Ultrasound of the spine for dysraphism

To look for occult spinal dysraphism

Clinically features suggestive for occult spinal dysraphism:
- Sacral dimple
- Tuft of hair
- Vascular patch / haemangioma
- Overlying skin appendage / skin tags
- Other anomalies which maybe associated with tethered cord eg imperforate anus, lower limb neurology

When to do / When not to do:
- Avoid performing if patient <2/52 old (often not enough CSF). Can do if high clinical probability.
- 2/52 to 4-6/12
- Not ideal if >6/12 old as spinous processes starts to ossify, obscuring the view

Preparation:
Patient relaxed eg just finished feeding, sleeping
Position: Prone or lying on side
High resolution linear probe

What to look for / document:
Sagittal view: (through the cartilaginous spinous processes)

1. Level of conus: L2/L3 disk or above, may be lower if pre-term
- If 'low lying' in pre-term, followup scan at 40wk after corrected age.
- Low lying cord may imply cord tethering
- Count the vertebral levels (reference point):
-- from below: sacrum or 1st coccygeal segment
-- from above: last rib
- may be supplemented with lateral spine radiograph to aid in counting in difficult cases, marker can be placed at the level of conus termination

2. Morphology of conus: Normally tapers down.

3. Normal pulsating motion of the spinal cord
- Absence in tethering

4. Dependent position of spinal cord (difficult to ascertain if not enough CSF as in the case of performing in patient below 2/52 old)
- Normal: Lie on anterior 1/3 or halfway in the canal.

5. Filum terminale thickness
- Normal </=2mm

Transverse view:

6. Spinal vertebral dysraphism (posterior elements)