Intermediolateral nucleus

The intermediolateral nucleus (IML) is a column of neurons found in the lateral horn of the spinal cord's gray matter. It is primarily located in the thoracic and upper lumbar segments (T1 to L2) of the spinal cord. The IML is a critical component of the autonomic nervous system, specifically the sympathetic nervous system.

Structure

The intermediolateral nucleus is situated in the lateral horn of the spinal cord, which is a small lateral projection of the gray matter. The gray matter of the spinal cord is organized into three main columns: the dorsal horn, the ventral horn, and the lateral horn. The IML is found in the lateral horn and is composed of preganglionic sympathetic neurons.

Function

The primary function of the intermediolateral nucleus is to serve as the origin of the preganglionic sympathetic fibers. These fibers exit the spinal cord through the ventral roots and synapse in the sympathetic ganglia located in the sympathetic trunk. From there, postganglionic fibers extend to various target organs, where they exert their effects, such as increasing heart rate, dilating bronchi, and inhibiting gastrointestinal motility.

Clinical significance

Damage to the intermediolateral nucleus can result in a loss of sympathetic function, which may manifest as Horner's syndrome, characterized by ptosis, miosis, and anhidrosis. Additionally, lesions affecting the IML can lead to autonomic dysreflexia, a condition often seen in individuals with spinal cord injuries above the T6 level.

Also see

• Sympathetic nervous system
• Spinal cord
• Autonomic nervous system
• Gray matter