Multiple Schwannomas Arising from A Single Nerve Root of the Cauda Equina
Corresponding author: Dr. Masatoshi Teraguchi, Wakayama Medical University Kihoku Hospital, 219 myoji, Katsuragi town, Ito, Wakayama, Japan, Tel: +81-736-22-0066; E-mail: firstname.lastname@example.org
Schwannoma is the most common intradural extramedullary spinal tumor [1-3]; however, multiple schwannomas of the cauda equina nerve roots are very rare, except in patients with neu- rofibromatosis (von Recklinghausen disease) [4-8]. Our case is further unique because the spinal nerve root tumors showed a bead-like component in single nerve root.
A 60-year-old male presented with severe acute low back pain (LBP) and left lower limb pain with numbness of 2 weeks’ dura- tion. No motor weakness of the lower limbs was noted. On neu- rological examination, the left straight leg raising (SLR) test was positive and deep reflexes were diminished bilaterally. There was no evidence of skin pigmentation abnormality or familial history of neurogenic tumors. The patient was previously diagnosed with lumbar disc herniation at an outpatient clinic. Magnetic resonance imaging (MRI) revealed two spinal lesions at the L1 level and one spinal lesion of the cauda equina at the L3 level (Figure 1A, B). Gadolinium enhanced MRI showed homogenous enhancement of all lesions (Figure 1C). Computed tomograph- ic (CT) myelography demonstrated intradural extramedullary tumors, it could not be determined on these studies if the lesions originated from a single nerve root in the cauda equina (Figure 2).
Figure 1. T1 (A) and T2 weighted (B) magnetic resonance imaging (MRI) revealed 2 homogenous spinal lesions of the cauda equina at the L1 vertebral level and 1 homogenous spinal lesion of the cauda equina at the L3 vertebral level. Gadolinium enhanced MRI (C) showed homogenous enhancement of all 3 spinal nerve tumors.
Figure 2. CT myelography revealed intradural extramedullary spinal tumors in the cauda equina at the L1 and L3 vertebral levels on sagittal and coronal views.
The patient underwent tumor resection via osteoplastic laminot- omy from L3 to L1. After opening the dura, a 2.0 × 2.0 cm reddish tumor was found at the L3 vertebral level, and tubercular tumors measuring 2.0 × 2.0 cm and 1.5 × 1.5 cm, respectively, were iden- tified originating from a single root nerve of the cauda equina at the L1 vertebral level. All tumors were attached the involved nerve root, creating a bead-like type appearance of multiple tumors
on a single nerve root (Figure 3). The uninvolved nerve roots of the cauda equina showed no abnormalities. Histopathological examination revealed that these tumors were typical schwanno- mas (Antoni type A) (Figure 4). The postoperative course was uneventful and the patient’s symptoms resolved completely.
Figure 3. Multiple bead-like type tumors were macroscopically observed on a single nerve root of the cauda equina.
Figure 4. Photomicrograph showing a characteristic Antoni type A schwannoma. The tumor consists of spindle cells with variable cellularity. The paucicellular areas are myxoid. Small whorl forma- tion is observed in the lower area of the photograph (hematoxy- lin-eosin (HE) stain, ×100).
The etiology of multiple schwannomas originating from a single nerve root of the cauda equina appearing as a string of bead-like structures is unclear, based on our case and previously published reports [5-15]. Table 1 summarizes data on reported patients with bead-like multiple schwannomas in the single nerve of the cauda equina since 1980. We identified reports describing 12 cases, in- cluding 11 in the Japanese literature and 1 in the English literature [5-15].
Seven of the 12 cases were male, and the average age was 58 years (range, 40 to 67 years) [5-15]. The primary symptom of Schwannoma is LBP, followed by lower limb pain, numbness, and neurological deficits, making it difficult to differentiate the diagnosis from more common disorders such as lumbar disc herniation [16-18]. One previously reported case stated that a patient with multiple schwannomas in the single nerve of cauda equina was misdiagnosed with lumbar disc herniation after discectomy surgery based on lumbar CT (9). Differentiation of cauda equina tumors and disc herniation based solely on symp- toms, physical examination, and simple CT is difficult. Therefore, we agree with previous reports recommending that MRI should be utilized as a first-line tool to assist in the diagnosis of severe acute LBP, especially when atypical clinical features are present. If possible, gadolinium enhanced MRI is suggested to confirm the diagnosis [1-15]. MRI can confirm the presence of intradural extramedullary tumor preoperatively. Moreover, myelography and CT myelography may be useful in the diagnosis of multiple small spinal tumors despite having lower resolution than MRI
[5-15]. Unfortunately, it is difficult to determine preoperatively whether multiple tumors originate from a single nerve root or from multiple nerve roots. Therefore, a careful surgical strategy using preoperative standard MRI, gadolinium enhanced MRI, myelography, and CT myelography is warranted.
Additionally, the bead-like tumor was composed of the cells typical of schwannoma (Antoni type A) on histopathological examination in our patient; however, one previous report found Antoni type A cells in one tumor and Antoni type B cells in a second tumor present on the same nerve root .
We report a rare case of multiple schwannomas arising from a single nerve root of the cauda equina. We emphasize that a careful surgical strategy should be applied using enhanced MRI, myelography, and CT myelography to differentiate these tumors from other lumbar diseases. Furthermore, despite their rarity, multiple schwannomas must be included in the differential diagnosis for patients with back pain and lower limb pain with numbness.
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