Diagnosis and Discussion
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
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:
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.
· 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
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