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Spinal Cord Tumors
The most common spinal cord tumors are metastatic extradural lesions most commonly occurring in patients with already identified systemic cancers. Their presentation is often relatively acute, usually associated with focal back and/or radicular pain. On occasion, these lesions are the initial clinical manifestation of a heretofore unsuspected systemic malignancy. In contrast, primary intradural spinal cord tumors occur infrequently; typically their presentation is a relatively subtle one, ingravescent in temporal profile. Spinal cord and spinal column tumors are best classified within two categories: extradural, occurring outside of the dura, and intradural, contained within the dura mater ( Table 50.1 ; Fig. 50.1 ).
TABLE 50.1
Classification of Magnetic Resonance Imaging Abnormalities a
| Extradural Extramedullary | Intradural Extramedullary | Intradural Intramedullary |
|---|---|---|
| Intervertebral disc disease | Neurinoma | Syringomyelia |
| Metastasis | Meningioma | Ependymoma |
| Lymphoma | Ependymoma | Glioma |
| Sarcoma | Medulloblastoma | Hemangioblastoma |
| Plasmacytoma | Cauda equina lesions | Myelitis |
| Primary bone tumor | Scarring | Edema |
| Scarring | Hypertrophic neuropathy | Lipoma |
| Abscess | Lymphoma | Abscess |
| Hemangioma | Metastasis | Hematoma |
| Hemorrhage | Hemangioblastoma | Varix with arteriovenous malformation |
| Neurilemmoma | Lipoma | Lymphoma |
| Chordoma | Dermoid | Neuroblastoma |
| Epidermoid cyst | Metastasis | |
| Hemorrhage |
a Dermoid or epidermoid, teratoma, lipoma, and cysts are often associated with spinal dysraphism. In this setting, many tumors are intradural, although they may involve all three areas.
Classification of Spinal Tumors.
Intradural tumors are further categorized as extramedullary or intramedullary, depending on their relationship to the spinal cord. Intradural extramedullary tumors, usually meningiomas or schwannomas, arise outside the spinal cord parenchyma. These are initially clinically silent; however, with time these tumors surreptitiously enlarge. Once a critical mass is reached, spinal cord compression occurs and symptoms develop. In contrast, intradural intramedullary tumors, such as gliomas and ependymomas, originate within parenchyma of the spinal cord. As these intramedullary malignancies primarily expand, important neurologic pathways and cell populations are subsequently compromised and eventually destroyed.
Extradural tumors generally are derived from metastatic lesions to vertebral bodies with extension into the epidural space, causing external compression of the thecal sac and its contents. Primary bony vertebral tumors also occur, both malignant (i.e., myeloma) and benign (i.e., hemangioma or osteoid osteoma).
Extradural Spinal Tumors
Clinical Vignette
A 62-year-old postal carrier presented with midthoracic pain, rapidly progressive weakness and numbness in both legs and difficulty initiating his urine stream. During the preceding 6 weeks, he intermittently awakened with midthoracic vertebral pain that increasingly radiated to his epigastrium. This was particularly precipitated by lifting, bending, or straining at stool. An initial gastrointestinal evaluation was normal. Twenty-four hours before admission, he began to experience progressive difficulty standing, walking, and voiding. The morning of this evaluation, he was unable to get out of bed on his own and was totally unable to void. During the past 3 months, he had noted an increasingly irritating cough; he was a 60-pack-year smoker.
Neurologic examination demonstrated a T9 “cord level” to both pinprick and temperature. Muscle stretch reflexes were absent at the knees and ankles, and plantar stimulation was flexor. There was mild tenderness to palpation over the lower thoracic spine. He became incontinent of urine. Rectal sphincter tone was reduced.
Spinal radiographs revealed destruction of the T9 vertebral body. Magnetic resonance imaging (MRI) demonstrated a soft tissue mass involving most of the T9 vertebral body, extending into the pedicle, with epidural extension of the tumor into the spinal canal leading to marked compression of the spinal cord. Immediate dexamethasone therapy and subsequent radiation therapy were unsuccessful in reversing his clinical course. Chest radiograph ( Fig. 50.2 ) demonstrated a left main stem bronchus tumor that on biopsy proved to be a primary small cell lung cancer.
Spinal neoplasms are predominantly secondary to metastatic cancer. This occurs in up to one-third of cancer patients. Lung, breast, prostate, and lymphoma are the most common metastatic lesions leading to spinal cord compression.
Clinical Presentation
Severe focal vertebral pain is frequently the presenting symptom of a metastatic spinal cancer (see Fig. 50.2 ). Unfortunately, back pain is such a ubiquitous complaint that the serious nature of a newly occurring pain is often not appreciated even when there is no history of recent trauma. Sometimes, it is difficult to distinguish pain of a metastatic spinal tumor from the much more common mechanical, degenerative, or osteoarthritic musculoskeletal lower back and/or nerve root disorders. However, pain of metastatic spinal cancer origin is often persistent, frequently unrelated to posture, and tends to increase at night. In contrast to more common mechanical back pain, this pain can be of more recent origin.
Progressive neurologic symptoms often vary and are related to the precise level of spinal column involvement; typically the temporal profile is relatively rapid. Tumors at the cervical and thoracic spinal cord levels present with progressive weakness, numbness, and sphincter dysfunction at levels below the tumor. Sphincter difficulties are nonspecific symptoms per se that may develop with tumors at any spinal level. On occasion, bladder and bowel dysfunction per se may be the initial presenting symptom related to a conus medullaris tumor at the distal tip of the spinal cord. The essential message is that whenever sphincter problems develop in a patient with a known cancer, one needs to be alert to the potential of a spinal metastasis. Examination usually reveals hyperreflexia, Babinski signs, and other long tract signs at spinal levels below the tumor involvement.
When evaluating patients with recent-onset sphincter difficulties and suspicion for a metastatic lesion, it is important to recognize that differentiation of conus medullaris lesions at the spinal cord tip versus those within the cauda equina may be difficult. Classically when the clinical findings are symmetric and relatively equally involving both lower extremities, the conus medullaris is much more likely the site of the specific pathology. In contrast, cauda equina lesions often lead to an asymmetric distribution of signs and symptoms because not all nerve roots within the cauda equina are equally affected.
Typically, the course of extradural metastatic spinal tumors is more rapid than intradural tumors. It is not unusual for these lesions to have an almost precipitous onset, often producing rapidly evolving motor and sensory deficits within just a few hours to a day or so ( Fig. 50.3 ). A prior diagnosis of either a cancer or a lymphoma will alert the astute clinician to the precise pathophysiologic nature of the spinal lesion. However, occasionally a spinal metastasis may be the initial presentation of a metastatic malignancy.
Diagnostic Approach
MRI is the standard for evaluating potential metastatic spine lesions, especially those with evolving cord compression. When an MRI is contraindicated, such as with a patient who has a pacemaker, computed tomography (CT) myelogram is still indicated and potentially diagnostic. An initial preliminary spinal tap is best avoided in these patients because it can change pressure dynamics when there is an obstructing focal cord lesion. If a spinal tap is performed, this study can precipitate a rapid worsening of the patient's neurologic deficits.
If a primary cancer has not been previously found, a histologic diagnosis becomes mandatory to confirm the nature of the lesion. In some instances, there is a primary bony malignancy such as multiple myeloma originating within the vertebrae ( Fig. 50.4 ). Currently, percutaneous CT-guided needle biopsy is often the most useful procedure if no primary is immediately apparent, such as occurred in this chapter's opening vignette, where a routine chest radiograph led to a diagnostic lung biopsy. When there is no evidence of a primary lesion identified on body CT, an image-guided biopsy by interventional radiology or an open surgical procedure, such as neurosurgical spinal cord decompression with a conjoint biopsy, is very important.
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