Cluster headache and risk of chronic transformation
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Cluster headache and risk of chronic transformation Luca Giani 1 & Alberto Proietti Cecchini 1 & Massimo Leone 1
# Fondazione Società Italiana di Neurologia 2020
Cluster headache (CH) is characterized by excruciatingly painful attacks [1] and when it has a chronic course (chronic CH—CCH) provokes deep negative changes in patients’ lives. CCH may arise de novo from the onset of CH or may take the place of a pre-existing episodic CH (ECH). Episodic CH patients are scared to become CCH. The chronic CH form accounts for about 10% of cases, ranging from 5 to 20% [2]. Clinic-based case series have tried to evaluate the risk of developing a chronic form after an episodic onset, with estimated risk ranging from 2 to 19% [2]. Differences in patients’ selection, length of follow-up, statistical methods, and sample size can explain the discrepancy. Survival analysis comprises a set of statistical methods used to investigate the time until occurrence of an event of interest. The distinguishing feature of survival data is that at the end of the observation period, the event will probably not have occurred for all the patients. For these patients, the data is incomplete, and the time is said to be censored. We do not know when or whether the patient will experience the event, only that she/he has not done so by the end of the observation. The Kaplan-Meier (KM) method is a non-parametric method used to estimate the survival probability from observed survival times in the presence of censored cases. Another instrument in survival analysis, the log-rank test, tests the null hypothesis that survival curves of two or more groups do not differ, considering the whole follow-up period. In the present study, we estimated the probability of ECH to transform in CCH within 5, 10, 20, and 30 years of disease onset; then, we questioned if sex and age at onset (clearly definable, invariable, and easily accessible factors) could influence the transformation. Other proposed unstable risk factors for transformation from ECH to CCH include smoking and drinking habits, head injuries, high frequency of clusters, and shorter duration of remission periods [3];
* Luca Giani [email protected] 1
Neuroalgology Unit, Fondazione IRCCS Istituto Neurologico “Carlo Besta”, Via Celoria, 11, 20133 Milan, Italy
people can start or stop smoking or drinking, or have multiple head injuries over the disease course and therefore these factors are not suitable for the KM method. Also, they are sometimes difficult to define or measure, or they are not suitable for long-term prediction (e.g., changes in cluster frequency). We analyzed the clinical documentation of all patients with a diagnosis of CH visited between 1/1/2011 and 19/3/2020 at the Headache Center of the Foundation IRCCS Neurological Institute C. Besta in Milan. This is a tertiary national referral center for cluster headache and related disorders. Clinical records of 539 CH patients were analyzed. Episodic CH were 357 (66.2%) and CCH were 182 (33.8%); 449 (83.3%) were ma
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