Brain surgery following a head injury is not that common. The brain is not like skin or muscle tissue that can be stitched back together when it’s damaged. The brain is more like very thick Jello and doesn’t suture well. So when brain surgery is needed, it is for one or more of these purposes:
- Controlling pressure inside the skull
- Alleviating brain swelling
- Repairing blood vessels and removing blood clots or foreign matter
Controlling Pressure Inside the Skull
If a head injury causes fluid to build up inside the skull or causes the brain to swell, the pressure inside the skull increases. Excessive intracranial pressure (”ICP”) can cause damage to delicate brain tissues leading to additional brain injury and lasting disability. Even higher pressure can cause death.
Physicians will suspect problems with intracranial pressure buildup based on the patient’s age, description of the injury and the onset of symptoms, examining the pupils of the eyes and CT scans, and evaluating the patient’s Glasgow Coma Score. When these indicate potential pressure on the brain, a hole is drilled in the skull (a “burr hole”) for placing one of four types of devices:
- Subdural or epidural monitor
- Subarachnoid bolt
- Intraparenchymal monitor
- Intraventricular catheter
A subdural or epidural monitor is inserted in the burr hole made in the skull. The subdural monitor penetrates the dura – the leathery outer membrane surrounding the brain – while the epidural monitor does not. Neither of these monitors can drain cerebrospinal fluid (”CSF”) to relieve ICP. And neither is as accurate and reliable as the intraventricular catheter or intraparenchymal monitor. These simpler pressure monitors may be the best choice, however, when an experienced surgeon is not immediately available to place the more invasive devices
A subarachnoid bolt extends deeper into the skull, penetrating both the dura and the arachnoid membranes. To maintain its position in the small subarachnoid space, the sensor is physically attached to the skull when its inner and outer halves are screwed together. It does not provide for drainage of CSF.
The intraparenchymal monitor is inserted into actual brain tissue (the “parenchyma”). It provides a fast, accurate and reliable way to monitor ICP, but does not provide a way to relieve pressure by draining cerebrospinal fluid. This method is used when draining CSF is not expected to be necessary or when placing an intraventricular catheter is not possible.
The intraventricular catheter is by far the most preferred device for managing intracranial pressure. In a procedure called a ventriculostomy, the catheter is inserted through brain tissue into one of the vacant areas (”ventricles”) deep within the brain. The ventricles are filled with cerebrospinal fluid making this device the most accurate and reliable, as well as allowing it to drain excess cerebrospinal fluid to actually reduce ICP.
Alleviating Brain Swelling
Physicians will first try non-surgical methods for controlling brain swelling (or “edema”) and the resulting problems from excessive intracranial pressure. Draining CSF, using specific drugs, medically inducing a coma, or hypothermia treatments are all non-surgical options.
To alleviate brain swelling surgically, the neurosurgeon may perform a craniectomy. In this procedure, the surgeon removes a section of the skull (a “bone flap”) giving the swelling brain room to expand. If the amount of bone removed is large, the procedure is called a hemicraniectomy.
If the surgeon attempts to save the bone to be surgically reimplanted later, the first operation is called a craniotomy, and the procedure to replace the bone is cranioplasty. To save the bone for later use, it may be frozen, or implanted under the skin of the abdomen until needed.
If parts of the brain tissue are obviously injured and recovery in the injured area is unlikely, the surgeon may remove the damaged brain tissue to create additional space in the skull to relieve the pressure caused by swelling. This is a partial lobectomy.
Repairing Blood Vessels and Removing Blood Clots or Foreign Matter
Bleeding inside the skull also causes an increase in intracranial pressure and can be identified using CT scans.
If the injury is an open head wound, bits of bone or foreign matter may need to be removed from the brain tissue, and the membrane covering the brain repaired.
To correct these problems, the neurosurgeon performs a craniotomy to gain access to the injured brain area. He can then remove foreign materials or clots, evacuate blood, repair blood vessels, and suture the dura as needed.
When the bone is replaced after the surgery, temporary metal plates may be installed to hold the bone flap in place while the bone knits. The metal plates are removed after the bone heals.
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