Rare association of spondylo costal dysostosis with split cord malformations type II: A case report and a brief review of literature.

Spondylo costal dysostosis (SCD) is a genetic skeletal disorder characterized by a variety of costo-vertebral malformations. SCD with type I split cord malformation (SCM) have been reported in the literature. We report an unusual association of SCD with type II SCM. Imaging studies revealed multiple vertebral segmentations, rib malformations, spina bifida and low lying cord with type II SCM at the D12-L3 level. She underwent detethering of the cord. To the best of our knowledge, this is the first report of the association of SCD with type II SCM.

Introduction

Spondylo costal dysostosis (SCD) is a rare genetic skeletal disorder characterized clinically by short trunk dwarfism, chest wall deformity and scoliosis, and radiographically by multiple segmentation defects of the vertebrae and asymmetric rib malformation (rib fusion, misalignment and/or abnormal rib number).[1] Additional anomalies such as neural tube defects, genitourinary tract malformations have been reported.[234] Split cord malformations (SCMs) are classified based on the midline septum and the dural sleeve into type 1 and type 2. To the best of our knowledge, this is the first case report of an association of type II SCM with SCD.

Case Report

An 8-year-old girl presented to our hospital with 1-month history of pain in the mid back, paresthesias over both lower limbs and urinary incontinence. The cognitive and language developmental milestones were normal. She was the second offspring of nonconsanguineous parents, her two male siblings were normal and there was no history of similar deformities in any of her family members. At birth, she had an abdominal wall defect below the left subcostal region which closed spontaneously over a period of 6 months.

Physical examination revealed thoracic cage asymmetry, thoracic kyphoscoliosis and discoloration of the skin in the left subcostal region. There were no other dysmorphic features or obvious external malformations. Her anthropometric measurements were as follows: height 124 cm (25th centile), arm span 124 cm, upper segment: lower segment ratio 0.88:1 and head circumference 51 cm (50th centile). On neurological examination, power was 4 ± 5 in both the lower limbs, deep tendon reflexes were sluggish, plantar response was equivocal on the right side and extensor on the left and superficial sensations were decreased below the D11 level by 20%. Her higher mental functions, cranial nerve examination and upper limb motor and sensory functions were normal.

Thoracic and lumbar radiographs showed thoracic scoliosis with convexity toward the right, multiple vertebral segmentation anomalies at the D8-D12 level including hemivertebra at D8 and butterfly vertebra at D10, multiple levels of spina bifida at D8-L2 and L3-S1 levels and rib anomalies including irregular fusion of the lower ribs with absent ribs on the left side [Figure 1]. Magnetic resonance imaging of the dorsolumbar spine with screening of the whole spine showed diplomyelia from D12 to L3 without any bony spur. The two hemicords were asymmetric and were surrounded by a single dural tube. There was evidence of low lying cord extending up to L3 level and multiple levels of spina bifida involving the lower dorsal and lumbosacral region [Figure 2].

Figure 1

Computed tomography dorsal spine showing hemivertebra at D8, butterfly vertebra at D10 and absent ribs on left side

Figure 2

Magnetic resonance imaging of the dorso lumbar spine showing diplomyelia from D12 to L3 without bony spur

The patient underwent D11 to L3 laminectomy. Intraoperatively, two hemicords with a single dural tube were noted and no bony or fibrous septum was found. Thick arachnoidal adhesions were found between the two hemicords, which were released. Primary dural closure was performed, and sectioning of thick fatty filum terminale was done. Post operatively, the patient did not have new neurological deficits, her scoliosis showed mild improvement and she is on follow-up.

Discussion

The first report of congenital malformation syndrome involving vertebral segmentation defects and rib anomalies was published by Jarcho and Levin in 1938 and was termed the Jarcho-Levin syndrome.[56] Since then, the term has been loosely used for all genetic costo vertebral malformations. Subsequent studies have now made it evident that congenital costo vertebral malformations can be of two distinct subtypes: the SCD and the spondylo thoracic dysostosis (STD).[7] Patients with SCD have intrinsic rib malformations (broadening, fusion, missing ribs, abnormal orientation, bifurcation, irregularity of shape and size) in addition to multiple vertebral segmentation defects as in our case.[8] Those with STD have multiple vertebral anomalies with posterior fusion of the ribs giving a “fan” like configuration of the ribs and “crab” like appearance of the thorax and do not have intrinsic rib malformations.[9] The vertebral defects in both SCD and STD include decreased number of vertebrae with segmentation and formation defects like block vertebrae, hemi vertebrae, butterfly vertebrae, missing vertebra and fused vertebrae. All cases of STD and majority of SCD have an autosomal recessive pattern of inheritance and, therefore, have a 25% risk of recurrence in siblings. Prenatal diagnosis can be offered to parents of affected children through either targeted mutation analysis in the fetal DNA or through targeted fetal anomaly scanning at 18–23 weeks gestation, to prevent birth of further affected children in the family.[1011] Clinically children with SCD will have scoliosis and respiratory difficulties due to mechanical restriction. Aggressive neonatal management, treatment of pneumonia and ventilator care if necessary are required. Chest wall reconstructions have also been performed.[112] Management of scoliosis requires bracing, hemivertebra excision, convex hemiepiphysiodesis, spinal instrumentation and thoracoplasty with a vertical expansion prosthetic titanium rib.[13]

Neural tube defects such as spina bifida, meningocoele, myelomeningocoele, and SCMs etc., have been reported in association with Jarcho-Levin syndrome in literature.[14] Although spina bifida appears to be a commonly associated finding in Jarcho-Levin syndrome, association of SCMs is uncommon and until date only six cases of split cord malformations with Jarcho-Levin syndrome have been reported in the literature.[151617181920] All these reported cases had SCM type I in which the two hemicords are surrounded by two separate dural sheaths and separated by a bony spur. Our case is unique in that it is the first report of an association of a type II SCM with SCD. Surgical management is indicated in type I SCM whereas fully preserved cases of type II SCM can be followed conservatively.

Conclusion

Identification of costo vertebral malformations and classifying them can be helpful in genetic counseling of the parents and predict prognosis. Management strategies and prognosis differ according to the type of SCM.