Intramedullary spinal cord lesions occur within the spinal cord itself while extramedullary lesions occur outside the spinal cord. Intramedullary lesions typically cause symmetrical symptoms that affect motor and sensory functions diffusely down the spinal cord, often with early sphincter involvement. In contrast, extramedullary lesions usually cause asymmetrical symptoms, with local or radicular pain and early upper motor neuron signs but later lower motor neuron signs and sensory involvement in the affected segment.

1. Intramedullary vs extramedullary spinal
cord lesions
By Dr. Yagnik Chhotala

3. SYSTEM FEATURES EXTRAMEDULLAR
Y
INTRAMEDULLAR
Y
HISTORY Onset Asymmetrical Symmetrical
Pain Local or vertebral
(extradural)
Radicular
(intradural)
Funicular or tract
pain
MOTOR UMN signs early late
LMN signs segmental diffuse
SENSORY Sensory
involvement
Ascending (sacral
involvement)
Descending (sacral
sparing)
Dissociated sensory
loss
absent present
AUTONOMIC Sphincter
involvement
late early

4. Spinal lesions above conus either
extramedullary or intramedullary tend to be
associated with sphincter distrubances only with
extensive bilateral damage