Name of the Procedure:

Wada Activation Test for Hemispheric Function, also known as the Intracarotid Amobarbitol Procedure (IAP).

Summary

The Wada test is a diagnostic procedure that helps to identify which side of the brain handles language and memory functions. During the test, medication is injected into one of the brain’s carotid arteries to temporarily shut down one hemisphere at a time while the patient performs cognitive tasks. This is accompanied by electroencephalographic (EEG) monitoring to record brain activity.

Purpose

The Wada test is primarily used to evaluate brain function before epilepsy surgery. It helps to ensure that critical areas responsible for language and memory are not adversely affected by the surgery.

Indications

• Patients being considered for epilepsy surgery
• Individuals with brain lesions or abnormalities that may affect cognitive functions
• Patients with an abnormal EEG suggesting lateralized brain function issues

Preparation

• Patients may be asked to fast for several hours before the test.
• Pre-procedure imaging studies, such as MRI or CT scans, might be required.
• Medication adjustments may be necessary under medical advice.

Procedure Description

1. The patient lies on an examination table.
2. A catheter is inserted into a blood vessel, usually in the groin, and guided to the carotid artery.
3. Amobarbitol is injected into the carotid artery to temporarily anesthetize one hemisphere of the brain.
4. The patient is asked to perform tasks such as speaking, counting, and recalling images or words, while their cognitive abilities are evaluated.
5. EEG monitoring is used throughout to record brain activity.
6. The procedure is then repeated on the other side of the brain.

Duration

The entire process typically takes 1 to 2 hours.

Setting

The Wada test is performed in a hospital setting, often in a specialized radiology or neurodiagnostic department.

Personnel

• Neurologist or neuropsychologist
• Radiologist
• EEG technician
• Anesthesiologist (if needed)
• Nursing staff

Risks and Complications

• Stroke or transient ischemic attack (TIA)
• Allergic reactions to the medication
• Bleeding or infection at the catheter insertion site
• Temporary speech or memory disturbances

Benefits

• Identifies critical brain areas related to language and memory, ensuring their preservation during surgery.
• Provides crucial information for surgical planning, enhancing the safety and effectiveness of epilepsy surgery.

Recovery

• Patients are monitored for a few hours after the test.
• They are advised to rest for the remainder of the day.
• Normal activities can usually be resumed the next day.
• Follow-up appointments for surgical planning may be scheduled.

Alternatives

• Functional MRI (fMRI): Non-invasive, but may not provide as precise localization in some cases.
• Magnetoencephalography (MEG): Another non-invasive technique with good spatial and temporal resolution.
• Direct cortical stimulation mapping: Performed intraoperatively but carries higher risks.

Patient Experience

• Mild discomfort at the catheter insertion site.
• Possible anxiety during the test, but staff will provide support.
• Temporary speech or memory issues during and shortly after the procedure.
• Pain management is generally not required but can be addressed if needed.