The Taxonomy of Headache Disorders
“Migraine with aura”, What’s that? That’s a great question, you may be asking yourself, haven’t we already discussed what Migraine Disease is? Indeed we have but, I suggest you read “Migraine: Going Beyond The Headache” where I describe what Migraine Disease is from a broad perspective. To revisit the original question, “Migraine with aura, what’s that?”. Headache is difficult to diagnose because there are over two-hundred disorders. Like other specialties, Headache Medicine has a special manual tool at their disposal to help differentiate between them.
The tool that I am referring to is the diagnostic manual published by the International Headache Society which describes the Headache disorders, it’s called the International Classification of Headache Disorders. This taxonomy is divided into four parts, Part one: the Primary Headache Disorders, Part two: the Secondary Headache Disorders, Part three: painful cranial neuropathies, other facial pains, and other headaches, and an appendix. Let us begin with the Primary Headache Disorders.
Part one: the primary headache disorders
A Primary Headache Disorder is a special breed of headache disorder because they have no known cause. This chapter is where diseases such as Migraine, Tension-type headache, Trigeminal autonomic cephalgia’s (TACs), and a few others reside at the time of writing this. The only way to diagnose these disorders by capturing a detailed and thorough history. The history combined with a process of elimination by way of tests like neuroimaging in the form of a Magnetic Resonance (MR) or Computed Tomography (CT) study or an Electroencephalogram (EEG). If we can’t directly diagnose the Primary headache disorders, then what about the Secondary headache disorders?
Part two: the secondary headache disorders
Unlike the Primary Headache Disorders, Secondary Headache Disorders have a known cause. There are instances where one may have migraine-like symptoms as a result of a brain tumor, thus the cause would be the tumor. Thus, from the example given in ICHD-3, the classification would be: “Headache attributed to intracranial neoplasia (or one of its subtypes)”. This is one reason why neuroimaging is often used to eliminate the possibility of a Secondary Headache Disorder. The final part before the Appendix is Part three: painful cranial neuropathies, other facial pains, and other headaches.
Part three is
Part three is only comprised of two chapters but they are no less important than any other. The first is Chapter 13, Painful lesions of the cranial nerves and other facial pain. This section is where the Neuralgias reside along with some neuropathies as well as Burning Mouth Syndrome (BMS), Persistent idiopathic facial pain (PiFP), and Neck-Tongue Syndrome, just to name a few. Chapter 14, the second and final section of part three is special because it contains two subtypes. The first is, 14.1, Headache not elsewhere classified, which is a classification for “Headache with characteristic features suggesting that it is a unique diagnostic entity”, as stated in the ICHD-3. The presentation also does not fulfill criteria for any of the headache orders listed in the earlier parts. Now the, we get to my favorite part, the Appendix.
The Appendix is important because often someone say some strange diagnosis which doesn’t make sense. Unlike the previous sections the entries in the Appendix aren’t tied to ICD-10 codes, the codes which healthcare providers use to bill for treatment. This primary function of this section of the taxonomy is to present research criteria for entities which haven’t been validated. In some instances, it also presents alternative criteria. Sometimes the healthcare provider’s experience combined with some amount of published evidence may suggest that this alternate criterion is preferable. Even with this the committee that oversee the classification does not yet feel that the evidence is substantial enough to modify the main taxonomy. Finally, this section also is utilized as the first step in the process to removing disorders which were included as diagnostic entities in previous editions of ICHD, but for which there has not been enough evidence published.
What Can You Do?
One thing that we all should do is be mindful of the language we use when talking about Migraine Disease or any headache disorder. Remember that we live with the disease every day from birth, it’s encoded in our genetics. When it flares up we are experiencing a Migraine Attack. What are your thoughts? Tell me in the comments below or send me a message on Twitter at @MigraineAssist.