Ultrasound Evaluation of the Neonate Spine Harry H. Holdorf 1

Indications Ultrasound of the neonate spine can be an accurate, fast, and cost-effective alternative to MRI imaging. Evaluations include: Congenital or acquired abnormalities of the neonate or young infant spinal canal.

The Neonatal Spine Embryology Anatomy Function Indications Sonographic Technique Sonographic Appearance Pathology

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 mesoderm - tissue that forms on the lateral aspect of neural tube that eventually form the vertebral column 4

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

Embryology – Primary Neurulation

Embryology – Primary Neurulation

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) 8

Embryology – Secondary Neurulation http://php.med.unsw.edu.au/embryology/index .php?title=Development_Animation_- _Secondary_Neurulation

Embryology – Secondary Neurulation

Anatomy -Vertebrae Vertebrae - Cervical, thoracic, lumbar Sacrum – consists of 5 fused vertebrae Coccyx – 3 or 4 fused vertebrae

Vertebrae C7 - T12 -L5 - S5

Sacrum

Anatomy – Spinal Cord 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

Anatomy

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

Why Sonography? 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 17

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

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

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

Sonographic Appearance (Rumack) Spinal Cord is hypoechoic; size and shape vary with location Cervical – oval Thoracic – circular Thoracolumbar - thicker Central Echo complex – echogenic line within the cord; may see fluid within (see Rumack) Filum Terminale – Center is relatively hypoechoic with bright outer margins (see Rumack); may not be distinguishable from nerve fibers

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 Under normal conditions, the spinal cord should float freely within CSF Will move with breathing and pulsations from vasculature

Normal Neonatal Spine

Normal Neonatal Spine

Conus medularis

Transverse lumbar sonogram shows normal anatomy as labeled Transverse lumbar sonogram shows normal anatomy as labeled. V = vertebra, transverse process (arrowhead).

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

Pathology – Tethered Cord Can be associated with other anomalies, i.e. 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

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

Pathology In occult spinal dysraphism, ≥ 1 vertebrae do not form normally, and the spinal cord and meninges may also be affected. In spina bifida cystica, the protruding sac can contain meninges (meningocele), spinal cord (myelocele), or both (meningomyelocele).

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. 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). 32

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.

Pathology Occult 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

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.

Spinal Lipoma

Meningocele (Rumack) Cystic herniation of CSF and meninges Neural elements not involved; cord usually develops normally Uncommon 37

Meningocele

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 39

Diastamatomyelia A sagittal division of the cord into hemicords, each containing a central canal and nerve roots 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

Diastamatomyelia

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

Hydromyelia

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.

Dorsal Dermal Sinus

Dorsal Dermal Sinus

References ACR-AIUM Practice Guidelines for the Performance of an Ultrasound Examination of the Neontal Spine; October, 2007. Images on slides 22-25 were obtained from The pediatric spinal canal.ppt. Original author unknown. Image Slide 5 from http://www.ncbi.nlm.nih.gov/books/NBK10080/figure/A2873/?report=objectonly retrived on Sept 12, 2012 Image Slide 6 from http://www.ncbi.nlm.nih.gov/books/NBK10080/figure/A2879/?report=objectonly; retrieved on Sept. 12, 2012 Image Slide 8 http://php.med.unsw.edu.au/embryology/index.php?title=Development_Animation_-_Secondary_Neurulation Image Slide 9 http://www.radsource.us/clinic/0807 Image Slide 14 http://www.childrensmercy.org/content/view.aspx?id=6196 Image Slide 30 – Meningelocele, myelocel, http://www.merckmanuals.com/professional/pediatrics/congenital_neurologic_anomalies/spina_bifida.html Image Slide 40 –Diastamatomyelia http://www.jultrasoundmed.org/content/29/9/1357/F2.expansion?ck=nck Image Slide 42 – Hydromyelia -http://www.ultrasoundcases.info/Slide-View.aspx?cat=507&case=2168 Image Slide 41 – Dorsal Dermal Sinus http://www.minnisjournals.com.au/ajum/article/Ultrasound-examination-of-the-neonatal- spine-24 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 Image slide 44 - http://www.ultrasoundcases.info/Slide-View.aspx?cat=507&case=4224 Images Slide 45 - http://www.ultrasoundcases.info/Slide-View.aspx?cat=507&case=4224 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 7:325-331, 325-331. 47