In short, this study has revealed important differences between migraine and TTH. Migraineurs had progressive illness with increasing severity, frequency and duration of each headache episode as compared to TTH subjects; in other words, they were moving toward chronification.
Along with the headache, they more commonly suffered orthostatic pre-syncope, palpitations, nausea, vomiting, phonophobia, photophobia, and osmophobia. Their pain tended to be aggravated by head bending and exercise. Analgesics were more likely to relieve pain in migraineurs. Similarly, CAS were more likely to be seen in migraineurs. In addition, post-headache lethargy was more frequent among the migraineurs.
On the other hand, stressful situations used to trigger TTH and muscle parafunction was more common in TTH patients. Even though a few TTH subjects did show CAS, they were never lateralized. Hence, these factors may be used to differentiate both the headaches from each other.
This study suggests that migraine is more likely to progress over time in terms of frequency, severity and illness as compared to TTH. This suggests that migraine is more likely to be complicated then TTH. Chronic migraine is considered as a complication of the episodic migraine and likely to evolve owing to multiple factors.[16
] These factors may include associated illnesses and frequency of medication overuse secondary to the intolerability of the migraine pain.[1
] What makes the TTH worse is still an enigma and further research is required to clarify this issue.
Weather, smell, smoke and light were reported as the precipitating factors that differentiate migraine from TTH.[19
] It was reported that stress was a precipitating factor for both migraine and TTH.[19
] Contrary to this, we found that stress was more likely to precipitate TTH as compared to migraine. Similar results were reported by Donias et al
] who found that negative emotions more commonly precipitated TTH than migraine. They suggested that TTH subjects could be having different or defective cognitive schemata that process the given emotional stimuli in their own way to start the pain as compared to migraineurs. Though they had suggested that these schemata work in a stereotyped manner, this does not seem to be a case as stress did not precipitate the pain at all times as we see in clinical practice. Moreover, stress was not the precipitating factor in all TTH subjects in this study; rather, it was just more frequent in this group. Hence, this issue requires more investigation in future with improved methodology.
In concordance with the previous study,[19
] our study confirms that in addition to light and noise head bending, smells and straining/exercise increase the pain in migraineurs but not in TTH subjects. Whether this can truly differentiate the TTH subjects from migraineurs is still an illusion, but our results, especially the absence of phonophobia and photophobia in TTH subjects, are consequent to the strict adherence to the ICHD-2. However, it is still not uncommon to find out the TTH subjects with these features in clinical practice and even in literature.[9
] Our experience suggests that most of these TTH subjects later on develop migraine or that they have any family member suffering from migraine. This notion can be explained on the basis of modular headache theory.[21
Osmophobia during migraine is an important symptom that has gained acceptance among the scientific community in the past.[22
] A number of studies confirm its association with migraine and it is now proposed to be included in the ICHD diagnostic criteria. Similarly, orthostatic pre-syncope as well as the palpitations were more common in migraineurs. This confirms the previous reports of autonomic disturbances among these patients.[8
] Why the disturbances are limited to the migraineurs and are not seen during the TTH is still an enigma and requires further research.
Analgesics were more likely to relieve migraine headache as compared to TTH. Not only the relieving factors but also the pain-relieving behavior may be used to differentiate both these headaches. Previous literature suggests that migraineurs frequently engage in a number of activities like pressing and applying cold stimuli to the painful site, trying to sleep, changing posture, sitting or reclining in bed, isolating themselves, using symptomatic medication, inducing vomiting, changing diet and becoming immobile during the attacks.[25
] On the contrary, TTH patients use only the scalp massage.[25
Until recent past, CAS were considered to be the hallmark of cranial autonomic cephalalgias.[6
] Their presence was never considered important in migraine till a few reports were published emphasizing upon these symptoms.[26
] Later on, these were also reported in TTH subjects.[30
] However, during our previous study and even during the present study, we found that mostly they were only partially lateralized.[26
] Unilateral symptoms were reported in a small number of migraineurs only.[26
] This goes in concordance with the modular headache theory.[21
Muscle parafunction was more common in the TTH subjects as compared to the migraineurs, as well as stress was more commonly a triggering factor for it. This has been reported in the past.[19
] The muscle hypertrophy is consequent to the activation of muscles owing to the stress or it could be related to the central sensitization.[32
] Central sensitization is known to occur in both migraine as well as TTH;[34
] however, in this study, central sensitization was more frequent among migraineurs as compared to the TTH subjects. Cognitive stress is known to evoke muscle pain in the pericranial areas and this response differs between migraineurs and TTH subjects.[36
] TTH subjects had more pain in the temporalis and frontalis, whereas migraineurs developed more pain in splenius and temporalis. Contrary to migraineurs, TTH subjects had delayed pain recovery in all muscle regions.[36
] However, we did not study the regional difference in the hypertrophy in this study and this is clearly an area for future research.
However, this study has some limitations. Firstly, strict inclusion criteria in this study preclude from generalizing the results as subjects with such isolated illness are not very common in the clinics. Hence, results must be applied with caution in the general population. Secondly, sample size of the study was small relative to the prevalence of the illnesses in question owing to strict exclusion criteria. We suggest inclusion of a larger sized sample in the future studies.
In conclusion, certain symptoms not mentioned in the ICHD-2 can be used to differentiate between migraine and TTH patients.