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

Explanation

## Spinothalamic Tract: Anatomy and Function **Key Point:** The spinothalamic tract (STT) is a crossed (contralateral) pathway that transmits pain, temperature, and crude touch from the body to the thalamus and cerebral cortex. ### Decussation Pattern - **Level of crossing:** Crosses within 1–2 spinal segments of entry (at the spinal cord level) - **Contrast with dorsal columns:** Dorsal column fibres (fasciculus gracilis and cuneatus) ascend ipsilaterally for many segments before decussating in the medulla - This early decussation is clinically significant: a unilateral spinal cord lesion produces contralateral loss of pain and temperature below the level of injury ### Organization | Feature | Spinothalamic Tract | Dorsal Columns | | --- | --- | --- | | **Sensation** | Pain, temperature, crude touch | Fine touch, vibration, proprioception | | **Decussation** | 1–2 segments above entry | Medulla (internal arcuate fibres) | | **Crossing pattern** | Ipsilateral → contralateral | Ipsilateral → contralateral | | **Clinical sign** | Contralateral loss below lesion | Ipsilateral loss below lesion | **High-Yield:** In **Brown-Séquard syndrome** (hemisection of spinal cord), the spinothalamic tract lesion produces contralateral pain/temperature loss 1–2 levels below the injury, while dorsal column damage causes ipsilateral fine touch loss at the same level. **Mnemonic:** **STT = Spinothalamic = Thermal** (temperature) — remember this tract carries temperature sensation and crosses early. **Clinical Pearl:** Syringomyelia (fluid-filled cavity in cord) classically destroys crossing spinothalamic fibres first, producing a "cape-like" distribution of pain/temperature loss over the shoulders and arms (suspended sensory loss).