Surgical Evaluation Process

Finding the right surgery for your LGS loved one takes time and careful planning. The full evaluation process usually takes a few weeks to a few months. While this might feel like a long wait, getting a thorough picture of what’s happening in the brain is really important. This time is also a great opportunity to build a relationship with your medical team, get your questions answered, and talk openly about how you’re feeling about the possibility of surgery. 

It is important to remember each person’s journey to epilepsy surgery will be different.

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Step 1: Initial Testing (Pre-Surgical Evaluation)

The first phase of testing focuses on finding exactly where in the brain seizures are starting. Not every person will need every test, your doctors will decide which ones make the most sense for your loved one.

Standard tests include:

• Baseline EEG (Electroencephalography) – Sensors placed on the scalp track electrical activity in the brain, giving doctors a general idea of which areas may be involved in seizures.
• Video EEG in an Epilepsy Monitoring Unit (EMU) – This combines brain activity recordings with video of the body during a seizure, helping the team more precisely pinpoint where seizures are starting.
• MRI (Magnetic Resonance Imaging) – Takes detailed pictures of the brain to look for any unusual areas that might be causing seizures. Because staying completely still is essential, some individuals may need sedation or anesthesia during the scan.

If more information is needed, doctors may also use:

• Invasive EEG monitoring – If a standard EEG can’t find the seizure source, electrodes may be surgically placed on or in the brain to provide a clearer picture of where seizures begin. 
• Video EEG with surgically placed electrodes – Brain activity and video are recorded during a hospital stay while your loved one is awake. Anti-seizure medicines may be temporarily reduced or stopped under close medical supervision so seizures can be safely recorded and studied. 
• PET Scan (Positron Emission Tomography) – Measures how the brain is functioning between seizures. This is especially helpful when an MRI looks normal but seizures are still occurring.
• SPECT Scan (Single-Photon Emission Computerized Tomography) – Measures blood flow in the brain, which is typically higher in the area where a seizure starts. This scan can be done during a seizure or between seizures.
• MEG (Magnetoencephalography) – A non-invasive test using sensitive sensors to detect magnetic fields created by brain activity, helping map normal versus abnormal brain areas. Doctors may recommend this if other scans haven’t given clear enough answers.

Protecting Important Brain Functions

Before surgery, the team will map parts of the brain that control critical functions like speech, movement, and memory, so surgeons can do everything possible to protect those areas. Tests used for this may include:

• Functional MRI – Identifies exactly where motor and movement functions are controlled in the brain.
• Wada Test – Determines which side of the brain handles language and memory. A sedative is injected to temporarily quiet one side of the brain at a time while the other side is tested.
• Brain Mapping – Small electrodes placed on the brain’s surface record activity while your loved one performs simple tasks like speaking or moving. This creates a precise map of which brain areas control which functions.

A neuropsychologist will also run tests covering language, memory, and attention. These help the team understand how seizures are affecting brain function and provide a helpful baseline to compare with after surgery.

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Step 2: More In-Depth Surgical Testing (If Needed)

After the first phase, the medical team will review everything and decide on next steps. Sometimes it’s clear whether surgery is a good option. Other times, more detailed testing is needed first.

This second phase involves surgical procedures, so your LGS loved one will first go through a pre-operative evaluation including a physical exam, X-rays, an ECG, blood tests, and a meeting with an anesthesiologist. The team will also carefully walk you through all potential risks before moving forward.

Surgical tests in this phase include:

• • Subdural Strip and Grid Electrodes – A thin, flexible sheet of tiny electrodes is placed directly on the surface of the brain. Because it’s in direct contact with the brain, it can provide more detailed information about brain activity than scalp electrodes alone. 
  • Intracranial Depth Electrodes (Stereo-EEG or sEEG) – Thin electrode probes are placed deep inside the brain to find the exact region where seizures begin. They can also gently stimulate different areas to map motor and language functions before surgery.

• ECoG (Electrocorticography) / iEEG (Intracranial EEG) – Done in the operating room for individuals with implanted electrodes, this test pinpoints exactly where seizures start and checks whether that area overlaps with parts of the brain controlling important functions like movement or language.

Your medical team is with you every step of the way, and no question is too small. Take the time you need to understand each step before moving forward. 

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Updated 09/08/26 (KK)