Tomáš Sieger presents Prepulse inhibition of the blink reflex in functional neurological disorder

Prepulse inhibition reflects subcortical sensory integration, where a
low-intensity peripheral stimulus (prepulse) reduces the amplitude of a reflex
response to a subsequent high-intensity stimulus. As a measure of pre-attentive
sensory gating, prepulse inhibition has been found to be altered in small
cohorts of patients with functional disorders, including functional motor
disorder and fibromyalgia, suggesting a shared deficit in sensory information
processing. However, prior studies have not demonstrated consistent
associations between prepulse inhibition abnormalities and clinical measures.

We hypothesized that widespread pain and somatic symptoms in somatic symptom
disorders may result from a general deficit in the interpretation of bodily
signals, potentially linked to abnormalities in sensory filtering as measured
by prepulse inhibition.

In this study, we examined 140 participants across four age- and sex-matched
groups: 35 patients clinically categorized with functional motor disorder
without fibromyalgia, 35 with both functional motor disorder and fibromyalgia,
35 with fibromyalgia only, and 35 healthy controls. A weak electrical stimulus
to the index finger served as the prepulse, delivered 100 ms before
supraorbital nerve stimulation to elicit the R2 component of the blink reflex.
Prepulse inhibition was calculated as the percent reduction in R2 amplitude.

Across all groups, lower prepulse was significantly associated with higher
scores on the Fibromyalgia Severity Scale, consisting of Widespread Pain Index
and Symptom Severity Scale. In patients with functional motor disorder, no
association was found between prepulse inhibition size and objectively rated
motor symptom severity.

These findings suggest that impaired early sensory processing at subcortical
level is related to “fibromyalgianess” in people with functional motor
disorder and fibromyalgia. Abnormal prepulse inhibition may serve as an
objective transdiagnostic marker of fibromyalgia symptomatology or
fibromyalgianess, including widespread pain and other non-motor symptoms in
functional disorders, highlighting a potential role of sensory gating deficits
in the pathophysiology of fibromyalgia-spectrum manifestations.

[20 min talk + 10 min discussion]