A subdural hematoma (SDH) is a collection of blood on the surface of the brain, underneath its protective outer layer. This condition often results from a head injury that causes veins to tear and bleed. When a blood clot is large enough to compress brain tissue, an evacuation surgery is performed to remove it. The goal is to relieve pressure on the brain and prevent further neurological damage.
When Evacuation is Necessary
The decision to surgically evacuate a subdural hematoma depends on clinical and imaging indicators. Neurosurgeons assess the hematoma’s size and its effect on the brain. A key measurement from a computed tomography (CT) scan is the thickness of the blood collection. An acute SDH thicker than 10 millimeters requires surgical evacuation because a clot of this size exerts significant pressure on the brain.
Another measurement from the CT scan is the midline shift. This term describes the degree to which the brain’s central structures are pushed sideways by the hematoma’s pressure. A midline shift greater than 5 millimeters is a common indicator for surgery, as this signifies enough pressure to deform the brain and disrupt its function.
A patient’s neurological status is also a factor. A decline in consciousness, measured by the Glasgow Coma Scale (GCS), can prompt surgery even if the hematoma does not meet size criteria. If a patient’s GCS score drops by two or more points from injury to hospital admission, or if they develop fixed and dilated pupils, surgeons will likely proceed with evacuation to relieve intracranial pressure.
Types of Evacuation Surgery
Surgeons employ different techniques to evacuate a subdural hematoma, with the choice depending on the age and consistency of the blood clot. For chronic hematomas, where blood has liquefied over weeks, a procedure called burr hole trephination is common. In this method, one or two small holes are drilled into the skull over the hematoma, and a flexible tube is inserted to drain the fluid. This minimally invasive approach is often performed under local or general anesthesia.
In cases of acute subdural hematoma, where the blood is clotted and solid, a more extensive surgery called a craniotomy is the standard approach. This procedure involves making an incision in the scalp and temporarily removing a section of the skull bone to access the brain’s surface. With the brain’s protective covering, the dura, opened, the surgeon can use suction and irrigation to remove the solid clot.
Once the hematoma is removed and bleeding is controlled, the bone flap is secured back in place with small titanium plates and screws. A craniotomy is always performed under general anesthesia. It is reserved for situations where burr holes would be insufficient to remove the thick, clotted blood.
The Surgical and Hospital Stay
The patient journey for an SDH evacuation begins with pre-operative preparations, including a final review of brain scans and baseline neurological assessments. The surgical team then positions the patient to provide the best access to the hematoma site.
Immediately following the surgery, patients are transferred to a neurosurgical intensive care unit (ICU). Here, they are closely observed for changes in neurological function, and vital signs like blood pressure and oxygen levels are continuously tracked.
An intracranial pressure (ICP) monitor, a small device placed inside the skull during surgery, may be used to measure pressure within the brain. This monitoring helps the medical team ensure that pressure remains within a safe range, typically below 20 mm Hg.
A temporary drain is often placed in the surgical site to remove any residual blood or fluid, helping to prevent the hematoma from recurring. This drain is usually removed within a few days. The length of the hospital stay varies; a burr hole procedure may require a few days, while recovery from a craniotomy can require a longer stay.
Recovery and Rehabilitation
The recovery trajectory after subdural hematoma evacuation is highly individual. The process of regaining function begins in the hospital and continues long after discharge, often requiring structured rehabilitation to address any physical, cognitive, or functional deficits.
Physical therapy is a frequent component of the rehabilitation plan. Therapists work with patients to restore strength, improve balance, and regain mobility. Exercises are tailored to each person’s abilities, gradually increasing in difficulty to rebuild endurance and coordination for activities like walking.
Occupational therapy focuses on helping patients relearn the skills needed for daily living, such as dressing, cooking, or managing personal finances. For individuals with cognitive challenges, speech therapy may be recommended. A speech-language pathologist can help with communication difficulties and address issues with memory, attention, and problem-solving skills.
Surgical Risks and Prognosis
Surgery for a subdural hematoma, while often life-saving, carries inherent risks. One of the most common complications is the recurrence of the hematoma, where blood collects again, sometimes requiring a second operation. Other potential issues include surgical site infections and seizures that can occur from irritation to the brain tissue.
The long-term prognosis after SDH evacuation varies widely. Factors influencing the outcome include the patient’s age, their neurological condition before surgery, and the severity of the initial brain injury. Some individuals may experience a complete recovery, while others may be left with permanent neurological deficits, such as weakness or cognitive impairment.
The surgery addresses the blood clot itself, but it does not reverse any underlying brain damage sustained from the initial injury or the period of compression. For this reason, even with successful surgical evacuation, the road to recovery can be long. The outcome is often a reflection of the combined effects of the injury, surgery, and subsequent rehabilitation.