Trigeminal SSEP assesses sensory conduction to the brainstem and somatosensory cortex. Short-latency responses (W₁–W₃, < 10 ms) reflect peripheral conduction to the brainstem; medium- and long-latency components (N13, P19, N27, P34) reflect thalamocortical pathways. Per Cruccu et al. (2008) and IFCN recommendations, within-subject side-to-side comparison is the most reliable criterion for trigeminal pathway injury.
Trigeminal (SEP)
| Parameter | Side R | Side L | Diff. R–L | Limit | Result |
|---|
Trigeminal SSEP: latencies and interpretation
Trigeminal SEP: subcortical components W₁–W₃ (Leandri) and cortical N13/P19 (Cruccu/IFCN). Assess interside asymmetry and absolute latencies per references.
Trigeminal SSEP evaluation comprises subcortical (peripheral conduction to the brainstem) and cortical (thalamocortical) responses. Normative data below support International Federation of Clinical Neurophysiology (IFCN) recommendations.
1. Short-latency (subcortical) potentials
Recorded within the first 10 ms; «W» morphology described by Leandri et al.
| Component | Generator site | Mean latency | Reference |
|---|---|---|---|
| W₁ | Gasserian ganglion / peripheral nerve | 1.8 ± 0.2 ms | Leandri et al. (1985) |
| W₂ | Root entry zone (REZ) | 2.5 ± 0.2 ms | Leandri et al. (1985) |
| W₃ | Trigeminal sensory nuclear complex | 3.5 ± 0.2 ms | Leandri et al. (1985) |
2. Medium- and long-latency (cortical) potentials
Slight variation by stimulated branch (mental vs infraorbital). Alternative nomenclature varies across laboratories.
| Component | Alt. name | Generator site | Mean latency | Reference |
|---|---|---|---|---|
| N13 | N1 / N14 | Primary somatosensory cortex (arrival) | 12.5 – 14.1 ms | Singh et al. (1982) / Rossini et al. (2006) |
| P19 | P1 / P20 | Primary somatosensory cortex | 18.5 – 20.6 ms | Stöhr et al. (1981) / Cruccu et al. (2008) |
| N27 | N2 / N26 | Early associative parietal cortex | 26.0 – 27.6 ms | Findler et al. (1984) / Rossini et al. (2006) |
| P34 | P2 / P30 | Late cortical component | 34.0 ± 6.8 ms | Rossini et al. (2006) |
Abnormality criteria (Cruccu et al., 2008)
- Latency asymmetry: N13/P19 difference > 0.6–1.0 ms between affected and unaffected side - most reliable conduction delay marker (selectable in the calculator).
- Amplitude asymmetry: N13–P19 peak-to-peak reduction > 50% vs the asymptomatic side - suggests axonal loss or severe conduction block.
See also: SSEP median and tibial · SSEP pudendal · SSEP lateral femoral cutaneous
Clinical support tool only. Does not replace a report from a clinical neurophysiology specialist.
Frequently asked questions
What is trigeminal SSEP used for?
Evaluates trigeminal somatosensory pathways in neuralgia, multiple sclerosis, brainstem lesions and trigeminal neuropathy.
Which components to report?
Subcortical W₁, W₂, W₃; cortical N13/P19; interside differences per Cruccu/IFCN protocol.