Tumor Medulla Spinalis

01Pathophysiology

Spinal cord neoplasms are broadly categorized by their anatomical relationship to the dura and the spinal cord itself, and this classification directly determines both the clinical presentation and the likely histology.

Extradural tumors are the most common spinal tumors overall and are almost always metastatic. Cancers of the lung, breast, prostate, kidney, and lymphoma reach the vertebral body through hematogenous spread via the Batson venous plexus, a valveless network of epidural veins that communicates with the systemic venous circulation. Once tumor seeds into the vertebral body, it can grow posteriorly into the epidural space and compress the spinal cord from outside the dura. This explains why the first symptom is typically localized back pain from periosteal stretching and vertebral destruction, followed later by myelopathic signs as the cord becomes compressed.

Intradural-extramedullary tumors arise within the dura but outside the cord parenchyma. The two classic examples are meningiomas (arising from arachnoid cap cells, most common in middle-aged women, typically thoracic) and schwannomas/neurofibromas (arising from Schwann cells of the dorsal nerve root). Because these tumors sit adjacent to the cord rather than within it, they compress one side of the cord first. This produces a Brown-Sequard pattern: ipsilateral upper motor neuron weakness and loss of proprioception/vibration below the lesion, with contralateral loss of pain and temperature sensation one to two levels below the lesion. This hemisection pattern is a high-yield exam clue that the lesion is extramedullary.

Intramedullary tumors grow within the cord substance itself. Ependymomas are the most common intramedullary tumor in adults and typically arise in the central canal region, while astrocytomas predominate in the pediatric population. Because these tumors begin centrally and expand outward, they first disrupt the anterior white commissure, where the spinothalamic fibers cross. This produces the classic cape-like (suspended) dissociated sensory loss: bilateral loss of pain and temperature in a dermatomal band at the level of the tumor, with preserved light touch and proprioception (carried in the posterior columns, which are affected later). As the tumor enlarges, it eventually compresses the corticospinal tracts and posterior columns, producing upper motor neuron weakness and loss of proprioception below the lesion.

The distinction between "pain worse at night or when lying down" and mechanical back pain is pathophysiologically important. Tumor-related pain worsens with recumbency because the epidural venous plexus engorges when supine, increasing pressure on already compressed neural structures. Mechanical pain, by contrast, worsens with activity and improves with rest. This single clinical detail is frequently the pivotal clue in a vignette.

02Classification and Clinical Manifestation

The concept of sacral sparing versus early sacral involvement is a commonly tested discriminator between intramedullary and extramedullary lesions. Because the spinothalamic tract is somatotopically organized with sacral fibers laminated most laterally (outermost), an external compression affects sacral fibers first (early sacral loss), while an internal expanding lesion affects sacral fibers last (sacral sparing).

03Diagnostic Workup

MRI with gadolinium is both the best initial test and the gold standard for spinal cord neoplasms. There is no separate "screening" and "confirmatory" test here; MRI accomplishes both. On the exam, the moment a vignette describes progressive neurological deficits with back pain, the next best step is always MRI of the spine. Ordering the scan of the entire spine is important because metastatic disease is frequently multifocal, and a single-level study may miss additional lesions that change management.

The imaging findings differ by compartment in characteristic ways. Extradural tumors show vertebral body destruction with an epidural soft tissue mass compressing the thecal sac. Intradural-extramedullary tumors appear as well-defined, homogeneously enhancing masses with a meniscus sign (CSF capping above and below the mass) and displacement of the cord to the opposite side. Intramedullary tumors show fusiform expansion of the cord itself, with variable enhancement and frequently an associated syrinx (fluid-filled cavity within the cord).

On plain films, the "winking owl" sign describes loss of a pedicle shadow on anteroposterior view, resulting from metastatic destruction. This is a classic radiographic finding but has low sensitivity compared to MRI.

If the clinical picture strongly suggests metastatic disease, the workup should also include CT of the chest, abdomen, and pelvis to find the primary tumor, along with relevant tumor markers (PSA for prostate, etc.). Lumbar puncture is generally avoided when there is a complete spinal block because of the risk of neurological deterioration from shifting pressure gradients.

04Management and Treatment

Acute management of suspected spinal cord compression is time-sensitive. The single most important initial step is dexamethasone, which reduces peritumoral vasogenic edema and can temporarily halt or reverse neurological decline. This should be given immediately, even before imaging is completed, if clinical suspicion is high. Dexamethasone is the "next best step" answer whenever a vignette describes acute or subacute cord compression with neurological deficits.

For metastatic epidural cord compression, the landmark Patchell trial established that surgical decompression followed by radiation is superior to radiation alone in patients who are surgical candidates with a single area of compression, an expected survival of at least 3 months, and who are not completely paraplegic for more than 48 hours. However, radiation alone remains the standard approach for patients with radiosensitive tumors (lymphoma, myeloma, small cell lung cancer), those who are poor surgical candidates, or those with multilevel disease.

For primary spinal cord tumors, surgery is the mainstay. The key teaching point is the difference between ependymoma and astrocytoma: ependymomas are well-demarcated with a clear cleavage plane, making gross total resection feasible and often curative, while astrocytomas are infiltrative and rarely fully resectable, necessitating adjuvant radiation.

Contraindications and cautions: Prolonged high-dose corticosteroids carry risks of hyperglycemia, immunosuppression, gastric ulceration (prophylax with a proton pump inhibitor), and proximal myopathy. In patients with diabetes, blood glucose must be monitored closely. Radiation carries a risk of radiation myelopathy, which is a delayed (months to years) progressive myelopathy that can mimic tumor recurrence.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students get questions on spinal cord neoplasms wrong is by failing to recognize the compartment-based logic that governs this topic. Exam questions are not simply asking "is there a spinal cord tumor?" They are testing whether you can determine where the tumor is based on the neurological examination pattern, and then match it to the correct tumor type.

The first trap involves confusing intramedullary and extramedullary presentations. If a vignette describes sacral sparing with a cape-like sensory deficit, the tumor is intramedullary. If the vignette describes early sacral loss with a Brown-Sequard pattern, it is extramedullary. Selecting the wrong compartment leads you to the wrong tumor type and wrong management.

The second trap is the "pain worse at night" clue. Students who have drilled mechanical back pain differentials may dismiss night pain as a red flag without connecting it to neoplasm. On the exam, back pain that is worse at night, unrelieved by rest, progressive over weeks, and accompanied by weight loss or a history of cancer should immediately trigger concern for metastatic cord compression, and the next step is always MRI, not conservative management or physical therapy.

A third trap is ordering the wrong imaging study. Plain radiographs and CT scans are insufficient to evaluate the spinal cord itself. A vignette may tempt you with a plain film showing a normal-appearing spine (intradural tumors cause no bony changes), leading you to falsely reassure the patient. The correct answer is always MRI with gadolinium when myelopathy is suspected.

Finally, students frequently forget that dexamethasone is the immediate first step in acute cord compression, even before arranging definitive imaging. The vignette may present an oncology patient with rapidly progressive leg weakness and a sensory level, and ask for the "next best step." The answer is dexamethasone, not MRI, not radiation, not surgery. Imaging follows immediately afterward, but the steroid is given first to halt ongoing cord injury from edema.

The core competency tested across all spinal cord neoplasm questions is the ability to localize the lesion based on clinical findings, select the appropriate imaging, and initiate time-sensitive treatment for cord compression.