A 52-year-old woman with a history of cervical spondylosis presents with weakness of wrist extension and sensory loss over the dorsal hand and middle finger. Which nerve root level is most likely compressed, and what is the best discriminating feature between C6 and C7 radiculopathy?

Explanation

## Discriminating C6 from C7 Radiculopathy **Key Point:** The most reliable discriminator between C6 and C7 radiculopathy is the **sensory distribution**: C6 affects the thumb and index finger (radial/lateral hand), while C7 affects the middle finger and dorsal hand (central distribution). ### Dermatome Comparison Table | Feature | C6 Radiculopathy | C7 Radiculopathy | |---------|------------------|------------------| | **Sensory Loss** | Thumb, index finger, lateral forearm | Middle finger, dorsal hand, central palm | | **Motor Loss** | Biceps, wrist flexors, supinators | Triceps, wrist extensors, finger extensors | | **Reflex Loss** | Biceps reflex | Triceps reflex | | **Pain Distribution** | Lateral shoulder, lateral arm | Posterior arm, dorsal forearm | ### Clinical Correlation In this case, the patient has: - **Wrist extension weakness** → suggests C7 (wrist extensors are C7-innervated) - **Sensory loss over dorsal hand and middle finger** → confirms C7 dermatome **High-Yield:** The **middle finger is the pathognomonic sensory marker for C7 dermatome**. If middle finger sensation is lost, think C7. If thumb/index is lost, think C6. **Mnemonic:** **WRIST** = **W**rist extension loss → **C7** (C7 controls wrist extensors). **BICEPS** = **C6** (C6 controls biceps). ### Why Sensory Distribution is the Best Discriminator Motor findings can overlap (both C6 and C7 affect forearm muscles), and reflex loss may not always be present. However, **dermatome sensory loss is anatomically fixed and highly specific**: C6 always spares the middle finger, while C7 always involves it.