Reversible cerebral vasoconstriction syndromes (RCVS) comprise a group of diverse conditions, all characterized by reversible multifocal narrowing of the cerebral arteries heralded by sudden (thunderclap), severe headaches with or without associated neurologic deficits. Reversible cerebral vasoconstriction syndromes are clinically important because they affect young persons and can be complicated by ischemic or hemorrhagic strokes. The differential diagnosis of RCVS includes conditions associated with thunderclap headache and conditions that cause irreversible or progressive cerebral artery narrowing, such as intracranial atherosclerosis and cerebral vasculitis. Misdiagnosis as primary cerebral vasculitis and aneurysmal subarachnoid hemorrhage is common because of overlapping clinical and angiographic features. However, unlike these more ominous conditions, RCVS is usually self-limited: Resolution of headaches and vasoconstriction occurs over a period of days to weeks. In this review, we describe our current understanding of RCVS; summarize its key clinical, laboratory, and imaging features; and discuss strategies for diagnostic evaluation and treatment.

After the introduction of chronic migraine and medication overuse headache as diagnostic entities in The International Classification of Headache Disorders, Second Edition, ICHD-2, it has been shown that very few patients fit into the diagnostic criteria for chronic migraine (CM). The system of being able to use CM and the medication overuse headache (MOH) diagnosis only after discontinuation of overuse has proven highly unpractical and new data have suggested a much more liberal use of these diagnoses. The International Headache Classification Committee has, therefore, worked out the more inclusive criteria for CM and MOH presented in this paper. These criteria are included in the appendix of ICHD-2 and are meant primarily for further scientific evaluation but may be used already now for inclusion into drug trials, etc. It is now recommended that the MOH diagnosis should no longer request improvement after discontinuation of medication overuse but should be given to patients if they have a primary headache plus ongoing medication overuse. The latter is defined as previously, i.e. 10 days or more of intake of triptans, ergot alkaloids mixed analgesics or opioids and 15 days or more of analgesics/NSAIDs or the combined use of more than one substance. If these new criteria for CM and MOH prove useful in future testing, the plan is to include them in a future revised version of ICHD-2.

(Headache 2010;50:921‐936) Objective.— To assess the efficacy, safety, and tolerability of onabotulinumtoxinA (BOTOX®) as headache prophylaxis in adults with chronic migraine. Background.— Chronic migraine is a prevalent, disabling, and undertreated neurological disorder. Few preventive treatments have been investigated and none is specifically indicated for chronic migraine. Methods.— The 2 multicenter, pivotal trials in the PREEMPT: Phase 3 REsearch Evaluating Migraine Prophylaxis Therapy clinical program each included a 24‐week randomized, double‐blind phase followed by a 32‐week open‐label phase (ClinicalTrials.gov identifiers NCT00156910, NCT00168428). Qualified patients were randomized (1:1) to onabotulinumtoxinA (155‐195 U) or placebo injections every 12 weeks. Study visits occurred every 4 weeks. These studies were identical in design (eg, inclusion/exclusion criteria, randomization, visits, double‐blind phase, open‐label phase, safety assessments, treatment), with the only exception being the designation of the primary and secondary endpoints. Therefore, the predefined pooling of the results was justified and performed to provide a complete overview of between‐group differences in efficacy, safety, and tolerability that may not have been evident in individual studies. The primary endpoint for the pooled analysis was mean change from baseline in frequency of headache days at 24 weeks. Secondary endpoints were mean change from baseline to week 24 in frequency of migraine/probable migraine days, frequency of moderate/severe headache days, total cumulative hours of headache on headache days, frequency of headache episodes, frequency of migraine/probable migraine episodes, frequency of acute headache pain medication intakes, and the proportion of patients with severe (≥60) Headache Impact Test‐6 score at week 24. Results of the pooled analyses of the 2 PREEMPT double‐blind phases are presented. Results.— A total of 1384 adults were randomized to onabotulinumtoxinA (n = 688) or placebo (n = 696). Pooled analyses demonstrated a large mean decrease from baseline in frequency of headache days, with statistically significant between‐group differences favoring onabotulinumtoxinA over placebo at week 24 (−8.4 vs −6.6; P < .001) and at all other time points. Significant differences favoring onabotulinumtoxinA were also observed for all secondary efficacy variables at all time points, with the exception of frequency of acute headache pain medication intakes. Adverse events occurred in 62.4% of onabotulinumtoxinA patients and 51.7% of placebo patients. Most patients reported adverse events that were mild to moderate in severity and few discontinued (onabotulinumtoxinA, 3.8%; placebo, 1.2%) due to adverse events. No unexpected treatment‐related adverse events were identified. Conclusions.— The pooled PREEMPT results demonstrate that onabotulinumtoxinA is an effective prophylactic treatment for chronic migraine. OnabotulinumtoxinA resulted in significant improvements compared with placebo in multiple headache symptom mea...