Fatty
accumulations within the spinal
cord represent 70% of the
lesions associated with
tethering and take three
different forms. The
lipomyelomeningocele is a
subcutaneous lipoma within the
spinal cord that extends through
a defect of the lumbosacral
fascia, lamina, dura, and pia
into a low-lying spinal cord. It
is the most common form of
spinal lipoma. Patients with
these lesions usually come to
clinical attention within the
first few months to years of
life. A subset of the
lipomyelomeningocele is the
lipoma of the conus medullaris.
The intradural lipoma (spinal
cord lipoma) is a rare
intramedullary lesion that is
usually found within the
thoracic spinal cord. It is not
associated with cutaneous or
bone anomalies and often
presents with symptoms of spinal
cord compression.
The fatty filum involves fatty
infiltration the whole length or
part of the terminal filum. The
fat within the short, thick
filum is discernible by
unenhanced CT or MR imaging. The
occurrence of incidental fat
within the terminal filum in the
normal adult population has been
estimated to be 3.7% in
cadaveric studies 22 and 1.5 to
5% in MR imaging studies.
Lipomyelomeningoceles may be
diagnosed by the associated
subcutaneous lumbosacral mass
that is found in approximately
90% of patients or by
sagittal MR imaging (Figure 4)
or ultrasonography studies. For
those who come to medical
attention before the age of 1
year, 59% of patients with the
lipomyelomeningocele or fatty
filum are asymptomatic whereas
41% are symptomatic. Of those
patients with symptoms in one
study, 60% presented with
urological symptoms and 58% with
neurological symptoms, whereas
58% presented with orthopedic
abnormalities (extremity
abnormalities and scoliosis). Of
patients presenting with motor
deficits, 50 to 70% do not
experience improvement after
surgery. Surgical intervention
in the symptomatic patient has
been advocated by many authors
to prevent further decline in
the neurological status.[7,33]
A few authors believe that some
of the lower motor neuron
symptoms and orthopedic symptoms
cannot be prevented by surgery.
Figure 4 (click image to
zoom) . Sagittal MR images
demonstrating a
lipomyelomeningocele. A: The
spinal cord extends to the level
of the sacrum. An associated
superficial subcutaneous lipoma
is discernible. B: The spinal
cord extends to the level of the
sacrum. A syrinx is present.
The
operation for
lipomyelomeningoceles has been
significantly advanced by the
use of the carbon dioxide laser
and the ultrasonic aspirator.
Intraoperative monitoring of
nerve roots may be useful to
distinguish those that are
functional from those that are
not. Once the spinal cord has
been untethered, closure and
enlargement of the dura with a
graft material has been
recommended. In one study
of those patients younger than 1
year of age who underwent an
untethering procedure for
lipomyelomeningocele or fatty
filum and who presented with
motor, urological, or orthopedic
symptoms, 39% improved, 58%
stabilized, and 3% worsened as a
result of surgical intervention.
