Twist-Drill Craniostomy With Pressure-Controlled Fibrinolytic Irrigation Therapy for the Evacuation of Acute Traumatic Subdural Hematoma in Patients Not Requiring Immediate Craniotomy

Abstract

BACKGROUND AND OBJECTIVES:

Acute subdural hematoma (aSDH) ranks among the most prevalent conditions in neurosurgery. Depending on the hematoma and neurological condition, management is surgical or conservative. Open craniotomy is the mainstay of therapy if evacuation is mandated but is associated with considerable risks. We present a novel minimally invasive approach—twist-drill craniostomy with pressure-controlled subdural fibrinolytic irrigation (TDC-FIT)—for safe and efficient removal of aSDH in patients not requiring immediate evacuation and evaluate the outcome.

METHODS:

From June to December 2023, 10 patients with aSDH, Glasgow Coma Scale ≥13, hematoma thickness ≥7 mm, moderate neurological deficits without symptom progression, and no need for immediate evacuation were treated with TDC-FIT. A catheter with pressure-controlled irrigation containing an electrolyte solution with 200 000 IU/L urokinase at a target rate of 100 mL/h was inserted into the aSDH through a 3.5 mm TDC under local anesthesia. Irrigation was performed until radiological clearance of the aSDH was obtained. Outcome was compared with 30 historical matched controls treated with open craniotomy (Craniotomy cohort).

RESULTS:

In the TDC-FIT cohort, a near-complete hematoma resolution was observed in 9 (90%) patients, with 1 later recurrence of a chronic SDH, which subsequently resolved without additional sequelae after a conventional TDC. A total of 9 (90%) patients achieved independence (modified Rankin Scale 0-3) at 3 months, compared with 17 (56.7%) in the Craniotomy cohort (P = .012). One (10%) patient necessitated an open craniotomy because of neurological deterioration. The Craniotomy cohort experienced perioperative complications in 17 (56.7%) cases. Aphasia occurred in 2 (6.7%), hemiparesis in 4 (13.3%), epilepsy in 8 (26.6%), rehemorrhage in 2 (6.7%), meningitis in 1 (3.3%), and death in 2 (6.7%) patients.

CONCLUSION:

TDC-FIT on aSDH may offer a safe and effective alternative to open surgery in patients not requiring immediate evacuation.

ABBREVIATIONS:

aSDH

acute subdural hematoma

LOS

length of stay

TDC-FIT

twist-drill craniostomy with pressure-controlled fibrinolytic irrigation therapy.

Acute subdural hematoma (aSDH) is a common and serious condition in neurosurgery, often requiring prompt intervention to prevent further neurological deterioration.¹ Given the high morbidity and mortality rates associated with craniotomy, there is a growing interest in exploring minimally invasive techniques, particularly for patients who do not require immediate evacuation of the hematoma. These approaches aim to reduce surgical trauma and complications and to expedite recovery. Several minimally invasive devices have been developed specifically for the evacuation of subdural hematomas.^2,3

To avoid craniotomy in neurologically stable patients with aSDH, we introduced percutaneous twist-drill craniostomy with pressure-controlled fibrinolytic irrigation therapy (TDC-FIT) in our department in 2023. This new method offers a bedside, minimally invasive alternative to open craniotomy for aSDH evacuation. By using fibrinolytic agents to dissolve the hematoma and using irrigation to remove the liquefied clot, this method can effectively decompress the brain and alleviate mass effect without the need for extensive surgical exposure. Here, we present this novel approach in patients not requiring urgent evacuation and report on the clinical results. Furthermore, we compared perioperative complications, hospitalization, surgical time, and neurological outcome after 3 months with matched cases admitted before implementation of the TDC-FIT.

METHODS

We conducted a retrospective review of patients diagnosed with isolated aSDH who received treatment at our tertiary neurosurgical center between January 2020 and December 2023. Pressure-controlled subdural fibrinolytic irrigation was implemented in our department in June 2023 (TDC-FIT cohort). We report intrathecal application of urokinase, which represents off-label use. The selection process targeted patients with moderate neurological deficits and a need for surgical hematoma removal: The inclusion criteria were (1) a Glasgow Coma Scale (GCS) score of 13-15, (2) a minimum hematoma thickness of 7 mm as determined by computed tomography (CT), (3) the absence of immediate evacuation indications based on clinical assessment, and (4) no symptom progression in the first 3 hours. Patients with concomitant epidural and intracerebral hematomas, as well as those with mass effect, were excluded.

Baseline characteristics included age, sex, GCS at admission, intake of any antithrombotic medication, thickness of the hematoma (in mm), volume of the hematoma measured in cm³ (measured with BrainLab Iplan v.4.5, BrainLab), and midline shift (in mm). Perioperative variables included surgical duration, rate and volume of irrigation for patients treated with TDC-FIT, total length of stay (LOS) at the hospital, LOS at the intensive care unit (ICU), and postoperative complications. Neurological outcomes were evaluated at the 3-month mark using the modified Rankin Scale (mRS). Data collection was performed by evaluating electronic medical records, surgical notes, and radiological imaging. To evaluate the effectiveness and safety of the TDC-FIT, perioperative complications and neurological outcomes were compared with matched cases (Craniotomy cohort), covering the period from January 2020 to June 2023. There were no missing data. Although there were more patients in the Craniotomy cohort than in the TDC-FIT cohort, the matched cohort included only those patients who met the TDC-FIT inclusion criteria. This approach ensures comparability across both groups, despite the overall difference in sample size.

The study adhered to ethical guidelines and was conducted in accordance with the Declaration of Helsinki. Institutional Review Board approval was obtained before the initiation of the study (number 24-1201-S1-retro). Patient confidentiality and data anonymization were ensured throughout the research process. Written informed consent was waived by our Institutional Review Board.

Operative Procedure

The patient was positioned in right lateral decubitus position for left-sided hematomas and left lateral decubitus position for right-sided hematomas. The puncture site was determined using 3-dimensional CT data sets, typically planned at the frontal or parietal eminence (Figure 1A). After hair shaving, if necessary, local anesthesia was administered with 5 mL of 2% scandicaine. A 3.5-mm TDC was performed tangentially to the skullcap, as previously described (Figure 1B).^4–6 A dual-lumen catheter designed for pressure-controlled irrigation was carefully inserted into the subdural hematoma through the craniostomy. The correct placement was confirmed by the outflow of hematoma (Figure 1C). Once the catheter was in place and secured with 2-0 nylon suture (Figure 1D), the dual-lumen catheter was connected (Figure 1E), and fibrinolytic irrigation was initiated using an electrolyte solution (Jonosteril®, Fresenius-Kabi GmbH) containing 200 000 IU/L urokinase (Syner-KINASE, Syne-Medica BV) through one lumen, while the outflow was collected and recorded from the other lumen (Figure 1F).

FIGURE 1.

A, Preoperative preparation and administration of 5 mL of 2% scandicaine subcutaneously. Here, the parietal eminence was identified (arrow). B, A skin incision was made, and a 3.5-mm TDC was performed. C, A dual-lumen catheter was inserted into the hematoma, confirmed by the outflow of hematoma (arrow). D, The catheter was secured with a 2-0 suture. E, The IRRAflow® system was connected. F, Fibrinolytic irrigation was initiated using an electrolyte solution with 200 000 IU/L urokinase, infused at a target rate of 100 mL/h for 3 to 5 days (long arrow). Outflow (short arrow) is collected and measured. This figure is original to this submission, so no credit or license is needed. TDC, twist-drill craniostomy.

The infusion was administered at a target rate of 100 mL/h, facilitating the gradual dissolution of the hematoma over a period of approximately 3 to 5 days. Continuous intracranial pressure (ICP) monitoring was achieved through the pressure-controlled catheter, and drainage was monitored every 60 min. Radiological clearance, indicating successful evacuation of the hematoma, served as the endpoint for fibrinolytic irrigation, typically achieved 3 to 5 days postsurgery when the outflow appeared clear. A passive drainage was then continued until the outflow ceased. The catheter was subsequently removed, and the wound was closed with one 3-0 nylon suture. The radiological course in 2 patients treated with TDC-FIT is shown in Figure 2A-2H.

FIGURE 2.

Radiological course of 2 patients treated with pressure-controlled fibrinolytic subdural irrigation. Both patients presented with an aSDH and an Glasgow Coma Scale of 13 at admission. A, Preoperative CT scan showing a left-sided hematoma with midline shift. B, Day 1 CT scan demonstrating correct placement of the subdural catheter and partial hematoma clearance after 24 h. C, Day 6 CT scan taken before catheter removal, showing near-total hematoma clearance. D, Six-week follow-up CT scan showing complete resolution of the hematoma. E, Preoperative CT scan showing a right-sided hematoma with midline shift. F, Immediate postoperative CT scan demonstrating correct subdural catheter placement before initiating fibrinolytic irrigation therapy. G, Day 5 CT scan before concluding irrigation therapy, showing hematoma regress. H, Six-week follow-up CT scan showing near-complete resolution of the hematoma. This figure is original to this submission, so no credit or license is needed. aSDH, acute subdural hematoma; CT, computed tomography.

IRRAflow® System

The IRRAflow® System (IRRAS AB) introduces a dual-lumen approach, combining automated irrigation, controlled drainage, and ICP monitoring within a single device. Comprising an Intelligent Digital Cassette, an IRRAflow® catheter, and a control unit, the system operates cyclically, transitioning between irrigation, monitoring, and drainage modes. Users have control over irrigation volume and rate. ICP alarms prevent excessive irrigation or overdrainage. The IRRAflow® catheter system features a dual-lumen 400 or 381 mm, 9F catheter with a built-in safety mechanism to prevent overirrigation or underirrigation. The system is programmed to operate within predefined ICP thresholds. If the ICP exceeds the upper limit, the system halts irrigation and enters a drainage-only mode for 2 min while alerting the user. Conversely, if ICP falls below the lower alarm limit, the system stops both irrigation and drainage, issuing an alert. The principle of pressure-controlled fibrinolytic irrigation system is shown in Figure 3.

FIGURE 3.

Schematic representation of the minimally invasive pressure-controlled fibrinolytic subdural irrigation therapy with 200 000 IU/L urokinase at 100 mL/h. The subdural positioning of the dual-lumen catheter and the outflow of hematoma rendered fluid by urokinase are depicted. This figure is original to this submission, so no credit or license is needed.

Statistical Analysis

Statistical analysis was performed using Microsoft Excel version 16.88 for Mac (Microsoft Corporation) and Wizard Pro Version 1.9.42 (Evan Miller). The Fisher exact test examined associations between categorical variables, while the Mann-Whitney U test analyzed associations between nonparametric continuous variables, and the Student t test analyzed associations between parametric continuous variables. Normally distributed patient characteristics were presented as means with SD, non-normally distributed characteristics as medians and interquartile range, and categorical characteristics as frequencies and percentages. A P-value of <.05 was considered statistically significant.

RESULTS

From January 2020 to December 2023, a total of 377 patients diagnosed with isolated aSDH were treated at our tertiary neurosurgical department. Among these, 40 patients (10.6%) met the inclusion criteria for minimally invasive therapy using TDC-FIT. Of these, 30 patients were treated with conventional hematoma evacuation through an open craniotomy between January 2020 and June 2023 (Craniotomy cohort). The remaining 10 patients, treated between June and December 2023, underwent the novel minimally invasive TDC-FIT procedure (TDC-FIT cohort).

In the Craniotomy cohort, 18 (60%) of patients were male, the median age was 81 (range, 61-84) years, 23 (77%) patients used antithrombotic medication, the mean GCS score at admission was 13.9 (SD 2.2), 18 (60%) patients had a left-sided hematoma, the median hematoma thickness was 10.2 (IQR 7-14) mm, the median hematoma volume was 109.5 (IQR 98-120) cm³, and a midline shift was observed in 24 (80%) patients with a median midline shift of 4.1 (IQR 1-10) mm. In the TDC-FIT cohort, 5 (50%) patients were male, and the median age was 84 (range, 76-85) years. Seven (70%) patients were on antithrombotic medication. The mean GCS at admission was 14.1 (SD 1.9). Six (60%) patients had a left-sided hematoma. The median hematoma thickness was 12.2 (IQR 10-16) mm, the median hematoma volume was 118.9 (IQR 108-130) cm³, and a midline shift was observed in 7 (70%) patients, with a median midline shift of 4.6 (IQR 3-10) mm. Both cohorts were comparable in age, hematoma thickness, hematoma volume, intake of antithrombotic medication, initial GCS score, midline shift, and hematoma location. The results are summarized in Table 1.

TABLE 1.

Comparison of Preoperative Baseline Demographics and Clinical Characteristics

Characteristics	Craniotomy cohort (n = 30)	TDC-FIT cohort (n = 10)	P value
Men, no. (%)	18 (60)	5 (50)	.65
Age, median (range), y	81 (61-84)	84 (76-85)	.11
Antithrombotic medication, no. (%)	23 (77)	7 (70)	.69
GCS at admission, mean (SD)	13.9 (2.2)	14.1 (1.9)	.72
Left-sided hematoma, no. (%)	18 (60)	6 (60)	.91
Hematoma thickness, median (IQR), mm	10.2 (7-14)	12.2 (10-16)	.11
Hematoma volume, median (IQR), cm3	109.5 (98-120)	118.9 (108-130)	.82
Midline shift, no. (%)	24 (80)	7 (70)	.68
Midline shift, median (IQR), mm	4.1 (1-10)	4.6 (3-10)	.69

GCS, Glasgow Coma Scale; TDC-FIT, twist-drill craniostomy with pressure-controlled fibrinolytic irrigation therapy.

The Craniotomy cohort exhibited a mean surgical duration of 112 (SD 58) minutes, a median LOS in the ICU of 9.7 (IQR 5-13) days, and a median LOS of 20.5 (IQR 11.5-28) days. The TDC-FIT cohort exhibited a mean surgical duration of 21 (SD 9) minutes, a median LOS at the ICU of 6.4 (IQR 4-9) days, and a median LOS of 14.2 (IQR 9-26) days. Statistically significant differences between the 2 cohorts were observed in surgical duration (112 vs 21 min, P < .001) and total LOS at the hospital (20.5 vs 14.2 days, P = .047).

In the TDC-FIT cohort, the median infusion rate was 72.9 (IQR 33.3-84) mL/h. With an urokinase concentration of 200 IU/mL in the electrolyte solution, the median urokinase administration rate was 14 580 (IQR 6 680-16 800) IU/h. This infusion rate was not consistently achieved in 9 of 10 cases, as the actual infusion rate was lower than the target rate of 100 mL/h. The median drainage rate across the cohort was 76.1 (IQR 47-101) mL/h. According to the electronic patient charts, fibrinolytic irrigation was automatically discontinued on 23 occasions due to negative ICP and twice due to elevated ICP. In both instances of elevated ICP, the readings were falsely high due to by fibrin clots, which resolved after flushing the catheter system.

In the Craniotomy cohort, perioperative complications occurred in 17 of 30 (56.7%) patients, including aphasia in 2 (6.7%), hemiparesis in 4 (13.3%), epilepsy in 8 (26.7%), recurrent hemorrhage in 2 (6.7%), and meningitis in 1 (3.3%). During the postoperative treatment, death occurred in 2 (6.7%) patients. At the 3-month mark, 17 (56.7%) patients attained functional independence (mRS 0-3). Nine (30%) patients showed asymptomatic subdural fluid collection in the volumetric analysis, with a median fluid volume of 8.7 (IQR 6.5-11.2) cm³.

In the TDC-FIT cohort, 1 (10%) patient, an 81-year-old man with a ventriculoperitoneal shunt, was converted to open craniotomy because of clinical deterioration before initiating subdural fibrinolytic therapy. The patient recovered to mRS 3 after 3 months. In addition, there was one instance of a chronic subdural hematoma diagnosed 6 weeks after surgery with a volume of 154 cm³, which resolved without sequelae after a TDC (no symptomatic chronic subdural hematomas were recorded in the Craniotomy cohort). A volumetric analysis after 3 months showed 2 cases of asymptomatic patients with a median subdural fluid collection of 10.2 (IQR 7.8-12.4) cm³, where no surgical intervention was necessary. No further perioperative complications or neurological deficits were observed, and no deaths occurred. After 3 months, 9 (90%) patients in this cohort achieved functional independence (mRS 0-3).

Statistically significant differences between the Craniotomy cohort and the TDC-FIT cohort were observed in postoperative complication rate (56.7% vs 10%, P = .012) and in functional outcome (mRS 0-3: 56.7% vs 90%, P = .012). The results from the surgical data and outcome are summarized in Table 2.

TABLE 2.

Comparison of Outcome and Complications

Outcome	Craniotomy cohort (n = 30)	TDC-FIT cohort (n = 30)	P value
LOS at ICU, median (IQR), d	9.7 (5-13)	6.4 (4-9)	.17
LOS, median (IQR), d	20.5 (11.5-28)	14.2 (9-26)	.047
Surgical duration, mean (SD), min	112 (58)	21 (9)	<.001
mRS 0-3 at 3 mo, no. (%)	17 (56.7)	9 (90)	.012
Death, no. (%)	2 (6.7)	None
Irrigation, median (IQR), mL/h		72.9 (33.3-84)
Drainage, median (IQR), mL/h		76.1 (47-101)

	No. (%)	No. (%)
Postoperative complications	17 (56.7)	1 (10)	.012
Rebleeding	2 (6.7)	1 (10)	.76
Aphasia	2 (6.7)	None
Hemiparesis	4 (13.3)	None
Epileptic seizure	8 (26.7)	None
Meningitis	1 (3.3)	None

ICU, intensive care unit; LOS, length of stay; mRS, Modified Rankin Scale; TDC-FIT, twist-drill craniostomy with pressure-controlled fibrinolytic irrigation therapy.

DISCUSSION

Our findings suggest that TDC-FIT is a promising, minimally invasive alternative to traditional open craniotomy, particularly in neurologically stable patients with moderate impairment in patients with aSDH. The significant reduction in surgical duration and LOS observed in the TDC-FIT cohort highlights its potential for improving outcomes by reducing surgical trauma and expediting recovery, especially in elderly patients.

The strategy mostly used in mild symptomatic patients with aSDH is to adopt a conservative approach, allowing the hematoma to spontaneously liquefy to minimize the risk associated with invasive open craniotomy. However, these patients often develop progressive neurological deficits, such as paresis, aphasia, or recurrent seizures, which may ultimately necessitate an open hematoma evacuation instead of burr-hole hematoma evacuation, which poses challenges, particularly in older patients with existing medical conditions.^7,8 This study provides an important evaluation of TDC-FIT for the management of isolated mild symptomatic aSDH without severe traumatic brain injury.

Specifically, there were fewer neurological deficits and no perioperative deaths in the TDC-FIT group. At 3 months, 90% of patients in the TDC-FIT cohort achieved functional independence (mRS 0-3), which is significantly better than the 56.7% seen in the craniotomy cohort (P = .012). Patients treated with TDC-FIT also experienced a significant reduction in perioperative complications, with only 1 (10%) patient in the TDC-FIT cohort experiencing conversion to open surgery. Close examination of this specific case, however, highlights important limitations of this novel therapy, emphasizing the critical need for proper patient selection and appropriate indication. The case involved an 81-year-old patient with a ventriculoperitoneal shunt for the treatment of normal pressure hydrocephalus, who was urgently admitted to the ICU. This patient, the fourth treated with TDC-FIT in our series, presented with a GCS of 13 and was initially deemed a suitable candidate for TDC-FIT after a shunt disconnection procedure to mitigate the risk of shunt overdrainage. In the immediate postoperative period, before initiating subdural irrigation after the TDC, the patient experienced significant clinical deterioration, marked by worsening neurological status. This unexpected progression necessitated an emergent conversion to craniotomy for definitive surgical management. A review of this case suggests that the complication was likely due to suboptimal patient selection. Specifically, the presence of a ventriculoperitoneal shunt may have contributed to an unstable subdural hematoma, preventing the hematoma from maintaining the static configuration required for the controlled execution of the TDC-FIT procedure. This case underscores the critical importance of rigorous patient selection criteria for minimally invasive hematoma evacuation techniques such as TDC-FIT. Stable hematoma morphology is a fundamental prerequisite for ensuring the success and safety of this method.

Another critical aspect identified in our analysis is that the target infusion rate of 100 mL/h was not consistently achieved in most cases (9 of 10 patients). This deviation from the intended infusion rate may affect the efficacy of fibrinolytic therapy, as suboptimal infusion rates could compromise the effective dissolution of the hematoma. Although the median drainage rate of 76.1 mL/h indicated successful fluid removal, it also underscored the variability in procedural execution and highlights the challenges in maintaining consistent flow rates during treatment. Despite the target infusion rate not being achieved in 9 of 10 patients, no acute rebleeding occured, suggesting that even lower irrigation rates may be sufficient for hematoma liquefaction. Further studies are needed to determine the optimal rate and dosage for fibrinolytic irrigation.

In addition, the automatic cessation of fibrinolytic irrigation on 23 occasions due to negative ICP, and twice due to elevated ICP, highlights the need for careful interpretation of ICP measurements from the pressure-controlled irrigation system. In both instances of high ICP, the readings were falsely elevated, which further underscores the potential challenges posed by ICP monitoring in the context of TDC-FIT. These erroneous ICP readings may have led to premature discontinuation of the fibrinolytic infusion, potentially limiting the effectiveness of the fibrinolytic treatment. The occurrence of both falsely elevated and negative ICP suggests the need for more reliable and accurate ICP monitoring techniques when implementing TDC-FIT, as well as careful consideration of the patient's clinical status and imaging data to guide therapy decisions.

Recent advancements in neurosurgical techniques have sparked a paradigm shift toward exploring minimally invasive alternatives to craniotomy.^2,3,9 Recent studies underscore the efficacy of minimally invasive fibrinolytic techniques for aSDH evacuation.^10,11 For instance, Ryu et al¹¹ reported successful outcomes in a retrospective analysis of patients who underwent burr-hole surgery followed by fibrinolytic treatment involving injection of a mixture of 1 mL saline and 1 mg recombinant tissue plasminogen activator through the catheter for 2 days at 12-hour intervals.

Similarly, self-irrigating catheter systems have shown promise in treating chronic subdural hematomas and intraventricular hemorrhage, with studies reporting shorter hospital stays and favorable safety profiles.^12,13 Our group recently reported a reduced recurrence rate of chronic subdural hematomas with the use of TDC-FIT.¹⁴ These findings collectively highlight the promise of minimally invasive, fibrinolytic-based techniques as transformative alternatives in neurosurgical practice.

TDC-FIT offers several key advantages over traditional craniotomy, including reduced surgical trauma, shorter operative time, and decreased hospital LOS. In addition, as TDC-FIT can be performed bedside without the need for general anesthesia, it facilitates quicker recovery.

Limitations

Although our study provides valuable insights into the efficacy of minimally invasive approaches for aSDH evacuation, it is essential to acknowledge its limitations. The retrospective design and relatively small sample size may limit the generalizability of our findings. Although we made efforts to reduce bias through the matched pairs analysis, we cannot fully exclude heterogeneity within the groups used for comparison. Furthermore, the matched cohort of patients undergoing craniotomy was selected as a convenience sample from the period before the introduction of TDC-FIT at our institution. This time-based sampling introduces the potential for bias, as it may not entirely account for changes in patient management practices over time.

In addition, it is important to note that the significant outcomes observed in this study are primarily derived from univariate analysis rather than multivariate analysis. This raises the possibility of interference or confounding factors, which could lead to erroneous conclusions. Future research should aim to compare the long-term outcomes and complications of minimally invasive techniques with traditional craniotomy in larger, randomized cohorts. In addition, exploring the cost-effectiveness of these approaches should be prioritized in future studies.

CONCLUSION

TDC-FIT is a safe alternative to open craniotomy evacuating stable traumatic aSDH that does not require emergency evacuation. First results indicate lower complications and improved functional outcomes.

Funding

The article processing charge was funded by the University Medical Center Freiburg from the internal funding program of the Department of Neurosurgery. We acknowledge support by the Open Access Publication Fund of the University of Freiburg.

Disclosures

The authors have no personal, financial, or institutional relationship in any of the material or devices that could be construed as potential conflicts of interest.

COMMENTS

The authors report a novel approach to the problem of elderly patients with minimally symptomatic acute subdural hematomas. These are a challenging group, because a standard craniotomy typically needs to be fairly large to evacuate the hematoma and in elderly patients, certainly can have risks. Often, we are left using a “wait and see” approach to determine if the subdural hematoma will become chronic and be a candidate for middle meningeal artery embolization or standard burrhole evacuation.

This approach using the IRRAflow system with infusion of thrombolytic (urokinase in this case due to availability) is novel in that the medication can be delivered continuously as opposed to in boluses. While the authors fortunately only observed one case of rebleeding, this will still be a concern and having the safety mechanism to stop the irrigation and alert the user to elevated intracranial pressure seems rational. While the comparison data with standard craniotomy are useful, they are probably not directly comparable groups since one of the entry criteria for the novel approach was that the patients did not need immediate craniotomy.

If neurosurgeons are considering implementing such a similar approach, it is important to note the authors' selection criteria and lessons learned. Specifically, in the case of the presence of ventriculoperitoneal shunt, the risk of expansion could be increased. The patients had relatively mild neurologic deficits and a lack of “mass effect”. While all such patients have local mass effect, one must be careful to avoid patients with signs of elevated intracranial pressure or herniation. The authors also avoided “thin rim” subdural hematomas (<7 mm). Finally, other injury types such as contusions or epidural hematoma were also avoided.

In summary, this may be a very promising technique for elderly patients with isolated stable acute subdural hematomas with mild neurologic impairment. More patient numbers are needed to better determine the selection criteria and other treatment elements such as use of alteplase, the rate of irrigation, and even the type of irrigation (saline versus artificial cerebrospinal fluid), which may affect recurrence and efficacy of the approach.

Andrew P. Carlson

Charlottesville, Virginia, USA