Thoracic Spinal Nerves

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Introduction

The thoracic spine has 12 nerve roots (T1 to T12) on each side of the spine that branch from the spinal cord and control motor and sensory signals mostly for the upper back, chest, and abdomen.

Each thoracic spinal nerve is named for the vertebra above it. eg the T4 nerve root runs between the T4 vertebra and T5 vertebra.

There are 12 thoracic spinal nerve root pairs (two at each thoracic vertebral level), starting at vertebral level T1-T2 and going down to T12-L1.

Function

• Each thoracic nerve root exits the spinal canal through an intervertebral foramen (formed by two adjacent vertebrae, and its size and shape can slightly shift as the vertebrae move).
• After branching from the spinal cord and traveling through the foramen, a thoracic nerve root branches into two different nerve bundles that feed into the rami ie ventral ramus and dorsal ramus.

At the T1 through T11 levels:

• Ventral ramus eventually becomes an intercostal nerve that travels along the same path as the ribs (specifically between the innermost and internal intercostal muscles that connect adjacent ribs). At T12, the ventral ramus becomes a subcostal nerve that travels beneath the twelfth rib.
• Dorsal ramus go into the back muscles and also provides sensation to the skin.

The motor and sensory functions provided by a thoracic nerve root are determined by its vertebral level. These functions can slightly vary from person to person but typically are as follows:

• T1 and T2 (top two thoracic nerves) feed into nerves that go into the top of the chest as well as into the arm and hand.
• T3, T4, and T5 feed into the chest wall and aid in breathing.
• T6, T7, and T8 can feed into the chest and/or down into the abdomen.
• T9, T10, T11, and T12 can feed into the abdomen and/or lower in the back