Lumbosacral dural ectasia in type 1 neurofibromatosis. Report of two cases.

Dural ectasia denotes circumferential expansion or dilatation of the dural sac, and has been frequently reported in association with type 1 neurofibromatosis (NF1). The pathogenesis has not been defined, but its correlation with NF1 infers a congenital malformative hypothesis. The neural elements in the dilated sleeve typically are not enlarged or abnormal, nevertheless the enlarged area contain an increased amount of cerebrospinal fluid. The dura in the area of ectasia is extremely thin and fragile, and erodes the surrounding bony structures destabilising the spine and permitting spectacular spinal deformities. We present two cases with lumbosacral dural ectasia, enlargement of the intervertebral foramina and posterior scalloping of vertebral bodies. Neurological examination showed sciatic nerve irritation. As the etiology of this malformation remains uncertain and dysplastic changes of the spine may be intrinsic or secondary controversies remain about optimum treatment. We conclude that patients affected by NF-1 require an accurate neuroradiological study of the whole spine in order to detect possible dural and spinal anomalies. Surgical treatment is indicated only in patients with progressive neurological deterioration. The thin dural sac predisposes to a high morbidity if surgery is undertaken.