gms | German Medical Science

54. Jahrestagung der Norddeutschen Orthopädenvereinigung e. V.

Norddeutsche Orthopädenvereinigung

16.06. bis 18.06.2005, Hamburg

Laser-evoked potentials: a diagnostic approach to the dorsal root

Meeting Abstract

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  • corresponding author M. Quante - Klinik und Poliklinik für Allgemeine Orthopädie/Universitätsklinikum Münster, Orthopädie, Münster
  • M. Hauck - Hamburg
  • J. Lorenz - Hamburg
  • E. Hille - Hamburg

Norddeutsche Orthopädenvereinigung. 54. Jahrestagung der Norddeutschen Orthopädenvereinigung e.V.. Hamburg, 16.-18.06.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05novP13

The electronic version of this article is the complete one and can be found online at:

Published: June 13, 2005

© 2005 Quante et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




The functional diagnostic of the dorsal root is especially effective via nociceptive fibers on account of less intersegmental overlap compared to large diameter fibers of the mechanoreceptive afferents. Laser evoked potentials (LEP) are induced by short, painful heat stimuli. Aim of this work was to document interside differences of dermatomal LEP in healthy subjects and to describe changes of the LEP in patients with acute monosegmental dorsal root affection.

Materials and Methods

Dorsal root function was tested in 12 healthy subjects and 40 patients suffering from acute radiculopathy (one of the segments L4 to S1). Mechanosensibility and thermosensibility were clinically investigated. LEP were induced by slightly painful stimuli (80 on the affected and 80 on the contralateral unaffected dermatome). The LEP were evaluated by amplitude of the averaged electroencephalogram (eeg). In addition a subjective pain rating was recorded after each stimulus.


Norm data revealed normal interside latency differences of ±16 % for the N-component and ±13 % for the P-component and normal interside amplitude differences of ±30%. Over all 22 patients showed pathological LEP-changes (amplitude decrease 30-50%: 7 patients, >50%: 8 patients, loss of LEP 3 patients, latency changes: 9 patients).


In patients with acute radiculopathy LEP changes allow a graduation of loss of dorsal root function. It is discussed what mechanisms are responsible as concerns deafferentiation and neuropathy of the dorsal root fibers. We assume that LEP changes have prognostic relevance in patients with dorsal root affection.