Chronic subdural hematoma (cSDH) is a slow accumulation of blood beneath the dura mater, typically developing over weeks to months. It occurs most commonly in older adults typically following head trauma or falls, and its incidence is increasing with an aging population [1], [2]. As life expectancy and the use of antithrombotic medication increase, cSDH is projected to become one of the most common intracranial pathologies in the elderly [1], [3], [4].

Clinically, cSDH presents with a wide spectrum of symptoms, including headache, gait disturbances, focal neurological deficits, cognitive decline, and altered mental status. Among these, headache is the most frequently reported symptom, occurring in approximately 30–80 % of cases [5], [6], [7], [8], [9]. However, symptom presentation is highly variable and often nonspecific, especially in older adults, which can lead to delays in diagnosis [10], [11]. For instance, Huang et al. reported that patients with bilateral cSDH exhibited fewer focal neurological deficits compared to those with unilateral hematomas, potentially confounding clinical recognition and postponing appropriate treatment [12].

The pathophysiology of headache in cSDH is still not fully understood. While mass effect —compression of the cerebral hemisphere and subsequent elevation of intracranial pressure (ICP)— is thought to play a significant role, studies investigating hematoma pressure and its association with headaches have yielded mixed results [13], [14]. This suggests that pressure alone may not fully account for headache occurrence [13], [14]. Moreover, the relationship between headache presentation and hematoma volume remains poorly defined in the literature. Although hematoma size often informs surgical decision-making, its connection to specific presenting symptoms, such as headaches, is less well established [15], [16].

A clearer understanding of the relationship between headache and hematoma size could improve early diagnostic accuracy and enhance our understanding of headache pathophysiology in cSDH. Hence, this study aimed to investigate the association between headache presentation and hematoma size in patients with cSDH while attempting to clarify a critical size threshold for headache development.