T4 spinal nerve

Nervus spinalis T4

NervousNervesThoraxLeft and right

View left in 3D View right in 3D

What it is
The T4 spinal nerve leaves the spinal canal between T4 and T5. Its sensory (dorsal) and motor (ventral) roots meet just beyond the dorsal root ganglion; the short mixed nerve then splits into a small dorsal ramus for the back muscles and skin and a larger ventral ramus, which becomes the 4th intercostal nerve.
Function
Carries motor fibres to the muscles of its segment (myotome) and sensation back from its strip of skin (dermatome): a band of skin around the chest at the level of the nipples.
Size
About 2-3 mm thick; the mixed nerve is only ~1 cm long before it divides
Clinical note
T4 at the nipple is the classic landmark for mapping the sensory level of a spinal cord injury.

Nearby nervous structures 1st intercostal nerve, 3rd intercostal nerve, T1 spinal nerve, T2 spinal nerve, T3 spinal nerve, T5 spinal nerve, T6 dorsal root ganglion, T6 spinal nerve, T7 spinal nerve, T8 spinal nerve