Spinal manifestations in MPS IVA / Morquio-Brailsford Syndrome

With incidences ranging between 1 in 76,000 in Ireland and 1 in 750,000 in Australia, Morquio-Brailsford syndrome is a rare disease. It is a genetic disorder, classified as mucopolysaccharidosis IVA. First cases were described around 1900 by Hunter and Hurler. Luis Morquio, an Uruguayain paediatrician and James F. Brailsford of Children's Hospital in Birmingham, England, listed common radiological features of case series in 1929.

Pathophysiologically, there are several defects in N-acetyl galactosamine-6-sulphatase in MPS IVA, which ultimately lead to a lack of development in the metaphyses of bones.

Spinal manifestations are characteristic, but not pathognomonic. Dens hypoplasia or an os odontoideum are present in nearly all patients with varying degrees of cord compression due to anterior MPS depositions, non-ossified cartilage, thickening of ligaments and consequent indentation of the spinal cord by the posterior atlantic arch. Additionally, the ring closure of C1 may remain incomplete due to a failure of ossification of the cartilaginous elements anteriorly and posteriorly. Further spinal characteristics are:

• Platyspondly
• os odontoideum or hypoplastic odontoid
• C1-2 subluxation
• anterior beaking of the vertebral body
• posterior scalloping of the vertebral body
• rounding of vertebral bodies 

On level C3, the spinal canal in patients with Moquilo-Brailford syndrome is as narrow as 8.5 mm, while normal values range between 14 and 22 mm. The CBR (canal/body ratio) is significantly lower compared to non-MPS controls (c. 0.8 vs. 1.0). Signs of myelopathy are negative predictors for successful surgical decompressions. Cervical myelomalacia is a common encounter in MPS IVA. MRI of the entire spine with special attention to the craniocervical junction is recommended in all cases.

Fig. 1A: Flattening of vertebral bodies, posterior scalloping and loss of physiological spine curvature. B: Myelomalacia at C0, narrowing of the spinal canal, impaired development of the odontoid. C: posterior vertebral body scalloping leads to a severe spinal canal stenosis in the lower thoracic spine. Both adjacent discs are of normal intermediate signal, making a posterior disc bulging or herniation impropable. (c) Solanki et al., 2013, 10.1007/s10545-013-9586-2