Case Review
Volume 4, No.2
October 2000
 Carroll J Green
 Mokbel K Chedid
 Department of Neurosurgery
 Genesys Regional Medical
 Center
 Grand Blanc, MI 48439
 USA
 Correspondence:
 Dr. Carroll J Green
 G 3104 W. Carpenter Rd.
 Flint, MI 48504
 USA
 Fax: (1) 810 606 9512
 

Intramedullary Thoracic Cord Subependymoma - Case Report

   ABSTACT
Subependymomas are benign slow growing tumours, the majority of which are found at the time of autopsy. Scheinker in 1945 was the first to describe this type of tumour as a separate entity. Subependymomas are not easily recognised or diagnosed; there have been only 19 intramedullary spinal subependymomas reported in the literature.(14) The majority of these spinal cord subependymomas reported in the literature were located in the cervical region. This study reports successful treatment of a thoracic cord subependymoma and is presented along with review of previous literature.

Objective and importance: The origin of subependymomas remains controversial. The thoracic spinal cord subependymomas are rare; a literature review reveals 19 previous subependymoma cases, with only three of these being thoracolumbar intramedullary subependymoma cases.

Clinical presentation and intervention: This report describes a case of intramedullary thoracic cord subependymoma. The ultrastructure and pre and post-operative management are described. The tumour was successfully removed and the patient left with positive prognosis.

Conclusion: An awareness of subependymomas occurring in the spinal cord should lead to increased frequency of the diagnosis and a better understanding of these tumours.

Keywords: Subependymomas, tumour and spinal cord.
   INTRODUCTION
Subependymomas are usually seen as incidental findings within the ventricular system. On occasion, they present with signs of cerebro spinal fluid obstruction. Scheinker was the first to differentiate this type of tumour and it was recently addressed by Jallo, et al.(2,14) Such tumours identified by Jallo were shown to be well-demarcated tumours located eccentrically within the spinal cord.(8) The only definitive diagnostic modality to confirm these tumours is the pathological examination. History, physical, radiographic and gross observations intraoperatively are not conclusive in diagnosing subependymomas. A review of the literature found only 19 intramedullary spinal subependymomas reported previously. The majority of these subependymomas were located in the cervical region, with only three reported in the thoracolumbar region. In this report, a rare thoracic cord subependymoma is presented and the corresponding diagnosis and literature reviewed.

   CASE REPORT
This 68-year-old female had multiple medical problems: hypertension, insulin dependent diabetes mellitus, coronary artery disease, hypercholesterolemia, depression, severe joint disease and arthritis. She presented with complaints of back pain, which had been treated in the past, getting progressively worse in severity over two months prior to evaluation. She had been incapacitated and had difficulty walking due to joint problems. Additionally, for approximately two months, the patient was having numbness and spasticity of the legs. She also reported epigastric area, left chest cage and intrascapular area pain. There was no history of recent trauma, bowel or bladder dysfunction.

The patient walked with the aid of a cane and the gait was abnormal with increased tone in the lower extremities. The legs were stiff and spastic. Muscle strength in the lower extremities were 4+/5 on the right and 2/5 on the left. The toes were up going on the left side, weakness greater on the left and sensory level around T9 area. There was absent ankle reflex on the right side. She was able to move upper extremities well and had no weakness. There was also preservation of sacral sensation, position and vibration sense and rectal tone.

Magnetic resonance imaging (MRI) of the thoracic spine was performed, pre and post gadolinium administration (Fig. 1) revealed an enhancing 8 mm mass on the left side of the cord. There was a small amount of fluid within the central cord just superior and inferior to this mass extending for approximately 1 cm superiorly and 12 mm inferiorly. The AP width of the fluid collection was approximately 4 mm. These findings were most consistent with an intramedullary tumour. With a pre-operative diagnosis of ependymoma, surgical excision was carried out.

 
Figure 1 —  Sagittal MRI T1- and T2-weighted, demonstrating intradural lesion from T7 to T12.
Operation: An incision was made from T9 to T11. While obtaining exposure, it was noted that there was not much epidural fat. The dura was exposed and opened. The pia looked greyish in colour rather than yellowish, as is usually seen in the spinal cord. Using the operating microscope, a myelotomy was initiated. During the dissection the lesion was noted to be well demarcated. It was not very vascular. Frozen sections were not very diagnostic at the time. The tumour had a multilobular surface. The abnormal lesion extended over two segments and was shelled out from the spinal cord. It had a different colour and texture than the spinal cord.

Post-operative Course: Neurological examination in the immediate post-operative period revealed no worsening of the existing deficit or any onset of a new deficit. The patient reported numbness and weakness in the left lower extremity to the hip. The patient had normal tone in the right lower extremity. Dorsiflexors were 5/5, plantar flexors 5/5, 5/5 knee extensors and 4+/5 knee flexors. The patient had 3+/5 hip flexors and 4+/5 hip extensors. In the left lower extremity, the patient had complaints of parethesia. There was decreased sensation to pinprick and light touch in the entire left lower extremity. There were 4/5 toe extensors and toe flexors, but less than antigravity dorsiflexors and plantar flexors. The patient was unable to raise and had less than antigravity hip flexors. Sensations in the upper extremities as well as the right reflexes were hyperactive in both lower extremities. There was two beat clonus noted in the left, zero on the right. Upper extremity reflexes were 2+ and symmetrical. There was gradual improvement in function during a two-week stay in rehabilitation. Upon discharge from rehabilitation patient was independent with activities of daily living and was ambulating seventy feet with the use of a walker. There was no radiation therapy recommended.

Microscopic description: Five specimens were sent for evaluation. Review of the frozen section of the A material revealed normocellular tissue with irregularly shaped spaces between some of the cells and a lack of neoplasm or inflammatory cells. There was some nuclear pleomorphism. The permanent section of the A tissue sample revealed the same cytoplasmic degenerative changes or micro cystic change in this tissue. Review of the B tissue sample frozen section revealed tissue like specimen A. There was no whirling or changes indicative of a neurilemmatous type of tumour. Again, there was some nuclear pleomorphism. Scattered extracellular round blue bodies were admixed with the tissue. The frozen sample C had morphology like that described in A and B. In the permanent sections of C, large irregular empty spaces were present with no appreciable content or lining. Review of sample D revealed tissue with a morphology like described above. Irregular deposits of calcium were present in the permanent sections. The nuclei of the cells were irregularly distributed. Tissue sample E revealed dense eosinophillic and cornified tissue with sparse amount of parakeratotic tissue attached. There is no suggestion of micro mineralisation, ossification, malignancy, inflammation or granulomatous disease.

 
Figure 2 — MRI with contrast. (a) T1 sagittal with contrast, demonstrating lesion enhancement. (b) Axial views with contrast, delineating the lesion.
    Figure 3 — Sagittal T1-weighted MRI, post-resection, demonstrating generous decompression of the spinal cord.  

    Figure 4 — Axial T1-weighted MRI, post-resection, showing the decompression of the spinal cord and excision of the lesion.  


Pathological diagnosis:

    1. ependymomatous variant
    2. second diagnosis by Mayo Clinic – subependymoma
    3. subependymoma diagnosis by Armed Forces Institute of Pathology (AFIP)

Table 1 — Subependymomas reported previously in the literature.

Series (Reference No)

Age (yr) Sex

Length of History (yr)

Location

Boykin, et al, 1954 (3)

49 M

7

C4-C6

Pluchino, et al, 1984 (11)

16 M

2

C2-T1

Salcman & Mayer, 1984 (13)

44 F

4

C3-T1

Cervos-Navarro, et al, 1986 (4)

6 M

25

L2-L5

45 M

4

T2-T3

73 M

3

C7-T3

Lee, et al, 1987 (9)

48 M

6

C6-T2

22 M

1

C2-C6

Bardella, et al, 1988 (2)

60 M

6

C3-C7

Vaquero, et al, 1989 (15)

50 F

5

C3-T1

Artico, et al, 1989 (1)

47 M

2

C4-C6

Guha, et al, 1989 (6)

35 M

2.5

T7-L1

Pagni, et al, 1992 (10)

53 M

15

C5-T1

Jallo, et al, 1996 (8)

26 F

C6-T1

41 M

T11-L2

39 M

C4-T1

50 M

C7-T1

64 M

C2-C5

66 F

C1-C3

Green & Chedid 1999 (6)

63 F

1.5

T10-T11

   DISCUSSION
Scheinker in 1945 proposed the origin of subependymomas to be from the subependymal plate which is also known as the “residual peri-ventricular matrix layer” because of the histological appearances of this region.(14) Subependymomas of the spinal cord have distinct histological appearance. The tumour shows sparse cellularity, clustering of cells, and a dense fibrillary stroma occasionally containing microcysts. At present, most pathologists and neurosurgeons believe that the subependymoma is an ependymoma variant in which ependymal cells are sparsely dispersed among the predominant fibrillary astrocytes.(3,12) In 1954, Boykin, et al reported nine cases and thought these tumours originated from the subependymal astrocyte lining the walls of the ventricular system or the central canal of the spinal cord.(3) Fu, et al concluded that a subependymoma was a variant of ependymoma and that the astrocytic component was a reactive component.(5) It was previously concluded that subependymomas were a separate entity from ependymomas and astrocytomas but that they arose from the ependymal glial precursor cells in the subependymal cell layer. Tancytes cells, named by Horstman in 1954, have an ultrastructure of both astrocytes and ependymomas, similar to the findings in subependymomas.(7) This cell is considered by some to be the origin of the subependymoma tumour line. After the initial report of spinal cord subependymomas by Boykin, et al, no other reports followed in the literature for 30 years.(3) A literature review yielded a total of 19 cases (Table 1) including the present one, with the majority being in males (14 cases). The patient ages ranged from 6 to 73 years and the majority of the tumours found were in the cervical region with the exception of five cases. The thoracolumbar region tumour in the present case suggests that as more of these tumours are recognised, they may well be found throughout the various levels of the spinal cord. Pain and non-specific motor and sensory deficits of the extremities were the usual presenting complaints and were present for a period of 3 months to 15 years. Surgical resection is mandatory in symptomatic subependymomas, because they are benign tumours and thus total removal usually results in complete recovery. No other adjunct therapy is indicated after complete removal of the tumour. The neurosurgeon and pathologist need to keep these tumours in mind at frozen section examination, since it has been stressed that subependymomas are avascular and well-demarcated from surrounding tissue, and that the diagnosis influences the extent of the resection. These tumours are often mistaken on frozen section for astrocytoma, which has a less favourable prognosis.
   REFERENCES
1. Artico M, Bardella L, Ciappetta P, Rato A: Surgical treatment of subependymomas of central nervous system. Acta Neurochir (Wien) 1989, 98: 25-31
2. Bardella L, Artico M, Nucci F: Intamedullary subepen-dymoma of the cervical spinal cord. Surg Neurol 1988, 29: 326-329
3. Boykin FC, Cowen D, Ianueci CAJ, Wolf A: Subepen-dymal glomerate astrocytomas. J Neuropathol Exp Neurol 1954, 13: 30-49
4. Cervos-Navarro J, Artigas J, Perez-Canto A: Clinical and immunohistological findings in subependymomas of the spinal cord. Verh Dtsch Ges Pathol 1986, 70: 376-379
5. Fu Y, Chen AT, Kay S, Young H: Is subependymoma (subependymal glomerate astrocytoma) an astrocytoma or ependymoma? A comparative ultrastructural and tissue culture study. Cancer 1974, 34: 1992-2008
6. Guha A, Reseh L, Tator CH: Subependymoma of the thoracolumbar cord. Case report. J Neurosurg 1989, 71: 781-787
7. Hortsmann E: Die fasengia des selachiergehirns. Z Zellforschun 1954, 39: 588-617
8. Jallo GI, ZagZag D, Epstein F: Intramedullary subepen-dymoma of the spinal cord. Neurosurg 1996, 38: 251-257
9. Lee KS, Angelo JN, McWhorter JM, Courtland HD Jr: Symptomatic subependymoma of the cervical spinal cord. Report of two cases. J Neurosurg 1987, 67: 128-131
10. Pagni CA, Canavero S, Giordana MT, Mascalchi M, Arnetoli G: Spinal intramedullary subependymomas. Case report and review of the literature. Neurosurg 1992, 30: 115-117
11. Pluchino F, Lodrini S, Lasio G, Allegranza A: Complete removal of holocord subependymoma. Case report. Acta Neurochir (Wein) 1984, 73: 243-250
12. Russell DS, Rubinstein LJ: Pathology of tumours of the nervous system. Williams & Wilkins, Baltimore, 1989, (Ed.) 5, pp 262-265
13. Salcman M, Mayer R: Intramedullary subependymoma of the cervical spinal cord. Case report. Neurosurg 1984, 14: 608-611
14. Scheinker IM: Subependymoma: A newly recognized tumor of subependymal derivation. J Neurosurg 1945, 2: 232-240
15. Vaquero J, Martinex R, Vegazo I, Ponton P: Subependymoma of the cervical spinal cord. Neurosurg 1989, 24: 625-627

 


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