Unmyelinated trigeminal pathways as assessed by laser stimuli in humans

Giorgio Cruccu, E. Pennisi, A. Truini, G. D. Iannetti, A. Romaniello, D. Le Pera, L. De Armas, M. Leandri, M. Manfredi, M. Valeriani

Research output: Contribution to journalArticle

122 Citations (Scopus)

Abstract

Laser pulses excite superficial free nerve endings innervated by small-myelinated (Aδ) and unmyelinated (C) fibres. Whereas laser-evoked scalp potentials (LEPs) are now reliably used to assess function of the Aδ-fibre nociceptive pathways in patients with peripheral or central lesions, the selective activation of C-fibre receptors and recording of the related brain potentials remain difficult. To investigate trigeminal C-fibre function, we directed laser pulses to the facial skin and studied sensory perception and scalp evoked potentials related to Aδ- or C-fibre activation in healthy humans and patients - one having a bilateral facial palsy, two a trigeminal neuropathy, and two a Wallenberg syndrome. We also measured afferent conduction velocity and, with source analysis, studied the brain generators. Whereas laser pulses of low intensity and small irradiated area elicited pinprick sensations and standard Aδ-LEPs, laser pulses of very-low intensity and large irradiated area elicited warmth sensations and scalp potentials with a latency compatible with C-fibre conduction (negative wave 280 ms, positive wave 380 ms); the estimated conduction velocity was 1.2 m/s. The main waves of the scalp potentials originated from the anterior cingulate gyrus; they were preceded by activity in the opercular region and followed by activity in the insular region. The patient with bilateral facial palsy, who had absent trigeminal-facial reflexes, had normal Aδ- and C-related scalp potentials; the patients with trigeminal neuropathy, characterized by loss of myelinated and sparing of unmyelinated fibres, had absent Aδ- but normal C-related potentials; and the patients with Wallenberg syndrome had absent Aδ- and C-related potentials. We conclude that laser pulses with appropriate characteristics evoke brain potentials related to the selective activation of trigeminal nociceptive Aδ or thermal C fibres. The trigeminal territory yields rewarding LEP findings owing to the high density of thermal receptors and, because the short conduction distance, minimizes the problem of signal dispersion along slow-conducting unmyelinated afferents. The opercular-insular region and the cingulate gyrus are involved in the processing of C-fibre trigeminal inputs. The method we describe may prove useful in patients with lesions affecting the trigeminal thermal pain pathways.

Original languageEnglish
Pages (from-to)2246-2256
Number of pages11
JournalBrain
Volume126
Issue number10
DOIs
Publication statusPublished - Oct 2003

Fingerprint

Unmyelinated Nerve Fibers
Scalp
Lasers
Trigeminal Nerve Diseases
Lateral Medullary Syndrome
Hot Temperature
Facial Paralysis
Gyrus Cinguli
Brain
Myelinated Nerve Fibers
Nerve Endings
Evoked Potentials
Reflex
Pain
Skin
Laser-Evoked Potentials

Keywords

  • Laser evoked potentials
  • Thermal-pain perception
  • Trigeminal nerve
  • Trigeminal nerve biopsy
  • Unmyelinated fibres

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Cruccu, G., Pennisi, E., Truini, A., Iannetti, G. D., Romaniello, A., Le Pera, D., ... Valeriani, M. (2003). Unmyelinated trigeminal pathways as assessed by laser stimuli in humans. Brain, 126(10), 2246-2256. https://doi.org/10.1093/brain/awg227

Unmyelinated trigeminal pathways as assessed by laser stimuli in humans. / Cruccu, Giorgio; Pennisi, E.; Truini, A.; Iannetti, G. D.; Romaniello, A.; Le Pera, D.; De Armas, L.; Leandri, M.; Manfredi, M.; Valeriani, M.

In: Brain, Vol. 126, No. 10, 10.2003, p. 2246-2256.

Research output: Contribution to journalArticle

Cruccu, G, Pennisi, E, Truini, A, Iannetti, GD, Romaniello, A, Le Pera, D, De Armas, L, Leandri, M, Manfredi, M & Valeriani, M 2003, 'Unmyelinated trigeminal pathways as assessed by laser stimuli in humans', Brain, vol. 126, no. 10, pp. 2246-2256. https://doi.org/10.1093/brain/awg227
Cruccu G, Pennisi E, Truini A, Iannetti GD, Romaniello A, Le Pera D et al. Unmyelinated trigeminal pathways as assessed by laser stimuli in humans. Brain. 2003 Oct;126(10):2246-2256. https://doi.org/10.1093/brain/awg227
Cruccu, Giorgio ; Pennisi, E. ; Truini, A. ; Iannetti, G. D. ; Romaniello, A. ; Le Pera, D. ; De Armas, L. ; Leandri, M. ; Manfredi, M. ; Valeriani, M. / Unmyelinated trigeminal pathways as assessed by laser stimuli in humans. In: Brain. 2003 ; Vol. 126, No. 10. pp. 2246-2256.
@article{17db57637306426784ccfd3ba5ef102d,
title = "Unmyelinated trigeminal pathways as assessed by laser stimuli in humans",
abstract = "Laser pulses excite superficial free nerve endings innervated by small-myelinated (Aδ) and unmyelinated (C) fibres. Whereas laser-evoked scalp potentials (LEPs) are now reliably used to assess function of the Aδ-fibre nociceptive pathways in patients with peripheral or central lesions, the selective activation of C-fibre receptors and recording of the related brain potentials remain difficult. To investigate trigeminal C-fibre function, we directed laser pulses to the facial skin and studied sensory perception and scalp evoked potentials related to Aδ- or C-fibre activation in healthy humans and patients - one having a bilateral facial palsy, two a trigeminal neuropathy, and two a Wallenberg syndrome. We also measured afferent conduction velocity and, with source analysis, studied the brain generators. Whereas laser pulses of low intensity and small irradiated area elicited pinprick sensations and standard Aδ-LEPs, laser pulses of very-low intensity and large irradiated area elicited warmth sensations and scalp potentials with a latency compatible with C-fibre conduction (negative wave 280 ms, positive wave 380 ms); the estimated conduction velocity was 1.2 m/s. The main waves of the scalp potentials originated from the anterior cingulate gyrus; they were preceded by activity in the opercular region and followed by activity in the insular region. The patient with bilateral facial palsy, who had absent trigeminal-facial reflexes, had normal Aδ- and C-related scalp potentials; the patients with trigeminal neuropathy, characterized by loss of myelinated and sparing of unmyelinated fibres, had absent Aδ- but normal C-related potentials; and the patients with Wallenberg syndrome had absent Aδ- and C-related potentials. We conclude that laser pulses with appropriate characteristics evoke brain potentials related to the selective activation of trigeminal nociceptive Aδ or thermal C fibres. The trigeminal territory yields rewarding LEP findings owing to the high density of thermal receptors and, because the short conduction distance, minimizes the problem of signal dispersion along slow-conducting unmyelinated afferents. The opercular-insular region and the cingulate gyrus are involved in the processing of C-fibre trigeminal inputs. The method we describe may prove useful in patients with lesions affecting the trigeminal thermal pain pathways.",
keywords = "Laser evoked potentials, Thermal-pain perception, Trigeminal nerve, Trigeminal nerve biopsy, Unmyelinated fibres",
author = "Giorgio Cruccu and E. Pennisi and A. Truini and Iannetti, {G. D.} and A. Romaniello and {Le Pera}, D. and {De Armas}, L. and M. Leandri and M. Manfredi and M. Valeriani",
year = "2003",
month = "10",
doi = "10.1093/brain/awg227",
language = "English",
volume = "126",
pages = "2246--2256",
journal = "Brain",
issn = "0006-8950",
publisher = "Oxford University Press",
number = "10",

}

TY - JOUR

T1 - Unmyelinated trigeminal pathways as assessed by laser stimuli in humans

AU - Cruccu, Giorgio

AU - Pennisi, E.

AU - Truini, A.

AU - Iannetti, G. D.

AU - Romaniello, A.

AU - Le Pera, D.

AU - De Armas, L.

AU - Leandri, M.

AU - Manfredi, M.

AU - Valeriani, M.

PY - 2003/10

Y1 - 2003/10

N2 - Laser pulses excite superficial free nerve endings innervated by small-myelinated (Aδ) and unmyelinated (C) fibres. Whereas laser-evoked scalp potentials (LEPs) are now reliably used to assess function of the Aδ-fibre nociceptive pathways in patients with peripheral or central lesions, the selective activation of C-fibre receptors and recording of the related brain potentials remain difficult. To investigate trigeminal C-fibre function, we directed laser pulses to the facial skin and studied sensory perception and scalp evoked potentials related to Aδ- or C-fibre activation in healthy humans and patients - one having a bilateral facial palsy, two a trigeminal neuropathy, and two a Wallenberg syndrome. We also measured afferent conduction velocity and, with source analysis, studied the brain generators. Whereas laser pulses of low intensity and small irradiated area elicited pinprick sensations and standard Aδ-LEPs, laser pulses of very-low intensity and large irradiated area elicited warmth sensations and scalp potentials with a latency compatible with C-fibre conduction (negative wave 280 ms, positive wave 380 ms); the estimated conduction velocity was 1.2 m/s. The main waves of the scalp potentials originated from the anterior cingulate gyrus; they were preceded by activity in the opercular region and followed by activity in the insular region. The patient with bilateral facial palsy, who had absent trigeminal-facial reflexes, had normal Aδ- and C-related scalp potentials; the patients with trigeminal neuropathy, characterized by loss of myelinated and sparing of unmyelinated fibres, had absent Aδ- but normal C-related potentials; and the patients with Wallenberg syndrome had absent Aδ- and C-related potentials. We conclude that laser pulses with appropriate characteristics evoke brain potentials related to the selective activation of trigeminal nociceptive Aδ or thermal C fibres. The trigeminal territory yields rewarding LEP findings owing to the high density of thermal receptors and, because the short conduction distance, minimizes the problem of signal dispersion along slow-conducting unmyelinated afferents. The opercular-insular region and the cingulate gyrus are involved in the processing of C-fibre trigeminal inputs. The method we describe may prove useful in patients with lesions affecting the trigeminal thermal pain pathways.

AB - Laser pulses excite superficial free nerve endings innervated by small-myelinated (Aδ) and unmyelinated (C) fibres. Whereas laser-evoked scalp potentials (LEPs) are now reliably used to assess function of the Aδ-fibre nociceptive pathways in patients with peripheral or central lesions, the selective activation of C-fibre receptors and recording of the related brain potentials remain difficult. To investigate trigeminal C-fibre function, we directed laser pulses to the facial skin and studied sensory perception and scalp evoked potentials related to Aδ- or C-fibre activation in healthy humans and patients - one having a bilateral facial palsy, two a trigeminal neuropathy, and two a Wallenberg syndrome. We also measured afferent conduction velocity and, with source analysis, studied the brain generators. Whereas laser pulses of low intensity and small irradiated area elicited pinprick sensations and standard Aδ-LEPs, laser pulses of very-low intensity and large irradiated area elicited warmth sensations and scalp potentials with a latency compatible with C-fibre conduction (negative wave 280 ms, positive wave 380 ms); the estimated conduction velocity was 1.2 m/s. The main waves of the scalp potentials originated from the anterior cingulate gyrus; they were preceded by activity in the opercular region and followed by activity in the insular region. The patient with bilateral facial palsy, who had absent trigeminal-facial reflexes, had normal Aδ- and C-related scalp potentials; the patients with trigeminal neuropathy, characterized by loss of myelinated and sparing of unmyelinated fibres, had absent Aδ- but normal C-related potentials; and the patients with Wallenberg syndrome had absent Aδ- and C-related potentials. We conclude that laser pulses with appropriate characteristics evoke brain potentials related to the selective activation of trigeminal nociceptive Aδ or thermal C fibres. The trigeminal territory yields rewarding LEP findings owing to the high density of thermal receptors and, because the short conduction distance, minimizes the problem of signal dispersion along slow-conducting unmyelinated afferents. The opercular-insular region and the cingulate gyrus are involved in the processing of C-fibre trigeminal inputs. The method we describe may prove useful in patients with lesions affecting the trigeminal thermal pain pathways.

KW - Laser evoked potentials

KW - Thermal-pain perception

KW - Trigeminal nerve

KW - Trigeminal nerve biopsy

KW - Unmyelinated fibres

UR - http://www.scopus.com/inward/record.url?scp=0242336436&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0242336436&partnerID=8YFLogxK

U2 - 10.1093/brain/awg227

DO - 10.1093/brain/awg227

M3 - Article

C2 - 12847077

AN - SCOPUS:0242336436

VL - 126

SP - 2246

EP - 2256

JO - Brain

JF - Brain

SN - 0006-8950

IS - 10

ER -