Ectopic Ganglion in Cauda Equina: Case Report

case report J Neurosurg Spine 24:937–940, 2016

Ectopic ganglion in cauda equina: case report

Andrew K. Conner, MD,1 Kar-Ming Fung, MD, PhD,2 Jo Elle G. Peterson, MD,2 Chad A. Glenn, MD,1 and Michael D. Martin, MD1

Departments of 1Neurosurgery and 2Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma

Macroscopic ectopic or heterotopic ganglionic tissue within the cauda equina is a very rare pathological finding and is usually associated with spinal dysraphism. However, it may mimic genuine neoplasms of the cauda equina. The authors describe a 29-year-old woman with a history of back pain, right leg pain, and urinary incontinence in whom imaging demonstrated an enhancing mass located in the cauda equina at the L1–2 interspace. The patient subsequently underwent biopsy and was found to have a focus of ectopic ganglionic tissue that was 1.3 cm in greatest dimension. To the authors’ knowledge, ectopic or heterotopic ganglionic tissue within the cauda equina in a patient without evidence of spinal dysraphism has never been reported. This patient presented with imaging and clinical findings suggestive of a neoplasm, and an open biopsy proved the lesion to be ectopic ganglionic tissue. The authors suggest that ectopic ganglionic tissue be added to the list of differential diagnoses of a space-occupying lesion arising from the cauda equina. http://thejns.org/doi/abs/10.3171/2015.11.SPINE141304 Key Words ectopic ganglion; cauda equina tumors; spinal oncology; ectopic dorsal root ganglion; paraganglioma; lumbar

enuine neoplasms arising from the filum termi- Case Report nale are uncommon with ependymal tumors, par- History and Examination ticularly myxopapillary ependymoma as the most common,G followed by paraganglioma. Other genuine The patient was a 29-year-old woman who presented neoplasms (such as teratomas) and tumor-like conditions with a long history of back pain, several months of inter- (such as lipomas and malformations) can also affect the mittent incontinence, and new-onset pain and numbness sacrum, with involvement of the filum terminale. Micro- in her right leg. On physical examination the patient ap- scopic clusters of ganglionic cells have been described in peared healthy and in no acute distress. No constitutional normal human filum terminale.5 Heterotopic dorsal root conditions were noted. Her neurological examination re- ganglion cells and ganglionic tissue have been described vealed normal strength and sensation, and examination of in patients with spinal malformations including spina bifi- her spine demonstrated no stigmata of congenital anoma- da6 and diastematomyelia.4,9 We report a centimeter-sized, lies. Urological evaluation, including formal urodynamic heterotopic ganglion in the filum terminale that was not studies, revealed neurogenic bladder. associated with malformation of the spinal cord or vertebral column. This lesion mimics a neoplasm on imag- Imaging Findings ing, and on clinical presentation it was initially thought An MRI study of the lumbar spine demonstrated a to account for the patient’s subjective symptoms. To our small nodule, 1.3 × 0.5 × 0.7 cm, located at the cauda equi- knowledge, no instance of ectopic or heterotopic ganglia na at the L1–2 level. The lesion was well circumscribed, within the cauda equina, in the absence of preexisting isointense to the spinal cord on T1-weighted images, and neural tube pathology, has been described in the English- showed focal enhancement (Fig. 1A and B). The T2- language scientific literature. weighted images demonstrated a hypointense lesion that

SUBMITTED December 22, 2014. ACCEPTED November 3, 2015. include when citing Published online February 12, 2016; DOI: 10.3171/2015.11.SPINE141304.

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changed. Her lumbar wound was noted to have superficial breakdown. This was managed with local wound care. Urological function at this time was also unchanged, re- vealing persistent neurogenic bladder. Unfortunately, 4 months after surgery the patient suffered a fall that re- sulted in further wound breakdown, prompting surgical exploration and debridement. The patient was discharged home on antibiotics. Follow-up at 7 and 9 months revealed the lumbar wound to be well healed and the patient’s preoperative neuropathic pain to be absent. At last follow-up, the patient continued to demonstrate a neurogenic bladder. Her neurological examination was otherwise unchanged. Pathological Findings Intraoperative cytological preparations demonstrated a high number of huge, round cells with centrally located large round nuclei and large nucleoli that were diagnos- tic of normal-appearing ganglionic cells (Fig. 2A). These cells were admixed with small spheroids of tightly packed cells that had small nuclei without nuclear atypia. No men- ingeal or glial components were noted. Histological sections showed classic features of a ganglion that included ganglionic neurons rimmed by sustentacular cells and embedded in a background of Schwann cells with susten- FIG. 1. A and B: Preoperative MRI studies demonstrate a 1.3 × 0.5–cm, well-demarcated, enhancing nodule (arrow) at the L-1 level on T1- tacular cells (Fig. 2B and C). On immunohistochemistry weighted imaging with Gd enhancement. C and D: The lesion is low on (Fig. 2D–F), the Schwann cells but not the ganglionic cells T2-weighted imaging. were positive for S100 protein (Polyclonal, Ventana). The ganglionic cells were positive for synaptophysin (Clone SP11, Ventana) and neurofilament proteins (Clone FNP7, was not consistent with intensity of CSF (Fig. 1C and D). Invitrogen). Note that peripheral nerve bundles were No evidence of malformation of the spine or spinal cord highlighted by immunohistochemistry for neurofilament was noted. proteins (arrow in Fig. 2F). Immunohistochemistry was performed by a Benchmark Autostainer (Ventana) with Operation protocols provided by the vendor. An L-1 laminectomy was performed. After intraoperative localization with ultrasound, the dura mater was opened with a midline incision. The lesion was immedi- Discussion ately apparent. It was spherical, flesh-colored, and located The histology and immunohistochemical profile in this at the cauda equina, with multiple small nerve roots cours- case was that of a peripheral nerve ganglion. The elec- ing over all surfaces of the mass. Using intraoperative elec- trophysiological observation that this nodule was closely trical stimulation, we found the mass to be densely associ- associated with functional nerve fibers, the surgical ob- ated with functioning neural tissue, and therefore it could servation that nerve fibers coursed around the nodule, and not be resected en bloc. Multiple attempts were made to the fact this nodule could not be cleanly dissected from define tissue planes between the nerves and the lesion, but other fibers confirmed that this was an ectopic ganglion these were unsuccessful due to the densely packed nerve and probably electrically active. Our report is the first de- rootlets coursing through and around the mass. Two bi- scription in the English-language literature of an ectopic opsy samples were sent for frozen section and revealed ganglion that presented as a tumor of the filum terminale. the presence of ganglionic cells, with normal ganglionic Microscopic clusters of ganglionic cells have been de- tissue and ganglionic paraganglioma included as 2 of the scribed in normal human filum terminale.5 Heterotopic possible differential diagnoses. A surgical decision was dorsal root ganglion cells are found in 66.3% of cases of made to stop the procedure and close the incision, because spina bifida aperta, according to 1 study.6 Small ectopic total resection appeared to be impossible without certain ganglionic tissue intercalated in the ventral root of 1 hemi- neurological damage. cord has been described in an asymptomatic 63-year-old patient with sacral diastematomyelia,9 and paramedian Postoperative Course dorsal root ganglia have been described in an 18-month- The patient awoke without neurological deficits. She ex- old infant with a split cord malformation.4 The etiology of perienced transient neuropathic pain that was successfully these rare findings is thought to be associated with abnor- treated with steroids and gabapentin. She was discharged mal migration of neural crest cells during primary neu- home in good condition after a 2-day hospital stay. At rogenesis—more specifically, secondary to a premature 1-month follow-up, the right lower-extremity neuropathic division of the neural plate prior to closure of the neural pain had resolved, whereas her numbness remained un- tube.3,6

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FIG. 2. Photomicrographs of tissue sections. A: Large ganglionic cells and spheroids of spindle cells are noted in the cytological preparation. B and C: The classic features of a ganglion, including clearly identifiable sustantecular cells (arrow in C) around ganglionic neurons, are present (frozen section). D: The stromal component but not the bodies of the ganglionic cells are positive for S100 protein. E and F: The bodies of the ganglionic cells are positive for synaptophysin and neurofilament in panels E and F, respectively. Note that axons in the peripheral nerve bundle of the ganglion are highlighted by immunohistochemistry for neurofilament proteins, which also highlighted the peripheral nerve bundle (arrow in F). H & E (panels A–C) and immunostaining (panels D–F). Original magnification ×40 (A), ×60 (C), and ×20 (B, D–F).

The nodule in this case was 1.3 cm in greatest dimen- cal overlap with ectopic ganglionic tissue. Demonstration sion and was far larger than any of the aforementioned ec- of areas with the classic paraganglioma component is the topic ganglionic tissue nodules associated with spinal and/ best way to differentiate these tumors from ectopic gan- or vertebral malformations.2 This unique case illustrates glionic tissue. that ectopic or heterotopic ganglionic tissue can occur in the absence of underlying spinal dysraphism. Radio- Conclusions graphically, the current lesion raises a concern of paragan- Although this patient’s lesion did not represent a neo- glioma. Clinical findings (midline location, urodynamic plasm, its appearance on imaging and the clinical pre- studies, and radiculopathy) seem to be of no value in dif- sentation warranted biopsy. The patient’s preoperative ferentiating this congenital lesion from an acquired lesion neuropathic pain resolved after biopsy of the lesion. Al- in the filum terminale. though the lesion resembled neural tissue on intraopera- Space-occupying lesions arising from the filum ter- tive inspection, pathological identification of spinal mass minale are essentially intradural extramedullary lesions. lesions remains dependent on obtaining tissue. The deci- Spinal intradural extramedullary tumors are uncommon, sion whether to perform a biopsy is dependent on the lo- and the more commonly encountered entities include calizing quality and severity of the patient’s symptoms as schwannoma, meningioma, neurofibroma, myxopapillary well as radiographic and intraoperative findings. At this ependymoma, paraganglioma, and leptomeningeal metas- 10 point, the patient’s pain is being successfully managed tasis. Among these entities, myxopapillary ependymoma with neuropathic pain medications. Given her limited but and paraganglioma typically arise from the cauda equina present urinary and bowel function, complete resection of and/or filum terminale. Recognition of myxopapillary ep- this lesion has not been pursued. endymoma radiographically, grossly at surgery, or through pathological examination is usually not a major challenge. References Paraganglioma is unique in that it often presents as a single round nodule hanging by the filum terminale. In 1. Burger PC, Scheithauer BW: Tumors of paraganglionic tissue, in Tumors of the Central Nervous System. Atlas of most situations, recognition of this entity is not difficult. Tumor Pathology. Washington, DC: Armed Forces Institute Paraganglioma, however, can have gangliocytic differen- of Pathology, 1994, 317–320 1 tiation. Nearly half of cauda equina paragangliomas con- 2. Cohen MS, Wall EJ, Brown RA, Rydevik B, Garfin SR: 1990 tain mature ganglion cells and cells that are transitional AcroMed Award in basic science. Cauda equina anatomy. II: between chief and ganglion cells. These tumors are often Extrathecal nerve roots and dorsal root ganglia. Spine (Phila referred to as gangliocytic paraganglioma. Interestingly, Pa 1976) 15:1248–1251, 1990 gangliocytic paraganglioma are frequently seen in the du- 3. Dryden RJ: Duplication of the spinal cord: a discussion of 7 8 the possible embryogenesis of diplomyelia. Dev Med Child odenum, and a concomitant ganglioneuroma component Neurol 22:234–243, 1980 has also been described. Whereas classic paraganglioma 4. Hamasaki T, Makino K, Morioka M, Hasegawa S, Kurino M, can be easily distinguished from ectopic ganglionic tis- Kuratsu J: Histological study of paramedian dorsal root gan- sue, gangliocytic paraganglioma and paraganglioma with glia in an infant with split cord malformation. Case report. J a ganglioneuromatous component have certain histologi- Neurosurg 104 (6 Suppl):415–418, 2006

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5. Kural C, Guresci S, Simsek GG, Arslan E, Tehli O, Solmaz Disclosures I, et al: Histological structure of filum terminale in human The authors report no conflict of interest concerning the materi- fetuses. J Neurosurg Pediatr 13:362–367, 2014 als or methods used in this study or the findings specified in this 6. Lendon RG, Emery JL: Heterotopic dorsal-root ganglion paper. cells around the spinal cord in children with spina bifida aperta. Dev Med Child Neurol Suppl 37:16–21, 1976 Author Contributions 7. Okubo Y, Wakayama M, Nemoto T, Kitahara K, Nakayama H, Shibuya K, et al: Literature survey on epidemiology and Conception and design: Martin, Conner, Fung. Acquisition of pathology of gangliocytic paraganglioma. BMC Cancer data: Conner, Peterson. Analysis and interpretation of data: Con- 11:187, 2011 ner, Fung, Peterson. Drafting the article: Martin, Conner, Peter- 8. Pytel P, Taxy JB, Krausz T: Ganglioneuromatous paragan- son, Glenn. Critically revising the article: Martin, Conner, Glenn. glioma of the cauda equina–a pathological case study. Hum Reviewed submitted version of manuscript: Conner, Fung, Glenn. Pathol 36:444–446, 2005 Statistical analysis: Fung. Administrative/technical/material sup- 9. Ross GW, Swanson SA, Perentes E, Urich H: Ectopic mid- port: Conner, Fung, Peterson. Study supervision: Martin, Fung. line spinal ganglion in diastematomyelia: a study of its con- nections. J Neurol Neurosurg Psychiatry 51:1231–1234, Correspondence 1988 Michael D. Martin, Department of Neurosurgery, The University 10. Wein S, Gaillard F: Intradural spinal tumours and their of Oklahoma Health Sciences Center, 1000 N. Lincoln Blvd., mimics: a review of radiographic features. Postgrad Med J Ste. 400, Oklahoma City, OK 73104. email: michael-martin@ 89:457–469, 2013 ouhsc.edu.

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