title: Abnormal cortical responses to somatosensory stimulation in medication-overuse headache.
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.
authors.affiliation: G.B. Bietti Eye Foundation-IRCCS, Dept of Neurophysiology of Vision and Neurophthalmology, Rome, Italy. gianluca.coppola@uniroma1.it
authors.forename: Gianluca
authors.initials: G
authors.lastname: Coppola
authors.forename: Antonio
authors.initials: A
authors.lastname: Currà
authors.forename: Cherubino
authors.initials: C
authors.lastname: Di Lorenzo
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Parisi
authors.forename: Manuela
authors.initials: M
authors.lastname: Gorini
authors.forename: Simona Liliana
authors.initials: SL
authors.lastname: Sava
authors.forename: Jean
authors.initials: J
authors.lastname: Schoenen
authors.forename: Francesco
authors.initials: F
authors.lastname: Pierelli
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D051271:Headache Disorders, Secondary / Q000139:chemically induced* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013003:Somatosensory Cortex / Q000503:physiopathology*