Occult spinal dysraphism

Case contributed by Dr Varun Babu

Presentation

Chronic constipation, with a sacral dimple - to rule out spinal abnormalities.

Patient Data

Age: 2 years
Gender: Male
X-ray

Abdominal radiograph

Supine radiograph shows air-filled small and large bowel loops right till rectum. This was imaged when he presented with constipation. Winking owl sign or the absent pedicle sign of left posterior element of L3 vertebra. 

X-ray

Abdominal radiograph 6 months later

Present supine radiograph identified an absent left L3 pedicle.

Annotated image with post-processing 'inversion' to highlight the absent left pedicle of L3.

MRI

MRI of whole spine

Cervicodorsal spine shows normal cervicomedullary junction. No tonsillar herniation or cord compression. Normal posterior fossa. 
Normal lying conus at L1-2 with central canal dilatation from dorsal cord extending to tip of conus. No cord tethering.
Coronal T2 demonstrates dilated central canal of cervicaldorsal spinal cord seen mainly in the mid to lower half of dorsal spine. Absent left posterior arch of L3 with an apparent fusion of L2-3 vertebral spinous processes. Central canal dilatation of spinal cord with compression and thinning of dorsal and ventral ganglia. There is no diastametomyelia or paramedian syrinx. Thin element of T1 and T2 linear hyperintense signal is seen in the posterior thecal sac in the lumbosacral segment - consistent with an intrathecal lipomatous component. 
Thinner heavy T2 weighted images(Axial 3D FIESTA) showing central canal dilatation of spinal cord with compression and thinning of dorsal and ventral ganglia. There is no diastametomyelia or paramedian syrinx.

Case Discussion

This baby was admitted with long standing history of constipation under evaluation. The child had no neurological deficits and was symptomatically treated with milk of magnesia. The persistent symptoms led to a detailed clinical and neurological evaluation which identified a sacral dimple. This prompted the clinician to send the patient for a screening MRI.

Prior to the MRI the previous radiographs were evaluated and this identified a subtle yet key pointer to the condition. The absent pedicle sign or the winking owl sign are pathognomic of posterior element affliction that can be identified on frontal radiographs of the spine. 

A detailed MRI study including screening of the whole spine is a good pointer to identify any underlying congenital neural tube defects. 

This baby had dorsal and lumbar cord hydromyelia extending to conus with vertebral defect and intrathecal lipomatous component - all fitting in with a picture of occult spinal dysraphism. Babies may present with only constipation and this is one of the final diagnoses considered if no cutaneous markers or any neurologic deficits are identified. 

Take home message: Every pediatric case with constipation - careful assessment of the spine and cutaneous markers will enable early diagnosis and management. 

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Case information

rID: 42433
Published: 22nd Jan 2016
Last edited: 26th Aug 2019
Inclusion in quiz mode: Included

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