What does 'intramedullary' mean for a spinal tumour?

It means the tumour arises within the spinal cord tissue itself, as opposed to extramedullary tumours that grow alongside the cord inside the dura or extradural tumours outside the dura; the distinction is fundamental to imaging interpretation and surgical approach.

Why does tumour type matter for these lesions?

Because growth pattern differs by histology: well-demarcated tumours such as many ependymomas tend to have a definable interface with the cord, whereas infiltrating astrocytomas characteristically blend into surrounding tissue, a contrast that strongly influences how the lesions are studied and managed.

Intramedullary Spinal Tumor

An intramedullary spinal tumor is a neoplasm that arises within the substance of the spinal cord itself, in contrast to tumours that grow outside the cord or within the dura. The most common types in adults are ependymomas and astrocytomas. Because the tumour is embedded in functioning neural tissue, its growth distorts and compresses the cord from within, and its histology shapes how surgically separable it is.

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Definition

An intramedullary spinal tumor is a neoplasm originating within the parenchyma of the spinal cord, most commonly an ependymoma or astrocytoma, that expands and damages the cord from within.

Scope

The topic covers the defining intramedullary location, the principal tumour types and how their growth pattern relates to surgical separability, the typical insidious presentation, and the role of imaging and histopathological classification. It treats the subject as a reference orientation within spinal cord pathology and does not specify surgical indications, extent-of-resection goals, or adjuvant therapy.

Core questions

What distinguishes intramedullary tumours from extramedullary and extradural spinal tumours?
How do ependymomas and astrocytomas differ in growth pattern and surgical separability?
Why is the typical presentation insidious, and how does imaging characterise these lesions?
How does histopathological classification inform their study?

Key concepts

Intramedullary versus extramedullary location
Ependymoma
Astrocytoma
Cleavage plane and surgical separability
Associated syrinx or cyst
Gadolinium enhancement on MRI
WHO CNS tumour classification

Mechanisms

An intramedullary tumour grows within the cord parenchyma, expanding it and disrupting ascending and descending tracts as well as central grey matter, often with an associated cyst or syrinx above or below the solid component. Ependymomas, which typically arise centrally and are relatively well demarcated, tend to present a recognisable cleavage plane from surrounding cord, whereas infiltrating astrocytomas characteristically lack such a plane (McCormick, 1990). This difference in growth pattern is central to how the lesions are conceptualised, and the tumour's histological type, defined within the WHO classification of central nervous system tumours, anchors prognosis and study (Louis, 2021).

Clinical relevance

Intramedullary tumours are an important cause of intrinsic, progressive cord dysfunction, and understanding the contrast between well-demarcated and infiltrating lesions underpins critical reading of the surgical and oncological literature. This entry is a reference description and is not a basis for individual diagnosis, surgical decision-making, or treatment selection, which rest with treating clinicians.

Epidemiology

Intramedullary tumours are uncommon and represent a minority of spinal tumours overall; in adults ependymomas and astrocytomas predominate, while the relative frequency differs in children (McCormick, 1990). Detailed incidence figures by type and age are not summarised here.

History

Surgery within the spinal cord substance was long considered hazardous, but improvements in microsurgical technique, intraoperative monitoring, and magnetic resonance imaging made resection of well-demarcated intramedullary tumours feasible. McCormick and colleagues' work on intramedullary ependymoma helped define the contrast between separable and infiltrating lesions, and evolving WHO classifications have refined how these tumours are categorised (McCormick, 1990; Louis, 2021).

Key figures

Paul McCormick
Bennett Stein
David Louis

Seminal works

mccormick-1990

Frequently asked questions

What does 'intramedullary' mean for a spinal tumour?: It means the tumour arises within the spinal cord tissue itself, as opposed to extramedullary tumours that grow alongside the cord inside the dura or extradural tumours outside the dura; the distinction is fundamental to imaging interpretation and surgical approach.
Why does tumour type matter for these lesions?: Because growth pattern differs by histology: well-demarcated tumours such as many ependymomas tend to have a definable interface with the cord, whereas infiltrating astrocytomas characteristically blend into surrounding tissue, a contrast that strongly influences how the lesions are studied and managed.