The Trigger of the First Trial Effect: examing pure Sensory Polyneuropathy Patients

The balance of people can be reliably examined by posturography: a
sophisticated way to analyse the balance of subjects on a fast moving tilting
platform. The first response to a perturbation in healthy people shows that it
is substantially different from the response to all subsequent perturbations,
but only when each successive perturbation is identical. The response to the
first perturbation (also called the First Trial Response) is accompanied by an
excessively high degree of instability (which can be established by measuring
the Center of Mass). This instability decreases rapidly when the subject comes
into contact with a series of identical balance disturbances, but surprisingly
immediately reappears as soon as the nature of the perturbation is adjusted. It
is unclear which sensory mechanism in the body detects whether there is a new
perturbation. Better understanding of this is desirable. First, it is to
understand the normal physiology of human balance better, second, it is to
reduce the incidence of falls in patients with balance disorders and ultimately
to achief a better treatment. Our hypothesis is that proprioceptive information
from the feet and lower legs are the crucial source of information that informs
the CNS about the presence of a new kind of perturbation. This hypothesis can
be investigated by analysing specifically patients with a selective loss of
proprioceptive information from the feet and lower legs. This occurs for
example in patients with diabetes mellitus and selective sensory and length
dependent polyneuropathy.

To determine the influence of a pure sensory polyneuropathy on balance
correction in light of the first trial response and in light of multiple
succesive identical perturbations, compared to healthy control subjects.

observational study

Subjects will be asked to come to the neurology clinic at UMC St. Radboud to
receive a physical examination. They will also be asked to complete a
questionnaire regarding medical history and the balance in the daily life of
the subject. Also, the balance will be briefly tested under different
conditions. For the study subjects will make a trip to the university hospital
in Basel, Switzerland. The experiment will be conducted the day after arrival
and on that day, the subjects also travel back to the Netherlands. Travel and
accommodation costs are fully reimbursed. The research itself is completely
safe, since in previous studies in more than 100 patients (usually with severe
balance disorders) no incidents have accured. During the study electrodes will
be attached to ten places. Beforehand the skin will be shaved if necessary and
disinfected at the sites. This could possibly cause a slight temporary
irritation.