Rau, Jill C.

Abstract Objective The objective of this study was to summarize the available evidence regarding the clinical value and trend over time of lumbar cerebrospinal fluid (CSF) opening pressure utilization to diagnose spontaneous intracranial hypotension (SIH). Background CSF opening pressure obtained via lumbar puncture is one of the diagnostic criteria for SIH based on the International Criteria for Headache Disorders, 3rd Edition (ICHD‐3), but it has questionable utility as an initial investigation for diagnosing SIH. Methods The authors performed a systematic literature review and meta‐analysis. PubMed/MEDLINE, Scopus, and Cochrane Library were searched from inception to October 2022. Original studies and case series in English reporting three or more patients with suspected or known SIH and CSF pressure measurement were included. Meta‐analyses and meta‐regression were used to calculate pooled estimates and examine the impact of age, sex, and publication year on outcomes, including CSF pressure < 60 mm CSF, orthostatic headache, and positive findings on brain magnetic resonance imaging (MRI), spinal imaging, and radionuclide studies. Results For every 1‐year increase in the year of publication, the odds of reporting low CSF pressure decreased by 6.20% (adjusted odds ratio [aOR] = 0.94, aOR 95% confidence interval [CI] = [0.90, 0.97], p = 0.001), the odds of reporting a positive brain MRI increased by 4.67% (aOR = 1.05, aOR 95% CI = [1.01, 1.09], p = 0.026), and the odds of reporting orthostatic headache increased by 9.13% (aOR = 1.09, aOR 95% CI = [1.03, 1.15], p = 0.002). Each 1% increase in the percentage of patients with orthostatic headache was associated with a 3.13% increase in the odds of low CSF pressure (aOR = 1.03, aOR 95% CI = [1.01, 1.05], p = 0.003). Similarly, as the percentage of patients with low CSF pressure increased by 1%, there was a 2.53% increase in the odds of orthostatic headache (aOR = 1.03, aOR 95% CI = [1.01, 1.04], p = 0.005). It was estimated that 31.9% of patients with SIH had normal opening pressure (95% CI = [24.0%, 40.8%], prediction interval = [5.0%, 80.5%]). Every 1% increase in the percentage of patients with positive brain MRI was associated with a 5.25% increase in the odds of positive spinal imaging (aOR = 1.05, aOR 95% CI = [1.00, 1.11], p = 0.047). Age and positive radionuclide study did not significantly impact the outcomes measured. The corresponding I 2 for each outcome was reduced by controlling for study‐wide covariates believed to impact the prevalence of each outcome. Sensitivity analyses did not reveal discrepancies in results when studies requiring outcomes of interest were removed. Conclusion Our analysis found that recent studies indicate a reduced reliance on opening pressure for diagnosing SIH. Rather, results suggest an increasing reliance on contrast‐enhanced brain MRI, spine imaging, and clinical features for SIH diagnosis.

Background Women with endometriosis are more likely to have migraine. The mechanisms underlying this co-morbidity are unknown. Prolactin, a neurohormone secreted and released into circulation from the anterior pituitary, can sensitize sensory neurons from female, but not male, rodents, monkeys and human donors. Methods We used a syngeneic model of endometriosis to determine whether elevated prolactin levels can sensitize trigeminal ganglion neurons and increase vulnerability to migraine pain. Results Mice with endometriotic lesions showed increased serum prolactin levels and developed persistent abdominal, but not cephalic, allodynia. However, inhalation of a transient receptor potential ankyrin 1 agonist, umbellulone, a known environmental trigger of headache in some patients, elicited cephalic allodynia in mice with endometriosis but not sham controls, suggesting that endometriosis can promote sensitization of trigeminal neurons and migraine attacks. Endometriosis dysregulated the expression of prolactin receptor isoforms in trigeminal neurons and increased their excitability measured by in vitro patch clamp electrophysiology. Inhibition of pituitary prolactin following a 2-week treatment with a dopamine receptor agonist, cabergoline, prevented cephalic allodynia elicited by activation of trigeminal afferents with umbellulone. Cabergoline treatment also normalized the expression of prolactin receptor isoforms in trigeminal ganglia and the hyperexcitability of trigeminal neurons. Conclusions These data demonstrate that circulating prolactin in endometriosis promotes vulnerability to migraine through sensitization of trigeminal afferents. Clinically available dopamine receptor agonists or novel monoclonal antibodies targeting prolactin signaling may be effective for migraine prevention in women with endometriosis.

Abstract Migraine and sleep disorders are common co-morbidities. Patients frequently link their sleep to migraine attacks suggesting a potential causal relationship between these conditions. However, whether migraine pain promotes or disrupts sleep or whether sleep disruption can increase the risk of migraine remains unknown. We assessed the potential impact of periorbital allodynia, a measure consistent with migraine-like pain, from multiple preclinical models on sleep quantity and quality. Additionally, we evaluated the possible consequences of sleep deprivation in promoting susceptibility to migraine-like pain. Following the implantation of electroencephalogram/electromyography electrodes to record sleep, mice were treated with either single or repeated systemic injections of nitroglycerin at the onset of their active phase (i.e. nocturnal awake period). Neither single nor repeated nitroglycerin affected the total sleep time, non-rapid eye movement sleep, rapid eye movement sleep, sleep depth or other measures of sleep architecture. To account for the possible disruptive effects of the surgical implantation of electroencephalogram/electromyography electrodes, we used immobility recordings as a non-invasive method for assessing sleep-wake behaviour. Neither single nor repeated nitroglycerin administration during either the mouse sleep (i.e. daylight) or active (i.e. night) periods influenced immobility-defined sleep time. Administration of an inflammatory mediator mixture onto the dura mater at either sleep or active phases also did not affect immobility-defined sleep time. Additionally, inhalational umbellulone-induced migraine-like pain in restraint-stressed primed mice did not alter immobility-defined sleep time. The possible influence of sleep disruption on susceptibility to migraine-like pain was evaluated by depriving female mice of sleep over 6 h with novel objects, a method that does not increase circulating stress hormones. Migraine-like pain was not observed following acute sleep deprivation. However, in sleep-deprived mice, subthreshold doses of systemic nitroglycerin or dural calcitonin gene-related peptide induced periorbital cutaneous allodynia consistent with migraine-like pain. Our data reveal that while migraine-like pain does not significantly disrupt sleep, sleep disruption increases vulnerability to migraine-like pain suggesting that a therapeutic strategy focused on improving sleep may diminish migraine attacks.

Background Medication overuse is a significant issue that complicates the treatment of headache disorders. The most effective medications for the acute treatment of migraine all have the capacity to induce medication overuse headache (MOH). Novel acute migraine-specific treatments are being developed. However, because the mechanism(s) underlying medication overuse headache are not well understood, it is difficult to predict whether any particular acute medication will induce MOH in susceptible individuals. LY573144 (lasmiditan), a 5-HT 1F receptor agonist, has recently been shown to be effective in the acute treatment of migraine in phase 3 trials. The aim of this study is to determine whether frequent administration of lasmiditan induces behaviors consistent with MOH in a pre-clinical rat model. Methods Sprague Dawley rats were administered six doses of lasmiditan (10 mg/kg), sumatriptan (10 mg/kg), or sterile water orally over 2 weeks and cutaneous allodynia was evaluated regularly in the periorbital and hindpaw regions using von Frey filaments. Testing continued until mechanosensitivity returned to baseline levels. Rats were then submitted to bright light stress (BLS) or nitric oxide (NO) donor administration and were again evaluated for cutaneous allodynia in the periorbital and hindpaw regions hourly for 5 hours. Results Both lasmiditan and sumatriptan exhibited comparable levels of drug-induced cutaneous allodynia in both the periorbital and hindpaw regions, which resolved after cessation of drug administration. Both lasmiditan and sumatriptan pre-treatment resulted in cutaneous allodynia that was evoked by either BLS or NO donor. Conclusions In a pre-clinical rat model of MOH, oral lasmiditan, like sumatriptan, induced acute transient cutaneous allodynia in the periorbital and hindpaw regions that after resolution could be re-evoked by putative migraine triggers. These results suggest that lasmiditan has the capacity to induce MOH through persistent latent peripheral and central sensitization mechanisms.

Background Acute and persistent post-traumatic headache are often debilitating consequences of traumatic brain injury. Underlying physiological mechanisms of post-traumatic headache and its persistence remain unknown, and there are currently no approved therapies for these conditions. Post-traumatic headache often presents with a migraine-like phenotype. As calcitonin-gene related peptide promotes migraine headache, we explored the efficacy and timing of intervention with an anti- calcitonin-gene related peptide monoclonal antibody in novel preclinical models of acute post-traumatic headache and persistent post-traumatic headache following a mild traumatic brain injury event in mice. Methods Male, C57Bl/6 J mice received a sham procedure or mild traumatic brain injury resulting from a weight drop that allowed free head rotation while under minimal anesthesia. Periorbital and hindpaw tactile stimulation were used to assess mild traumatic brain injury-induced cutaneous allodynia. Two weeks after the injury, mice were challenged with stress, a common aggravator of migraine and post-traumatic headache, by exposure to bright lights (i.e. bright light stress) and cutaneous allodynia was measured hourly for 5 hours. A murine anti- calcitonin-gene related peptide monoclonal antibody was administered after mild traumatic brain injury at different time points to allow evaluation of the consequences of either early and sustained calcitonin-gene related peptide sequestration or late administration only prior to bright light stress. Results Mice with mild traumatic brain injury, but not a sham procedure, exhibited both periorbital and hindpaw cutaneous allodynia that resolved by post-injury day 13. Following resolution of injury-induced cutaneous allodynia, exposure to bright light stress re-instated periorbital and hindpaw cutaneous allodynia in injured, but not sham mice. Repeated administration of anti-calcitonin-gene related peptide monoclonal antibody at 2 hours, 7 and 14 days post mild traumatic brain injury significantly attenuated the expression of cutaneous allodynia when evaluated over the 14-day post injury time course and also prevented bright light stress-induced cutaneous allodynia in injured mice. Administration of anti-calcitonin-gene related peptide monoclonal antibody only at 2 hours and 7 days after mild traumatic brain injury blocked injury-induced cutaneous allodynia and partially prevented bright light stress-induced cutaneous allodynia. A single administration of anti-calcitonin-gene related peptide monoclonal antibody after the resolution of the peak injury-induced cutaneous allodynia, but prior to bright light stress challenge, did not prevent bright light stress-induced cutaneous allodynia. Conclusions We used a clinically relevant mild traumatic brain injury event in mice along with a provocative stimulus as novel models of acute post-traumatic headache and persistent post-traumatic headache. Following mild traumatic brain injury, mice demonstrated transient periorbital and hindpaw cutaneous allodynia suggestive of post-traumatic headache-related pain and establishment of central sensitization. Following resolution of injury-induced cutaneous allodynia, exposure to bright light stress re-established cutaneous allodynia, suggestive of persistent post-traumatic headache-related pain. Continuous early sequestration of calcitonin-gene related peptide prevented both acute post-traumatic headache and persistent post-traumatic headache. In contrast, delayed anti-calcitonin-gene related peptide monoclonal antibody treatment following establishment of central sensitization was ineffective in preventing persistent post-traumatic headache. These observations suggest that mechanisms involving calcitonin-gene related peptide underlie the expression of acute post-traumatic headache, and drive the development of central sensitization, increasing vulnerability to headache triggers and promoting persistent post-traumatic headache. Early and continuous calcitonin-gene related peptide blockade following mild traumatic brain injury may represent a viable treatment option for post-traumatic headache and for the prevention of post-traumatic headache persistence. Abbreviations CA Cutaneous allodynia CGRP Calcitonin gene-related peptide mTBI Mild traumatic brain injury PTH Post-traumatic headache APTH Acute post-traumatic headache PPTH Persistent post-traumatic headache