To determine the utility of tissue plasminogen activator (tPA) in the clearance of chronic subdural hematomas (CSDH). Intra-catheter tPA will be administered during surgical procedure and allowed to break down blood clot to assist with removal/drainage during twist drill craniostomy procedure.

A chronic subdural hematoma (CSDH) is a collection of blood overlying the brain that can be seen, usually in the elderly with even minimal head trauma. These are usually treated by removing the collection of blood. This can be done through a small drill hole in the skull or by larger holes (one or two) the size of a nickel. Sometimes a larger piece of skull is removed to be able to remove the CSDH. The standard practice at our center is to do these procedures under local anesthesia with a twist drill craniostomy (small drill hole through the skull). In some cases, all the CSDH can not be removed the first time, requiring a second procedure or a larger procedure. This study plans to use a type of medication that breaks down the solid blood clot, enabling more of it to drain. This medication (tpa) is already used in other surgeries and is safe to use in humans. Our preliminary experience and that of others suggests very low risk at the dosages being used. We hope that using this new drug will decrease the chance of the CSDH collecting again and reduce the overall length of your stay in the hospital and reduce the need for further surgery.

Inclusion Criteria:

1. Adult patients (18 yrs or older)
2. Admitted to neurosurgery wing at the hospital
3. Symptomatic patients requiring surgical drainage by twist drill craniostomy

Exclusion Criteria:

1. Patients at increased risk of bleeding such as patients taking anticoagulation medication that required reversal at time of intervention، or those with coagulopathic disorder.
2. Patients on antiplatelets or anticoagulation medications (DOACs or warfarin) with appropriate holding period prior to drainage, those who are eventually minimized to a regular bleeding risk compared to the normal population, will be included in the study.
3. Patients with subdural empyema.
4. Redo twist drill craniostomy for residual cSDH within the same admission.
5. Drain accidentally removed during nursing care or patient transport before 24 hr interval scan.
6. Patients who are not expected to live more than three months.

Patient data will be de-identified and the data will be analyzed as a whole before becoming available to other researchers.

De-identified IPD may be shared with other researchers if necessary based on occurrence of adverse events occurrence, circumstantial findings, etc.