A 62-year-old woman from Tamil Nadu presents with acute onset of vertigo, nausea, vomiting, and loss of pain and temperature sensation over the left side of her face and right side of her body. On examination, she has left-sided Horner syndrome (miosis, ptosis, anhidrosis), nystagmus, and ataxia. MRI shows an acute infarct in the left lateral medulla. Which of the following structures are damaged in this classic brainstem syndrome?

Explanation

## Wallenberg Syndrome (Lateral Medullary Syndrome) **Key Point:** This is the **classic presentation of Wallenberg syndrome**, caused by infarction of the lateral medulla, typically from vertebral artery occlusion. The syndrome involves damage to multiple structures in a characteristic pattern. ## Clinical Features and Anatomical Correlation ### Patient's Presentation Breakdown | Clinical Finding | Anatomical Structure Damaged | Brainstem Level | |------------------|------------------------------|------------------| | Ipsilateral Horner syndrome (miosis, ptosis, anhidrosis) | Descending sympathetic fibers | Lateral medulla | | Ipsilateral facial pain/temperature loss | Spinal trigeminal nucleus (Sp5) | Lateral medulla | | Contralateral body pain/temperature loss | Spinothalamic tract (STT) | Lateral medulla | | Vertigo, nystagmus, ataxia | Inferior cerebellar peduncle (ICP) & vestibular nuclei | Lateral medulla | | Nausea, vomiting | Dorsal vagal complex | Lateral medulla | ## Lateral Medullary Cross-Section Anatomy ```mermaid flowchart TD A["Lateral Medullary Infarction"]:::urgent A --> B["Descending Sympathetic Fibers"]:::action A --> C["Spinal Trigeminal Nucleus & Tract"]:::action A --> D["Spinothalamic Tract"]:::action A --> E["Inferior Cerebellar Peduncle"]:::action A --> F["Vestibular Nuclei"]:::action B --> B1["Ipsilateral Horner Syndrome"]:::outcome C --> C1["Ipsilateral Facial Pain/Temp Loss"]:::outcome D --> D1["Contralateral Body Pain/Temp Loss"]:::outcome E --> E1["Ipsilateral Ataxia & Dysmetria"]:::outcome F --> F1["Vertigo, Nystagmus"]:::outcome ``` **High-Yield:** **Wallenberg syndrome = Lateral medullary syndrome**. Remember the classic triad: 1. **Ipsilateral Horner syndrome** (sympathetic fibers) 2. **Ipsilateral facial sensory loss** (spinal trigeminal nucleus) 3. **Contralateral body sensory loss** (spinothalamic tract) ## Mnemonic for Lateral Medullary Structures **SICK:** - **S**pinothalamic tract (contralateral pain/temp loss) - **I**nferior cerebellar peduncle (ataxia) - **C**ranial nerve nuclei (vagal, trigeminal) - **K**inetic/sympathetic fibers (Horner syndrome) ## Why This Is Lateral Medulla, Not Other Levels **Clinical Pearl:** The **combination of ipsilateral Horner syndrome + ipsilateral facial sensory loss + contralateral body sensory loss is pathognomonic for lateral medullary syndrome**. No other brainstem level produces this exact combination. - **Medial medulla:** Affects CN XII (tongue weakness), medial lemniscus (contralateral sensory loss), pyramidal tract (contralateral motor loss) — NO Horner syndrome, NO facial sensory loss - **Pons:** Affects CN VII (facial weakness), not sensory loss; no Horner syndrome - **Midbrain:** Affects CN III; no Horner syndrome or facial sensory loss **Warning:** Do not confuse lateral medulla with medial medulla — medial medullary syndrome (Dejerine syndrome) has tongue weakness (CN XII) and contralateral hemiparesis, NOT Horner syndrome or facial sensory loss.