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Neuroradiology Case of the Month

September 2001

Clinical Presentation: This patient is a 66-year-old female with Marfan syndrome and a history of aortic valve replacement. She presents with bilateral lower extremity weakness and lower back pain.

Radiographic Findings: This patient has diffuse mild degenerative disease throughout her thoracic, lumbar and sacral spine with osteophytes. T1 and T2 weighted images demonstrate scalloping of the posterior aspect of the lumbar and sacral vertebral bodies. A large cystic structure in the sacrum is contiguous with the thecal sac. It contains a small fluid-fluid level with a high signal on T1 and a low signal on T2-weighted images, consistent with hemorrhage into a large Tarlov cyst or meningocele. There is also a low T2 signal present on the surface of the spinal cord due to superficial siderosis. An aneurysm of the descending aorta is also evident on T2-weighted images.

Diagnosis: Marfan syndrome

Figure 1. Sagittal T2-weighted image illustrating posterior scalloping of the lumbar vertebral bodies (white arrows), a sacral Tarlov cyst and superficial siderosis of the thoracic spinal cord (black arrows).	Figure 2. Sagittal T1-weighted image demonstrating an enlarged sacral cystic structure contiguous with the thecal sac (black arrows), containing a fluid-fluid level (white arrows).

Figure 3. Sagittal T1 and axial T2-weighted image demonstrating an aneurysm of the descending aorta.

Etiology and Pathogenesis: Marfan syndrome is an inherited autosomal dominant connective tissue disorder, and is part of a spectrum of diseases involving the fibrillin-1 gene, such as variants of Ehlers-Danlos syndrome, MASS phenotype (mitral valve prolapse, myopia, mild aortic dilation, striae, skeletal features), mitral valve prolapse syndrome, familial aortic dissection, familial aortic aneurysm, familial ectopia lentis, congenital contractural arachnodactyly, and the Stickler syndrome [1]. Mutations of the gene encoding fibrillin-1, located on chromosome 15, were elucidated in 1991 [1]. Fibrillin monomers polymerize with other proteins to form microfibrils, the principal component of extracellular matrix [1]. The diverse function of microfibrils accounts for the multi-system involvement in patients with Marfan’s syndrome, with cardinal features in the ocular, musculoskeletal and cardiovascular systems [1].

Discussion: Dural ectasia is one of the major diagnostic criteria of Marfan’s syndrome [2]. It is defined as enlargement of the neural canal anywhere along the spinal canal, most often found in the lumbar and sacral region [2]. Dural ectasia in Marfan syndrome can be seen as posterior scalloping of the vertebral bodies, anterior and lateral sacral meningoceles, and expansion of the sacral spinal canal [2]. Because the structure of elastin fibers is altered in Marfan syndrome, the dura mater is weakened and the thecal sac progressively dilates, gradually eroding the vertebral bodies or forming a sacral meningocele [3]. Other diseases causing dural ectasia include Ehlers-Danlos syndrome and neurofibromatosis [3]. Dural pathology is also associated with chronic hemorrhage [4], which may explain the fluid-fluid level and superficial hemosiderosis noted in this case.

Aortic root dilation, aortic aneurysms, typically of the ascending aorta, and aortic dissections are also major diagnostic criteria of Marfan syndrome [2]. The differential for aortic aneurysms include atherosclerosis, post-traumatic, post-coarctation, syphilis, mycotic, Takayasu arteritis, Ehlers-Danlos and Marfan syndrome [5]. Cardiovascular complications are the most common cause of mortality among patients with Marfan syndrome.

The imaging studies did not explain this patient’s lower extremity weakness.

Reference

1. Goldman, Cecil. Textbook of Medicine. Saunders, 2000. pg. 1118-1119.
2. De Paepe, Anne. Dural ectasia and the diagnosis of Marfan’s syndrome. The Lancet, 1999. vol 354(9182): 878-79.
3. Fattori, Rossella et. al. Importance of dural ectasia in phenotypic assessment of Marfan’s syndrome. The Lancet, 1999. vol 354(9182): 910-913.
4. Fearnley JM, et al. Superficial siderosis of the central nervous system. Brain, 1995. vol 118:1051-1066.
5. Dahnert, Wolfgang. Radiology Review Manual. Williams and Wilkins, 1998. pg. 79-80.