A myelopathy is a disorder of the spinal cord. Such disorders may be further characterized according to whether the responsible lesion lies within or outside the spinal cord: intrinsic or intramedullary lesions are always intradural; extrinsic or extramedullary lesions may be intradural or extradural. It may be possible to differentiate intramedullary from extramedullary lesions on clinical grounds, although this distinction is never absolute because of clinical overlap.
- Clinical features of extrinsic/extramedullary myelopathy:
Motor: sequential spastic paraparesis below the level of the lesion; upper motor neurone (UMN) signs occur early; lower motor neurone (LMN) signs are unusual and have a segmental (radicular) distribution if present
Sensory: symptoms of pain may be radicular (e.g., secondary to a neurofibroma) or vertebral (e.g., secondary to neoplastic or inflammatory processes); sensory signs are not usually marked until the later stages, and all modalities are often involved. A Brown-Séquard syndrome may be commoner in extrinsic than intrinsic myelopathies
Sphincters: may have bladder urgency, impotence Pathologies commonly causing extrinsic myelopathy include:
Prolapsed disc, osteophyte bar Tumor (primary, secondary)
Arteriovenous malformation/hematoma Abscess
- Clinical features of intrinsic/intramedullary myelopathy:
Motor: LMN signs may be prominent and diffuse; UMN signs tend to occur late (spastic paraparesis below level of lesion). A combination of UMN and LMN signs is much more likely to reflect intrinsic than extrinsic pathology Sensory: symptoms of central (funicular) pain may occur; dissociated sensory loss (spinothalamic > dorsal column involvement, or vice versa), suspended sensory loss, and sacral sparing are characteristic of intramedullary lesions; a Brown-Séquard syndrome may occur. Vibratory sensibility is more often affected than proprioception
Sphincters: bladder involvement common, often early and slow to recover.
These features are dependent on the extent to which the cord is involved: some pathologies have a predilection for posterior columns, central cord, etc.
Pathologies commonly causing intrinsic myelopathy include: Multiple sclerosis or other inflammatory process causing trans
verse myelitis (complete or partial), e.g., viral infection, HTLV-1 infection, tabes dorsalis
Tumor (primary, secondary) Syringomyelia
Infarction, e.g., anterior spinal artery syndrome
Metabolic causes: vitamin B12 deficiency producing subacute combined degeneration of the cord.
Imaging of the cord, ideally with MRI, may be helpful in defining the cause of myelopathy.
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