Comparison of Evoked vs. Spontaneous Tics in a Patient with Trigeminal Neuralgia (Tic Doloureux)

David Borsook,Gautam Pendse,Matthew Aiello-Lammens,Sadie H Cole,Steven Scrivani,Lino R Becerra,Eric A Moulton,Susie Morris

doi:10.1186/1744-8069-3-34

Abstract

A 53-year old woman with tic doloureaux, affecting her right maxillary division of the trigeminal nerve (V2), could elicit shooting pains by slightly tapping her teeth when off medication. The pains, which she normally rated as > 6/10 on a visual analog scale (VAS), were electric shock-like in nature. She had no other spontaneous or ongoing background pain affecting the region. Based on her ability to elicit these tics, functional magnetic resonance imaging (fMRI) was performed while she produced brief shocks every 2 minutes on cue (evoked pain) over a 20 min period. In addition, she had 1–2 spontaneous shocks manifested between these evoked pains over the course of functional image acquisition. Increased fMRI activation for both evoked and spontaneous tics was observed throughout cortical and subcortical structures commonly observed in experimental pain studies with healthy subjects; including the primary somatosensory cortex, insula, anterior cingulate, and thalamus. Spontaneous tics produced more decrease in signals in a number of regions including the posterior cingulate cortex and amygdala, suggesting that regions known to be involved in expectation/anticipation may have been activated for the evoked, but not spontaneous, tics. In this patient there were large increases in activation observed in the frontal regions, including the anterior cingulate cortex and the basal ganglia. Spontaneous tics showed increased activation in classic aversion circuitry that may contribute to increased levels of anxiety. We believe that this is the first report of functional imaging of brain changes in tic-doloureaux.

Highlights

Trigeminal neuralgia, the most common craniofacial neuropathic pain disorder, is characterized by spontaneous, episodic, unilateral, electric-like shocks that arise from a consistent location in the face [1,2]
The aims of the study were (a) to determine a functional MRI paradigm that would allow us to measure pain associated with tics since a number of issues complicate this type of study including timing of the tic, movement associated with the tic; (b) to describe brain activation associated with this type of pain; (c) to differentiate between 'evoked' pain produced by cues and spontaneous pain in this patient and (d) to determine if there were any differences observed for activation patterns by tic pain with other pain activations in chronic pain patients
Motor systems could have been recruited during the subject's use of the dial to mark pain onset, and during possible ticinduced facial reflexes. We believe that this is the first report of brain activation in tic doloureaux

Summary

Introduction

Trigeminal neuralgia, the most common craniofacial neuropathic pain disorder, is characterized by spontaneous, episodic, unilateral, electric-like shocks that arise from a consistent location in the face [1,2]. Of the three divisions of the trigeminal nerve, the second (V2) is most commonly affected. A number of theories exist for trigeminal neuralgia, its mechanism remains unclear. Trigeminal neuralgia can arise spontaneously (page number not for citation purposes). Molecular Pain 2007, 3:34 http://www.molecularpain.com/content/3/1/34 without apparent damage to the trigeminal nerve, but can arise from compression or irritation of the dorsal root entry zone [3], or from damage such as tooth extraction [4]. Subjects with the condition have evoked pains (e.g., from touch, chewing, etc.) and/or spontaneous pain that emanates from the same location. The electric quality of this type of neuropathic pain differentiates it from the spontaneous burning pain or the evoked pains of allodynia and hyperalgesia, that are characteristic of other neuropathic pains [5]

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