Persistent post-traumatic headache and migraine are correlated  with differences in brain structure, suggesting differences in pathophysiology.

Many patients with post-traumatic headache (PTH) have characteristics that exhibits homogeneity with migraine phenotype. The only clinical feature that distinguishes PTH from migraine is the history of head injury. According to the International Classification of Headache Disorders (ICHD) 3 beta criteria, a PTH starts within 7 days of head injury or within 7 days of being able to detect headaches following a head injury. If the PTH persists for at least 3 months, it is classified as “persistent PTH” (PPTH). The above criteria do not comprise of any headache features that can distinguish between headache types such as migraine or tension-type headache (TTH). The diagnosis of PTH is easy in patients without any history of migraine but possess head trauma and develops headache immediately following the trauma. There are no clear evidences suggesting that head trauma leads to PTH or if the trauma unmasked an underlying propensity toward the development of migraine. Differentiating the pathophysiology of migraine and PTH can be helpful in establishing migraine and PTH as a separate ailment and plan a best suitable management plan.

Rationale behind the research:

There are no evidences supporting the notion that migraine and PTH are different. Therefore, this study relies on identification of differences between pathophysiology  of migraine and PTH that differentiates between migraine and PTH.

Objective:

To undergo a comparative analysis of measures of brain regional volume, cortical thickness, surface area, and brain curvature in patients with PPTH attributed to mild traumatic brain injury (mTBI) to patients with migraine.

Study outcome measures:

• The baseline characteristics include demographics charaacteristics, scores on questionnaires, and headache characteristics 
• The other outcome measures included evaluation of regional volumes, cortical thickness, surface area and curvature measurements calculated from T1-weighted sequences and comapred using ANCOVA and MRI data
  

Study outcomes

Baseline: There were no significant baseline differences between the groups. 

Other outcomes:

• There were significant differences observed in regional volumes, cortical thickness, surface area and brain curvature on comparison of the group of individuals with persistent post-traumatic headache and  the migraine group
• There were structural disimilarities between groups for regions within the right lateral orbitofrontal lobe, left caudal middle frontal lobe, left superior frontal lobe, left precuneus and right supramarginal gyrus (p<0.05) {Fig.1}

PPTH: Persistent post-traumatic headache

Figure 1. Structural disimilarities in brain areas PPTH and migraine group.

• There were differences observed between individuals with persistent post-traumatic headache and healthy controls within the right lateral orbitofrontal lobe, right supramarginal gyrus, and left superior frontal lobe, while no differences were observed when compared the migraine cohort to healthy controls
  

The result of this study determined the differences in brain structure between  PPTH and migraine patients. The results suggests that these two headache types are correlated with distinct underlying pathophysiology despite of substantial similarities in the symptoms. The differences in brain areas of  PPTH and migraine occur in lateral orbitofrontal, superior and middle frontal, precuneus and supramarginal gyrus regions. Frontal regions evaluates affective and cognitive pain and possess  abnormal structure, function, and functional connectivity in individuals with different headache types including migraine, cluster headache, and medication overuse headache. The  precuneus, a core region of the default mode network are involved in the diagnosis of pain sensitivity and pain thresholds. Whereas,  supramarginal gyrus help determining  atypical functions and structures in migraine and medication overuse headache patients. There exists a sufficient data explaining the role of these brain regions in pain and headache, but there is a need to evaluate the reason behing these dissimilarities in brain areas among PPTH and migraine patients. It is most likely that these brain regions are simply more susceptible to the effects of mTBI, causing initiation and persistence of PTH if destructed. Various measures used in this study include volume, area, cortical thickness, and curvature that provides complementary information about the brain structure. These are plastic measures of brain structure that change with aging, learning, and neurodegeneration related to disease. Brain curvature helps to evaluate cortical folding with increased curvature indicating areas of sharper cortical folds, white matter damage, aging, neurodegenderative disease, and mild TBI. Regional volumes are used to measure and compare brain structure between subject cohorts whereas area and  cortical thickness shows more sensitivity to small changes in brain structure. Regional brain area, cortical thickness, and volume have been previously identified to differ in cohorts with headache compared to healthy controls and to contribute to subclassification of headache types.