Neurological diagnosis--aspects of quantitative sensory testing methodology in relation to hand-arm vibration...

The objectives are to summarise the fundamental neurophysiological base for quantitative sensory testing (QST), and to discuss associated methodological and practical aspects necessary to consider with respect to applicability and reliability as a screening or diagnostic aid for vibration-induced sensory neuropathy.

QST is the use of psychophysical techniques to measure the intensity of stimuli needed to produce specific sensory perceptions. The physical components are graded stimuli presented to the skin, eye or ear. The psychological component is mental recognition of the physical stimulus. Sensory modalities are named after the subjective feelings elicited, i.e. touch, pressure, vibration, warmth, cold and thermal pain. Since an exposure to vibration may cause symptoms and signs of sensory neuropathy in the hand and arm, the use of QST as an aid for screening and diagnosis has gained an increasing interest. The "Stockholm Workshop" classification scale for sensorineural stages also requires QST. Further, QST has also spread into many other areas, such as in the screening and diagnosis of peripheral neuropathy or polyneuropathy induced by different types of illness, exposure to toxic substances, compression and nerve entrapment.

QST is in general easy to perform, usually not associated with pain (except thermal pain), suitable for screening and can readily be conducted in the field. QST is, however, known to be susceptible to the effects of multiple covariates and test methodologies. It is thus important that the relative influence on test results from all significant covariates are identified, and to standardise test methodology accordingly before QST can become a reliable and useful tool for diagnostic and screening purposes in the field of vibration-induced sensory neuropathy. The sensitivity, specificity and reliability of different methods for QST for this type of disorder is still very much unknown. Lack of normative values, standardisation of methods and of a "gold standard" for the presence of sensory neuropathy are some reasons.