Pathophysiology of Headaches Flashcards
What is hyperalgaesia?
Decreased pain threshold - nociception hypersensitivity
What is allodynia?
Innocuous stimuli perceived as noxious
Which nerve is involved in headaches and what does it innvervate?
Trigeminal (VI) nerve
Jaw and brain vasculature
Which brain areas cause descending pain inhibition?
PAG and RVM
What are the symptoms of a tension-type headache?
Bilateral pressure Not affected by movement No nausea/photophobia/phonophobia Pericranial muscle tenderness No pericranial muscle inflammation
What is the cause of episodic tension-type headache?
Peripheral neuron sensitised - more central neuron activation - stops without input from peripheral neuron
What is the cause of chronic tension-type headache?
Central neuron sensitised - remains active without input from peripheral neuron
What are the 3 types of trigeminal autonomic cephalagies and what are their characteristics?
SUNCT - short, very frequent
Paroxysmal hemicrania - moderate duration, moderate frequency
Cluster headache - long, infrequent
What are the symptoms of cluster headache?
Stabbing pain on one side of face
Autonomic features on one side of face - weeping eye, facial sweating, eyelid oedema
Bursts of attacks - divided by remission periods
What is the cause of TACs?
Hypothalamic malfunction
What are the symptoms of a migraine?
Aura/no aura Unilateral throbbing pain Nausea Photophobia/phonophobia/osmophobia Pain worsened by movement
What are the triggers of migraine?
Missing meals
Missing sleep
Hormones - in females
Stress
What are the phases of a migraine attack and what do they involve?
Premonitory - craving, yawning, heightened perception
Aura
Headache - nausea, hypersensitivity, poor concentration
Resolution - deep sleep, vomiting
Recovery - tired, hungover
Which condition is used to study migraine genetics?
Familial hemiplegic migraine
What is the overall effect of the genetic mutations involved in familial hemiplegic migraine?
Neuronal hyperexcitability
What is FHM1 and what is the effect of its mutation?
Ca2+ channel gene
Increased presynaptic Ca2+ influx
What is FHM2 and what is the effect of its mutation?
Na+/K+ ATPase gene
Decreases K+ and glutamate uptake into glia
What is FHM3 and what is the effect of its mutation?
Na+ channel gene
Increases high frequency discharges
What is the evidence for the hyperexcitability migraine theory?
Increased plasma and CSF glutamate in sufferers
Lower threshold for visual cortex excitation in sufferers
What type of brain activity occurs in the premonitory phase of migraine?
Increased hypothalamic activity
What is an aura?
Transient sensation - e.g. visual blindspot, tingling limbs
What type of brain activity occurs in the aura phase of migraine?
Cortical waves of spreading depression - initial excitation leaves wave of spreading depolarisation
Move at slow rate
Do not cross cerebral hemispheres or spread to deeper brain areas
Could release mediators - inducing headache
What is the effect of meninge stimulation?
Headache pain
What is the evidence for the role of the trigeminovascular system in migraine?
Calcitonin gene-related peptide (CGRP) increased in cranial circulation during migraine - may be trigeminal origin
NO and CGRP infusion causes vasodilation of intracranial blood vessels and headache in all - also delayed migraine only in sufferers
What is the evidence for the role of brainstem activation in migraine?
PAG, locus coeruleus, dorsal raphe nucleus, nucleus raphe magnus - activated on side ipsilateral to pain
What is the evidence of the role of thalamus activation in migraine?
Seen in brain imaging of spontaneous and induced migraine attacks
May be caused by initial hypothalamic activation - causes progression from premonitory to headache phase
