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Clinical applications of functional MRI in epilepsy.

Kesavadas C, Thomas B - Indian J Radiol Imaging (2008)

Bottom Line: It has become a noninvasive alternative to intraoperative cortical stimulation and the Wada test for eloquent cortex mapping and language lateralization, respectively.Its role in predicting postsurgical memory outcome and in localizing the ictal activity is being recognized.Illustrative cases have been discussed, wherein the fMRI results influenced the seizure team's decisions with regard to diagnosis and therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695 011, India.

ABSTRACT
The role of functional MRI (fMRI) in the presurgical evaluation of patients with intractable epilepsy is being increasingly recognized. Real-time fMRI is an easily performable diagnostic technique in the clinical setting. It has become a noninvasive alternative to intraoperative cortical stimulation and the Wada test for eloquent cortex mapping and language lateralization, respectively. Its role in predicting postsurgical memory outcome and in localizing the ictal activity is being recognized. This review article describes the biophysical basis of blood-oxygen-level-dependent (BOLD) fMRI and the methodology adopted, including the design, paradigms, the fMRI setup, and data analysis. Illustrative cases have been discussed, wherein the fMRI results influenced the seizure team's decisions with regard to diagnosis and therapy. Finally, the special issues involved in fMRI of epilepsy patients and the various challenges of clinical fMRI are detailed.

No MeSH data available.


Related in: MedlinePlus

BOLD signal shows initial dip and then a more prolonged ‘positive’ signal
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Figure 0001: BOLD signal shows initial dip and then a more prolonged ‘positive’ signal

Mentions: When the neurons are stimulated there is an increase in local oxygen consumption that results in an initial decrease of oxy-Hb and an increase in deoxy-Hb in the functional area. To provide the active neurons with oxygenated blood, perfusion in capillaries and draining veins is enhanced within several seconds. As a result of this process, the initial decrease of local oxy-Hb is equalized and then overcompensated.[9] The deoxy-Hb is progressively washed out. This causes a reduction of local field inhomogeneity and an increase of the BOLD signal in T2*W MRI images[10] [Figure 1]. Although the ‘initial dip’ corresponds to the neuronal activity both temporally and spatially, this is more difficult to measure in clinical settings.[11] Electrophysiologically, it is the local field potential that changes with an increase in the BOLD signal and not the neuronal firing rate.[12]


Clinical applications of functional MRI in epilepsy.

Kesavadas C, Thomas B - Indian J Radiol Imaging (2008)

BOLD signal shows initial dip and then a more prolonged ‘positive’ signal
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2747426&req=5

Figure 0001: BOLD signal shows initial dip and then a more prolonged ‘positive’ signal
Mentions: When the neurons are stimulated there is an increase in local oxygen consumption that results in an initial decrease of oxy-Hb and an increase in deoxy-Hb in the functional area. To provide the active neurons with oxygenated blood, perfusion in capillaries and draining veins is enhanced within several seconds. As a result of this process, the initial decrease of local oxy-Hb is equalized and then overcompensated.[9] The deoxy-Hb is progressively washed out. This causes a reduction of local field inhomogeneity and an increase of the BOLD signal in T2*W MRI images[10] [Figure 1]. Although the ‘initial dip’ corresponds to the neuronal activity both temporally and spatially, this is more difficult to measure in clinical settings.[11] Electrophysiologically, it is the local field potential that changes with an increase in the BOLD signal and not the neuronal firing rate.[12]

Bottom Line: It has become a noninvasive alternative to intraoperative cortical stimulation and the Wada test for eloquent cortex mapping and language lateralization, respectively.Its role in predicting postsurgical memory outcome and in localizing the ictal activity is being recognized.Illustrative cases have been discussed, wherein the fMRI results influenced the seizure team's decisions with regard to diagnosis and therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695 011, India.

ABSTRACT
The role of functional MRI (fMRI) in the presurgical evaluation of patients with intractable epilepsy is being increasingly recognized. Real-time fMRI is an easily performable diagnostic technique in the clinical setting. It has become a noninvasive alternative to intraoperative cortical stimulation and the Wada test for eloquent cortex mapping and language lateralization, respectively. Its role in predicting postsurgical memory outcome and in localizing the ictal activity is being recognized. This review article describes the biophysical basis of blood-oxygen-level-dependent (BOLD) fMRI and the methodology adopted, including the design, paradigms, the fMRI setup, and data analysis. Illustrative cases have been discussed, wherein the fMRI results influenced the seizure team's decisions with regard to diagnosis and therapy. Finally, the special issues involved in fMRI of epilepsy patients and the various challenges of clinical fMRI are detailed.

No MeSH data available.


Related in: MedlinePlus