Lateral Horn

cornu laterale medullae spinalis

The lateral horn is a small pointed projection of grey matter between the dorsal and ventral horns, present from T1 to L2. It contains the preganglionic sympathetic neurons (intermediolateral cell column), the starting point of the whole sympathetic nervous system. A similar but less visible column at S2-S4 holds the sacral parasympathetic neurons.

Anatomical Data

Structure & Connections

Location	Lateral part of the intermediate grey matter of the thoracic and upper lumbar spinal cord (T1-L2)
Parts	Intermediolateral cell column (sympathetic preganglionic neurons) Sacral parasympathetic nucleus (S2-S4, in the equivalent position)
Connections	Ventral roots and white rami communicantes to the sympathetic chain Hypothalamus and brainstem (descending autonomic pathways) Adrenal medulla (via splanchnic nerves) Pelvic splanchnic nerves (sacral part)
Blood Supply	Anterior spinal artery; Segmental medullary arteries

Biomechanics

Function & Actions

Sends sympathetic signals controlling heart rate, blood pressure, sweating, pupil size and organ function.

Clinical Relevance

Clinical Notes

Damage to the upper thoracic lateral horn or the descending pathways to it causes Horner syndrome on the same side. Spinal cord injury above T6 disconnects the lateral horn from brain control, leading to autonomic dysreflexia, a dangerous rise in blood pressure triggered by stimuli below the injury, such as a full bladder.

Pathology

Common Injuries & Conditions

Autonomic Dysreflexia

A sudden severe rise in blood pressure with slow pulse and flushing above the injury in people with spinal cord injury at or above T6, triggered by stimuli below the lesion.

Horner Syndrome from Cord Lesion

Drooping eyelid, small pupil and reduced sweating on one side from damage to the T1 lateral horn or its descending input.

Explore

More in Spine

Browse all of Spine →