Hemispherectomy

Hemispherectomy is a surgical technique where a diseased hemisphere of the brain is removed partially or totally or is disconnected from the normal hemisphere. The surgery is successful in stopping seizures in selected people.

Epilepsy is a typical condition that affects the brain, leading to frequent seizures. Seizures are electrical activities in the brain that temporarily affect its functioning. A hemispherectomy aims to remove the hemisphere that is used less and is the source of the seizures. A callosotomy (cutting of the corpus callosum that connects two parts of the brain ) is also performed during this procedure to prevent the seizures from spreading from one hemisphere to another hemisphere. 

The cerebrum, the largest part of the brain, is divided into two hemispheres - left and right. The left hemisphere plays a vital role in language, reading, verbal memory, arithmetic and writing. It is responsible for movement or sensation on the right side of the body. The right hemisphere also helps us understand what we touch and see, and controls music, non-verbal memory and emotions. It is responsible for movement and sensation on the left side of the body.

Hemispherectomy is generally considered when seizures have lasted for a maximum of two years (despite trying medications) and when tests before surgery show multifocal epilepsy, where seizures originate from various areas of the brain in one hemisphere.

Common diagnoses that indicate this procedure are as follows:

• Hemispheric malformations of cortical development (structural abnormalities of the cerebral cortex, the grey matter)
• Hemimegalencephaly (overgrowth of one side of the brain)
• Perinatal stroke (a stroke that happens to a baby between 20 weeks gestation and 28 days after birth)
• Sturge-Weber syndrome (a neurological disorder marked by a distinctive port-wine stain on the forehead, scalp or around the eye)
• Rassmussen’s encephalitis (rare, inflammatory neurological disease)

People with the following features on physical and neuroimaging tests may get hemispherectomy:

• Epilepsy that is difficult to control (intractable) with medicines with seizures originating from the affected side
• Weakness on one side of body with loss of dexterity of the hand with or without peripheral vision (side vision) loss
• Slowed or arrested development due to intractable seizures
• Diffuse abnormality of one cerebral hemisphere that leads to intractable epilepsy

The following are the symptoms of epilepsy:

• Fits (uncontrollable shaking and jerking)
• Becoming stiff
• Losing awareness, staring blankly into space
• Collapsing
• Unusual sensations like a rising feeling in the stomach, a tingling feeling in the arm or legs, and unusual smell or taste

Hemispherectomy may not be the choice of treatment in some cases like when seizures arise from many areas of the brain (more than one hemisphere) or the risk over the functions of brain may be too high. For such situations, alternative treatments are available.

Before going for a hemispherectomy, it is important to pinpoint the correct location in the brain where the seizures come from. To identify this, you need to get done the following tests:

• Magnetic resonance imaging (MRI): An MRI scan uses radio waves, large magnets and a computer to create images of the internal body.
• Computed tomography (CT) scan: A CT scan uses x-rays and a computer to make images of the internal body.
• Electroencephalography (EEG, outpatient): EEG records the electrical activity of the brain via sticky pads fixed to the scalp.
• Electroencephalography (inpatient): In some cases, a longer EEG is required for which you need to stay in the epilepsy monitoring unit.
• Magnetoencephalography (MEG) scan: MEG scan is a non-invasive test used to confine seizures and abnormal activity in the brain with the help of magnetic sensors. It can also be used to localize the parts of the brain that are responsible for control of motor and sensory (complications) and language.
• Positron emission tomography (PET) scan: PET scan can take detailed pictures of chemical and other changes in the brain that MRI and CT scans cannot show.
• Neuropsychological tests may be done to aid diagnosis. It helps to evaluate functions in various cognitive zones such as intelligence, memory, perception, language, and executive functions. These tests can be used to predict the results after surgery with respect to cognitive change and seizure control.
• A Wada test can be done to find out the dominant hemisphere responsible for important functions like speech and memory. Wada test helps the doctor to decide the appropriate method for preventing seizures while protecting the other parts of the brain.

Additionally, your health care provider will do an evaluation of your health, which includes the following:

• The medical history of your family.
• Your own medical history that will include information on the medications that you are on, your allergies, reactions to anaesthesia or previous surgeries. You should inform the doctor of all the medicines and supplements you are taking as some medicines will need to be discontinued.
• You will be asked to stop chewing tobacco or smoking one to two weeks before surgery to prevent bleeding problems.
• You will be asked to stop eating and drinking at least 12 hours before surgery.
• Complete seizure history like onset of epilepsy, frequency of seizures
• Neurologic examination based on motor and/or sensory-motor lateralized neurologic deficits
• You will need to sign a consent form to give permission to the doctor to perform the surgery.

Hemispherectomy is of three types – anatomic, functional and peri-insular hemispherectomy. 

• Functional hemispherectomy: In this procedure, only a small portion of the brain is removed. However, the diseased hemisphere of the brain is totally detached from the remaining normal brain. This disconnection includes corpus callosotomy and allows electrical isolation of the part that is left intact.
• Anatomic hemispherectomy: This procedure is preferred when seizures occur in spite of an earlier functional hemispherectomy. Anatomic hemispherectomy comprises physical removal of the whole diseases hemisphere. The main structures in the brain like thalamus and basal ganglia are left in place as they usually do not cause seizures.
• Peri-insular hemispherectomy: This method involves detaching fibers that connect the two hemispheres of the brain. This interferes with the communication network of the affected region of the brain and helps with seizure control.

The surgery is done in the following manner:

• The operation will be carried out under general anaesthesia, which will make you sleep.
• The surgeon will make an incision (cut) in your scalp, and remove a part of your skull to expose your brain.
• He/she will then remove the diseased or affected part of your brain and disconnect other parts based on the method of surgery being used.
• The corpus callosum will also be disconnected. It is cut to effectively stop communication between the two parts in order to prevent the spread of seizures.
• Finally, the surgeon will close the openings in your skull and scalp.

This surgery may typically take 12 hours.

You can expect the following after the surgery:

• You will be in the ICU and will be closely monitored until your vitals become stable.
• You will have a surgical drain in place to remove any accumulated fluid from the site of surgery.
• Once you are stable enough, you will be moved to your hospital room and evaluated by a physiotherapist and speech and occupational therapist.
• The dressing on the incision site will be removed before discharge. 
• The next day after surgery, you will be asked to get up and start walking with help.
• You will be given pain medicines to minimise the discomfort.
• It is common to have swelling near the incision site. It can be decreased by applying ice.
• You would be asked to keep your head raised under pillows while sleeping and be active throughout the day to reduce swelling.
• Isolated seizures may happen immediately after the surgery. So, a nurse will monitor your seizure activity and the doses of anticonvulsants (medicines used to control seizures).
• Some people may feel more anxiety or depression after the operation.
• You may have to stay in the hospital for two to five days, depending on the type of surgery that you underwent.

The benefits of functional hemispherectomy over anatomic hemispherectomy are:

• Shorter operation time
• Less need for blood transfusion
• Reduced blood loss
• Less chances of developing hydrocephalus (build-up of spinal fluid in the brain, causing increased pressure in the skull)

Follow the below-mentioned points to look after yourself at home after the operation.

• Wound care: Your doctor may allow you to shower and shampoo 3-4 days after surgery.
• Medications: You may have nausea or headache after the surgery, which can be managed with pain medicines. You should continue anticonvulsant medicines after the surgery. If you stay free from seizures for a long time, then the neurologist might slowly reduce or even stop these medications.
• Activity: Most people can resume regular activities by the time they are discharged. However, avoid working (children should not be sent to school) for a minimum of six weeks after surgery or till your first follow-up. Do not drive, lift heavy things or drink any alcoholic drinks until advised by your surgeon. 
• Rehabilitative care: You may be moved to a rehabilitation centre for intense occupational, physical, and speech therapy if indicated medically. This can be provided at home or on an outpatient basis if inpatient therapy is not required.

When to see the doctor?

You should immediately contact your doctor in case of allergic reactions, wound infection, or complications like:

• Fever
• Bleeding

The following risks are associated with a hemispherectomy:

• A need for blood transfusion
• Aseptic meningitis (inflammation in the brain’s covering)
• Hydrocephalus may occur immediately after the operation or many years later.
• Hypothermia (a condition where body loses heat more than it is produced, leading to low body temperature)
• Bleeding
• Scalp numbness
• Nausea
• Fatigue
• Depression 
• Headaches
• Difficulty with speech and memory
• Loss of feeling and/or movement in the right side of the body if the left hemisphere of the brain was removed and vice versa.

If you have had staples or sutures placed in your wound, they will be removed 7-14 days after your surgery. You will meet your neurologist and surgeon after six weeks of your surgery.

Disclaimer: The above information is provided purely from an educational point of view and is in no way a substitute for medical advice by a qualified doctor.