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ECR 2018 / C-1245
Ultrasound spinal cord of newborn and infants: normal radioanatomy and variant of normal.
Congress: ECR 2018
Poster No.: C-1245
Type: Educational Exhibit
Keywords: Neuroradiology spine, Ultrasound, Education, Education and training
Authors: B. Bannar1, D. BASRAOUI2, H. Jalal2; 1MARRAKECH/MA, 2Marrakesh/MA
DOI:10.1594/ecr2018/C-1245

Findings and procedure details

Technique of spinal ultrasound

 

•Spinal cord is easily analysable until 3rd month

 

• Through the posterior arches incompletely ossified.

 

• Infant in prone, with pillow under the abdomen or lateral decubitus.

 

• Linear probe of high frequency (at least 7 MHz) with axial and longitudinal cuts from the occiput to the sacrum.

 

•Analysis of the bulbo-medullary junction: flexion of the neck oor phased-array that follows the physiological cervical lordosis of the infant.

 

Indications

  1. Clinical lumbosacral anomaly :

Cutaneous stigma at high risk of dysraphism:

  •  Angioma on the midline, nevus.
  •  Subcutaneous mass.
  •  Tuft of hair or a pigmented spot.
  •  Caudal appendix.
  •  Aplasia or cutaneous hypoplasia.
  •  Dermal sinus.
  •  Sacred agenesis.
  •  High-risk coccygeal fossa: atypical fossa,> 5 mm in size and more than 2.5 cm from the anus.

Cutaneous stigma at high risk of dysraphism:

  • Simple  coccygeal fossa, <5 mm and <2.5 cm from the anal margin.
  • Or bony: hemi vertebrae, dehiscence of the posterior arch.

    2.  Anorectal malformation

 

   3. Fight Bladder, unexplained bladder  globe , or repetitive urinary tract infections.

 

    4. Abnormal neurological examination of the lower limbs.

 

A normal spinal ultrasound eliminates severe dysraphism and provides an MRI.

 

 Normal radio  anatomy of spinal ultrasound :

 

1) The spinal cord:

  • Marrow: hypoechoic tubular structure,
         thicker in the cone region (about 5.5 mm)
         thinner in the dorsal region (about 4.5 mm).
  • Centered by a hyperechoic echo"complex central echo" : at the acoustic interface between the anterior white commissure and the central part of the anterior median fissure.
  • Laterally, the marrow is fixed by the serrated ligaments (arachnoidal duplications) which appear as fine linear echoes oriented transversely.

 

Fig. 1: 1 Spinal cord 2 Central canal of the spinal cord 3 Spinous process 4 Body of vertebrae
References: - MARRAKECH/MA

 

Fig. 5: normal spinal cord
References: - MARRAKECH/MA

 

2) The cervico-occipital hinge

 

Sub-occipital sagittal section:

  • Large cistern 
  • Cerebellar tonsils to eliminate a chiari malformation. 
  • Analyze the pons, bulb and cervical spine
  •  Within the subarachnoid spaces

 

3) terminal conus medullaris :

  • Conus  medullaris : ends above L3.
    Its terminal portion gradually tapered  continues with the terminal filum whose thickness varies from 0.5 to 2 mm.
  • Filum terminale visualized on the median line, behind the roots. Its thickness is = or less than 2 mm.
    Fig. 2: filum terminale
    References: - MARRAKECH/MA

 

Fig. 4: filum terminale
References: - MARRAKECH/MA

•Lumbar and sacral roots (ponytail): echoic features, arranged around and below the terminal cone.

 

•The ending of the space dural is in S2.

Fig. 3: Lumbar and sacral roots
References: - MARRAKECH/MA

 

 

Simple clinical and ultrasound landmarks to identify vertebral bodies, and locate the terminal cone:

 

Clinical landmarks :
-  The tip of the last rib is L2.
-  The top of the iliac crest corresponds to L4.

Ultrasound landmarks :
-  Follow the 12th coast until T12
-  Visualization of the renal pedicle located at L2
- Possibly identifying the 1st sacral vertebra (in the absence of transitional anomaly).

 

The variants of the normal: 

 

In about 10% of newborns.

 

1)The dilation of the terminal ventricle (rare):

 

  •  Anechoic formation,
  • Ovoid v  Clear  limit
  • Hyperechoic in the filum or in the conus medullaris
  • Size <5mm  
  • Stability over time

2) Filum Terminale cyst:

 

  • Origin discussed
  • Arachnoid reflexion or embryonic remnant covered with ependymocytes.
  • Less visible on MRI
  • Strict criteria: 

                               -  Median line
                               -  In the filum, just below the spinal cone
                               -  Fusiform
                               - Well limited

                               - Anechoic as a simple cyst.

 

3)Transient dilatation of terminal ependymal canal:

Differential diagnosis of syringomyelia and terminal ventricle.

 

4) Pseudo dermal sinus

 

  •  Fibrous tissue extended: cutaneous dimple → coccyx.
  •  Dermal sinus is rarely located at the tip of the coccyx and often   more cranial.
  •  Search mass or liquid well along this fibrous tract.

 

5) Filum prominent

 

  • More visible compared to nerve roots.
  • Thickness> 1mm
  • median

 

6)  Coccyx:

•Many possible variations can be considered as a mass on palpation.

 

 

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