Intramedullary spinal cord Tumors

Intramedullary tumors are the tumors which are present in the spinal cord, i.e., inside the pial covering and substance of the spinal cord itself.

This diagram explains the location of the intramedullay tumors. Piamater is the innermost of three meninges ( Duramater, Arachnoid and Piamater). It covers the spinal cord. So the tumors outside of it may be IDEM ( intradural extramedullary) or extradural lesions. 

Spinal tumors are are classified as

 (1) extradural,

(2) intradural extramedullary, and

 (3) intradural intramedullary.

Extradural tumors are the most common spinal tumors and are usually of metastatic origin. 

Intradural Extramedullary (IDEM) tumors are mainly neurofibroma and meningioma.

Intradural intramedullary lesions comprise 20 to 30% of all primary spinal cord tumors.

Gliomas make up 80% of all intramedullary tumors. The gliomas are further subdivided into astrocytomas (60 to 70%) and ependymomas (30 to 40%). Hemangioblastomas are the third most frequent intramedullary spinal cord (IMSC) tumors, comprising 2 to 15% of all intramedullary tumors. Metastatic intramedullary tumors are rare but present in 2% of all intramedullary tumors. Lipomas are commonly associated with spinal dysraphism.

Intramedullary tumors constitute about 35-40% of all intraspinal tumors in children. In children intramedullary tumors are mainly developmental in origin, like dermoid, lipoma and epidermoid). In adults intramedullary tumors may arise later in life, like astrocytoma, ependymoma and hemangioblastoma.

Gliomatous and nongliomatous tumors constitute 90 and 10% respectively.

In 75% cases, the astrocytmas extend over 4 or less 4 vertebral segments. In some cases the lesions extends throughout the spinal cord, for example holocord astrocytomas.

Half of the central nervous system ependymomas are located in the spinal cord and, of these, 50% are located in the filum terminale. The next common site is the cervical cord.

Glioblastomas are not common.

Hemangioblastoms are rare, consist of less than 2% of primary spinal cord tumors.

Clinical presentation depends upon the site and size of the lesion.

MRI of spine with contrast is the investigation of choice.

                                  Intraoperative image of my adult patient where tumor is seen after posterior midline myelotomy. Histopathology of the tumor was suggestive of Pilocytic astrocytoma ( WHO grade 1 tumor)

The operating microscope, bipolar coagulators, intraoperative physiological monitoring ( somatosensory evoked potenial monitoring, motor evoked potential ) , microscissors, microdissectors, small tumor holding forceps, Cavitron Ultrasonic Surgical Aspirators (CUSA) , intraoperative USG ( Ultrasonography) are good for safe excision of intramedullary lesions.

References

Samartzis D, Gillis CC, Shih P, O'Toole JE, Fessler RG. Intramedullary Spinal Cord Tumors: Part I-Epidemiology, Pathophysiology, and Diagnosis. Global Spine J. 2015;5(5):425-35. And references as numbered below

Mechtler L L, Nandigam K. Spinal cord tumors: new views and future directions. Neurol Clin. 2013;31(1):241–268.

Grimm S, Chamberlain M C. Adult primary spinal cord tumors. Expert Rev Neurother. 2009;9(10):1487–1495.

DeSousa A L, Kalsbeck J E, Mealey J Jr, Campbell R L, Hockey A. Intraspinal tumors in children. A review of 81 cases. J Neurosurg. 1979;51(4):437–445.

Mandigo C E, Ogden A T, Angevine P D, McCormick P C. Operative management of spinal hemangioblastoma. Neurosurgery. 2009;65(6):1166–1177.

Ravi Ramamurthy. Spinal Intramedullary Tumours. Chapter 130, Volume 2, in Textbook of Operative Neurosurgery, B.I Publications Tvt Ltd, New Delhi, Pages1107-1113.