Purpose: There have been over 40 descriptions of the common developmental variants of the accessory ossicles of the feet. Although predominantly asymptomatic, they sometimes may be linked to painful conditions. One of the most common accessory ossicles in the foot is the accessory navicular bone (AN), located on the medial side of the foot. Our research provides a first meta-analysis on this topic that establishes its frequency by contrasting 39 studies from across the globe. Methods: Up to February 2024, PubMed and Embase databases were thoroughly searched for research on the AN. Eligible data regarding AN prevalence was extracted. This study strictly adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: A total of 39 studies, 11,015 patients, and 36,837 feet were analyzed in our study. The pooled prevalence estimate (PPE) of AN was found to be 17.5% (95%CI: 11.5–25.7) and 12.6% (95%CI: 10.1–15.5) in patients and feet analyses, respectively. Accessory navicular occurred bilaterally in 50.0% of patients, with similar distribution in gender-based groups (21.1% of males and 22.0% of females were confirmed with AN). Accessory navicular was most prevalent in the East Asian population (38.4%) and least prevalent in North Americans (8.0%). No significant differences in AN prevalence were found when comparing different imaging modalities (X-ray and cadaver dissection). Conclusion: Accessory navicular is a common finding in imaging studies. Its prevalence depends on the population covered by the study but is not affected by the patient’s gender or the imaging modality utilized for AN assessment.

Os trigonum (OT) is one of the most common accessory ossicles in the foot and ankle region. It is believed that OT was first described by Rosenmuller in 1804, but von Bardeleben is the one who coined the nomenclature for this anatomical variation in 1883. The literature indicates that OT is extremely variable in prevalence, with reported rates ranging from 1.7% to 32.5%. In clinical practice, OT is a considerable factor that may predispose patients to posterior ankle impingement syndrome (PAIS). The aim of this study was to provide comprehensive data on the prevalence and anatomical characteristics of OT. We conducted a comprehensive search of the main electronic databases to find the relevant research. Information concerning geographical origin, prevalence, gender distribution, imaging modality, and morphometry of OT was extracted. The PRISMA guidelines were strictly followed throughout the study. The reliability of the included studies was assessed using the AQUA tool. A total of 41 studies (n = 36,612 feet) were included in this meta-analysis. This meta-analysis showed that OT was present in 9.0% (95% CI: 7.4–10.8) of the feet, and was present bilaterally in 32.7% (95% CI: 23.3–43.7) of cases. Regarding the types of imaging modality used in the evaluation of OT by the included studies, prevalence assessed by X-rays was 8.2% (95% CI: 6.8–9.9), MRI was 24.2% (95% CI: 14.6–37.3), CT was 21.0% (95% CI: 12.8–32.5), and cadaveric dissection was 5.0% (95% CI: 3.4–7.4). OT was most commonly found in East Asia (11.0%, 95% CI: 7.1–16.8). Two studies provided enough data to calculate the odds ratio linking PAIS with OT. The analysis showed that patients with PAIS are almost 16 times more likely to have OT compared to those without PAIS (OR = 15.98, 95% CI = 0.255–1002.8). OT is a very common accessory ossicle and is present in nearly one in 10 feet. The highest prevalence is noted in the East Asian population. MRI and CT show the highest prevalence of OT. It is important to keep in mind the possible presence of OT when a patient is diagnosed with PAIS.

Trigeminal autonomic cephalgias (TACs) are a well-defined subset of uncommon primary headaches that share comparable onset, pathophysiology and symptom patterns. TACs are characterised by the presentation of one-sided and high-intensity trigeminal pain together with unilateral cranial autonomic signs, which can include lacrimation, rhinorrhea, and miosis. The International Classification of Headache Disorders 3rd Edition recognises four different headache entities in this group, with cluster headache as the most recognised among them. Hemicrania continua (HC) and paroxysmal hemicrania (PH) are both distinctive cephalgias of which the diagnostic criteria include an absolute response to indomethacin. Consequently, for this reason they are often referred to as ‘indomethacin-responsive’ TACs. The main focus of this review was to discuss the state of knowledge regarding the pathophysiology and key characteristics of PH and HC. Given the limited understanding of these conditions, and their exceptionally uncommon prevalence, a correct diagnosis can pose a clinical challenge and the search for an effective treatment may be prolonged, which frequently has a serious impact upon patients’ quality of life. The information provided in this review is meant to help physicians to differentiate indomethacin-sensitive cephalgias from other distinct headache disorders with a relatively similar clinical presentation, such as cluster headache, trigeminal neuralgia, and various migraine conditions. Keywords: trigeminal-autonomic cephalgias Sjaastad syndrome indomethacin hemicrania continua paroxysmal hemicrania