The use of subdural drains after surgical evacuation of chronic subdural hematoma (CSH) decreases the risk of recurrence and has become the standard of care. Halfway through the controlled, randomized TOSCAN (Randomized Trial of Follow-up CT after Evacuation of Chronic Subdural Hematoma) trial, the authors' institutional guidelines changed to recommend subgaleal instead of subdural drainage. The authors report a post hoc analysis on the influence of drain location in patients participating in the TOSCAN trial.
The study involved 361 patients enrolled in the TOSCAN trial. The patients were stratified according to whether they received surgery before (cohort A) or after (cohort B) the change in institutional protocol. An intention-to-treat analysis was performed with surgery for recurrence as the primary endpoint. Secondary endpoints were outcome-based on modified Rankin Scale scores, seizures, infections, parenchymal brain injuries, and hematoma diameter.
Of the 361 patients included in the analysis, 214 were stratified into cohort A (subdural drainage recommended), while 147 were stratified into cohort B (subgaleal drainage recommended). There was a 31.78% rate of crossover from the subdural to the subgaleal drainage insertion site due to technical or anatomical difficulties. No differences in the rates of reoperation (21.5% [cohort A] vs 25.17% [cohort B], OR 0.81, 95% CI 0.50-1.34, p = 0.415), infections (0.47% [cohort A] vs 2.04% [cohort B], OR 0.23, 95% CI 0.02-2.19, p = 0.199), seizures (3.27% [cohort A] vs 2.72% [cohort B], OR 1.21, 95% CI 0.35-4.21, p = 0.765), or favorable outcomes (modified Rankin Scale score 0-3) at 1 and 6 months (91.26% [cohort A] vs 96.43% [cohort B], OR 0.39, 95% CI 0.14-1.07, p = 0.067; 89.90% [cohort A] vs 91.55% [cohort B], OR 0.82, 95% CI 0.39-1.73, p = 0.605) were noted between the two cohorts. Postoperatively, patients in cohort A had more frequent parenchymal brain tissue injuries (2.8% vs 0%, p = 0.041). Postoperative absolute and relative hematoma reduction was similar irrespective of the location of the drain.
Subgaleal rather than subdural placement of the drain did not increase the risk for reoperation for recurrence of CSHs, nor did it have a negative impact on clinical or radiological outcome. The intention to place a subdural drain was associated with a higher rate of parenchymal injuries 1).
Subgaleal drainage system is relatively less invasive, safe, and technically easy. So it is applicable for aged and higher risk patients 2).
It significantly reduced the incidence of recurrence. Similar observations were made in the study of Gazzeri et al. 4)
They placed the tip of suction drain on burr hole which can assist in continuous evacuation of hematoma or collected air.
Yadav et al., placed suction tip away from burr hole site which could avoid accidental slippage of tip in subdural space. Subgaleal drainage could avoid the risk of an acute hemorrhage from neo membrane injury which may occur during introduction and the removal of a subdural drain. It also reduces chances of brain parenchymal injury especially after suction drain 5).
A major complication of intracerebral hemorrhage could be due to a blind placement of the subdural drain.
There is a report of one acute SDH after subgaleal drain 6).
The subgaleal drain reduced the chances of significant pneumocephalus in the study of Yadav et al. 7).
The placement of subgaleal suction catheter could prevent the collection of subdural air, thus minimizing the risk of recurrence 8).
Postoperative infection in the subgaleal space has also been reported after subgaleal drainage 9).
A total of 763 patients with surgically evacuated unilateral CSDH were included for analysis. The recurrence rate was 14% while 12% of patients died during follow-up (1 year). In a association model, hematoma size, drain type, drainage time, presence of complications, and Glasgow Coma Score were significantly associated to recurrence. Subdural drain was associated with a lower recurrence risk than subgaleal drain. The preoperative model included hematoma size, hematoma density, and history of hypertension. The postoperative model included further drain type, drainage time, and surgical complications.
The nomograms allow easy assessment of the recurrence risk for the individual patient, providing a better possibility for individual adjustment of treatment and follow-up. The predictive performance indicates that significant unaccounted or unknown factors still remain. The association test found passive subdural drain superior to passive subgaleal drain in minimizing the risk of CSDH recurrence 10).