Dural Ectasia-MRI Criteria

This is a 26yr old female with dural ectasia. Dural Ectasia is found in Marfan syndrome, Ehlers-Danlos syndrome, neurofibromatosis, ankylosing spondylitis, and osteogenesis imperfecta tarda .  It may occur as a very unusual complication of spinal surgery or trauma.

Case submitted by Dr MGK Murthy.

Diagnostic Criteria

A. Scalloping of vertebral bodies (Minor Criterion)

The superior and inferior diameters were added and then divided by two, and the midsagittal diameter was subtracted from this value . For this purpose, sagittal plane bony measurements were obtained from each outer black cortical vertebral margin. Ahn et al defined scalloping greater than 3.5 mm at the level of S1 as a minor criterion for dural ectasia. The presence or absence of an anterior sacral meningocele as the maximum manifestation of scalloping is usually followed
B. Dura sac Ratio(Minor Criterion)

A dural sac ratio is calculated for each level from L1 through S1 by dividing the dural sac diameter(perpendicular) by the vertebral body diameter. According to Oosterhof et al , normal cut-off values for levels L1 through S1 in adult patients were 0.64, 0.55, 0.47, 0.48, 0.48, and 0.57.

C. The maximum diameter of the nerve root sleeves on Transverse T1 was measured for each foramen at each level from L1 through S1. According to Ahn et al , a diameter exceeding 6.5 mm at the level of L5 represents a minor criterion

D. Major criterion for dural ectasia is met when the dural sac diameter at S1 is greater than that at L4, which demonstrates that the dural sac is not tapering off

Two standard accepted criterion

(i).Ahn et al described two major criteria for the presence of dural ectasia: width of the dural sac at a level below L5 greater than that above L4 and presence of an anterior sacral meningocele.

Minor criteria were defined as scalloping greater than 3.5 mm at the level of S1 and nerve root sleeve diameter greater than 6.5 mm at the level of L5.

They concluded that dural ectasia is present if one major or two minor criteria are present.

(ii). According to Fattori et al , the degree of dural abnormalities can be classified as follows:

grade 1, mild dural ectasia defined by bulging of the dural sac and lack of epidural fat at the level of the posterior wall of one vertebral body, by the presence of small radicular cysts, or by both features;

grade 2, moderate dural ectasia defined by bulging of the dural sac and lack of epidural fat at the level of the posterior wall of two or more vertebral bodies and presence of large radicular cysts; and

grade 3, severe dural ectasia defined by presence of an anterior sacral meningocele.