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Published on: July 29, 2021
Abnormal cortical responses to somatosensory stimulation in medication-overuse headache
Gianluca Coppola1, Antonio Currà, Cherubino Di Lorenzo
1G.B. Bietti Eye Foundation-IRCCS, Dept of Neurophysiology of Vision and Neurophthalmology, Rome, Italy. gianluca.coppola@uniroma1.it
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.
Insights
Medication-overuse headache (MOH) patients show increased cortical sensitization and lack of habituation in somatosensory evoked potentials (SEPs). This sensory sensitization may contribute to compulsive drug use in MOH.
Area of Science:
- Neuroscience
- Clinical Neurology
Background:
- Medication-overuse headache (MOH) is a common and disabling neurological disorder.
- Central sensitization is a key factor in MOH pathophysiology.
- The electrophysiological profile of central sensitization in MOH is not well understood.
Purpose of the Study:
- To investigate differences in somatosensory evoked potential (SEP) sensitization and habituation between patients with MOH and episodic migraine without aura (MOA).
- To explore the role of central sensitization in the pathophysiology of MOH.
Main Methods:
- Median-nerve SEPs were recorded in patients with MOH, episodic MOA (interictally and ictally), and healthy controls.
- SEP sensitization was assessed by initial amplitude (block 1), and habituation by amplitude changes across three sequential blocks.
Main Results:
- Episodic migraineurs showed a lack of SEP habituation between attacks.
- Patients with MOH exhibited larger initial SEP amplitudes and failed to habituate, indicating increased cortical sensitization.
- SEP amplitudes were lowest in triptan overusers and those with longer migraine history, and highest in those with longer headache chronification.
Conclusions:
- The somatosensory cortex in MOH patients, particularly those overusing NSAIDs, demonstrates heightened sensitization.
- This sensory sensitization may contribute to the behavioral sensitization driving compulsive medication intake.
- Findings suggest drug-induced alterations in central serotoninergic pathways may underlie MOH pathophysiology.
