Dr. Kocher is a Resident, Department of Radiology, Walter Reed Army Medical Center, Washington, DC; Dr. Smirniotopoulos is
Program Leader, Diagnostics and Imaging Center for Neuroscience and
Regenerative Medicine (CNRM), Professor of Radiology, Neurology and
Biomedical Informatics, and Chair of the Department of Radiology and
Radiological Sciences, Uniformed Services University, Bethesda, MD;
Washington, DC; and Dr. Smith is Chief, Neuroradiology,
Department of Radiologic Pathology, Armed Forces Institute of Pathology
Washington, DC and Assistant Professor of Radiology and Radiological
Sciences Uniformed Services, University of the Health Sciences,
Spinal lesions are usually classified into 2
broad categories: extradural and intradural. Extradural lesions are
located outside of the surrounding dural sac; they are often related to
lesions of the intervertebral disc or the spinal column. Intradural
lesions occur within the dural sac and are further classified as either
intradural intramedullary or intradural extramedullary lesions.
Intramedullary intradural lesions are within the substance of the cord.
Extramedullary lesions are located within the dural sac but exterior to
the spinal cord. This article will focus on the characteristic magnetic
resonance imaging (MRI) findings of the most common intradural lesions
and their differentiating imaging characteristics.
Intradural intramedullary lesions
lesions are recognized either because they alter the signal intensity
or attenuation of the spinal cord; or, because they change the shape and
size of the cord. The most common intramedullary lesions may be
neoplastic, inflammatory, vascular or congenital. Primary tumors are
usually glialastrocytoma in children and ependymoma in adults. Both
neoplasms expand the cord. In the absence of cord expansion, another
diagnosis, such as a demyelinating process, should be considered.
Ependymoma is the most common intramedullary spinal neoplasm in adults, representing 60% of all spinal cord glial tumors.1 The median age at presentation is 38.8 years, with a slight male predilection.1–3
Ependymomas arise from the ependymal cells lining the central canal of
the spinal cord, and would be expected to be centrally located; however,
only approximately 60% to 75% are centrally located.4,5 They are slow-growing and demonstrate well-demarcated symmetric expansion.6
These lesions are most common in the cervical region (44%), followed by
the thoracic (23%) and less common in the distal thoracic cord or conus
medullaris (6.5%).1–3 Clinical presentation includes neck
or back pain, sensory deficits, bowel or bladder dysfunction, and motor
weakness. Sensory symptoms are likely due to the central location within
the cord, and the close proximity to, and disruption of, the sensory
spinothalamic tracts that are crossing the midline.2
Ependymomas are typically confined to ≤5 vertebral segments.6 Associated intramedullary cysts have been documented in 50% of cases,7,8
and can be rostral or caudal to the neoplasm, intratumoral, or result
from reactive dilatation of the central canal. Hemorrhage is also
common, occurring in 19% of patients in Kahan’s study.4
Ependymomas tend to compress the adjacent spinal cord rather than
infiltrate it, making them amenable to microsurgical resection. Unlike
intracranial ependymomas, calcification is not common in spinal
Kahan et al. described the imaging characteristics
of ependymomas as isointense to hypointense on plain T1-weighted (T1W)
images, and hyperintense on T2-weighted (T2W) images. Classically,
ependymomas have shown intense, homogeneous and sharply demarcated focal
enhancement.1,2,9–11 However Kahan’s study of 26 cases
demonstrated only 38% of tumors with this pattern; 31% showed
heterogeneous enhancement (Figure 1); and, 19% showed ring enhancement.
Because of their tendency to bleed, a hypointense “hemosiderin cap” is
seen on T2W images in roughly one third of cases (Figure 2).
ependymoma (MPE) is a subtype of ependymoma that is predominantly found
in the region of the conus medullaris and filum terminale, and
represents 27% of all intraspinal ependymomas.12 MPE is also
the most common neoplasm of the conus medullaris. The mean age for
presentation of this tumor is in the fourth decade. Tumors, if small,
tend to displace the nerve roots of the cauda equina; whereas large
tumors often compress or encase them.4 These lesions are
often described as sausage shaped, well-demarcated and/or encapsulated.
They can be tethered both proximally and distally.4 Multiple lesions may be present in ≤40% of cases, which may be the result of the subarachnoid dissemination.13
The MPE subtype is prone to hemorrhage, and can present with
subarachnoid hemorrhage. Over time this may result in superficial
siderosis caused by the deposition of iron pigments on pial and
arachnoid surfaces.12 Imaging of superficial siderosis
reveals a thin hypointense line conforming to the surface of the spinal
cord, best seen on heavily T2-weighted images.
Kahan et al. found
that a significant number of myxopapillary ependymomas have high signal
on T1W images, unlike typical cellular ependymomas seen in the cervical
and thoracic cord. They postulate that this is the result of myxoid
material within the connective tissue elements. The increased T2 signal
and enhancement characteristics are similar to other ependymomas (Figure
Astrocytomas are the most
common intramedullary spinal cord tumor in children and are the second
most common in adult patients. Overall, they account for one third of
spinal cord gliomas.14 The mean age of presentation is 29, with a slight male predilection.14
The majority are low-grade (WHO I or II), and only 0.2% to 1.5% are
grade IV (glioblastoma multiform), unlike in the brain where grade IV
accounts for approximately 50% of gliomas.5,15
are typically located eccentrically within the cord, and may rarely be
exophytic. They are most commonly located in the thoracic region
(because there are more thoracic segments), followed by the cervical
cord, and rarely present as an isolated or focal lesion in the conus.14,16,17 In children, involvement of the entire cord is common; however, this is rare in adults.14,16
Unlike cerebral gliomas, contrast enhancement almost always occurs in
spinal astrocytomas, and is poorly correlated with tumor grade. The
higher grades may have leptomeningeal spread.
presentation depends upon the lesion location, and may include gait
abnormalities, pain and loss of previously attained motor skills.18 Symptoms tend to occur earlier in children than in adults.18
Astrocytomas tend to be more infiltrative than ependymomas, increasing
the morbidity resulting from, and decreasing the success of, surgical
resection. However, grade I astrocytomas in children tend to behave like
intracranial pilocytic astrocytomas, and displace the cord rather than
infiltrate it. Because surgery almost invariably leaves some neoplasm
behind, adjunctive radiation therapy is often required to manage these
Patel et al. described the characteristic imaging findings of astrocytoma,19
which include poorly defined margins, primarily hypointense on T1W
images, hyperintense on T2W images, and virtually all show at least
some enhancement18 (enhancement varies, and is usually
partial and mild to moderate) after administration of IV contrast
(Figure 4). Both intratumoral cysts and polar cysts can be present. The
distinguishing “hemosiderin cap” is not associated with astrocytomas.20
Spinal hemangioblastoma represents 1.6% to 7.2% of all spinal tumors and there is no gender predilection.14,21,22
They are low-grade neoplasms (WHO grade I), and are most commonly found
in patients <40 years. The thoracic cord is the most common site
involved (50%), followed by the cervical cord, with the lumbar and
sacral regions least common.23 Sixty percent are
intramedullary, 11% percent are both intramedullary and extramedullary,
21% are intradural extramedullary, and 8% are extradural in location.23
clinical presentation is nonspecific and includes pain and sensory and
motor deficits. Up to one third of patients will have von Hippel Lindau
syndrome (VHL). VHL commonly presents with multiple hemangioblastomas,
usually these are infratentorial affecting the cerebellum, brainstem,
spinal cord and eye. The retinal or cerebellar lesions are usually
symptomatic before the spinal-cord mass21,24 Surgical
resection of the lesion is the treatment of choice for solitary
hemangioblastomas. Additionally, preoperative embolization of these
highly vascular lesions has been utilized to reduce intraoperative
Chu et al. reported that MRI characteristics in
hemangioblastoma vary according to the size of the tumor. On T1W images,
small (<10 mm) hemangioblastomas are mostly isointense to the spinal
cord and hyperintense to the cord on T2W images, with homogenous
enhancement. However, larger tumors are usually hypointense or mixed
hypointense and isointense to the spinal cord on T1W images and are
heterogeneous on T2W images with heterogeneous enhancement (Figure 5).
Small hemangioblastomas are commonly found at the surface of the cord,
most often at the posterior aspect. This correlates with the cerebellar
hemangioblastomas that are usually in a superficial and subpial
location. These lesions are highly vascular and a finding, if present,
that is useful in separating hemangioblastomas from other intramedullary
tumors is macroscopic vascularity. Prominent flow voids are commonly
seen with lesions that are >24 mm. Rarely these lesions may be a
source of hematomyelia or subarachnoid hemorrhage. Symptomatic
hemangioblastomas commonly have an associated or secondary large syrinx,
found in 64% of intramedullary lesions in this study. Peritumoral edema
within the spinal cord is also often seen in symptomatic patients.25
sclerosis (MS) is most prevalent in the adult population between 20 and
40 years of age, although it can also occur in children. The
female-to-male ratio in adults is 1.7:1 vs. 2.1:1.26
one autopsy series of patients with known multiple sclerosis, Ikuta et
al. found spinal cord involvement in 86% of patients, with 13% having
only spinal cord lesions. The majority of MS lesions are identified in
the cervical cord.27 Lesions are typically located
peripherally within the cord (that is where the white matter lies),
involve less than half of the spinal cord’s cross-sectional area, and
typically are <2 vertebral body’s in vertical length.28 Medical therapy is the treatment of choice for MS management.
lesions in MS are typically isointense to the spinal cord on T1W
images, and hyperintense to the cord on T2W images (Figure 6). While
plaques primarily have no affect on cord morphology, Tartaglino et al.
found 12% of cases to cause cord atrophy and 6% of cases to cause cord
expansion, which may make it difficult to differentiate them from
neoplasms.29 Contrast enhancement can be nodular, ring or patchy and is indicative of an active lesion.29
like hydrocephalus, is an accumulation of cerebrospinal fluid (CSF)
within an ependymal-lined space, leading to distension of the central
canal of the spinal cord. In contrast, CSF dissecting into the adjacent
white matter, to form a paracentral cavity, is called syringomyelia. The
distinction between these is based on identifying the ependymal lining
of a hydromyelia. Unfortunately, the ependyma may be destroyed by
significant dilatation of the central canal. Because these 2 entities
may be hard to distinguish pathologically; and, because they may often
coexist, fluid spaces within the cord are often described as
There are multiple causes for
syringohydromyelic fluid cavities of the spinal cord. These include
posttraumatic cavities, those that communicate with the subarachnoid
space, tumor related cysts, arachnoiditis related, and idiopathic.30 A syrinx is commonly found in patients with Chiari malformations, found more often in patients with Chiari II (50% to 90%)31 than Chiari I (30% to 56%).32
and females are equally affected, and lesions are more often found in
adults than children. Although the clinical presentation varies widely, a
common presentation includes loss of pain and temperature sensation
with preservation of proprioception (position sense). Given the multiple
etiologies of syringohydromyelia, its treatment is multifactorial and
involves multiple surgical options.
often cause cord expansion. Pojunas et al. described the imaging
characteristics of syringes as following CSF signal; low signal on T1W
images and high signal on T2W images (Figure 7).33 The
lesion does not enhance after the administration of contrast material;
and, enhancement indicates a coexisting lesion, such as a glioma or
Intradural extramedullary lesions
Meningioma represents 25% of all intraspinal tumors34 and they are most commonly found in the intradural-extramedullary compartment, but rarely may be epidural in location.35
The majority of spinal meningiomas are WHO grade I. Most common in
women >40 years, these tumors are usually found in the thoracic
spine, followed by the cervical and lumbar spine. This distribution
probably reflects the greater length of the thoracic spinal cord more
than anything else. Clinical presentation is nonspecific and may include
sensory and motor symptoms, as well as bladder dysfunction. These
lesions are managed surgically.
On computed tomography (CT),
meningiomas are frequently hyperdense, reflecting their highly cellular
nature, and associated calcification. Takemoto et al. described the
typical imaging findings of meningioma to be isointense to the spinal
cord on T1W images, isointense to the cord on T2W images (Figure 8), and
intensely enhancing after contrast administration.36 As in
the skull, intraspinal meningiomas may have a broad base of dural
attachment, making them convex toward the cord and flat on the opposite
side toward the dura. They may result in hyperostosis of adjacent bone,
but this is less common than in intracranial meningiomas, which may be
due to the presence of the venous plexus and a greater amount of fat in
the epidural space of the spine. Meningiomas typically do not
demonstrate extension through the neural foramen in the spine, which can
help distinguish them from nerve sheath tumors.
Schwannomas are the most common intradural extramedullary spinal tumor, representing 43% to 67% of tumors in this category.37–40
Peak onset age ranges from 30 to 50 years of age, without a gender
predilection. They are typically solitary, but multiple schwannomas can
be seen in inherited tumor syndromes such as neurofibromatosis type 2
and Carney complex. Schwannomas are most often detected in the lumbar
spine. While most are incidental findings, clinical symptoms can include
weakness and bladder dysfunction. Schwannomas are encapsulated and
peripherally located along the affected nerve; making surgical resection
less complicated than in neurofibroma, which infiltrates the nerve
Schwannomas are primarily isointense to the spinal cord
on T1W images, hyperintense to the cord on T2W images, and show intense
enhancement after contrast administration (Figure 9).36 The imaging pattern will vary with the degree of cystic degeneration, presence of hemorrhage or fatty degeneration.
Neurofibromas account for 23% of all spinal tumors.41
They can be solitary, or multiple lesions may be seen in patients with
neurofibromatosis type 1. The peak age of onset is the third to fourth
decades. They may be plexiform, and can occasionally undergo malignant
degeneration. Hemorrhage and fatty degeneration are uncommon. Surgical
resection is the treatment of choice for neurofibromas and is
complicated by the infiltration of the lesion among the nerve fasicles,
requiring resection of the parent nerve with the tumor.
are usually isointense to hypointense to the spinal cord on T1W images,
hyperintense to the cord with central decreased intensity on T2W
images, and demonstrate enhancement after contrast administration
(Figure 10).37 The central T2W hypointensity is often
described as the “target sign,” which is suggestive, but not
pathognomonic, for neurofibromas. It can less commonly also be seen in
is a rare lesion in the spinal canal, occurring most often in the
extramedullary compartment typically in the cauda equina and filum
terminale compared to other spinal regions.43 Median age of presentation is 46 years, with slight male predominance.44
presentation includes lower lumbar pain, sensory or motor loss to the
lower extremities, and bowel and bladder dysfunction.45 Given the tumor’s vascularity, these lesions sometimes require preoperative embolization prior to surgical resection.
findings are nonspecific, with the tumor relatively isointense to the
spinal cord on T1W images, and hyperintense to the cord or heterogeneous
on T2W images. The salt-and-pepper appearance of head-and-neck
paragangliomas may also be seen on T2W images.46–51 Enhancement after contrast administration was noted in 5 of 11 cases (Figure 11).46–51
Intradural spinal lesions have a wide range
of etiologies, and it is important to distinguish between etiologies due
to the range of treatments and prognoses between the separate entities.
MRI findings, the patient’s demographic information and clinical
history are the best tools the radiologist can use to delineate one
cause from another.
The first step in identifying any intradural
lesion is distinguishing it by its location: either intramedullary
(within the cord substance) or extramedullary (outside the cord but
within the thecal sac).
Ependymomas are the most common
intramedullary lesions in adults, while astrocytomas are the most common
intramedullary lesions in children. Other factors used to distinguish
these 2 common lesions are position within the cord (central for
ependymomas, eccentric for astrocytomas). It is important to note that
≤38% of ependymomas may be eccentric in location. A hemosiderin cap can
be seen in up to one third of ependymomas—a finding not seen in
astrocytomas. Prognosis is better for ependymomas, given their tendency
not to infiltrate, allowing for easier surgical resection vs. the
infiltrating nature of astrocytomas.
Increased vascularity within
an intramedullary lesion with T2W flow voids is a distinguishing
characteristic of hemangioblastomas, which can be associated with von
Hippel Lindau syndrome.
Syringohydromyelia follows the CSF signal
without enhancement, unless an adjacent lesion is present.
Additionally, multiple sclerosis can cause a cord-expanding
intramedullary lesion that enhances in an active lesion, which tends to
be eccentric within the cord corresponding to the lateral position of
the white matter within the spinal cord. Multiple sclerosis does not
respect the boundary between white and gray matter.
evaluating extramedullary spinal lesions, many factors can be used to
delineate between common lesions. Meningiomas are most commonly found in
middle-aged women, and like their intracranial counterparts, often have
a broad base of dural attachment. Schwannomas have no gender
predilection, but are associated with neurofibromatosis type 2, and
should be strongly considered in an extramedullary lesion in this
population. Neurofibromas are associated with neurofibromatosis type 1,
and may demonstrate a target-sign pattern on T2W images, which is
suggestive, but not pathognomonic for neurofibroma. Additionally, an
extramedullary paraganglioma will sometimes show the salt-and-pepper
appearance seen in its head-and-neck counterparts, aiding in its
- Ferrante L,
Mastronardi L, Celli P, et al. Intra-medullary spinal cord ependymomas: A
study of 45 cases with long-term follow-up. Acta Neurochir. 1992;119:74-79.
- Epstein FJ, Farmer JP, Freed D. Adult intramedullary spinal cord ependymomas: The result of surgery in 38 patients. J Neurosurgery. 1993;79:204-209.
Hoshimaru M, Koyama T, Hashimoto N, Kikuchi H. Results of microsurgical
treatment for intramedullary spinal cord ependymomas: Analysis of 36
cases. Neurosurgery. 1999;44:264-269.
- Fine MJ, Kricheff II, Freed D, Epstein FJ. Spinal cord ependymomas: MR imaging features. Radiology. 1995;197:655-658.
- Koeller K, Rosenblum R, Morrison A. Neoplasms of the spinal cord and filum terminale: Radiologic-pathologic correlation. Radiographics. 2000;20:1721-1749.
- Kahan H, Sklar EM, Post MJ, Bruce JH. MR characteristics of histopathologic subtypes of spinal ependymoma. AJNR Am J Neuroradiol. 1996;17:143-150.
- Zimmerman RA, Bilaniuk LT. Imaging of tumors of the spinal canal and cord. Radiol Clin North Am. 1988;26:965-1007.
Slasky BS, Bydder GM, Niendorf HP, Young IR. MR imaging with
gadolinium-DTPA in the differentiation of tumor, syrinx, and cyst of the
spinal cord. J Comput Assist Tomogr. 1987; 11:845-850.
- Goy A, Pinto R, Raghavendra B, et al. Intramedullary spinal cord tumors: MR imaging with emphasis on associated cysts. Radiology. 1986;161:381-386.
- Parizel P, Baleriaux D, Rodesch G, et al. Gd-DTPA enhanced MR imaging of spinal tumors. AJR Am J Roentgenol. 1989;152:1087-1096.
- Rothwell CI, Jaspan T, Worthington BS, Holland IM. Gadolinium-enhanced magnetic resonance imaging of spinal tumours. Br J Radiol. 1989;62:1067-1074.
- Wagle W, Jaufman B, Mincy JE. Intradural extramedullary ependymoma: MR pathologic correlation. J Comput Assist Tomogr. 1988;12 (suppl 4):705-707.
- Wippold FJ, Smirniotopoulos JG, Moran CJ, et al. MR imaging of
myxopapillary ependymomas: Findings and value to determine extent of
tumor and its relation to intraspinal structures. AJR Am J Roentgenol. 1995;165:1263-1267.
- Brotchi J, Fischer G. Treatment. In: Fischer G, Brotchi J, Eds. Intramedullary spinal cord tumors. Stuttgart, Germany: Thieme; 1996;60-84.
- Bruner JM. Neuropathology of malignant gliomas. Semin Oncol. 1994:21:126-138.
- Epstein FJ, Farmer JP, Freed D. Adult intra-medullary astrocytomas of the spinal cord. J Neurosurg. 1992;77:355-359.
- Epstein F, Epstein N. Surgical treatment of spinal cord astrocytomas of childhood. A series of 19 patients. J Neurosurg. 1982;57:685-689.
- Constantini S, Houten J, Miller D, et al. Intramedullary spinal cord tumors in children under the age of 3 years. J Neurosurg. 1996;85: 1036-1043.
- Patel U, Pinto RS, Miller DC, et al. MR of spinal cord ganglioglioma.AJNR Am J of Neuroradiol. 1998;19:879-887.
- Froment JC, Baleriaux D, Turjman F, et al. Diagnosis: Neuroradiology. In: Fischer G, Brotchi J, eds. Intramedullary spinal cord tumors. Stuttgart, Germany: Thieme; 1996;33-
- Murota T, Symon L. Surgical management of hemangioblastoma of the spinal cord: A report of 18 cases. Neurosurgery. 1989;25:699-708.
Xu QW, Bao WM, Mao RL, Yang GY. Magnetic resonance imaging and
microsurgical treatment of intramedullary hemangioblastomas of the
spinal cord. Neurosurgery. 1994;35:671-676.
- Browne TR, Adams RD, Robertson GH. Hemangioblastoma of the spinal cord. Review and report of five cases. Arch Neurol. 1976;33: 435-441.
Neumann HPH, Eggert HR, Weigel K, et al. Hemangioblastomas of the
central nervous system: A 10 year study with special reference to von
Hippel Lindau syndrome. J Neurosurg. 1989; 70:24-30.
BC, Terae S, Hida K, et al. MR findings in spinal hemangioblastoma:
Correlation with symptoms and with angiographic and surgical findings. AJNR Am J Neuroradiol. 2001;22:206-217.
- Osborn Ag, Harnsberger HR, Smoker WRK, Boyer RS. Multiple sclerosis in adolescents: CT and MR findings. AJNR AM J Neuroradiol. 1990;11:489-494.
- Ikuta F, Zimmerman HM. Distribution of plaques in seventy autopsy cases of multiple sclerosis in the United States. Neurology. 1976; 8:26-28.
L, Friedman D, Flanders A, et al. Multiple sclerosis in the spinal
cord: MR appearance and correlation with clinical parameters. Radiology. 1995;195:725-732.
I, Bourgouin P, Lapierre Y, et al. Multiple sclerosis of the spinal
cord: Diagnosis and follow-up with contrast-enhanced MR and correlation
with clinical activity. AJNR Am J Neuroradiol. 1998; 19:1025-1033.
- Barnett HJM, Foster JB, Hudgson D. Syringomyelia. London: WB Saunders Co; 1973.
- Milhorat TH, Miller JI, Johnson, WD, et al. Anatomical basis of syringomyelia occuring with hindbrain lesions. Neurosurgery. 1993;32: 748-754.
- Elster AD, Chen MYA. Chiari I malformation: Clinical and radiologic reappraisal. Radiology. 1992;183:347-353.
- Pojunas K, Williams AL, Daniels DL, Haughton VM. Syringohydromyelia and hydromyelia: Magnetic resonance evaluation. Radiology. 1984;153: 679-683.
- Solero CL, Fornari M, Giombini M, et al. Spinal meningiomas: Review of 174 operated cases. Neurosurgery. 1989;25:153-160.
- Khamary SM, Alorainy IA. Case 100: Spinal epidural meningioma. Radiology. 2006;241:614-617.
K, Matsumura Y, Hashimoto H, et al. MR imaging of intraspinal
tumors—Capability in histological differentiation and
compartmentalization of extramedullarytumors. Neuroradiology. 1988;30:303-309.
- Hufana V,Tan JSH, Tan KK. Microsurgical treatment for spinal tumors. Singapore Med J. 2005;46:74-77.
Prevedello DM, Koerbel A, Tatsui CE, et al. Prognostic factors in the
treatment of the intradural extramedullary tumors: Astudy of 44 cases. Arq Neuropsiquiatr. 2003;61:241-247.
- El-Mahdy W, Kane PJ, Powell MP, Crockard HA. Spinal intradural tumors: Part I—Extramedullary. Br J Neurosurg. 1999;13:550-557.
- Garrido P, Laher-Mooncey S, Murphree NL, et al. Neoplasms involving the spinal cord in Zimbabweans: An analysis of 262 cases. Cent Afr J Med. 1994;40:201-204.
- Levy WJ, Latchaw J, Hahn JF, et al. Spinal neurofibromatosis: A case report of 66 cases and a comparison with meningiomas. Neurosurgery. 1986;18:331-334.
- Murphey MD, Smith SW, Smith SE, et al. Imaging of musculoskeletal neurogenic tumors: Radiologic-pathologic correlation. Radiographics. 1999;19:1253-1280.
- Binkley W, Vakili ST, Worth R. Paraganglioma of cauda equina. Case report. J Neurosurg. 1982; 56:275-279.
- Moran CA, Rush W, Mena H. Primary spinal paragangliomas: A clinicopathological and immunohistochemical study of 30 cases. Histopathology. 1997;31:167-173.
Sonneland PRL, Scheithauer BW, Lechago J, et al. Paraganglioma of the
cauda equina region: Clinico-pathologic study of 31 cases with special
reference to immunocytology and ultrastructure. Cancer. 1986;15:1720-1735.
- Hayes E, Lippa C, Davidson R. Paragangliomas of the cauda equina. AJNR Am J Neuroradiol. 1989;10:S45-S47.
- Pigott TJD, Lowe JS, Morrell K, Kerslake RW. Paraganglioma of the cauda equina: Report of three cases. J Neurosurg. 1990;72:455-458.
- Iliya AR, Davis RP, Seidman RJ. Paraganglioma of the cauda equina: Case report with magnetic resonance description. Surg Neurol. 1991;35:366-367.
- Wester DJ, Falcone S, Green BA, et al. Paraganglioma of the filum: MR appearance. J Comput Assist Tomogr. 1993;17:967-969.
- Aggarwal S, Deck JH, Kucharczyk W. Neuroendocrine tumor (paraganglioma) of the cauda equina: MR and pathological findings. AJNR Am J Neuroradiol. 1993;14:1003-1007.
- Boukobza M, Foncin JF, Dowling-Carter D. Paraganglioma of the cauda equina: Magnetic resonance imaging. Neuroradiology. 1993;35(6): 459-460.