Burr Hole Surgery - An Overview

What Are Burr Holes?

Burr holes are essential holes made in the skull with a surgical drill. It can be done at the beginning of a complicated major surgery or during the surgery itself. The brain is one of the body's largest and most complex organs. It controls all the functions, which makes it extremely important to protect it from external injuries; the skull does this. A bony structure envelopes the brain; however, in brain damage (due to an injury, tumor, or infection), an incision (cut) cannot be made in the skull to reach the brain.

The skull is very hard and needs a bone saw to section it. The risk with an electric bone saw is that no matter how trained the neurosurgeon is, it is difficult to control the blades without damage to the underlying brain, hence the burr holes. Think of them as connecting the dots; the neurosurgeon makes multiple holes with a drill, then uses a different tool to connect these holes and lifts a section of the skull (craniotomy), leaving a window for the surgeon to work on the brain. A burr hole can be a medical procedure to treat brain conditions such as hematoma (collection of blood often mixed with blood clots) to relieve intracranial pressure (pressure inside the brain).

What Is the Use of a Burr Hole?

A burr hole is used to access the brain; some of the reasons are-

• Subdural Hematoma - It is bleeding within the skull but outside the brain. A normal brain is covered by meninges (dura mater, arachnoid membrane, and pia mater) which separate it from the skull. Blood vessels that supply blood to the brain also supply to these layers and the skull. When a traumatic brain injury occurs, the aforementioned blood vessels get ruptured, and blood starts leaking; if the leak happens between the meninges, it is called an acute subdural hematoma. If the same injury happens in old age due to brain shrinkage and stretching of thin blood vessels, it is known as a chronic subdural hematoma.

• Epidural Hematoma - It is also called an extradural hematoma or intracranial hematoma; also seen in traumatic brain injury. Unlike subdural hematoma, the blood leaks into the space between the membranes and the skull.

• Hydrocephalus - Hydrocephalus is caused due to an imbalance in the amount of CSF produced and absorbed back into the bloodstream resulting in pressure that can damage the brain tissue.It is mostly seen in infants, where excess fluid builds up in the brain and puts pressure on it. Normally, the tissues in the brain continuously produce a colorless fluid called the cerebrospinal fluid (CSF) to cushion the brain from shock or trauma.

• Cancer - Burr holes as such can be used to take the biopsy of an underlying brain tumor; in a few cases, the neurosurgeon further extends the surgery to a craniotomy (sectioning of the skull) to remove the entire tumor.

• Infection - Meningitis (inflammation of meninges) and encephalitis (inflammation of the brain) caused by bacteria and viruses also increase intracranial pressure, occasionally requiring surgical intervention.

How Is the Burr Hole Procedure Done?

• A neurosurgeon maps out the location of the burr holes; they will use diagnostic imaging tests like computed tomography (CT) scans to assess the underlying condition and plan the treatment. It is done under general anesthesia; once the exact location for the burr holes is determined, the surgical team will shave and disinfect the area.

• The neurosurgeon makes an incision into the scalp and exposes the skull; a special drill is used to create the burr hole. The drills are designed to stop drilling once the skull is penetrated, thus preventing injury to the brain.

• The hole may be used immediately to drain blood or other fluids, causing pressure on the brain, often seen in ventriculostomy or decompression surgery. Depending on the underlying condition, it may be closed or left open to drain with a shunt.

• If the holes are proposed for a craniotomy or a craniectomy, the surgeon will use specialized tools to section the skull using the holes as a guide. This gives access to a wider brain area to perform complex brain surgeries. Once complete, they put the sectioned skull back immediately (as in craniotomy) or at a later stage (done in craniectomy). The overlying scalp is placed into its normal position, and sutures or staples are used to close the incision.

What Is the Difference Between Burr Hole, Craniotomy, and Craniectomy?

All the procedures mentioned above are done to treat problems in the brain. To reach the brain, the neurosurgeon needs to access it by cutting the skull; based on how the skull is sectioned, the surgeries can be divided into the following:

1. Burr Hole Drainage- A small hole measuring around 14 mm (standard diameter of an electric drill) is drilled into the skull to drain hematomas, and one hole is sufficient.

2. Craniotomy- Pre-planned multiple burr holes are made and joined with a craniotome saw to remove a section of the skull, done in cases like cranial subdural empyema or tumor, etc. After the surgeon is done working on the brain, the sectioned skull is positioned back in its original location with plates and screws.

3. Craniectomy- This also involves sectioning off the skull with the guidance of the burr holes. However, the surgeon does not immediately replace the removed piece; instead, the skull is left open until the underlying pressure comes down. This approach is mostly preferred in Chiari decompression surgery.

What Are the Complications of a Burr Hole Surgery?

Burr hole placement has significant risks; some of which are the following:

• Bleeding of the brain.

• Seizure.

• Stroke.

• Infection of the incision or brain.

• Brain damage includes sensory changes, memory problems, coordination difficulties, and speech impairment.

• Swelling of the brain and coma.

What Happens After a Burr Hole Procedure?

The patient is observed till all the vitals are stable and then transferred to an ICU (intensive care unit), where the staff can closely monitor the patient. Disinfection at the incision site is of utmost importance because a secondary infection can easily reach the brain from the suture site. In most cases, prophylactic antibiotics and nonsteroidal anti-inflammatories will be given to manage the pain.

Conclusion:

Burr hole is a serious procedure done by a neurosurgeon, whether it is for decompression or to allow for more complicated surgery. Post-surgery, the patient is checked for vitals and may need to stay in the hospital for a few days or weeks, depending on the severity. Recovery requires a significant amount of time compared to typical surgical procedures.