Objective: Chronic subdural hematomas (CSDHs) are the among the most common conditions treated by neurosurgeons. Midline shift (MLS) is used as a radiological marker of CSDH severity and the potential need for urgent surgical evacuation. However, a patient's age may affect the degree of MLS for a given hematoma volume. This study aimed to investigate the correlation between the patient's age and the MLS caused by CSDH.
Methods: The database of patients treated for CSDH was reviewed in a single institution. Patients with unilateral CSDH were included. To measure CSDH volume, the preprocedural head CT scans underwent 3D volumetric reconstruction using the TeraRecon software. The effect of age on MLS after adjusting for CSDH volume was investigated using linear regression analysis.
Results: Sixty-nine hematomas in 69 patients were included. The age of patients ranged from 25 to 94 years (mean 71.6 years). Hematoma volume and MLS ranged from 27.8 to 215 mL (mean 99.3 mL) and 0-17 mm (mean 6.5 mm), respectively. On multivariate regression analysis, MLS showed a significant independent negative correlation with age after adjusting for CSDH volume (OR -0.11, 95% CI -0.16 to -0.06; p < 0.001), meaning that for a fixed CSDH volume, with each 10-year increase in age the MLS will reduce by 1.1 mm. Moreover, MLS-to-volume ratio showed a significant negative linear correlation with age (r2 = 0.32; p < 0.001). Ten-milliliter increments in CSDH volume resulted in a 1.09-mm increase in MLS in patients younger than 60 years, which is 2.4-fold higher compared to the 0.46-mm increase in those older than 75 years (p < 0.001).
Conclusions: For a fixed CSDH volume, older age correlates with significantly lower MLS. This could be explained by higher parenchymal compliance in older individuals due to increased brain atrophy, and a larger subdural space. Clinical use of MLS to estimate severity of CSDH and gauge treatment decisions should take the patient's age into account.
Keywords: aging; brain herniation; cerebral atrophy; chronic subdural hematoma; compliance; intracranial pressure; midline shift; trauma.