Spinal Cord Anatomy
Describe the major sensory and motor pathways (including anatomy)
Spinal Cord Anatomy
The spinal cord in transverse section consists of a central section of grey matter containing neuronal cell bodies and synapses, and a peripheral section of white matter containing myelinated ascending and descending pathways. Important pathways are:
- Corticospinal tract
Motor function. Crosses at the brain stem.
- Dorsal column
Light touch and proprioception. Crosses at the brain stem.
Pain and temperature. Crosses within two vertebral segments.
Unconscious proprioception. Does not cross.
Spinal Cord Syndromes
Lesions to certain anatomical regions of the spinal cord produce a particular constellations of findings.
A complete transection results in loss of movement and sensation below the level of the lesion. Initially, paralysis is flaccid (and other signs, such as priapism, may be absent in this 'spinal shock' phase) becomes spastic after a few weeks. Bowel and bladder function is lost.
Lesions above T10 will result in impaired cough in the initial stage as the abdominal wall is unable to contract (intercostal muscle function may be impaired as well, but this is of less importance clinically).
Central Cord Syndrome
Central cord syndrome results in a flacid paralysis and loss of sensation of the upper limbs greater than the lower limbs.
Anterior Cord Syndrome
Anterior cord syndrome spares the dorsal columns only, therefore motor function and pain and temperature sensation are affected below the level of the lesion.
Hemisection of the cord results in:
- Ipsilateral loss of motor function below the level of the lesion
- Ipsilateral loss of light touch and proprioception below the level of the lesion
- Contralateral loss of pain and temperature sensation below the level of the lesion
- Ipsilateral loss of pain and temperature sensation at the level of the lesion
Cauda Equina syndrome results from compression of lumbosacral nerve roots below the level of the conus medullaris. It may produce a combination of UMN and LMN signs:
- Sacral sensory loss
- Asymmetric LMN weakness and atrophy
- Erectile dysfunction and inability to ejaculate
- Urinary retention and overflow incontinence
- Constipation and overflow incontinence
- Goldber S. Clinical Neuroanatomy Made Ridiculously Simple. 3rd Ed. Medmaster. 2005.
- McMinn, RMH. Last's Anatomy: Regional and Applied. 9th Ed. Elsevier. 2003.