Patients with Tourette Syndrome often state that their sensitivity to sensations is equally or more disruptive than are motor tics. However, their sensory sensitivity is not addressed by standard clinical assessments nor is it a focus of research. This lapse likely results from our limited awareness and understanding of the symptom. In this study we 1) defined the patients’ experience of sensitivity to external stimuli in detail, and 2) tested two hypotheses regarding its origin. First, we administered a lengthy questionnaire and in-depth interviews to adult Tourette patients (n=19) and age-matched healthy volunteers (n=19). Eighty percent of patients described a heightened sensitivity to external stimuli, with examples among all 5 sensory modalities. Bothersome stimuli were characterized as faint, repetitive or constant, and non-salient, whereas intense stimuli were well-tolerated. We then determined whether the sensitivity could be due to an increased ability to detect faint stimuli. After measuring the threshold of detection for olfactory and tactile stimuli among the patients and healthy volunteers, we found no significant difference for either sensory modality. These results indicate that patients’ perceived sensitivity derives from altered central processing rather than from enhanced peripheral detection. Lastly, we assessed one aspect of processing: the perception of intensity. When subjects rated the intensity of near-threshold tactile and olfactory stimuli, there was a surprising difference: Tourette patients more frequently used the lowest range of the scale compared with healthy volunteers. Future research is necessary to define the anatomical and physiological basis of the patients’ experience of heightened sensitivity.
Tourette syndrome (TS) is a neuropsychiatric disorder characterized by motor and vocal tics. Most patients describe uncomfortable premonitory sensations preceding the tics and a subjective experience of increased sensitivity to tactile stimuli. These reports indicate that a sensory processing disturbance is an important component of TS together with motor phenomena. Thus, we focused our investigation on the role of the sensorimotor cortex (SMC) in TS using multimodal neuroimaging techniques. We measured the gamma-aminobutyric acid (GABA)+/Creatine (Cre) ratio in the SMC using GABA 1H magnetic resonance spectroscopy. We recorded the baseline beta activity in the SMC using magnetoencephalography and correlated GABA+/Cre ratio with baseline beta band power. Finally, we examined the resting state functional connectivity (FC) pattern of the SMC using functional magnetic resonance imaging (fMRI). GABA+/Cre ratio in the SMC did not differ between patients and controls. Correlation between the baseline beta band power and GABA+/Cre ratio was abnormal in patients. The anterior insula showed increased FC with the SMC in patients. These findings suggest that altered limbic input to the SMC and abnormal GABA-mediated beta oscillations in the SMC may underpin some of the sensorimotor processing disturbances in TS and contribute to tic generation.
Background The underlying pathophysiologic mechanism for complex motor stereotypies in children is unknown with hypotheses ranging from an arousal to a motor control disorder. Movement-related cortical potentials (MRCPs), representing the activation of cerebral areas involved in the generation of movements, precede and accompany self-initiated voluntary movements. The goal of this study was to compare cerebral activity associated with stereotypies to that seen with voluntary movements in children with primary complex motor stereotypies. Methods Electroencephalographic (EEG) activity synchronized with video recording was recorded in 10 children diagnosed with primary motor stereotypies and 7 controls. EEG activity related to stereotypies and self-paced arm movements were analyzed for presence or absence of early or late MRCP, a steep negativity beginning about one second before the onset of a voluntary movement. Results Early MRCPs preceded self-paced arm movements in 8 out of 10 children with motor stereotypies and in 6 out of 7 controls. Observed MRCPs did not differ between groups. No MRCP was identified before the appearance of a complex motor stereotypy. Conclusions Unlike voluntary movements, stereotypies are not preceded by MRCPs. This indicates that premotor areas are likely not involved in the preparation of these complex movements and suggests that stereotypies are initiated by mechanisms different from voluntary movements. Further studies are required to determine the site of the motor control abnormality within cortico-striatal-thalamo-cortical pathways and to identify whether similar findings would be found in children with secondary stereotypies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.