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Challenge of the Unknowns—Unknown 4

Diagnosis and Discussion

DIAGNOSIS: Neurofibromatosis.

DISCUSSION: There was no specific information on these films that would have led you to the exact diagnosis of neurofibromatosis. Though the findings on these films are nonspecific, they are spectacular and lead us to the discussion of posterior vertebral body scalloping. This patient did have a known diagnosis of neurofibromatosis when the acute low back pain began. Because of her history an MRI was obtained to rule out a neural tumor. You might have enjoyed that piece of information a bit sooner, but this is way more fun.

The differential diagnosis included other conditions including normal variant, spinal tumor, acromegaly, Marfan's disease, and Ehler's Danlos syndrome.

Posterior vertebral body scalloping can be seen as a normal variant, especially in the lumbar spine. In this example, however, the scalloping is far too exaggerated to be considered "within normal limits" and common sense says that you are not likely to find a "normal study" in this program.

Spinal tumors such as ependymomas, lipomas, dermoids and meningiomas can produce posterior body scalloping from increased spinal pressure. With tumors, the posterior body scalloping occurs at the levels corresponding to the levels of the tumor. Scalloping is not likely to occur dramatically at multiple levels as it does in this case.

The posterior body scalloping that occurs in acromegaly actually occurs secondary to the pressure of thickened dura (dural ectasia) on weakened bone. The posterior scalloping in this case could look similar to the scalloping of acromegaly however, the other findings of acromegaly are lacking. In the spine acromegaly will produce an increased AP dimension of the vertebral bodies, osteoporosis, extensive spondylophytic formation, and discal calcification.

Patients with Marfan's disease are unusually tall and have long slender limbs and arachnodactyly (long slender fingers and toes). They are susceptible to dislocations of their sternoclavicular, wrist, and hip joints. They are prone to mitral valve abnormalities, and aneurysms - especially of the ascending aorta. Ehler's Danlos is similar to Marfan's with the addition of a few more manifestations. The skin of patients with Ehler's Danlos is hyperelastic and they get calcific deposits in their subcutaneous tissue. Also, patients with Ehler's Danlos will have blue sclera.

The spinal changes seen with neurofibromatosis are due to a mesodermal dysplasia. Up to 60% of patients with neurofibromatosis will have spinal changes, the most common is scoliosis which may be an ordinary scoliosis or a short kyphoscoliosis. Vertebral body scalloping at multiple levels are the result of dural ectasia, or expansion and dilatation of the dura. As mentioned above, neurofibromatosis is not the only condition to produce dural ectasia and other spinal findings that may be seen specifically with neurofibromatosis include neurofibromas and menigoceles.



The MRI shows clearly the marked posterior body scalloping from T12-L3. The signal characteristics of the soft tissues anterior to the conus medularis and cauda equina are consistent with hypertrophied CSF filled dura. There is no evidence of a spinal tumor. Again, these findings are nonspecific and though the MRI does exclude spinal tumors it still does not give us a definitive diagnosis of neurofibromatosis.

There are two types of neurofibromatosis : Type I and Type 2. Type 1 is considered "peripheral neurofibromatosis" and Type 2 is considered "central neurofibromatosis". This brief discussion will include only Type 1, which is the type manifested by this patient. Neurofibromatosis Type 1 is a common condition, affecting approximately 1 in 3000 people.

The diagnostic criteria for neurofibromatosis type 1 are as follows. A patient must have two or more of the following:

    · Six or more café au lait macules (over 5 mm in diameter before puberty, over 15 mm in diameter after puberty)

    · Two or more neurofibromas or one plexiform neurofibroma

    · Inguinal or axillary freckling

    · Optic glioma

    · Two or more lisch nodules (iris hamartomas)

    · Characteristic osseous lesions (sphenoid dysplasia, thinning of long bones)

    · First degree relative with neurofibromatosis

Neurofibromatosis is a mesodermal dysplasia, or phakomatosis, and the defects associated with it can affect all three cell layers. Fibroma molluscum are the soft, elevated, cutaneous lesions seen in neurofibromatosis patients which can grow quite large and become disfiguring. In addition to the spinal changes discussed above, neurofibromatosis may produce penciling or spindling of the ribs, bowing, pathologic fractures, or pseudoarthrosis of the long bones and pelvis.

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