Trunk nerves (intercostal, sympathetic, vagus nerve)
Lateral intermediate substance of the spinal cord
Substantia intermedia lateralis
- Origin
- Grey matter between the anterior and posterior horn, bulging laterally as the lateral horn (cornu laterale) from T1 to L2 and appearing again in S2-S4
- Insertion
- The preganglionic fibres leave the cord through the anterior root: sympathetic to the sympathetic trunk, parasympathetic (S2-S4) to the pelvic splanchnic nerves
- Function
- Autonomic nucleus of the spinal cord: origin of the preganglionic sympathetic neurons (intermediolateral nucleus, T1-L2) and of the sacral parasympathetic neurons (S2-S4)
- Innervation
- Visceromotor, that is autonomic
- Movement & chain
- Drives vascular tone, sweating, pupil size and the function of bladder, bowel and genitals
- Palpation
- Not palpable; assessed through autonomic functions such as blood pressure regulation, sweating pattern, bladder function and pupillary reactions
- Clinical
- Horner syndrome when the ciliospinal centre fails (C8-T2: ptosis, miosis, anhidrosis), neurogenic bladder and bowel dysfunction in a lesion above or within the sacral micturition centre, and autonomic dysreflexia in lesions above T6, where a stimulus below the level triggers an unopposed sympathetic discharge with hypertension and pounding headache.
- Segmental innervation
- Sympathetic T1-L2, parasympathetic S2-S4
- In clinical practice
- Bladder and bowel training in a neurogenic bladder, blood pressure monitoring and immediate action in autonomic dysreflexia (sit the patient up and find the stimulus below the level), and watching for orthostatic hypotension
- Region in the model
- Trunk nerves (intercostal, sympathetic, vagus nerve)