Original article
Interventional neurophysiology for pain control: duration of pain relief following repetitive transcranial magnetic stimulation of the motor cortexNeurophysiologie interventionnelle dans le contrôle de la douleur : la durée du soulagement de la douleur après la stimulation magnétique transcranienne répétitive du cortex moteur.

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Abstract

The chronic electrical stimulation of a motor cortical area corresponding to a painful region of the body, by means of surgically-implanted epidural electrodes is a validated therapeutical strategy to control medication-resistant neurogenic pain. Repetitive transcranial magnetic stimulation (rTMS) permits to stimulate non-invasively and precisely the motor cortex. We applied a 20-min session of rTMS of the motor cortex at 10 Hz using a ‘real’ or a ‘sham’ coil in a series of 14 patients with intractable pain due to thalamic stroke or trigeminal neuropathy. We studied the effects of rTMS on pain level assessed on a 0–10 visual analogue scale from day 1 to day 12 following the rTMS session. A significant pain decrease was observed up to 8 days after the ‘real’ rTMS session. This study shows that a transient pain relief can be induced in patients suffering from chronic neurogenic pain during about the week that follows a 20-min session of 10Hz-rTMS applied over the motor cortex.

Résumé

La stimulation électrique chronique de l’aire motrice corticale correspondant à une zone corporelle douloureuse, au moyen d’électrodes épidurales implantées chirurgicalement, est une stratégie thérapeutique validée pour contrôler les douleurs neurogènes résistantes aux médicaments. La stimulation magnétique transcranienne répétitive (SMTr) permet de stimuler le cortex moteur de façon non invasive et précise. Nous avons appliqué une séance de SMTr du cortex moteur à 10 Hz pendant 20 min, au moyen d’une bobine réellement efficace ou d’une bobine « placebo », chez 14 patients souffrant de douleurs résistantes au traitement médicamenteux et liées à un accident vasculaire thalamique ou à une neuropathie trigéminale. Nous avons évalué les effets de la SMTr sur le niveau de douleur estimé sur une échelle visuelle analogique échelonnée entre 0 et 10, du 1er au 12e jour suivant la séance de SMTr. Une réduction significative de la douleur fut observée jusqu’au 8e jour suivant la SMTr « réelle ». Cette étude montre qu’un soulagement de la douleur peut être obtenu chez des patients souffrant de douleurs neurogènes chroniques tout au long de la semaine qui suit une SMTr du cortex moteur appliquée pendant 20 min à 10 Hz.

Section snippets

Patients and methods

The study included 14 right-handed patients, eight females and six males, aged 34 to 80 years (mean 57.2 years). None had history of seizures. The patients presented chronic, drug-resistant, unilateral pain and were referred to our hospital to be treated by implanted motor cortex stimulation. The pain was due to a thalamic stroke (infarction or haemorrhage) (n = 7) or a trigeminal neuropathy (with past history of surgery in the trigeminal territory or thermocoagulation of the trigeminal

Results

No adverse effects of rTMS were observed immediately after the session or the days after; in particular no seizures were induced.

Figure 1 presents the mean daily VAS scores following ‘real’ and ‘sham’ 10Hz-rTMS session in the entire series of 14 patients. A significant reduction of the daily VAS scores was found from days 1 to 8 after ‘real’ 10Hz-rTMS session compared to ‘sham’ stimulation (P-values ranged between 0.013 and 0.049). From days 9 to 12, the difference between the two conditions

Discussion

This study shows for the first time that pain relief could last about a week after 10Hz-rTMS of the motor cortex in patients suffering chronic neurogenic pain of various origins. However, definitive conclusions could not be made considering separately the two types of pathologies assessed in this study, i.e. thalamic stroke and trigeminal neuropathy, due to the too small number of patients in each subgroup.

The lowest pain scores were observed between 2 and 4 days following the rTMS session, and

Acknowledgements

The authors are indebted to Isabelle Menard and Richard Morales for their technical assistance. The work was supported by a grant from the ‘Institut UPSA de la douleur’.

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