Spinal cord

Function

The spinal cord is the body's trunk cable: 42–45 cm of nervous tissue running from the medulla to L1, ensheathed in dura and suspended in CSF. Thirty-one pairs of spinal nerves branch off it, each serving a dermatome and myotome — the segmental map clinicians use to localise lesions.

Butterfly-grey central matter houses sensory and motor neurons; surrounding white matter carries ascending columns (pain in the spinothalamic tracts, touch and position in the dorsal columns) and descending corticospinal pathways. The cord ends as the conus medullaris at L1–L2 — below it, the cauda equina of nerve roots floats freely, making lumbar puncture safe at L3–L4.

Blood supply

Anterior spinal artery (two-thirds) and paired posterior spinal arteries; segmental medullary reinforcements.

Nerve supply

Thirty-one spinal nerve pairs; sympathetic chain lateral to it.

Clinical relevance

Cord compression

Tumour, disc or abscess compressing the cord demands emergency MRI and decompression — hours decide whether a patient walks.

Brown–Sequard syndrome

Hemisection of the cord causes ipsilateral paralysis and loss of position, with contralateral pain loss — the anatomy teaching classic.

Related conditions

• Multiple sclerosis
• Meningitis
• Motor neurone disease (ALS)