Use of the Rydel-Seiffer graduated tuning fork in the assessment of vibration threshold in postherpetic neuralgia patients and healthy controls

Background and aims: Afferent large fibre impairment has been reported as a useful predictor of postherpetic neuralgia (PHN) in patients with acute herpes zoster infection, using an electromechanical device to provide quantitative vibrametry. We aimed to demonstrate a clinically significant increase in vibration threshold in individuals with PHN compared to age-matched controls, using the portable and affordable Rydel-Seiffer graduated tuning fork. Methods: We studied 45 PHN subjects aged over 55 years, and 45 age-matched controls with no history of herpes zoster infection. We excluded subjects with a history of disorders associated with neuropathy or immunocompromise. Measurements were performed at the ulnar styloid process and the head of the first metatarsal on the right side, in a warm room with the subject seated. Readings were taken in triplicate and the data analysed by a repeated measures design. Results: We observed a significant difference in vibration threshold at both wrist and toe between the PHN and control groups (p < 0.001). Age-stratification of subjects produced an increased and clinically useful difference between the two groups at both sites in subjects between 55 and 70 years (p < 0.0001). Conclusions: We have shown a statistically significant decrease in vibration sensitivity in individuals with PHN aged 55-70 years compared to age-matched healthy controls, using the Rydel-Seiffer graduated tuning fork. A prospective study of patients with acute zoster infection is needed to determine the sensitivity and specificity of the graduated tuning fork in predicting PHN in patients with acute zoster infection. (c) 2004 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Ltd. All rights reserved.