Spinal cord metastasis are rarely seen. Intramedullary spinal metastasis rate was determined as 0.9-2.1% throughout all the autopsies of the cancer cases. Intramedullary spinal metastasis are constitute 8,5% of all cases which have CNS metastasis
(3,5). The frequency of the intramedullary metastasis is 3,9% in the subsequent researches and its reason may be the invention of MRI and the current developments in cancer therapy
(10). The reason for the lower incidence of the intramedullary spinal metastasis may be related to the ignorance of the spinal cord examination through a rutin autopsy. On the other hand, brain metastasis have been found at a rate of approximately 20% in the cancer autopsies
(1).
It is believed that arterial invasion is the most common mechanism of the intramedullary spinal metastasis. Pulmonary lesions are nearly characteristic in both intracranial and intramedullary metastasis(7). The difference between brain metastasis and intramedullary metastasis can be explained with the difference of arterial blood flow and venous drainage between the brain and spinal cord(4,17). The intradural invasion can be occured by direct invasion of the dorsal root or as a result of venous invasion by Batson plexus(2). Another way in invasion can be seen by perineural lymphatic channel in spinal nerve roots and transdural invasion(15,21).
The most frequent origin of the intramedullary spinal cord metastasis are lung cancers and especially the small cell carcinoma(2,7,16). The other types with smaller rates of frequency are, breast cancer, melanoma, renal cell carcinoma and lymphoma(2,7). Colorectal adenocarcinoma originated intramedullary spinal cord metastases are rarely seen and have been reported for only 9 times in the English literature(11,16-18,22). Colorectal adenocarcinoma originated intramedullary spinal cord metastases are seen at a rate of 3%(5). In a recent research, the spinal levels of the cases occurred metastasis on spinal cord are 42% for cervical, 26% for throracic and 32% for lumbar segments(12). Radiotherapy and chemotherapy are not indicated for these patients. Only three of previously reported patients were operated others were refused the therapy and died after a short time period from diagnosis.
The exact diagnosis can be difficult even the primer tumor is known because clinic findings cannot help separating intramedullary spinal cord metastasis from paraneoplastic necrotizing myelopathy. The possibility of the occurrence of the intramedullary spinal cord metastasis should be keep in mind a patient with neurological deficit which has a malign tumor. The occurrence of neurological deficit, remind us the possibility of a spinal tumor in this case. The fast progress of the symptoms helps to separate intramedullary spinal cord metastasis from primer intramedullary tumors. The symptoms of the primer intramedullary tumors slowly develops because the growing of the tumor is tended to be slow. But in the metastasis cases, the tumor rapidly grows and the symptoms develop accordingly(2,16). The symptoms in the presented case were rapidly developed. The period between the beginning of first symptoms and the development of the neurological deficits is less than one month in the ¾ of the reported patients(7).
If a spinal lesion is suspected in patients which have malignancy history, spinal MRI with gadolinium should be taken. Epidural or intradural lesions can be defined by MRI. Intradural extramedullary tumors are generally compresses the epidural adipose tissue or make expansion in the subarachnoidal region and compresses the spinal cord(13). Bening neoplasms are generally expanded the intervertebral foramen. Tumor is usually more isointense than the spinal cord in the T1 dominated metastasic cases and nodular involvement is seen after the contrast material. Intramedullary spinal cord lesions cause expansion in the spinal cord. If there exists a cystic formation it gives a different signal from BOS or primer neoplasm. The edema in the hyperintensity area can be evaluated in the T2-weighted MRI in metastasic neoplasms(6). Many authors recommended radiotherapy for the intramedullary spinal cord metastasis(4,7). The surgical removal of the tumor has been rarely taken into consideration. Tumor metastasis giving positive replies to the radiotherapy like lymphoma, breast cancer, and small cell carcinoma.. A great majority of the tumors in the former series consisted of these type of tumors. 5 years life expectancy is 8% for the colon cancer patients in terminal period(14). If there exist intramedullary spinal cord metastasis besides colon cancer, the life span of these patients rejecting the therapy is less than 1 month(19). Some authors also believes that radiotherapy, chemotherapy and surgical therapy does not provide a benefit in the patients with intramedullary spinal cord metastasis(9). But in our case, early diagnosis and the removal of the tumor with the appropriate microsurgical technique improved the life quality and prognosis. As intracranial metastasis, intramedullary spinal cord metastasis also provides possibility for the gross total removal by giving clivage from peripheral tissue(2,5). Hammerberg determined 74% neurological improvement in the cases which have spinal metastasis after surgery with development in the patient's life quality(8). The first option should be the removal of the tumor with microsurgical technique in the patients with unifocal intramedullary metastasis which are resistant to radiotherapy. More comfortable and trustable facilities have been provided to the surgeon due to the developments in instrumentation and stabilization.
In this case conus medullaris located tumor was removed totally with microneurosurgical technique. Because extensive total laminectomy was applied during the surgery, long segment posterior fixation and posterior fusion were added to surgery.
We are presenting colorectal adenocarcinoma originated metastasis to the conus medullaris for the first time in the literature with this case.
Received by: 06 September 2011
Revised by: 09 January 2012
Accepted: 10 April 2012
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