SAN DIEGO — Susceptibility to posttraumatic headache could be linked to mutations in ion channel and ion transporter genes, according to results from a preliminary study.
Posttraumatic headache is a common symptom of traumatic brain injury (TBI).
There is evidence that genetic mutations could play a role in both TBI development and response. In particular, the S213L mutation for familial hemiplegic migraine-1 (FHM1), found in the CACNA1A gene, can cause individuals carrying it to be highly sensitive to otherwise trivial head impacts, according to Lyn Griffiths, PhD.
The consequences can be posttraumatic headache but also seizures, cerebral edema, coma, or worse. Another form of FHM is associated with mutations in ATP1A2.
"This stimulated our interest in looking at genes that relate to TBI with a particular focus on ion channel genes," said Dr Griffiths, during a presentation of the study at the annual meeting of the American Headache Society.
The researchers analyzed data from 117 participants who had at least one concussion with a posttraumatic headache and recruited family members when possible. There were 15 participants who developed severe reactions to trivial head trauma, 13 who had been diagnosed with concussion and underwent imaging related to TBI-associated symptoms, 54 who had been recruited through local sporting groups campuses, and 35 recruited through a medical research foundation. Blood or saliva samples were used to perform whole exome sequencing.
The researchers looked for gene candidates within different tiers. Tier 1 included genes that had already been implicated in severe migraine. The second tier included 353 ion channel and iron transporter genes. Tier 3 comprised neurotransmission-related genes.
After sequencing, the researchers filtered genetic mutations to include only those that affected amino acid composition of the protein, were predicted by two or more in silico analysis tools to be damaging, and were identified in multiple, unrelated patients.
In tier 2, the greatest number of potential damaging variants were found in the SCN9A gene, which is involved in pain perception and processing. There were six variants found in eight cases. Of these eight individuals, three had suffered severe reactions to relatively minor head trauma.
In tier 3, the researchers identified mutations in eight neurotransmitter-related genes.
Through comparison with a general population control group, the researchers identified 43 different rare, amino acid–changing variants that occurred within 16 ion channel and ion channel transporter genes. These mutations were found in 53 individuals, at an approximately fivefold higher frequency than the control group (odds ratio, 5.6; P < .0001).
"We identified a number of rare genetic variants implicated in migraine — ion channel and other neurologically associated genes — in those suffering from posttraumatic headache," said Dr Griffiths. She also noted that the whole genomes they collected will allow for further analysis of other gene candidates in the future.
During the Q&A period, Dr Griffiths was asked if the research group tracked the severity of the TBIs suffered by participants. She responded that they had not, and this was a limitation of the study.
Another questioner asked if parents should consider genetic testing for susceptibility mutations when considering whether to allow a child to participate in sports or activities with elevated risk of TBI. "I don't necessarily think this is a bad thing," she said, though she conceded that the work is still immature. "It's probably a bit early because we haven't identified all the genes that are involved or all the specific mutations...but I think down the track, that makes perfect sense. Why would you not do some sensible preventive screening to aid with things like maybe you wear more headgear or you consider what's the appropriate sport for that person?"
Laine Green, MD, assistant professor of neurology at Mayo Clinic Arizona, Phoenix, who moderated the session, was asked for comment. "I think the idea of potentially identifying people that have more genetic susceptibility to injuries is very intriguing because posttraumatic headache and symptoms is always a difficult area to treat, potentially identifying those that with more genetic susceptibility might be helpful. It may also potentially allow us to target specific treatments, especially in this case, looking at different ion channels. There are medications that may work better at ion channel targets than other targets," said Dr Green.
He also endorsed the potential value of screening. "Speaking as a parent, I might like to know my child is at higher risk if they're going to participate in contact sports or other high-risk activities," he said.
Dr Griffiths and Dr Green have no relevant financial disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.