|LETTER TO EDITOR
|Year : 2019 | Volume
| Issue : 3 | Page : 180-183
Giant cystic schwannoma of the cauda equina
Meryem Himmiche1, Mohammed Benzagmout1, Badreeddine Alami2, Imane Staouni Benabdellah2, Khalid Chakour1, Mohamed E Chaoui1
1 Department of Neurosurgery, University Hospital of Fez, Fez, Morocco
2 Department of Biophysics and Clinical MRI Methods, University Hospital of Fez, Fez, Morocco
|Date of Web Publication||14-Aug-2019|
Dr. Mohammed Benzagmout
BP 8589, Atlas 30003, Fez
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Himmiche M, Benzagmout M, Alami B, Benabdellah IS, Chakour K, Chaoui ME. Giant cystic schwannoma of the cauda equina. Ann Afr Med 2019;18:180-3
Spinal schwannomas are benign tumors arising from the sheath of the spinal nerve roots and are frequently observed in the cauda equina. In this localization, schwannomas are often reaching a large volume without major disabling symptoms, and this could be explained by the expansion length of such tumors, roots mobility, and the wide intradural space in this area.
However, giant cauda equina schwannomas involving many nerve roots are quite rare and mainly confined to the sacral region. In this study, the authors report an unusual case of giant schwannoma of the cauda equina found in the lumbosacral region and discuss its pathogenesis, clinical profile, imaging features, and the treatment of this rare pathology.,,,,,,
A 44-year-old woman had a chronic history of low back pain since 2004. The patient consented formally. In April 2005, she began to complain of sciatica pain entirely involving her right lower limb and drastically deteriorating her low back pain. Lumbar computed tomography (CT) scan demonstrated protrusion of disc material in both L4–L5 and L5–S1 spaces without obvious discoradicular conflict [Figure 1]. These findings allowed to perform a surgical treatment in another hospital for lumbar disc herniation. However, her sciatalgia did not improve postoperatively, and the patient was referred for physiotherapy.
|Figure 1: Lumbar computed tomography scan showing protrusion of disc material in both L4–L5 and L5–S1 spaces without obvious discoradicular conflict|
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Despite the several sessions of physiotherapy and multiple symptomatic treatments, including diverse painkillers, myorelaxant, and nonsteroidal anti-inflammatory drugs, the patient status did not improve. In contrast, her low back pain and sciatica became severe and bilateral, respectively. The patient also started to feel numbness in both the legs with instability at walking accompanied with urinary incontinence and constipation. At this stage, lumbar magnetic resonance imaging (MRI) was done and revealed a giant intradural cystic cauda equina tumor extending from the lower part of L1–S2 (17 cm in length). The tumor was hypointense on T1-weighted images, hyperintense with a liquid–liquid interface, and hypointense sediments on T2-weighted images; it also showed peripheral contrast enhancement [Figure 2]. This tumor has caused large widening of the dural sac and enormous bone erosion of the opposite vertebral bodies mostly in L4 and L5 vertebrae.
|Figure 2: Magnetic resonance imaging in sagittal T1 (a), sagittal T2 (b), axial T2 (c), and sagittal gadolinium-enhanced T1-weighted images (d) demonstrating a giant intradural cystic cauda equina tumor extending from the lower part of L1–S2 with a peripheral contrast enhancement. The tumor is hypointense on T1-weighted images, hyperintense with a liquid–liquid interface, and hypointense sediments on T2-weighted sequences (arrow)|
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The patient was hospitalized in our university hospital in December 2008. At admission, the patient was not able to walk without help; her step was very unstable even with a cane. Both knee and ankle jerks were absent, and hypoesthesia was noted over the L3–S1 nerve-supplied zones. Motor examination showed weakness of both the lower limbs, which was more predominant distally. No signs of neurofibromatosis were present on physical examination.
The CT scan of the lumbar spine showed scalloping appearance of the posterior surface of the vertebral bodies extending from L2 to the sacrum with sclerotic margin. Increased interpedicular distance at L3–L5, erosion of the neural arch, and diminished height of the vertebral bodies at L4 and L5 were also noticed [Figure 3].
|Figure 3: Computed tomography scan showing a large widening of the lumbar spinal canal with scalloping appearance of the posterior surface of the vertebral bodies from L3 to the sacrum with sclerotic margin|
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The patient was operated on in the prone position. Through a posterior midline incision, the L1–S2 laminae were exposed, and a laminectomy of L2, L3, L4, L5, and S1 was done after dural opening. During surgery, we discovered a yellow tumor containing multilocular cysts that were boarded by thin septums and adhering intimately to the neighboring nerve roots [Figure 4]. The subtotal tumor was removed, and the septums of the cysts were excised until all cysts and the subarachnoid space were freely connected. At the end of the intervention and to avoid any potential future spinal instability, a posterior osteosynthesis from L2 to S2 was performed using pedicle screws in the lumbar vertebrae and hooks in the sacrum [Figure 5].
|Figure 4: Operative view showing a yellow tumor adhering intimately to the neighboring nerve roots (arrow)|
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|Figure 5: Plain radiography of control showing posterior osteosynthesis from L2 to S2|
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The histopathological study showed a characteristic pattern of an Antoni-A type schwannomas with no evidence of malignant changes in the tumor cells.
The postoperative course was unremarkable. The patient was allowed to walk after 3 weeks of bed rest using a hard brace and a walking aid. She reported neuropathic pain which was well controlled by carbamazepine (800 mg/daily). At the most recent follow-up visit, 2 years after the surgery, the low back pain had almost disappeared with great improvement of hypoesthesia in both the legs. Motor, bladder, and bowel functions showed good recovery. At present, the patient walks alone without a cane and has no urinary symptoms without any recurrences [Figure 6].
|Figure 6: The postoperative magnetic resonance imaging in sagittal T2 (a), sagittal T1 (b) and axial T2 (c), showing the full disappearance of schwannoma with evidence of no recurrence. This magnetic resonance imaging of control was performed 5 years after surgery|
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Schwannomas are benign tumors arising from neoplastic transformation of nerve sheath cells and typically found along peripheral nerve roots or cranial nerves. Spinal schwannomas are common intraspinal primitive tumors and accounting for 25% of intradural spinal tumors in adults.
Although they have larger size at diagnosis, spinal schwannomas are characterized by paucity of symptoms due to the longitudinal and indolent proliferation. In our case, the chronic history of low back pain, the normal aspect of the vertebrae in the first CT scan, and the scalloping of the posterior surface of the vertebral bodies at admission have strongly suggested a long-standing etiology.
Schwannomas are commonly forming a solid mass, but it might present degenerative changes such as calcification, hemorrhage, hyalinization, or cyst formation., Many theories were elaborated to explain this “intratumoral cystic phenomenon.” Cyst formation might result from degeneration of portions of the tumor, coalescence of many microcysts, and central ischemic necrosis induced by the tumor growth or by repeated episodes of intratumoral bleeding., The presence of a liquid–liquid interface and hypointense sediments on T2-weighted sequences is supporting repeated hemorrhagic episodes in our case.
The clinical symptoms include low back or lumbosacral pain, sciatica, diminished lower extremity sensation, motor weakness, and genitourinary dysfunction. The disease is usually diagnosed around the fourth and fifth decades of age with an equal male/female ratio.
MRI is a recommended tool for an accurate diagnosis of lumbar cystic schwannoma and the presurgical planning of the intervention.,,,,,,,,,,,,,, Besides, it is the most useful method to differentiate spinal tumors from other lesions such as lumbar disc herniation. Indeed, differentiation from herniated lumbar discs and spinal canal stenosis is quite easy, whereas spinal schwannomas are difficult to discern from other intradural tumors such as ependymomas, hemangioblastomas, and neurofibromas. Myxopapillary ependymoma is the major differential diagnosis with enhancement seen on postcontrast T1-weighted images with myxopapillary ependymoma, whereas myxopapillary schwannoma does not show any enhancement in the predominantly hypointense components. T2 images show similar hyperintense signal on both tumors.
Although it is inferior to the CT scan in evaluating the degree of bony destruction, MRI assessment shows the exact localization of the tumor as well as its extension within the neighboring structures. It allows also distinguishing the dumbbell growth pattern that is resulting from the tumor extension through the vertebral foramina. It is a very useful sign for an appropriate preoperative diagnosis and surgical planning in these patients.
Surgery is the treatment of choice for these tumors. Complete excision is recommended, whenever possible. However, this partial removal of this locally aggressive benign tumor carries a high risk of recurrence, which might require more definitive, difficult, and risky surgery in later stages. However, if the tumor adheres to many nerve roots, partial/incomplete removal is judicious to prevent the risk of postoperative neurologic impairment. In cases of incomplete removal of the cauda equina schwannomas, some authors advise long-term follow-up  and others recommend postoperative irradiation. Nevertheless, it is unknown whether irradiation is effective for benign schwannomas, but it is well established that recurrence after incomplete removal is rare irrespective of the irradiation.
Surgical treatment of giant cauda equina schwannomas must take into consideration, the problem of spinal instability, proportionally linked to the severity of osseous lesions at diagnosis.,
The outcome is generally correlated to the preoperative neurological condition of the patient.
In conclusion, the case tackles two fundamental issues: (i) lumbar schwannoma might be presented with nonspecific symptoms such as low back pain and sciatica and (ii) clinicians must be very careful in indicating surgical operation to treat lumbar disc herniation, especially if the imaging findings are not conclusive, to avoid unnecessary lumbar discectomy. The literature review found similar cases in which the spinal schwannoma of the cauda equina was firstly misdiagnosed as lumbar disc herniation.,,
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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