№ 177Neurology13 min read
S1, L5 radicular syndromes; ancillary investigations
1. Big picture
L5 and S1 radiculopathies are the classic lower lumbar root syndromes tested in neurology exams. They are most often caused by lumbar disk herniation, especially:
- L4–L5 disk herniation → usually compresses the L5 root
- L5–S1 disk herniation → usually compresses the S1 root
The examiner expects you to localize the lesion clinically from:
- Pain distribution
- Sensory loss
- Motor weakness
- Reflex abnormality
- Provocation signs, especially Lasègue sign
- Ancillary investigations, mainly magnetic resonance imaging and neurophysiology
The most important exam contrast is:
**L5 = dorsum of foot / big toe / foot dorsiflexi
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