Mechanismen neuropathischer Schmerzen am Beispiel der postherpetischen Neuralgie

Zusammenfassung

Die postherpetische Neuralgie ist eine häufige, mit schweren Schmerzen einhergehende Erkrankung. Anhand von Untersuchungen an Patienten und tierexperimentellen Daten zeigt sich, dass unterschiedliche pathophysiologische Mechanismen der Entstehung dieser Erkrankung zugrunde liegen. Bei einem Teil der Patienten besteht eine pathologische Spontanaktivität sensibilisierter C-Fasern (irritable nociceptors). Hierdurch entstehen sekundäre Veränderungen im Bereich des zentralen Nervensystems, die dazu führen, dass die Aktivierung mechanosensibler Aβ-Fasern als Schmerz wahrgenommen wird. Dies führt neben Spontanschmerzen und einer Hitzehyperalgesie zu einer ausgeprägten Allodynie. Bei einer anderen Gruppe von Patienten kann die Entzündung zu einer selektiven Degeneration schmerz- und temperaturleitender Nervenfasern führen. Diese ist gefolgt von einer anatomische Reorganisation auf Rückenmarksebene, die wiederum in einer Aktivierung primär schmerzleitender Neurone durch mechanosensible Aβ-Fasern resultiert. Klinisch besteht eine ausgeprägte Allodynie sowie eine durch die Degeneration der C-Fasern hervorgerufene thermische Hypästhesie. Schließlich kann durch die Affektion peripherer Nervenfasern eine Sensibilisierung nozizeptiver Fasern auf noradrenerge Substanzen erfolgen, die ebenfalls zur Unterhaltung der Schmerzen mit beitragen könnte.

Summary

Postherpetic neuralgia (PHN) is a common and often severely painful peripheral neuropathy. Our knowledge of the pain generating mechanisms in PHN has been increased by the comparison of PHN with experimental models of neuropathic pain. These studies suggest several pathophysiological mechanisms. In a subgroup of patients pathological active nociceptors can induce secondary changes in central processing leading to spinal cord hyperexcitability, that causes input from mechanoreceptive Aβ-fibres to be perceived as pain. These patients have serve allodynia and heat hyperalgesia. In another group of patients inflammation is followed by a degeneration of temperature and pain sensitive C-fibres, which leads to an impaired temperature perception. Anatomical reorganization in the dorsal horn resulting from degeneration may lead to Aβ-fibre mediated allodynia. Further on damaged peripheral nerve fibers are developing sensitivity to adrenergic substances, which is possible to contribute in generation of pain in PHN patients.

Schlüsselwörter

Postherpetische Neuralgie - Allodynie - Hyperalgesie - Pathophysiologie

Keywords

Postherpetic neuralgia - allodynia - hyperalgesia - pathophysiology

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