryology

• Neural plate - a thickened piece of ectoderm that
  becomes the neural tube
• Spinal meninges - membranes that cover the
  nervous system dura, arachnoid, pia mater
• Paraxial mesodern - tissue that forms on the
  lateral aspect of neural tube that eventually
  form the vertebral column

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Embryology

• Primary Neurulation process by which the
  ectoderm becomes the neural tube forms cervical
  through second sacral segment occurs between day
  18 to 28 of gestation
• ectoderm...neural plate...neural folds...neural
  tube (Medscape)
• Disjunction process by which neuroectoderm
  separates from cutaneous ectoderm

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Embryology

• Secondary Neurulation process that forms the
  conus medularis, cauda equina and filum terminale
  distal to S2 level
• Canalization - Distal neural tube forms from the
  caudal cell mass undifferentiated cells...caudal
  cell mass...neural tube. the ventriculus
  terminalis forms at the terminal end of the
  neural tube near the coccyx, marking the site of
  the future conus medularis.
• Retrogressive differentiation - tissue caudal to
  ventriculus terminalis forms the filum
  terminalle, cauda equina and the ascention of the
  conus (Medscape)

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Anatomy

• Vertebrae - Cervical, thoracic, lumbar
• Sacrum consists of 5 fused vertebrae
• Spinal cord extends from medulla oblongata and
  terminates at the filum terminale
• Conus medularis inferior end of cord that
  tapers into a V shape the tip should be lie at
  the L2-L3 interspace or above
• Filum terminale cordlike extension of the conus
  medularis should be less than 2 mm in diameter
• Cauda Equina group of nerve fibers that extend
  from the tip of the conus medularis

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Anatomy
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Vertebrae
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Sacrum
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Function

• Spinal column protects the spinal cord and nerves
• Provides support for body in upright position
• Provide base to which ribs can attach
• Nerves with cord carry impulses to/from brain

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Why Sonography? (Westbrook)

• Can be done on infants less than 6 months old
• Posterior spinous processes have not ossified
• Inexpensive
• No radiation
• Allows real-time visualization of cord movement
• No sedation
• Can be performed almost anywhere

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Indications (JRC-DMS)

• Sacral dimple (most common reason US ordered)
• Hemangioma
• Raised midline
• Hairy patch
• Tail-like projection of lower spine
• Dx of myelomeningocele or myeloschisis
• Lower extremity deformities

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Sonographic Technique

• Transducer - Highest frequency linear that
  enables visualization of anatomy
• Cervical spine use curvilinear tx
• Select appropriate system presets
• Patient Positions
• Prone
• Decubitus
• Upright (JCR-DMS)
• Scan entire back in long and transverse

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Sonographic Technique (AIUM)

• Determine level of conus medullaris
• Determine L5, then count cephalad
• Determine S1, then count cephalad (1st coccygeal
  segment is more rounded, sacral more squared)
• Last rib bearing vertebra is T12, then count
  caudal
• Skin marker at location of conus can be
  correlated with radiograph

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Sonographic Appearance (Rumack)

• Spinal Cord is hypoechoic size and shape vary
  with location
• Cerivcal oval
• Thoracic circular
• Thoracolumbar - thicker
• Central Echo complex echogenic line within the
  cord may see fluid within (see Rumack p 1797
  Figure 55-5).
• Filum Terminale Center is relatively hypoechoic
  with bright outer margins (see Rumack p 1797
  Figure 55-6) may not be distinguishable from
  nerve fibers

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Sonographic Appearance

• Nerve root interfaces are echogenic
• Filar Cyst Cystic structure at the tip of the
  conus medullaris at origin of filum terminale
• Also referred to as terminal ventricle
• Causes no clinical symptoms
• See Rumack p 1798 fig. 55-7.
• Under normal conditions, the spinal cord should
  float freely within CSF
• Will move with breathing and pulsations from
  vasculature

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Normal Neonatal Spine
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Normal Neonatal Spine
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Conus medularis
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Transverse lumbar sonogram shows normal anatomy
as labeled. V vertebra, transverse process
(arrowhead).
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Pathology Tethered Cord (Westbrook)

• Fixation of the spinal cord in an abnormal
  location
• Conus medullaris positioned below the level of L3
• Can be due to a thickened filum terminale
  (greater than 2 mm) or a meningomyelocele
• Can be associated with a lipoma, dermal sinus
  diastematomyelia
• Limited cord motion

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Pathology Tethered Cord

• Can be associated with other anomalies, ie spinal
  bifida, anorectal malformations, etc.
• May not be discovered until later in life when
  growth may strain cord and cause symptoms
• Weakness in muscles
• Scoliosis
• Changes in bladder function
• Sensory loss

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Pathology

• Spinal Dysraphism general term for congenital
  disorders that involve incomplete fusion of
  mesenchymal, bone and neural elements of the
  spine (Westbrook).
• Overt Open or uncovered lesions due to
  incomplete closure of posterior bony elements of
  spine
• Occult spinal anomalies that occur beneath
  intact skin

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Overt Lesions - Myelocele

• Cyst-like spinal lesion that exposes the neural
  placode (spinal cord) to the environment
• Spinal cord is flush with the plane of the dorsal
  skin. See Rumack p 1802, fig 55-14.
• Not covered with meninges or skin
• Usually at lumbosacral level
• Always associated with tethering of the spinal
  cord (Unsinn).
• Chiari II syndrome occurs in 99 of patients with
  myelocele or myelomeningocele (Unsinn).

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Overt Lesions - Myelomeningocele

• Low termination of cord with herniation of neural
  elements (CSF and nerves) beyond bony defect and
  through the skin
• Cord tethering is almost always involved
  (Westbrook).
• Almost always associated with Chiari II
  malformation
• Sonographic Findings - differentiate from
  meningocele detect associated anomalies
  (hydromelia, lipoma, etc.)
• See Rumack, p 1804, fig 55-15.

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PathologyOccult Spinal Dysraphism

• Spinal anomalies that occur beneath intact skin
• Frequently there are visual indications that a
  problem exists
• Some examples of occult lesions are
• Spinal lipoma
• Meningocele
• Myelocystocele
• Diastematomyelia
• Hydromyelia
• Dorsal Dermal Sinus

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Spinal Lipoma

• Fatty mass that extends into the spinal canal and
  can extend into subcutaneous tissue.
• Usually located at the level of the conus or
  filum terminale
• Can be associated with tethered cord
• Can be difficult to differentiate from teratoma
  use location of lesion to differentiate
• Sonographical findings echogenic mass
• See Rumack p 1805, fig. 55-16.

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Meningocele (Rumack)

• Simple - dorsal herniation of dura, arachnoid and
  CSF into subcutaneous tissue of the back neural
  elements not involved
• Complex - involves neural elements
• Lateral - extends laterally through an
  intervertebral foramen

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Myelocystocele

• Malformation in which the dilated central canal
  of the spinal cord protrudes dorsally through a
  bony defect (Rumack)
• Can occur in any region of spine
• Not usually associated with Chiari II malformation

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Diastamatomyelia

• A sagittal division of the cord into hemicords,
  each containing a central canal and nerve roots
  (Rumack) See Figure 55-22 p1809
• About ½ of patients will present with a surface
  stigmata of an underlying malformation
• Diagnosis sometimes delayed until child develops
  orthopedic and/or neurologic symptoms
• May occur alone or with other anomalies

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Hydromyelia (JRC)

• Dilatation of the central canal which may be
  diffuse or focal
• Associated with myelomeningocele and
  diastamotomyelia
• Sonographic findings separation of echogenic
  linear structures of the central canal

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Dorsal Dermal Sinus (Rumack)

• Fluid tract extending from skin that may or may
  not penetrate the dura
• Results from incomplete disjunction
• Most often seen in the lumbosacral area
• Skin opening usually is located cephalad to the
  sinus connection with the dura
• Can be attached to cord and cause tethering
• See Rumack p 1809, fig 55-20

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References

• ACR-AIUM Practice Guidelines for the Performance
  of an Ultrasound Examination of the Neontal
  Spine October, 2007.
• Images on slides 17-20 were obtained from The
  pediatric spinal canal.ppt. Original author
  unknown.
• Tethered Cord Syndrome a review of the
  literature embryology. Medscape News Today
  retrieved on May 30, 2011 from http//www.medscape
  .com/viewarticle/725080_2
• Unsinn, K., Geley T., Freund, M Gassner, I. US
  of the Spinal Cord in Newborns Spectrum of
  normal findings, variants, congenital anomalies,
  and acquired diseases
• Westbrook, C., Rouse, G. and DeLange, M.
  Sonographic evaluation of the Spine in infants
  and neonates. Journal of Diagnostic Medical
  Sonography 7325-331, 325-331.

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