Which spinal cord tract is responsible for transmitting crude touch, pressure, and temperature sensation and decussates within 1–2 segments of entry?

Explanation

## Spinothalamic Tract: Anatomy and Function **Key Point:** The spinothalamic tract (STT) is a crossed tract that carries crude touch, pain, and temperature sensation from the body to the thalamus and cortex. ### Anatomical Characteristics | Feature | Spinothalamic Tract | Dorsal Column–Medial Lemniscus | |---------|-------------------|------------------------------| | Sensation carried | Crude touch, pain, temperature | Fine/discriminative touch, vibration, proprioception | | First-order neuron synapse | Dorsal horn (within 1–2 segments) | Medulla (fasciculi gracilis/cuneatus) | | Decussation level | Spinal cord (ipsilateral dorsal horn) | Medulla (internal arcuate fibers) | | Pathway after crossing | Contralateral ventrolateral cord | Contralateral medial lemniscus | | Final destination | Contralateral VPL thalamus | Contralateral VPL thalamus | **High-Yield:** The STT decussates **within 1–2 segments of entry** at the spinal cord level, making it a **short-segment crossed tract**. This is why a unilateral spinal cord lesion at C5 causes loss of pain/temperature on the **contralateral side below C7** (the crossing occurs rostral to the lesion). ### Clinical Pearl **Syringomyelia** (central cord cavity) classically causes a **"cape-like" distribution** of pain/temperature loss over the shoulders and arms bilaterally, because the crossing spinothalamic fibers in the central cord are damaged first. **Mnemonic:** **STT = Short Tract Transverse** — it crosses early (within segments), carries crude sensation, and is located in the ventrolateral cord. [cite:Snell's Neuroanatomy Ch 4]