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Ictal depth EEG and MRI structural evidence for two different epileptogenic networks in mesial temporal lobe epilepsy.

Memarian N, Madsen SK, Macey PM, Fried I, Engel J, Thompson PM, Staba RJ - PLoS ONE (2015)

Bottom Line: MRI analysis found reduced cortical thickness correlated with longer duration of epilepsy.One, identified by HYP ictal onsets, chiefly involves hippocampus and is associated with excellent outcome after standardized anteromedial temporal resection, while the other also involves lateral temporal and orbitofrontal cortex and a seizure-free surgical outcome occurs less after this procedure.These results suggest that a more extensive tailored resection may be required for patients with the second type of MTLE.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America.

ABSTRACT
Hypersynchronous (HYP) and low voltage fast (LVF) activity are two separate ictal depth EEG onsets patterns often recorded in presurgical patients with MTLE. Evidence suggests the mechanisms generating HYP and LVF onset seizures are distinct, including differential involvement of hippocampal and extra-hippocampal sites. Yet the extent of extra-hippocampal structural alterations, which could support these two common seizures, is not known. In the current study, preoperative MRI from 24 patients with HYP or LVF onset seizures were analyzed to determine changes in cortical thickness and relate structural changes to spatiotemporal properties of the ictal EEG. Overall, onset and initial ipsilateral spread of HYP onset seizures involved mesial temporal structures, whereas LVF onset seizures involved mesial and lateral temporal as well as orbitofrontal cortex. MRI analysis found reduced cortical thickness correlated with longer duration of epilepsy. However, in patients with HYP onsets, the most affected areas were on the medial surface of each hemisphere, including parahippocampal regions and cingulate gyrus, whereas in patients with LVF onsets, the lateral surface of the anterior temporal lobe and orbitofrontal cortex showed the greatest effect. Most patients with HYP onset seizures were seizure-free after resective surgery, while a higher proportion of patients with LVF onset seizures had only worthwhile improvement. Our findings confirm the view that recurrent seizures cause progressive changes in cortical thickness, and provide information concerning the structural basis of two different epileptogenic networks responsible for MTLE. One, identified by HYP ictal onsets, chiefly involves hippocampus and is associated with excellent outcome after standardized anteromedial temporal resection, while the other also involves lateral temporal and orbitofrontal cortex and a seizure-free surgical outcome occurs less after this procedure. These results suggest that a more extensive tailored resection may be required for patients with the second type of MTLE.

No MeSH data available.


Related in: MedlinePlus

Color-coded probability or P-maps depicting the spatial pattern of significantly reduced gray matter thickness in patients with respect to controls.Lateral and medial views of cerebral hemisphere ipsilateral (A & C) and contralateral (B & D) to the SOZ in patients with hypersynchronous (HYP, top row) versus patients with low voltage fast (LVF, bottom row) onset seizures. P-maps in bottom row are the same as in rows above, but reoriented to more clearly show gray matter thickness changes on ventral, dorsal, and anterior aspects. In upper right, P-values scaled such that areas shaded green correspond to P<0.01 and blue P>0.05 (not significant).
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pone.0123588.g003: Color-coded probability or P-maps depicting the spatial pattern of significantly reduced gray matter thickness in patients with respect to controls.Lateral and medial views of cerebral hemisphere ipsilateral (A & C) and contralateral (B & D) to the SOZ in patients with hypersynchronous (HYP, top row) versus patients with low voltage fast (LVF, bottom row) onset seizures. P-maps in bottom row are the same as in rows above, but reoriented to more clearly show gray matter thickness changes on ventral, dorsal, and anterior aspects. In upper right, P-values scaled such that areas shaded green correspond to P<0.01 and blue P>0.05 (not significant).

Mentions: Overall, patients had reduced cortical thickness with respect to control subjects (ipsilateral p = 0.0001; contralateral p = 0.0009). The small sample size precluded meaningful comparisons between seizure clusters and instead was carried out at the level of ictal EEG onset pattern. Both HYP and LVF onset groups had significantly reduced cortical thickness that was widely distributed in areas ipsilateral and contralateral to the SOZ (Fig 3). In each group, cortical thickness changes were located primarily in superior, middle, and inferior frontal gyri, superior aspects of pre- and post-central gyri, superior parietal gyrus, lateral and medial surfaces of occipital lobe, and anterior and lateral regions of the temporal lobe. Compared to respective controls, a greater amount of GM loss was found in the HYP than LVF seizure onset group, but the spatial pattern of loss was similar between the two ictal EEG onset groups (S3 Fig).


Ictal depth EEG and MRI structural evidence for two different epileptogenic networks in mesial temporal lobe epilepsy.

Memarian N, Madsen SK, Macey PM, Fried I, Engel J, Thompson PM, Staba RJ - PLoS ONE (2015)

Color-coded probability or P-maps depicting the spatial pattern of significantly reduced gray matter thickness in patients with respect to controls.Lateral and medial views of cerebral hemisphere ipsilateral (A & C) and contralateral (B & D) to the SOZ in patients with hypersynchronous (HYP, top row) versus patients with low voltage fast (LVF, bottom row) onset seizures. P-maps in bottom row are the same as in rows above, but reoriented to more clearly show gray matter thickness changes on ventral, dorsal, and anterior aspects. In upper right, P-values scaled such that areas shaded green correspond to P<0.01 and blue P>0.05 (not significant).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388829&req=5

pone.0123588.g003: Color-coded probability or P-maps depicting the spatial pattern of significantly reduced gray matter thickness in patients with respect to controls.Lateral and medial views of cerebral hemisphere ipsilateral (A & C) and contralateral (B & D) to the SOZ in patients with hypersynchronous (HYP, top row) versus patients with low voltage fast (LVF, bottom row) onset seizures. P-maps in bottom row are the same as in rows above, but reoriented to more clearly show gray matter thickness changes on ventral, dorsal, and anterior aspects. In upper right, P-values scaled such that areas shaded green correspond to P<0.01 and blue P>0.05 (not significant).
Mentions: Overall, patients had reduced cortical thickness with respect to control subjects (ipsilateral p = 0.0001; contralateral p = 0.0009). The small sample size precluded meaningful comparisons between seizure clusters and instead was carried out at the level of ictal EEG onset pattern. Both HYP and LVF onset groups had significantly reduced cortical thickness that was widely distributed in areas ipsilateral and contralateral to the SOZ (Fig 3). In each group, cortical thickness changes were located primarily in superior, middle, and inferior frontal gyri, superior aspects of pre- and post-central gyri, superior parietal gyrus, lateral and medial surfaces of occipital lobe, and anterior and lateral regions of the temporal lobe. Compared to respective controls, a greater amount of GM loss was found in the HYP than LVF seizure onset group, but the spatial pattern of loss was similar between the two ictal EEG onset groups (S3 Fig).

Bottom Line: MRI analysis found reduced cortical thickness correlated with longer duration of epilepsy.One, identified by HYP ictal onsets, chiefly involves hippocampus and is associated with excellent outcome after standardized anteromedial temporal resection, while the other also involves lateral temporal and orbitofrontal cortex and a seizure-free surgical outcome occurs less after this procedure.These results suggest that a more extensive tailored resection may be required for patients with the second type of MTLE.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States of America.

ABSTRACT
Hypersynchronous (HYP) and low voltage fast (LVF) activity are two separate ictal depth EEG onsets patterns often recorded in presurgical patients with MTLE. Evidence suggests the mechanisms generating HYP and LVF onset seizures are distinct, including differential involvement of hippocampal and extra-hippocampal sites. Yet the extent of extra-hippocampal structural alterations, which could support these two common seizures, is not known. In the current study, preoperative MRI from 24 patients with HYP or LVF onset seizures were analyzed to determine changes in cortical thickness and relate structural changes to spatiotemporal properties of the ictal EEG. Overall, onset and initial ipsilateral spread of HYP onset seizures involved mesial temporal structures, whereas LVF onset seizures involved mesial and lateral temporal as well as orbitofrontal cortex. MRI analysis found reduced cortical thickness correlated with longer duration of epilepsy. However, in patients with HYP onsets, the most affected areas were on the medial surface of each hemisphere, including parahippocampal regions and cingulate gyrus, whereas in patients with LVF onsets, the lateral surface of the anterior temporal lobe and orbitofrontal cortex showed the greatest effect. Most patients with HYP onset seizures were seizure-free after resective surgery, while a higher proportion of patients with LVF onset seizures had only worthwhile improvement. Our findings confirm the view that recurrent seizures cause progressive changes in cortical thickness, and provide information concerning the structural basis of two different epileptogenic networks responsible for MTLE. One, identified by HYP ictal onsets, chiefly involves hippocampus and is associated with excellent outcome after standardized anteromedial temporal resection, while the other also involves lateral temporal and orbitofrontal cortex and a seizure-free surgical outcome occurs less after this procedure. These results suggest that a more extensive tailored resection may be required for patients with the second type of MTLE.

No MeSH data available.


Related in: MedlinePlus