Primary and Secondary Headaches – What Is The Difference?

Within the realm of medical conditions, headaches can be categorized as either primary or secondary, defined by their origins and causative factors. In essence, a primary headache manifests without discernible underlying causes, independent of any other medical condition. On the other hand, a secondary headache is the direct consequence of another disorder, activity, or state, interconnected through a causal relationship. If a headache promptly follows another disorder, or arises due to exposure to a substance, it is defined as “secondary.” For example, if a headache becomes manifest on a daily basis shortly after an accident where the patient hit a wall with their head, it is usually defined as secondary to the head traume.

Occasionally, a headache may exhibit characteristics of both primary and secondary types simultaneously, so let’s explore these two definitions in more detail.

Primary Headaches

Primary headaches constitute the most prevalent type, and include some of the most common disorders such as migraine,tension-type headaches (TTH), and cluster headache. They present themselves as frequent headaches devoid of any apparent cause beyond the headache itself. Primary headaches are genuine medical conditions requiring diagnosis and treatment based on their intrinsic nature rather than symptom intensity. In fact, secondary headaches can often be as distressing and protracted as primary ones, so distinguishing between them solely by symptoms is often not possible. On top of that, many secondary headaches manifest with symptoms that closely resemble one or more of the primary headache disorders.

According to the International Classification of Headache Disorders, primary headaches are categorized into four major groups:

• Tension-type headache (TTH)
• Migraine
• Trigeminal autonomic cephalalgias (TACs)
  • Cluster headache
  • Paroxysmal hemicrania
  • Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT)
  • Short lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA)
  • Hemicrania continua
• Other primary headache disorders

The mechanisms underpinning primary headaches remain incompletely understood, thus complicating the precise differentiation of individual types. For example, two patients may both receive a diagnosis of migraine, but the condition may present as weekly 12-hours long attacks in one patient, and monthly 48-hours long, severe headaches in the other.

Secondary Headaches

Secondary headaches invariably stem from another underlying disorder or substance, although pinpointing this cause precisely can sometimes be challenging. Typically, if headache attacks recur in close connection with another disorder or activity, or immediately following the diagnosis of another condition, they are classified as secondary. For instance, headaches arising after head or neck injuries fall into the secondary category, even if their symptoms mimic primary headaches such as migraines.

Another prevalent form of secondary headaches results from substance use, abuse, exposure, or even withdrawal. The most common secondary headaches falling into this sub-category are medication-overuse headaches and alcohol-induced hangover headaches. Additionally, acute or chronic exposure to certain substances like lead paints or carbon monoxide, or withdrawal from substances like opioids or caffeine can also provoke headaches which are classified them as secondary.

Headache Triggers in Primary Headaches

It’s important to differentiate between triggers in primary headaches and causative factors in secondary headaches. Certain substances are known to act as trigger in certain headaches such as migraine and cluster headache. For example, alcoholic beverages can be the immediate cause of a strong migraine attack in susceptible individuals, but the primary nature of the headache remains unchanged.

In fact, while the trigger might represent a causative factor, the very nature of the migraine itself is not dependent from the trigger, as the patient will suffer from other, multiple attacks independently from the exposure with that substance.

Mixed Primary and Secondary Headaches

There are some less common instances where a primary headache’s characteristics (severity, frequency, duration) significantly alter in close temporal association with another causative disorder or substance. For example, a patient affected by TTH may experience an increase in the frequency and pain severity of their attacks after their blood pressure start rising due to aging processes. Since headaches caused by hypertension are defined as secondary, in this example, these TTH headaches can be described as both primary and secondary at the same time.

Conclusion

In conclusion, understanding the distinction between primary and secondary headaches is essential for accurate diagnosis and effective treatment. By recognizing the differences between these two types, healthcare professionals can provide tailored care to alleviate symptoms and improve patients’ quality of life.

About the author:

Dr. Claudio Butticè, Pharm.D., is a former Pharmacy Director who worked for several large public hospitals in Southern Italy, as well as for the humanitarian NGO Emergency. He is now an accomplished book author who has written on topics such as medicine, technology, world poverty, human rights, and science for publishers such as SAGE Publishing, Bloomsbury Publishing, and Mission Bell Media. His latest books are “Universal Health Care” (2019) and “What You Need to Know about Headaches” (2022). A data analyst and freelance journalist as well, many of his articles have been published in magazines such as Cracked, The Elephant, Digital Journal, The Ring of Fire, and Business Insider. Dr. Butticè also published pharmacology and psychology papers on several clinical journals, and works as a medical consultant and advisor for many companies across the globe.

References:

1. Headache Classification Committee of the International Headache Society (IHS). (2018). The International Classification of Headache Disorders, 3rd edition. Cephalalgia, 38(1), 1-211. DOI: 10.1177/0333102417738202
2. Butticè, C. (2022). What you need to know about headaches. Santa Barbara: ABC-CLIO, LLC.
3. Diamond, Seymour. Headache and Migraine Biology and Management. Elsevier AP, 2015.
4. American Migraine Foundation. (n.d.). What Type Of Headache Do You Have? Retrieved from https://americanmigrainefoundation.org/resource-library/what-type-of-headache-do-you-have/
5. International Headache Society. (n.d.). Secondary Headache. Retrieved from https://ihs-headache.org/en/about-ihs/special-interest-groups/secondary-headache/
6. Chowdhury D. (2012). Tension type headache. Annals of Indian Academy of Neurology, 15(Suppl 1), S83–S88. https://doi.org/10.4103/0972-2327.100023
7. Kapoor S. (2013). Headache attributed to cranial or cervical vascular disorders. Current pain and headache reports, 17(5), 334. https://doi.org/10.1007/s11916-013-0334-y

Frequently Asked Questions (FAQs)

1. What are primary headaches, and how do they differ from secondary headaches?
   • Primary headaches are those that occur independently of any other medical condition, while secondary headaches arise as a result of another underlying disorder, activity, or substance.
2. What are some examples of primary headache disorders according to the International Classification of Headache Disorders (ICHD-3)?
   • Examples of primary headache disorders include tension-type headache, migraine, trigeminal autonomic cephalalgias (TACs), cluster headache, and other primary headache disorders listed in the ICHD-3.
3. How are primary headaches diagnosed and treated?
   • Primary headaches are diagnosed based on clinical evaluation, patient history, and symptom presentation. Treatment typically involves lifestyle modifications, medications, and sometimes preventive measures tailored to the specific type of headache.
4. What are the common causes of secondary headaches, and how can they be identified?
   • Common causes of secondary headaches include head or neck injuries, medication overuse, substance abuse, exposure to toxic substances, and withdrawal from certain substances. They can be identified by their close temporal association with another disorder or activity.
5. How can patients differentiate between triggers and causative factors in primary headaches?
   • Triggers are external factors that may precipitate a headache in susceptible individuals, while causative factors directly lead to the development of headaches. Patients can differentiate between them by observing whether the headache occurs consistently after exposure to a specific trigger or is a result of an underlying disorder or activity.
6. What are mixed primary and secondary headaches?
   • Mixed primary and secondary headaches refer to headaches that exhibit characteristics of both primary and secondary types simultaneously. This means that while the headache may have underlying causes or triggers, it also presents with features consistent with primary headache disorders.