KARNIK Alka

Alka KARNIK

Department of Ultrasound, Nanavati Superspeciality Hospital & Research Center, Mumbai

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Sonography of neonatal spine （SUS） is widely used to evaluate lumbar spine anomalies in infants younger than 4 months. Readily available, non-invasive, quick, relatively inexpensive, SUS is carried out at the bedside, does not utilize radiation & requires no sedation. Unossified posterior neural arches allow beam penetration to obtain high-resolution images of the intra-spinal contents. Linear array transducers with extended field-of-view now permit diagnostic sensitivity equal to MRI. Factors affecting MRI resolution like patient movement, pulsation & vascular flow do not affect SUS. We use SUS as first-line screening test in neonates with lumbosacral cutaneous stigmata & spinal dysraphism （SD） associated syndromes. It helps identify & characterize spinal abnormalities & guide timing of further imaging & intervention.
US anatomy: Posterior sagittal & coronal scans are obtained with the neonate in a prone position. A hypoechoic tubular structure with an echogenic central canal, the cord is positioned half-way between the anterior and posterior walls of spinal canal. Anteriorly is the subarachnoid space, dura & verterbral bodies ; posteriorly is the subarachnoid space, dura & neural arch. The cord tapers to form the conus medullaris, which continues as an echogenic cord-like filum terminale. Normal filum is 2 mm thick & surrounded by echogenic nerve roots. Real-time imaging visualizes oscillation of cauda equina nerve roots & movement of the cord during crying & flexion of the spine.
SD is classified by presence or absence of a soft-tissue mass & skin covering. Several cases of skin-covered SD & their US features are discussed.
Tethered cord: Conus below level of L2-3, posterior position of cord in the spinal canal & loss of oscillation of cauda equine suggest a tethered cord. May be associated with a thick filum, filar-fibrolipoma or sinus tracts.
Diastomatomyelia: Partial or complete sagittal clefting of the spinal cord by bony, cartilaginous or fibrous septum into symmetrical or assymetrical hemicords, which may re-unite caudally. Associated tethered cord or syrigomyelia may be seen.
Spina bifida occulta: Posterior bony elements are widely splayed. A skin-covered protrusion of various combinations of meninges, CSF,neural elements or adipose tissue seen.
In meningocele, anechoic CSF filled sac without neural tissue is seen in continuity with a tethered, low-lying spinal cord. In a myelomeningocele neural placode is seen in the sac.
In Lipomyelomeningocele skin-covered lipomatous tissue adherent to neural placode is seen elevating the skin surface.
Spinal lipomas may be intradural, extradural, are highly echogenic & easily seen on SUS
Caudal Regression Syndrome: There is a blunted distal cord. Often associated with regression of the coccyx, sacrum, & lumbar spine