Keywords meningocele - neurofibromatoses - spinal fusion - von Recklinghausen disease - spinal
instability
Introduction
Neurofibromatosis type 1 (NF1) is one of the most frequent neurocutaneous disorders,
presenting with multivarious central nervous and osseous malformations including spine
deformity or meningoceles (MC). Although MC and myelomeningoceles (MMC) predominantly
occur posteriorly,[1 ] numerous case reports also describe anterior manifestations of MC/MMC along the
cervical and thoracic spine.[2 ]
[3 ]
[4 ]
[5 ]
[6 ] Compared with those, descriptions of anterior lumbar MC/MMC in patients with NF1
are considerably more infrequent with only very few published cases so far.[7 ]
[8 ] Besides congenital deformation, it is believed that continuous pulsatile pressure
of the thecal sac presumably stresses the adjacent bone and therefore leads to osteolysis
and subsequent deformity and instability of the vertebrae.[9 ] Although spinal instrumentation without underlying MC/MMC as well as resection of
anterior celes without spondylodesis in patients with NF1 was previously described,[10 ]
[11 ] to our knowledge spondylodesis for spinal instability and deformity with surgery
for underlying MC/MMC has not yet been published. We report here on the surgical treatment
of a female NF1 patient with a lumbar spine deformity and anterior MC presenting with
lower back pain.
Case Report
In 1989, a 16-year-old young woman was initially subjected to surgery due to severe
lower back pain and lumbar lordotic deformation and an anterior MC. The diagnosis
of von Recklinghausen disease had already been established in childhood based on the
typical clinical stigmata. At that time, treatment included lumbar Harrington spondylodesis
ranging from T12 to S1 but excluded gathering or resection of the cele. Although the
back pain initially improved steadily after the operation, the patient developed secondary
lumbosacral pseudarthrosis. Due to progressive spondyloptosis, the left pole of the
Harrington spondylodesis induced late-onset disturbance of wound healing and ultimately
transcutaneous migration and subsequent wound infection. Thus the left pole of the
fixateur was shortened below L5 in 2005. Although wound healing had partially been
achieved, in 2013 the patient finally presented in our department with progressive
lower back pain and sacral skin perforation caused by the caudal part of the right
pole of the Harrington fixateur ([Fig. 1 ]). Radiographic imaging revealed a marked spine deformation due to lumbosacral pseudarthrosis
and lordotic spondyloptosis of the hypoplastic lumbar vertebrae, which were largely
osteolytic and tilted ventrally toward the lesser pelvis despite the fixateur ([Fig. 1 ]). Spondyloptosis was considered progressive comparing the current scans with computed
tomography (CT) scans from 2008 ([Fig. 2A, B ]). The Harrington fixateur, however, was shown to be deficient due to the removal
of the left-sided sacral screw and evulsion of the right S1 screw. Additional magnetic
resonance imaging depicted the large anterior MC prolapsing through an osseous defect
of the scarce remnants of the lumbar vertebrae into the lesser pelvis ([Fig. 3A, B ]). Because spondyloptosis was considered progressive and the inlaying fixateur as
insufficient and infested, we planned a three-stage surgical revision.
Fig. 1 (A) Caudal end of the right spondylodesis pole perforating the sacral skin 14 years
after initial surgery. (B) Three-dimensional reconstructed computed tomography scan
reveals posterior fusion from T12 to S1 (Harrington) with secondary shortened pole
below L5 on the left and the evulsion of the S1 screw on the right side.
Fig. 2 Sagittal computed tomography scans from (A) 2008 and (B) 2013 revealing osteoporosis
with progressive spondyloptosis toward the lesser pelvis. (C) After removing the Harrington
system, a low-profile fixateur was implanted. (D) After gathering the meningocele,
resection of the lumbar vertebrae L2–L4 with subsequent implantation of an anteflexed
titanium mesh (100 × 17 × 22 mm) was performed.
Fig. 3 (A) T2-weighted sagittal and (B) transversal magnetic resonance imaging reveals deformity
of the lumbar spine and the extensive meningocele that is partially filling the lesser
pelvis. (C) Axial computed tomography scan after the final operation reveals persistence
of the lateral parts of the cele (asterisks) whereas the median parts had been gathered.
Surgical Technique
After removal of the fixateur interne in a first step and a 3-week course of antibiotics,
the patient was subjected to dorsal stabilization under neurophysiologic monitoring.
Regarding clearly reduced subcutaneous soft tissue due to cachexia, the decision was
made to use a low-profile fixateur. Intraoperatively, cranial fixation was performed
with bilateral pedicle screws from T10 to L1 ([Fig. 2C ]). A left-sided S2 screw could not be placed due to osseous instability of the sacrum,
and stability was finally achieved using a transversal pole connecting the left with
the right sacral screws. Pseudarthrosis was further treated by the implantation of
12 mg recombinant bone morphogenetic protein-2 as well as autologous bone flakes mixed
with tricalcium phosphate. About 3 weeks later, access to the anterior MC and lumbar
spine was achieved through an anterior transabdominal approach under neurophysiologic
monitoring in a collaborative operation with a vascular surgeon. After resection of
vertebrae L2, L3, L4, and partially L5, the MC was mobilized and subsequently gathered
at its median parts. However, because the wall of the cele appeared to consist solely
of a thin arachnoid layer and was therefore hardly stitchable, we decided not to perform
complete resection to minimize the risk of a large cerebrospinal fluid fistula but
reconstructed ventral parts of the dural sleeve with layers of TachoSil (Taceda Pharmaceuticals
International, Zurich, Switzerland), DuraSeal (Covidien, Dublin, Ireland), and Tutopatch
(Bess Medizintechnik, Berlin, Germany). Subsequently, a customized oval, slightly
lordotic titanium mesh (100 × 17 × 22 mm) was implanted ([Figs. 2D ], [3C ], and [4 ]).
Fig. 4 Postoperative reconstructed three-dimensional computed tomography scan demonstrating
posterior fusion and vertebral replacement by a customized slightly flexed titanium
mesh.
After the final operation, due to intraoperative dural incision, 7 days of bed rest
were prescribed, and the patient recovered well without any focal neurologic deficit.
Wound healing was unremarkable, and lower back pain was reduced to a minimum at the
time of discharge to neurophysiologic rehabilitation. At clinical presentation 3 months
after surgery, the patient was mobile without neurologic deficits and considerably
reduced low back pain and was looking forward to integration into employment.
Discussion
Anterior MC and MMC occasionally occur in patients with NF1 and are predominantly
in a thoracic location,[2 ]
[3 ]
[5 ]
[6 ] whereas lumbar location is uncommon and has only been described in two patients.[7 ]
[8 ] In non-NF1 patients, although cases of anterior celes along the thoracolumbar[12 ] and sacral[9 ] spine have been published, reports about MC restricted to the lumbar spine are lacking.
Due to their anatomical location, anterior celes often prolapse into the thoracic
and abdominal visceral cavities and can therefore remain asymptomatic.[9 ] Apart from this, clinical manifestation of anterior thoracolumbar or sacral MC can
be manifold and include, for example, abdominal and lower back pain, infertility,
bladder retention, constipation, or purulent meningitis.[13 ]
[14 ] Although commonly regarded as a defect in neural tube formation,[1 ] there is still uncertainty concerning the etiology of anterior celes of the caudal
parts of the spine and their frequently associated osseous malformations. As a possibly
underlying mechanism, continuous pulse synchronous stress caused by the cele is assumed
to induce erosion and subsequent lysis and deformation of the underlying bony structures
of the spine, causing variable size osseous defects.[9 ] Thus it is certainly conceivable that occurrence of an anterior MC/MMC with attended
osseous malformation could affect the shape and stability of the involved spine segments.
Surgery for symptomatic sacral anterior celes is advised in numerous reports with
a large variety of surgical procedures (e.g., laparoscopic, posterior [through a sacral
laminectomy], or through anterior transabdominal approaches).[9 ]
[13 ]
[15 ] Surgical procedures in these cases exclusively deal with isolation and resection
of the thecal sac. Conversely, although spinal instrumentation in the case of deformity
in NF1 patients has been published,[10 ]
[11 ]
[16 ] descriptions about underlying MC/MMC are lacking. A literature search revealed one
report from Ebara et al describing a 59-year-old patient with NF1 who received both
resection of an intrathoracic MC and extensive posterior fusion. Presenting with severe
dyspnea, resection of the cele was initially performed through a wide laminectomy
from T2 to T5. Because the patient subsequently developed neurologic deterioration
due to spinal instability, spondylodesis was finally indicated from C3 to L2. In contrast
to our case, the authors considered extended laminectomy as the cause of the spinal
instability in their case.[2 ]
Conclusion
Anterior lumbar MC is rarely observed in both NF1 and non-NF1 patients. Although pathogenesis
is not fully understood, in severe cases celes are assumed to cause osteolysis due
to the pulsatile erosion of the adjacent bone. Because this may lead to instability
with spondyloptosis and subsequent deformity, surgery should aim at spinal reconstitution
with stabilization and, if possible, gathering or resection of the cele. Depending
on the approach and extent of surgery, we advise a multistaged procedure in an interdisciplinary
collaboration.
