Osseous dysraphism hamartoma with lipomeningomyelocele

An 8 months old male child presented with swelling over the lumbosacral region (grossly stable in size since birth) and left lower limb weakness since 2 weeks. MRI of the lumbosacral spine with screening of the whole spine and brain was performed for further evaluation of swelling.

Spina bifida seen from L3 level to all sacral vertebra. Spinal cord was low lying, seen up to L3 level. There was herniation of subcutaneous fat through spina bifida from L3-S1 levels, into the spinal canal with lipoma-placode interface seen outside spinal canal and dilated subarachnoid spaces seen in the subcutaneous plane. The terminal cord showed dilated central canal. Multifocal syrinx were seen from D5 level to termination. Well-formed bone was seen in the subcutaneous lipoma which articulated with posterior aspect of right iliac bone and measured approximately 4 cm in length. Posterior fossa appeared small with Chiari I malformation.

Background

The presence of ossified bone in spinal dysraphism is referred to as ossified dysraphic hamartoma, which is extremely rare with only few case reports available in literature and very few of them associated with lipomyelomeningocele [1].

Clinical Perspective

The patient usually presents with grossly visible swelling in the back. The clinical features of lipomyelomeningocele usually depend on the (a) level of involvement (b) presence of hydrocephalus and (c) associated brain abnormalities. In the presence of hydrocephalus; clinical signs of raised intracranial pressure may be present. Impairment in sensory, motor and sphincter function depends on the lesion level [2].  

Imaging Perspective

There is herniation of the subcutaneous fat into spinal canal through defects in posterior elements of the vertebrae. Sagittal T1w images show high-intensity fat on the dorsal aspect of the placode which is continuous with the adjacent subcutaneous fat. There is expansion of subarachnoid space anterior to the cord pushing the neural placode-lipoma interface posteriorly to lie outside the boundaries of spinal canal. There is evidence of bony component within the lipoma, either lying freely or articulating with a normal bone.

Outcome

Surgery remains the mainstay of treatment.

Take home message/ Teaching points:

The osseous component may have undergone partial or complete development. It may articulate with the adjacent bony structures or could be freely located in the lipomatous component. Detecting heterotopic bone especially the ones articulating with adjacent bones is important for surgical planning [3].