Lateral femoral cutaneous SSEP records the P31–N49 complex after LFC stimulation at the anterior superior iliac spine. It is indicated in meralgia paresthetica (LFC neuropathy, ICD G57.1) and in evaluation of L2–L3 radiculopathy. The difference between tibial P40 and LFC P31 on the same side helps distinguish peripheral LFC injury from more proximal involvement.
Lateral Femoral Cutaneous — LFC (P31 – N49)
| Parameter | Side R | Side L | Diff. R–L | Limit | Result |
|---|
Tibial P40 – LFC P31 comparison
Ref.: Caramel / EPMEnter tibial P40 on the same side (or use the median and tibial SSEP calculator).
- Tibial P40 – LFC P31 difference (ms)
- Enter tibial P40 and LFC P31
- Interpretation
- Normal: > 5.0 ms Borderline: 4–5 ms Abnormal: < 4.0 ms
About LFC SSEP
Synek (1983) published P31–N49 complex values with Cz'–Fz recording (~30 ms). Liveson & Ma provides latency and minimum amplitude limits. The tibial–LFC gap compares lower-limb sensory pathways within the same cortical hemisphere.
See also: SSEP median and tibial · SSEP trigeminal · SSEP pudendal
Clinical support tool only. Does not replace a report from a clinical neurophysiology specialist.