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Isolated Cervical Intradural Schwannoma With Intramedullary Extension

INTRODUCTION

Schwannomas are mostly intradural extramedullary tumors originating from the Schwann cells. They correspond to 30% of spinal tumors and are generally associated with neurofibromatosis types 1 and 2(1). Because the Schwann cell are normally not found within the parenchyma of the brain and the spinal cord it these lesions are rare in this location Intramedullary lesions represent 0.3% of all medullary tumors and 1.1% of spinal schwannomas(2). Most of these intramedullary tumors are confined to parenchyma of brain and spinal cord without extramedullary extension and are diagnosed on histopathology. We at our institution describe a rare intraoperative finding in which a case of suspected intradural extramedullaryschwannoma had an intra medullary extension.

 CASE REPORT

A  22year female presented in our hospital with complaints of pain neck radiating to occipital region of 2 yrs duration. She had  stiffness  and gradually progressive weakness all four limbs left more than right for past 6 months. There was no family history of  Von Recklinghausen's disease. Neurological examination revealed spastic quadriparesis, prominent in the left extremities. Posterior column sensations were lost in all four limbs. Deep tendon reflexes were exaggerated in all four limbs. A positive Hoffman s and Babinsky signs and  sign were present bilaterally.  Gait was broad-based due to spasticity. Difficulty in urination was present .MRI of cervical spine was done at some other institute  revealed  a large well defined homogenously enhancing  intradural extramedullary  mass  at C1-2 level on left side markedly compressing the cord, there was associated cord edema  at adjacent cervical levels(fig.1&2). A provisional diagnosis of schwannoma or neurofibroma was kept since there was no dural tail or broad based attachment of tumor to dura.

Patient was advised  surgical removal of tumour . Tumor was approached via midline incision in neck and C-1 to C-3 laminectomy was done. Dura was opened under microscope and tumor was found on left side and whole of the tumor was intra arachnoidal. To our surprise though  tumor was mainly extra medullary on left side ,it had an  intra-medullary extension. Extramedullary component was completely removed followed by intatumoral decompression of intra medullary part.Capsule of  intramedullary component was densely adherent to spinal cord and small amount of tumor tissue had to be left behind to avoid post operative neurological deficit(fig.4). Duraplasty was done. In the postoperative period the power of the patient improved gradually and by the end of the first week she could walk without support and at the end of one month power in all four limbs was 5/5 , though spasticity remained in all four limbs. Her gait remain broad based and there is clumsiness while walking.

DISCUSSION

 Intramedullary schwannomas are rare tumors . The first surgical description of a spinal tumor was made in 1888 by Sir Victor Horsley(3). In 1907  Von Eiselberg published the successful resection of an intramedullary neurofibrosarcoma. First intramedullary schwannoma was reported by Kernohanin1952 though  Penfield had already described an intramedullary lesion with schwannoma characteristics in 1932(4).

We found 52 cases in the literature, in addition to our case. Of these cases only three have been reported as having both  intramedullary and extramedullary component . Gorman etal., have reported the extramedullary component to be an exophytic extension of the intramedullary tumor from the enlarged spinal cord(5).

Mean age at presentation of these lesions is   40-years . They are usually single lesions affecting the cervical spinal cord (63%), the thoracic spinal cord (26%) and the lumbar spinal cord (11%). They have a slow growth pattern and because of this the average interval between first symptoms and diagnosis is 28.2 months (from six months to 20 years)(6). The most described clinical manifestation is the pyramidal syndrome followed by sensitivity complaints and sphincter dysfunction(6).

The absence of schwann cells within the brain and spinal cord in normal individuals has raised speculation as to the pathogenesis of these tumors(7.8,9,10). Hypoteses have discussed the possibility that these tumors arise from proliferation of schwann cells in the perivascular plexuses within the central nervous system(7,10,11,12) . Alternatively, the disordered migration of the neural crest elements at the moment of neural tube closure during the fourth week of embryogenesis may result in these tumors. But the most acceptable theory was reported by Rusell and Rubenstein in 1971. According to them, these tumors emerge from the transformation of neuroectodermal pial cells into Schwann cells, leading to a possible fast neoplastic growth of Schwann cells located in a “critical area” in the dorsal roots.(9,10,11,13)

Most of the cases described in the literature are primarily intramedullary in nature .Our case is one of the four cases described till  date  which had both intra as well as extramedullary component.  The other three cases had small exophytic but a large intra medullary component(5,14) but  our case had smaller intramedullary component. In all the cases intramedullary component  was diagnosed to be present preoperatively but in our case intramedullary component was not suspected preoperatively but was found intraoperatively only . However we retrospectively analyzed the radiology in our case there were few subtle  hints on radiology which suggested possible intramedullary extension.On  T-2  wighted coronal sequences though tumour appeared to be well defined and separated from cord there was a lot of edema in the cervical cord suggesting an intraparenchymal involvement(fig.3) . On searching literature we found out that  this sign had been described by Colosimo etal in two of their cases in 2003. They suggested that  MR imaging evidence of a small- or medium-sized well-marginated intramedullary spinal cord tumor in a patient in whom no syringomyelia is present but in whom moderate edema with marked Galodinium  enhancement can be seen should be considered in the differential diagnosis of intramedullary spinal cord schwannoma(15). Thus marked cord edema in the presence of intradural extramedullary mass should be considered as an indication of intramedullary extension . In cases in which an associated thickened Gd-enhancing spinal nerve root is seen the diagnosis of schwannoma should be assumed.

 CONCLUSIONS

Schwannomas are usually benign, well delineated and posteriorly located tumors, and are eminently suited for surgical excision. In the literature it is reported that the use of ultrasonic aspirator and surgical microscope facilitate the removal of intramedullary tumors with minimal damage to adjacent cord substance. Gross total resection is the goal but sometimes this cannot be accomplished due to the infiltrative characteristic of the tumor.MRI can be used to predict intramedullary extension, if it shows no syringomyelia but moderate cord  edema. In cases in which an associated thickened Gd-enhancing spinal nerve root is seen the diagnosis  of schwannoma should be assumed .

 FIGURES AND LEGENDS

Fig-1

Saggital post contrast image showing large IDEM at C-1 and C-2 levels

Neurosurgery in Chandigarh

 FIG-2

Post contrast Axial image showing Large intradural IDEM with enhancing left Nerve Root

FIG-3 Coronal T-2 weighted image showing  large IDEM with lot of associated edema in cervical cord below the lesion. This edema can suggest intra medullary extension of tumors and can be differentiated from syringomyelia on post contrast scans where it will not enhance but syrinx cavity will show contrast uptake.

FIG-4.

Postoperative Contrast enhanced  saggital image  showing small remnant of tumor capsule left behind after surgery

Dr. Vineet Saggar (MCh)
Neuro Surgeon / Spinal Surgeon
Chandigarh, Mohali -
Ivy Hospital Sector 71
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