Is Palinopsia in Migraineurs a Phenomenon of Impaired Habituation of Visual Cortical Neurons?

Palinopsia in migraine has been reported recently, which may be due to the dysexcitability of visual cortical neurons. In this cross-sectional study, we report the correlation of neuronal dysexcitability with palinopsia using pattern shift visual evoked potential (PSVEP) in 91 migraineurs and 25 healthy controls. The presence of palinopsia was evaluated using a novel objective method, and revealed more frequent palinopsia in the migraineurs compared to the controls (53 of 91 [58.2%] vs 3 of 25 [12%]; P < .001). Five consecutive blocks of PSVEP were recorded for the evaluation of sensitization and impaired habituation. Amplitudes of N75 and P100 in block 1 were considered for sensitization. Impaired habituation of N75 and P100 was considered if any amplitudes in blocks 2 to 5 were higher than block 1. Impaired habituation was more frequent in migraineurs compared with the controls, and was more marked in wave N75 (81.3% vs 32%; P < .001) than wave P100 (63.7% vs 44%; P = .12). Impaired habituations of wave N75 (81.7% vs 58.9%; P = .008) and wave P100 (71.7% vs 46.4%; P = .008) were more frequent in those with palinopsia compared with those without. There was a lack of suppression of P100 amplitude in block 3 in the palinopsia group compared to the controls. The duration of palinopsia correlated with the extent of impaired habituation of N75. It can be concluded that the impaired habituation of PSVEP waveforms is a biomarker of palinopsia in migraine.

MIGRAINE MONITORING IN THE TIME OF COVID-19: TRIGGERS AND PROTECTORS DURING A PANDEMIC

OBJECTIVE

Aim of the present observational study was to assess the impact of COVID-19 quarantine on migraine and evaluate potential influencing factors. Previous studies reported mixed results regarding clinical outcome during quarantine in patients with migraine. In particular, data from areas strongly affetcted by COVID-19 pandemic are missing.

METHODS

One-hundred and seventy patients, previously assessed at the Headache Centre - ASST Spedali Civili Brescia, underwent a telephonic interview regarding migraine features and clinical, occupational and lifestyle variables.

RESULTS

Compared to baseline, during quarantine, we found a significant overall reduction in migraine days (14.7±0.6 vs 12.3±0.7, p <0.001), with 47.1% patients reporting a clinical improvement. Outdoor living spaces (OR 2.3, 95% CI 1.7-3.07, p = 0.009), a positive attitude throughout quarantine (OR 4.12, 95% CI 2.3-7.1, p = 0.03), working full-time (OR 1.03, 95% CI 0.5-1.9, p < 0.001) and a baseline diagnosis of chronic migraine (OR 1.4, 95% CI 1.1-2.02, p = 0.002) were associated with an increased chance of migraine improvement. Being single (OR 1.5, 95% CI 1.1-2.01, p = 0.05) and physical inactivity (OR 1.3, 95% CI 1.1-1.6, p = 0.02) were associated with an increased risk of worsening.

CONCLUSIONS

Quarantine had an overall positive impact on migraine. Based on our results, we hypothesize the reduction of daily hassles and challenges might be the main reason for such improvement.

Neuronal Dysexcitability May Be a Biomarker of Migraine: A Visual Evoked Potential Study

We report neuronal sensitization and impaired habituation in migraine using pattern reversal visual evoked potential (PRVEP) and correlate these with clinical characteristics of migraine. Sixty-five migraineurs and 30 healthy controls were included. A detailed clinical examination was done and migraine characteristics, including migraine trigger, photophobia, phonophobia, and allodynia were noted. Consecutive 5 blocks of PRVEP were recorded averaging 100 epochs at 3 Hz stimuli. The amplitude of N75 and P100 were measured. Amplitude of first block was considered for sensitization, and impaired habituation was considered if any subsequent block was not suppressed. Migraineurs had sensitization of P100 (14.01 ± 6.02 vs 11.60 ± 5.17 µV; P = .049), but not of N75 (42.22 ± 4.79 vs 11.08 ± 4.56 µV; P = .27) compared with the controls. Impaired habituation of N75 was more marked and persisted up to fourth block of VEP recoding. Impaired habituation of P100 was significant only in the third block. Baseline N75 and P100 amplitudes were higher in females, and N75 was also higher in those with longer duration of illness. These phenomena did not correlate with visual triggers. Sensitization and impaired habituation were marked during headache. Based on the PRVEP findings, it may be concluded that migraineurs have sensitization of P100 and impaired habituation of N75 especially during headache. These phenomena may be useful for therapeutic monitoring.

Hypothalamic and basal ganglia projections to the posterior thalamus: possible role in modulation of migraine headache and photophobia

Migraine attacks are typically described as unilateral, throbbing pain that is usually accompanied by nausea, vomiting, and exaggerated sensitivities to light, noise and smell. The headache phase of a migraine attack is mediated by activation of the trigeminovascular pathway; a nociceptive pathway that originates in the meninges and carries pain signals through meningeal nociceptors to the spinal trigeminal nucleus and from there to the cortex through relay neurons in the thalamus. Recent studies in our lab have identified a population of trigeminovascular neurons in the posterior (Po) and lateral posterior (LP) thalamic nuclei that may be involved in the perception of whole-body allodynia (abnormal skin sensitivity) and photophobia (abnormal sensitivity to light) during migraine. The purpose of the current study was to identify sub-cortical areas that are in position to directly regulate the activity of these thalamic trigeminovascular neurons. Such process begins with anatomical mapping of neuronal projections to the posterior thalamus of the rat by performing discrete injections of the retrograde tracer Fluorogold into the Po/LP region. Such injections yielded retrogradely labeled neurons in the nucleus of the diagonal band of Broca, the dopaminergic cells group A11/A13, the ventromedial and ventral tuberomammillary nuclei of the hypothalamus. We also found that some of these neurons contain acetylcholine, dopamine, cholecystokinin and histamine, respectively. Accordingly, we speculate that these forebrain/hypothalamic projections to Po and LP may play a role in those migraine attacks triggered by disrupted sleep, skipping meals and emotional reactions.

Odorant substances that trigger headaches in migraine patients

OBJECTIVES

Our objective was to determine odorants that trigger migraine attacks and the time of onset of headache after exposure.

METHODS

Migraine or tension-type headache patients, diagnosed according to the criteria of the International Classification of Headache Disorders-II, were interviewed about lifetime prevalence of headaches triggered by odors and time of onset of pain, after exposure of the patient to the odor.

RESULTS

We studied 200 migraine patients and 200 tension-type headache patients. There were odor-triggered headaches after 25.5 ± 1.9 minutes of exposure in 70.0% (140/200) of migraine patients and none with tension-type headache, which ran at low sensitivity (70.0%, 95% CI 63.1-76.2) and high specificity (100.0%, 95% CI 97.6-100.0). Odor-triggered headaches are distributed in the following order of frequency: perfumes (106/140, 75.7%), paints (59/140, 42.1%), gasoline (40/140, 28.6%) and bleach (38/140, 27.1%). There was significance in the association of odor-triggered migraine, especially among perfume with cleaning (phi = -0.459), cooking (phi = 0.238), beauty products (phi = -0.213) and foul odors (phi = -0.582).

CONCLUSIONS

Odorants, isolated or in association, especially perfume, may trigger migraine attacks after a few minutes of exposure.