Pitfalls remain in diagnosing headache
Clinicians often face the dilemma of overinvestigating headaches caused by benign ailments and overlooking headaches that are manifestations of serious underlying conditions, despite advances in diagnostic techniques.
“Headaches are classified as primary and secondary. Primary headache, such as migraine, tension-type headache and trigeminal autonomic cephalalgia, is a syndrome in which headache is the disease process. Secondary headache is a symptom of an underlying pathology, such as trauma, tumour or infection,” explained Dr Windsor Mak of the Department of Medicine, The University of Hong Kong. “Despite advances in genetics, imaging and laboratory testing, the majority of primary headache syndromes are diagnosed clinically.”
“In my opinion, the International Classification of Headache Disorders 3rd edition [ICHD-3] algorithm for the diagnosis of migraine may be too complicated for some clinicians,” he said. [Cephalalgia 2013;33:629-808]
“There is a simple three-question screening test for migraine which I find very useful,” continued Mak. “A patient is likely to suffer from migraine if he/she has recurrent headaches that interfere with work, family or social functions, has headaches that last at least 4 hours, and did not have new or different headaches in the past 6 months.” [Headache 2004;44:323-327]
“Thunderclap headache is the most common type of headache presenting to the emergency department. It is characterized by abrupt onset that reaches maximum intensity within 1 minute. Importantly, around 10 to 25 percent of thunderclap headaches are caused by aneurysmal subarachnoid haemorrhage [SAH], which is potentially fatal,” he said. “Clinicians should perform noncontrast brain CT scan and/or lumbar puncture in patients with thunderclap headache to look for any signs of aneurysmal SAH.”
Mak also advised clinicians to check for red flags suggestive of secondary headache before confirming the diagnosis of primary headache. The red flags include:
· Abrupt onset or new headache, change in headache pattern or severity (especially for patients aged >50 years);
· Neurological symptoms and signs, such as focal signs, seizure, reduced sensorium or cognition;
· Symptoms of raised intracranial pressure, papilloedema;
· Fever, neck rigidity;
· Recent trauma; and
· Features of systemic diseases, such as brain metastasis, immunocompromising condition and coagulopathies.
“Nevertheless, pitfalls remain in the diagnosis of headache. For example, the diagnostic criteria for primary headache are often also applicable to secondary headache. In other words, secondary headache can mimic a pre-existing primary headache,” pointed out Mak.
In addition, he highlighted four potential cognitive biases among clinicians that may lead them to overlook a secondary headache disorder:
· Availability bias: the tendency to believe in first impression;
· Confirmation bias: the tendency to selectively pick up information that is in favour of the first-impression diagnosis;
· Anchoring bias: the reluctance to deviate from the first impression;
· Choice-supportive bias: the tendency to find excuses to justify a wrong impression.
“There are no simple rules to guide GPs in the referral of headache cases to specialists for further investigations,” noted Mak.