Guidelines to Map Brain Before Epilepsy Surgery Revealed by American Academy of Neurology

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Highlights
  • American Academy of Neurology has provided guidelines for brain imaging for people with epilepsy undergoing surgery.
  • People with medial temporal epilepsy should have their brain mapped to identify language and memory centers.
  • Wada test is invasive while Functional Magnetic Resonance Imaging (fMRI) is non-invasive and can also be used for predicting the outcome.
The American Academy of Neurology has published guidelines which state that brain imaging of regions associated with language and memory can be performed before surgery for epilepsy rather than the currently used invasive methods. The guidelines were provided after evidence was found, which makes this the first ever systematically reviewed guideline.
Guidelines to Map Brain Before Epilepsy Surgery Revealed by American Academy of Neurology
Guidelines to Map Brain Before Epilepsy Surgery Revealed by American Academy of Neurology

There was a note of caution that was also included, stating that the evidences that were available were not very conclusive as they involved small study samples and were carried out at only one institution.

Surgery for epilepsy is required only when medications cannot control seizures. The region of the brain where the seizures begin to develop are removed or intervention strategies are used to prevent or restrict the spread of seizure. As a part of the brain could be removed during epilepsy surgery, the research team of this current study caution that a brain map of the region for language and memory is essential to prevent loss.

Guidelines

The research team compared the imaging results of an fMRI and the commonly used procedure intracarotid amobarbital procedure, which is also called the Wada test that is conducted during angiography. 

Wada Test

A medication is injected into main artery of the neck, which is the carotid artery. An EEG recording at the same time confirms that the injected side of the brain is inactive as a neurologist performs a neurological examination. The neurologist engages the patient in a series of language and memory related tests. They evaluate the memory by showing a series of items or pictures to the patient and—within a few minutes, as soon as the effect of the medication dissipates—testing the patient's ability to recall. The test is typically administered by a neuropsychologist as a result of expertise in psychometric testing. Since this test is invasive, there are certain risks that are involved.

Functional MRI (fMRI)

This imaging technique detects activity in the brain by measuring the flow of blood. Since this procedure is not invasive, it is considered to be safe.

Both these techniques are carried out to ensure that regions of the brain that are associated with language and memory are not affected during surgery for epilepsy.

Dr. Jerzy Szaflarski who is the lead author of the study said "Because fMRI is becoming more widely available, we wanted to see how it compares to the Wada test. While the risks associated with the Wada test are rare, they can be serious, including stroke and injury to the carotid artery."

The guidelines found evidence that the use of fMRI was a better alternative to the Wada test for evaluating the language and memory centers of the brain for people who have medial temporal epilepsy. The evidence obtained was not sufficient enough for recommendations for people ailing with temporal tumors or with temporal neocortical epilepsy.

Predicting Outcome
  • The fMRI technique can also be considered for predicting verbal memory outcome after the surgery and the guidelines state that moderate level of evidence was obtained to carry out this procedure. Patients who are to undergo left medial temporal lobe surgery can use the fMRI to understand the position of the language and memory centers as well as to determine the level of language after the surgery. 
  • Visuospatial memory outcomes can be predicted using fMRI for people undergoing temporal lobe surgery. The guidelines obtained weak evidence for the same.
The research team concludes by stating that larger studies are required to increase the evidence that is currently available. Both Wada test and fMRI are procedures that have not yet been standardized.  They also state that doctors should exert caution while using the techniques and should explain the benefits of both the procedure to patients. These guidelines are supported by the American Academy of Neurology.

Epilepsy

Epilepsy is a neurological condition, that is characterized by many different disorders that are caused due to the tendency to have seizures in the brain. This condition is normally identified in an individual after the first episode of seizure. Though not all seizures are due to epilepsy, and other conditions like fainting or low blood sugar can be confused for epilepsy.

This condition can develop at any stage in life and is found in all races. The most commonly affected people are children and adults over 65 years of age. More than half a million people have epilepsy, which makes it one in every 100.

Causes for Epilepsy

There are different epilepsies with varying causes. It could be caused due to one or more of the following:
  • A genetic condition that is passed on from the parents.
  • A genetic condition that is caused due to mutation but not inherited
  • Structural change in the brain due to brain injury, meningitis tumor or stroke.
References:
  1. Causes of epilepsy - (https:www.epilepsysociety.org.uk/causes-epilepsy#.WHWoXFN97IU)
Source: Medindia

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