GABA and Glutamate in Pediatric Migraine

Tiffany Bell; Mehak Stokoe; Akashroop Khaira; Megan Webb; Melanie Noel; Farnaz Amoozegar; Ashley D. Harris

Disclosures

Pain. 2020;162(1):300-308. 

In This Article

Materials and Methods

Ethics Statement

The study protocol was approved by the Conjoint Health Research Ethics Board (CHREB), University of Calgary. All the study participants provided informed assent and their parents provided informed consent at time of enrollment.

Participants

Thirty-five children with migraine (migraine group) aged 7 to 13 years with a diagnosis of migraine from their family physician were recruited from the Vi Riddell Pain Clinic at the Alberta Children's Hospital and the local community. Participants were included if they had received a physician diagnosis of migraine, which was confirmed using the ICHD-III beta diagnostic criteria,[32] with no other accompanying neurological, psychiatric, or systematic disorders (eg, Attention Deficit Hyperactivity Disorder (ADHD), autism), they met the standard Magnetic Resonance Imaging (MRI) safety criteria (eg, no metal implants or devices), and were not taking preventative medications such as triptans.

Thirty-one age- and sex-matched children without migraine (control group) were recruited using the Healthy Infants and Children Clinical Research Program (HICCUP). The same exclusion criteria of no neurological, psychiatric, or systemic disorders and standard MRI safety criteria were applied for the control participants; in addition, control participants were excluded if they had any history of migraine or other headache disorder.

Migraine Diary

The parents of children with migraine were asked to keep a migraine diary for 30 days preceding their appointment and 7 days after, which was sent to their computer or mobile device. In this diary, they were asked to record if their child had had a migraine that day and, if so, the length and pain level of the attack using the Wong–Baker FACES pain rating scale[49] from 1 to 10, along with how they treated the migraine. If the child did not have a migraine in the 7 days after the appointment, they were asked to provide the date of the following migraine. Using the migraine diaries, the "position in the migraine cycle" at the time of scanning was calculated as the number of days since the last migraine divided by the number of days between the last migraine and the next. A higher number represents being further along in the cycle and, subsequently, closer to the next migraine, while accounting for interindividual differences in overall length of the migraine cycle. Children with migraine were excluded if they did not experience a migraine in the 30 days preceding their appointment, or if they experienced a migraine on the day of the appointment.

Questionnaires

All participants completed the following questionnaires: Headache Impact Test (HIT-6),[27] Pediatric Migraine Disability Assessment (PedMIDAS),[23] Revised Children's Anxiety and Depression Scale (RCADS) short version,[14] Puberty Status Scale,[6] and the Edinburgh Handedness Scale.[35] The HIT-6 is a 6-item self-report survey that assesses the negative impact of headaches on normal daily activity. Responses range from 36 to 78, with higher scores representing more negative impact. PedMIDAS is a pediatric version of the self-report Migraine Disability Assessment (MIDAS) questionnaire commonly used in adults, and has been validated in children and adolescents ranging from 6 to 18.[23] Responses range from 0 to 90 with higher scores representing more negative impact. The RCADS is a self-report measure developed to assess anxiety and depression symptoms among children and adolescents, and has been validated in children and adolescents ranging from 6 to 18.[8] Responses range from 0 to 45 for anxiety and 0 to 30 for depression, with higher scores representing more symptoms. The Pubertal Status Scale is a self-report measure based on the Tanner pubertal staging, and scores are categorised into the following stages: prepubertal, early pubertal, midpubertal, late pubertal, and postpubertal.[6]

MR Acquisition

Scanning was performed on a 3T GE 750w MR scanner using a 32-channel head coil. A T1-weighted anatomical image was collected for voxel placement (BRAVO; TE/TR = 2.7/7.4 ms, 1 mm3 isotropic voxels). The 3 × 3 × 3 cm3 voxels were placed in the thalamus (midline centred), right sensorimotor cortex (the hand-knob of the motor cortex was used for initial localization and then the voxel was centered between the precentral gyrus and postcentral gyrus; the voxel was then rotated such that the coronal and sagittal planes aligned with the cortical surface[53]), and the occipital cortex (as close to aligning with the parieto-occipital sulcus as possible, without including cerebellum, midline centred; Figure 1). GABA-edited spectroscopy data were collected using macromolecule-suppressed MEGA-PRESS (TR/TE = 1800/80 ms, 20 ms editing pulses at 1.9 and 1.5 ppm, 256 averages) from each brain area. Separate PRESS data (TR/TE = 1800/35 ms, 64 averages) were also acquired from each region to quantify glutamate.[3]

Figure 1.

Example voxel placement (top row) and overlay of all (migraine and control) MEGA-PRESS (middle row) and PRESS spectra (bottom row) for (A) thalamus, (B) sensorimotor cortex, and (C) visual cortex.

Magnetic Resonance Spectroscopy Analysis

MEGA-PRESS data were analysed using Gannet3.1,[15] which included the following preprocessing steps: coil combination, frequency and phase correction, apodization, and down-weighting of motion-corrupted averages. Tissue correction, including tissue-specific water visibility, and T1 and T2 relaxations of both water and metabolites, was performed using voxel tissue fractions obtained by generating a subject-specific voxel mask registered to each individual tissue segmented T1 anatomical image.[21] GABA was quantified relative to water.

PRESS data were preprocessed with the FID-A[42] toolbox using the following preprocessing steps: coil combination, removal of motion-corrupted averages, frequency drift correction, and zero-order phase correction.[34] LCModel Version 6.3–1J[40] was used to apply eddy current correction and quantification relative to water. Basis sets for quantification (including alanine, aspartate, glycerophosphocholine, phosphocholine, creatine, phosphocreatine, GABA, glutamate, glutamine, lactate, inositol, N-acetyl aspartate, N-acetylaspartylglutamate, scyllo-inositol, glutathione, glucose, and taurine) were simulated using the FID-A toolbox based on exact sequence timings and RF pulse shapes. Metabolite values were corrected for tissue composition, including tissue-specific water visibility, and T1 and T2 relaxations of both water and metabolites[17] using the tissue fractions generated from Gannet3.1. Glutamate was quantified both on its own (Glu) and as a combination (Glx) of glutamate and its precursor, glutamine. Glutamate and glutamine overlap on the spectra due to their similar chemical compositions; subsequently, it is difficult to separate the individual signals. Data quality was assessed by visual inspection and metabolite linewidth, and spectra with a linewidth over 0.1 ppm were excluded.

Statistical Analysis

Statistical analysis was conducted using SPSS (IBM. 2017. IBM SPSS Statistics for Macintosh, Version 25.0. Armonk, NY: IBM). Demographic data (Table 1) were compared between children with and without migraine using independent t-tests for age, and χ 2 tests for sex and pubertal status. Clinical migraine scores and anxiety and depression scores were compared between groups using analyses of covariance (ANCOVAs) with age included as a covariate. In addition, voxel tissues fractions were compared across groups using ANCOVAs with age included as a covariate (no significant differences were seen in voxel tissue fractions; see Supplemental Table 1, available at http://links.lww.com/PAIN/B134).

GABA, Glx, glutamate, and GABA/Glx from all 3 brain areas were compared between children with migraine and controls using ANCOVAs with age included as a covariate. In addition, data from the visual cortex of children with migraine were also subdivided into 2 groups based on whether the child experienced visual aura symptoms (migraine with aura and migraine without aura) due to known functional and structural differences between the 2 migraine subtypes.[26] A 3-group ANCOVA was then used to compare GABA, Glx, glutamate, and GABA/Glx from the visual cortex between migraine with aura, migraine without aura, and controls.

Partial correlation analyses, controlling for age, were used to test the relationship between metabolite levels and migraine characteristics within the migraine group (migraine with aura + migraine without aura). Specifically, the relationship between metabolite levels and (1) how long the child had suffered from migraines (years with migraines), (2) migraine burden as measured by the PedMIDAS, and (3) the position in the migraine cycle.

In a secondary analysis, N-acetyl aspartate, creatine, choline, and inositol were compared between children with and without migraine using ANCOVAs with age as a covariate. No significant differences were detected between groups (see Supplemental Table 2, available at http://links.lww.com/PAIN/B134).

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