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Open Access Research article

Abnormal cortical responses to somatosensory stimulation in medication-overuse headache

Gianluca Coppola1*, Antonio Currà2, Cherubino Di Lorenzo34, Vincenzo Parisi1, Manuela Gorini2, Simona Liliana Sava4, Jean Schoenen4 and Francesco Pierelli25

Author Affiliations

1 G.B. Bietti Eye Foundation-IRCCS, Dept of Neurophysiology of Vision and Neurophthalmology, Rome, Italy

2 Dept of Medical and Surgical Sciences and Biotechnologies, "Sapienza" University of Rome Polo Pontino, Italy

3 Don Carlo Gnocchi Onlus Foundation, Rome, Italy

4 Headache Research Unit. University Dept. of Neurology & GIGA-Neurosciences, Liège University, Liège, Belgium

5 INM Neuromed IRCCS, Pozzilli (IS), Italy

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BMC Neurology 2010, 10:126  doi:10.1186/1471-2377-10-126

Published: 30 December 2010

Abstract

Background

Medication-overuse headache (MOH) is a frequent, disabling disorder. Despite a controversial pathophysiology convincing evidence attributes a pivotal role to central sensitization. Most patients with MOH initially have episodic migraine without aura (MOA) characterized interictally by an absent amplitude decrease in cortical evoked potentials to repetitive stimuli (habituation deficit), despite a normal initial amplitude (lack of sensitization). Whether central sensitization alters this electrophysiological profile is unknown. We therefore sought differences in somatosensory evoked potential (SEP) sensitization and habituation in patients with MOH and episodic MOA.

Methods

We recorded median-nerve SEPs (3 blocks of 100 sweeps) in 29 patients with MOH, 64 with MOA and 42 controls. Episodic migraineurs were studied during and between attacks. We measured N20-P25 amplitudes from 3 blocks of 100 sweeps, and assessed sensitization from block 1 amplitude, and habituation from amplitude changes between the 3 sequential blocks.

Results

In episodic migraineurs, interictal SEP amplitudes were normal in block 1, but thereafter failed to habituate. Ictal SEP amplitudes increased in block 1, then habituated normally. Patients with MOH had larger-amplitude block 1 SEPs than controls, and also lacked SEP habituation. SEP amplitudes were smaller in triptan overusers than in patients overusing nonsteroidal anti-inflammatory drugs (NSAIDs) or both medications combined, lowest in patients with the longest migraine history, and highest in those with the longest-lasting headache chronification.

Conclusions

In patients with MOH, especially those overusing NSAIDs, the somatosensory cortex becomes increasingly sensitized. Sensory sensitization might add to the behavioral sensitization that favors compulsive drug intake, and may reflect drug-induced changes in central serotoninergic transmission.