Exploring the diagnosis of cluster headache : a multi-method study

Background: Cluster headache (CH) is a severe primary headache affecting 1/1000 people of the general population. The diagnostic delay, misdiagnosis and mismanagement of CH are well evidenced in the literature. The aim of this doctoral research is to understand the under- recognition by exploring the diagnosis of CH.Methods: Multi-method study comprised of four main parts:(1) A systematic literature review on the delays in diagnosis and misdiagnosis of CH;(2) A literature review on the pathophysiology of CH;(3) A prospective observational study of a novel screening tool with images depicting headache pain that could differentiate between CH and migraine. Images depicting headache pain were assessed on healthy participants to test if they depict a range of pain severities. The screening tool was tested and refined in a pilot study and subsequently assessed in a larger-scale study. The total screening tool score (which ranged between 3-32) was used as predictor of CH.(4) A qualitative study with semi-structured interviews that explored the perceptions on the CH diagnosis among three key stakeholder groups: participants with CH, GPs and neurologists. Results:(1) The systematic literature review brought together the existing evidence on diagnostic delays, numerous misdiagnosis, consultation of multiple clinicians and mismanagement of CH. (2) The literature review on the pathophysiology of CH summarised the research on the biomedical aspects of CH and informed on the imaging, peptide and genetic studies in CH. (3) Six images depicting headache pain tested on 150 healthy participants showed a range of severities from mild to excruciating. The screening tool was piloted on 100 patients with migraine and 16 patients with CH. The refined screening tool was assessed on 81 patients with CH and 215 patients with migraine. Patients with CH had a higher mean test score compared to patients with migraine (28.4 versus 19.5). At a cut-off score of >25 out of 32, the screening tool for CH had a sensitivity of 86.4% and a specificity of 92.0%.(4) The qualitative data set that included 26 patients with CH, eight GPs and eight neurologists identified prolonged diagnostic journey of CH with significant impact on social life and mental health. Both patient and clinician’s factors are involved in the diagnostic delay.Conclusions: This multi-method study identified challenges around the timely diagnosis of CH and multiple factors involved in the under-recognition of CH. The screening tool could be a useful instrument to aid the diagnosis of CH. Validation in other medical settings including primary care is required