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Intramedullary Spinal Cord Lesions


Summary of Key Points

  • Intramedullary lesions of the spinal cord encompass a wide range of histopathology. The majority of these lesions are benign and amenable to surgical resection.

  • Unlike primary intracranial tumors, most intramedullary spinal cord tumors are histologically benign and do not demonstrate progressive anaplasia.

  • The primary goal of surgery for intramedullary tumors is long-term tumor control or cure with preservation of neurological function.

  • Midline myelotomy through the posterior median septum provides safe access for the removal of most intramedullary glial tumors.

  • Virtually all patients will note some posterior column neurological deficit following posterior midline myelotomy.

  • Most hemangioblastomas arise from the pia and present with both an exophytic and an intramedullary component. Circumferential detachment of the pial origin is the key to safe removal of these highly vascular lesions.

  • Radiation therapy is of uncertain value for benign intramedullary tumors. It is usually considered when only limited resection of an intramedullary tumor is possible.

  • Sensitivity of spinal cord imaging with magnetic resonance imaging (MRI) exceeds specificity in the identification of intramedullary pathology. Many incidental tumors, as well as intrinsic, nonsurgical conditions affecting the spinal cord, are increasingly identified on MRI and can present a challenge in differential diagnosis and surgical indications.

The vast majority of intramedullary tumors are histologically benign and biologically indolent, with limited tendencies for marginal infiltration into surrounding spinal cord tissue. Long-term tumor control or cure, with preservation of neurological function, can be achieved in most patients with microsurgical removal alone. , , , The benign nature of most intramedullary neoplasms, advances in microsurgical techniques, early clinical diagnosis with magnetic resonance imaging (MRI), and the ineffectual or inconsistent treatment response of most intramedullary tumors to radiation therapy largely account for the expanded role of surgery in the management of these lesions. , , , Therefore optimization of surgical treatment is the key to successful management of patients with intramedullary masses. This includes early diagnosis and aggressive primary treatment, the avoidance of technical and judgmental errors and their associated complications, and a strict adherence to contemporary microsurgical technique.

Patient Evaluation

The predominant benefit of surgery for an intramedullary tumor is prophylactic. Preservation, rather than restoration, of neurological function is the most likely outcome after successful surgical treatment. In fact, significant improvement of a severe or longstanding preoperative neurological deficit rarely occurs after a technically successful surgical excision. Surgical morbidity is also greater in patients with more significant preoperative deficits. This creates a therapeutic irony in which the risk of surgery is actually less in patients with minimal or no objective neurological deficit. Thus, early clinical diagnosis and, if possible, definitive initial treatment are critical to the successful management of most intramedullary tumors. A therapeutic dilemma arises, however, in the asymptomatic patient in whom an incidental intramedullary spinal cord lesion has been discovered ( Fig. 49.1 ). A posterior column deficit is a common consequence of a dorsal median myelotomy; thus, some degree of neurological morbidity often accompanies even the most successful surgical removal. , In completely asymptomatic patients, therefore, observation with serial clinical and radiological follow-up may be an appropriate management strategy. This is also true for patients with conditions such as neurofibromatosis or von Hippel–Lindau disease. ,

Fig. 49.1, T1 contrast-enhanced magnetic resonance imaging (MRI) demonstrates a small, centrally-located, uniformly enhancing intramedullary tumor in a patient with mild neck pain and no neurological signs or symptoms. No surgery was recommended. Periodic clinical and MRI surveillance was performed.

Because of the slow growth rate of benign tumors and the availability of MRI, most patients with intramedullary tumors are diagnosed before the development of significant neurological deficit. Gadolinium-enhanced MRI is the procedure of choice for imaging and preoperative evaluation of an intramedullary tumor. Spinal cord enlargement and tumor enhancement are the characteristic findings ( Fig. 49.2 ). Cysts at the poles of the mass are often present. Ependymomas are usually symmetrically located and exhibit uniform tumor enhancement, whereas astrocytomas are associated with a more variable appearance with respect to tumor margins and enhancement patterns ( Fig. 49.3 ). Hemangioblastomas usually appear as intensely enhancing eccentric masses or nodules. There is often diffuse spinal cord enlargement that may extend a considerable distance from the tumor ( Fig. 49.4 ). The cause of this tumor enlargement is most likely vasogenic edema. Prediction of these tumor types on MRI appearance is often inaccurate, predominantly because of the variability of presentation on imaging, and is therefore avoided because it may unfairly influence the surgical objective.

Fig. 49.2, Gadolinium-enhanced sagittal magnetic resonance imaging shows an upper cervical intramedullary enhancing mass. Significant spinal cord enlargement is present over several spinal cord segments, although the solid tumor extends only from C2 to C5. A small rostral and a large caudal polar cyst account for the remainder of the spinal cord enlargement. At surgery, a benign ependymoma was totally removed.

Fig. 49.3, Gadolinium-enhanced sagittal ( A ) and ( B ) axial magnetic resonance imaging scans show a focal, uniformly enhancing intramedullary mass. Irregular tumor margins are apparent on the axial view. At surgery, a focal benign astrocytoma with infiltrating margins was radically, but subtotally, resected. An intraoperative photograph after tumor resection ( C ) demonstrates indistinct infiltrating tissue margins.

Fig. 49.4, A, Sagittal magnetic resonance imaging demonstrates a focal dorsal mass at the C2 level. Note diffuse spinal cord enlargement. B, An intraoperative photograph demonstrates an orange pia-based hemangioblastoma with associated epipial draining veins.

Patient Selection

Whereas early diagnosis is routinely achieved with gadolinium-enhanced MRI, the sensitivity of MRI has far exceeded its specificity. Acute inflammatory conditions or demyelinating conditions, such as multiple sclerosis or transverse myelitis, are exquisitely imaged with MRI. These are not surgical lesions, and biopsy for diagnosis usually reveals only a nonspecific inflammatory response. This rarely provides a specific diagnosis, a prognosis, or a treatment option. In most cases, patients with these conditions can be distinguished on the basis of clinical presentation and MRI appearance. These patients usually have symptoms of either acute or subacute onset of significant neurological deficit. MRI typically shows patchy or focal gadolinium enhancement that may be confined to the white matter ( Fig. 49.5 ). Spinal cord enlargement is subtle or, more likely, absent. In contrast, patients with benign intramedullary tumors usually experience a significant spinal cord enlargement with minimal, if any, objective neurological deficit. Thus a patient who shows symptoms of an acute or subacute onset of a significant neurological deficit in the absence of obvious spinal cord enlargement usually harbors a nonsurgical inflammatory lesion.

Fig. 49.5, Gadolinium-enhanced sagittal ( A ) and axial ( B ) magnetic resonance imaging scans in a patient with acute onset of significant neurological deficit demonstrate patchy white matter enhancement without spinal cord enlargement. The clinical presentation and radiographic appearance are consistent with transverse myelitis. Surgery is not indicated for this patient.

Obviously, there are exceptions. Malignant or hemorrhagic tumors may have a rapidly progressive or acute presentation in the absence of significant spinal cord enlargement. Conversely, chronic inflammatory or demyelinating conditions, such as sarcoidosis or multiple sclerosis, may have a more insidious or chronic progressive course that may mimic an intramedullary neoplasm ( Fig. 49.6 ). Surgical exploration for diagnostic biopsy may be required in some cases, but only after all other less invasive methods for diagnosis have been exhausted.

Fig. 49.6, T1 enhanced cervical magnetic resonance imaging in a patient with subacute, slowly progressive myelopathy shows an eccentric but well-defined, peripherally enhancing lesion with some enlargement. Biopsy revealed a nonspecific inflammatory process. The patient was ultimately diagnosed with multiple sclerosis (tumefactive multiple sclerosis).

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