A 68-year-old woman from Mumbai presents with acute-onset right-sided weakness and loss of pain sensation on the left side of her body below the level of T10. Vibration and proprioception are normal bilaterally. Examination shows right lower limb hyperreflexia and Babinski sign, but left lower limb reflexes are normal. MRI spine shows an acute infarct in the right anterior spinal artery territory at T10. Which combination of tracts is damaged?

Explanation

## Clinical Syndrome Recognition This patient presents with **Brown-Séquard syndrome** (hemisection of spinal cord): | Finding | Side | Interpretation | |---------|------|----------------| | Weakness, hyperreflexia, Babinski | Right | Right-sided motor pathway damage | | Loss of pain/temperature | Left | Contralateral sensory pathway damage | | Preserved vibration/proprioception | Bilateral | Dorsal columns intact | ## Anatomical Basis of Brown-Séquard Syndrome ### Motor Loss (Ipsilateral to lesion) **Key Point:** The corticospinal tract decussates in the **medullary pyramids** (above the spinal cord). Therefore, a spinal cord lesion damages the **already-crossed fibers**, causing **ipsilateral weakness** below the lesion. - Right-sided lesion → right-sided corticospinal tract damage → **right-sided weakness** ### Sensory Loss (Contralateral to lesion) **Key Point:** The spinothalamic tract decussates **within 1–2 segments of entry** at the spinal cord level. A right-sided lesion damages the **crossing fibers** destined for the left side, causing **left-sided pain/temperature loss**. - Right-sided lesion → damages left-bound crossing STT fibers → **left-sided pain/temperature loss** ### Why Dorsal Columns Are Spared The dorsal columns decussate in the **medulla** (internal arcuate fibers), well above the spinal cord. A T10 lesion cannot damage them. ## Mnemonic: **BROWN-SÉQUARD = Motor Ipsilateral, Sensory Contralateral** **High-Yield:** - **Ipsilateral motor loss** = corticospinal tract (decussates in medulla) - **Contralateral pain/temperature loss** = spinothalamic tract (decussates at cord level) - **Preserved vibration/proprioception** = dorsal columns intact (decussate in medulla) **Clinical Pearl:** Brown-Séquard syndrome is rare in complete form but is the classic teaching example of understanding spinal cord anatomy. Anterior spinal artery infarction commonly produces this pattern because the ASA supplies the anterior 2/3 of the cord (motor and spinothalamic tracts) but spares the dorsal columns (supplied by posterior spinal arteries).