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Brief description/objective

Objective: To assess whether the presence
of a sensory trick (ST) is associated with
altered temporal discrimination in patients
with adult-onset primary cervical dystonia
(AOPCD).
Background: One of the most distinctive
features of primary focal dystonia is the improvement
with STs. The involvement of the
sensory system in primary focal dystonias is
also reflected by subclinical impairment of
tactile spatial and temporal discrimination.
Methods: Patients with AOPCD were included.
TWSTRS score was applied for clinical
assessment. ST was scored according to the
TWSTRS score with 0 point for an absent
effect, 1 point for a partial improvement of abnormal
posture and 2 points for a complete
resolution of involuntary muscle activity.Temporal
discrimination thresholds (TDT) were
assessed using unimodal paradigms (two electrical
[tactile] stimuli or two visual [LED]
stimuli) and with a crossmodal paradigm (one
tactile and one visual stimulus). Interstimulus
intervals (ISI) were increased with steps of
10 ms starting from an ISI of 0 ms.
Results: 33 patients (24 female / 9 male)
with AOPCD were included. Mean age was
56 years with a mean disease duration of
12.3 years and a mean TWSTRS score of 25.
A complete ST was present in 23%, a partial
in 52% and absent in 21%. A shorter disease
duration correlated with the presence of an
ST ([cc: –0.382] p = 0.028) but not current
age [cc: –0.017]. Tactile and crossmodal (cm)
TDTs were lower in patients with a complete
ST (cm TDT: 106.8 ms; cm TOJ [temporal
order judgment]: 115.9 ms) compared to patients
without the presence of an ST (cm TDT:
136 ms; cm TOJ: 141 ms). In female patients
the presence of an ST was significantly correlated
with lower TDTs in the crossmodal
paradigm (TDT: [cc: –0.560] p = 0.004; TOJ:
[cc: –0.579] p = 0.003) whereas unimodal (tactile
or visual) TDTs did not reach significance.
In all dystonia patients (females and males)
there was a strong trend (cm TDT: [cc: –0.333]
p = 0.058; cm TOJ: [cc: –0.325] p = 0.065) without
reaching significance.
Conclusion: The presence of an ST is
strongly correlated with better performance
in crossmodal (tactile/visual) temporal discrimination
in female patients with AOPCD.
The parietal cortex is an important structure
of multimodal sensory integration and also
shows activation (superior and inferior parietal
lobule) during ST application in functional
imaging studies.