Chronic Subdural Hematoma: Incidence, Outcome and Cost

Chronic subdural hematoma (CSDH) represents a common disease in neurosurgical practice, especially among elderly patients. The degeneration of the brains allows the space for CSDH to develop. Other well-known risk factors for CSDH include trauma, alcohol overuse, and antithrombotic therapy. Surgery is recommended for CSDH patients with neurological symptoms. Burr- hole drainage is the preferred technique. Recurrence is common, ranging from 5% to 30%. The recurrence rate can be decreased with the use of external drains. Follow-up head computed tomography (CT) scans have been used to assess the possible recurrence of CSDH and the best time to restart antithrombotic therapy, if necessary, or allow the patient to begin exercising or driving again. However, the benefits and costs of routine follow-up head CT scans need to be evaluated. No consensus for how long these patients should continue to be followed exists. CSDH has long been considered as a benign condition with an excellent outcome. This conclusion arises from the study of selected surgically treated patients. The statistics on the incidence, outcome and cost of all CSDH patients are not so well established. In general, CSDH patients come from an age group with a high baseline mortality. The excess mortality potentially resulting from CSDH needs to be compared to a matched sample from the general population. As the global population of people aged 80 and older is expected to more than triple between 2015 and 2050, CSDH represents an important issue in public health. This study first aimed to determine the population-based epidemiology of CSDH over a 26-year period from 1990 to 2015 in a defined Finnish population. A large unselected patient cohort (n=1,148) was collected by reviewing consecutive CSDH cases who had lived in the Pirkanmaa region and were treated in the Tampere University Hospital between 1990 and 2015. Also, death certificates for clinically undiagnosed CSDH (n=20) from this period were reviewed. The second objective was to assess possible long-term excess mortality and the causes of death of patients with CSDH. We compared our CSDH patient cohort to the general population from the same region, matched by sex, age, and calendar time. The causes of death of the CSDH patients were compared to a separate matched reference group. Thirdly, the study intended to estimate the total direct hospital costs of CSDH treatment from hospital admission until the last neurosurgical follow-up visit in a neurosurgical clinic during a 26-year study period. Related to the costs, we also aimed to evaluate the necessity of a pre-scheduled routine follow-up CT after CSDH. We concluded that the burden of CSDH has increased markedly in the Pirkanmaa region from 1990 to 2015. The overall incidence of CSDH doubled from 8 to 18/100,000/year. Among adults under 70 years old, the incidence remained quite stable, whereas the incidence nearly tripled among the over 80-year old population, from 47 to 130/100,000/year. The incidence was higher for men than for women after the age of 60 years. The use of antithrombotics has increased (27%-49%), but no change has occurred regarding the ratio between a traumatic (60%) and a spontaneous (40%) CSDH etiology. Patients with CSDH had long-term excess mortality, which cumulated over time from 9% at one year to 48% at 20 years after CSDH diagnosis. Patient-related characteristics, especially chronic alcohol abuse, anticoagulant medication use, and neurological disability both at admission and at discharge were strongly associated with excess mortality, whereas specific CSDH-related findings were not. A subgroup of patients (n=206) with no comorbidities displayed no excess mortality. The overall prevalence of dementia in CSDH patients aged 70 years or older was 12%, which is comparable to the prevalence in the population. Even so, dementia represented the most common cause of death among the CSDH patients (21%), but the third most common cause in the reference group (15%, p<0.001). As a cause of death, dementia occurred later in CSDH patients than in the reference group. CSDH seemed to increase the risk of dementia. Despite the increased number of cases, direct hospital costs declined in more recent years. This have occurred in large part due to shortened hospital stays and fewer recurrences of CSDH related to use of subdural drains. The mean cost per patient treated surgically was 4,140 € (min-max=2,170-30,100 €) during the latest study period 2011-2015. The total direct hospital costs averaged 231,000 € per year in 2011-2015, of which 4% (8,300 €) occurred thanks to non-operatively treated patients. Head CT scans accounted for 12% (28,100 €) of the total cost. Routine four to six weeks’ postoperative follow-up head CT scans increased the number of reoperations and thus costs, because asymptomatic patients were operated on due to radiological CSDH recurrence. The majority (92%) of recurrences occurred within 60 days. A two-month follow-up period after CSDH seems sufficient for most, and head CT scan controls are advocated only for symptomatic patients. In conclusion, the incidence of CSDH has increased markedly among the elderly population. Some excess mortality related to CSDH has occurred, but the comorbidities of CSDH, rather than the disease itself, appear the cause of this excess mortality. Preventive measures that consider prior health conditions as well as fall- related injury risk factors that predispose patients to CSDH should be implemented. Direct hospital costs have not increased in the most recent years, because the mean hospital costs per patient have decreased. The use of follow-up head CT scans for asymptomatic CSDH patients should be minimized.