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Updated: Aug 15, 2026
A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy
Published on: November 13, 2016
Localization of temporal lobe epileptic foci with iodine-123 iododexetimide cholinergic neuroreceptor single-photon
K L Boundy1, C C Rowe, A B Black
1Nuclear Medicine Department, Queen Elizabeth Hospital, Adelaide, Australia.
Abstract:
There is evidence suggesting that muscarinic cholinergic neuroreceptors (mChR) are reduced at seizure foci. Iodine-123 (I-123) iododexetimide (IDEX) single-photon emission computed tomography (SPECT) permits in vivo imaging of mChR. We assessed 23 patients with temporal lobe epilepsy (TLE) undergoing preoperative assessment. Regions of interest were placed over the amygdala, hippocampus, and lateral temporal cortex on IDEX SPECT images. Eighteen patients had unilateral TLE. In these, IDEX binding in the ipsilateral hippocampal region was reduced by 19.1 +/- 12%. This was significantly greater than blood flow asymmetry (p < 0.02 by Wilcoxon's signed-rank test). Changes were less marked in the amygdala (11.3 +/- 6.4%) and lateral cortex (7.6 +/- 12.1%). Blinded visual analysis gave correct localization in 14 (78%) patients, and hexamethylpropylenamine oxide (HMPAO) SPECT gave correct localization in 50%. MRI revealed hippocampal sclerosis in 13 (72%) patients and was normal in 5 patients. Of the latter group, four were correctly localized by IDEX. This study confirms that mChR receptors are altered in medial temporal lobe structures in TLE. IDEX SPECT appears to be superior to interictal HMPAO SPECT and complimentary to MRI for seizure focus localization.
Insights
Iodine-123 iododexetimide (IDEX) SPECT imaging reveals reduced muscarinic cholinergic neuroreceptors (mChR) in the hippocampus of temporal lobe epilepsy (TLE) patients. This technique aids in localizing seizure foci, showing promise beyond MRI and HMPAO SPECT.
Area of Science:
- Neuroscience
- Nuclear Medicine
- Epilepsy Research
Background:
- Muscarinic cholinergic neuroreceptors (mChR) are implicated in epilepsy, with evidence suggesting their reduction at seizure foci.
- In vivo imaging of mChR is crucial for understanding epilepsy pathophysiology and localization.
- Temporal lobe epilepsy (TLE) is a common form of epilepsy often requiring precise localization for surgical planning.
Purpose of the Study:
- To assess the utility of Iodine-123 iododexetimide (IDEX) SPECT for imaging mChR in patients with TLE.
- To compare the efficacy of IDEX SPECT with MRI and HMPAO SPECT in localizing seizure foci in TLE.
- To investigate the extent of mChR reduction in specific medial temporal lobe structures in TLE patients.
Main Methods:
- Twenty-three patients with TLE underwent preoperative assessment using IDEX SPECT.
- Regions of interest were defined over the amygdala, hippocampus, and lateral temporal cortex on IDEX SPECT images.
- IDEX SPECT findings were compared with MRI and hexamethylpropylenamine oxide (HMPAO) SPECT results.
Main Results:
- IDEX binding was significantly reduced by 19.1% in the ipsilateral hippocampus of patients with unilateral TLE, exceeding blood flow asymmetry.
- Reductions in the amygdala (11.3%) and lateral cortex (7.6%) were less pronounced.
- Blinded visual analysis of IDEX SPECT correctly localized the seizure focus in 78% of patients, compared to 50% for HMPAO SPECT.
Conclusions:
- This study confirms alterations in mChR in medial temporal lobe structures in TLE.
- IDEX SPECT imaging is a valuable tool for localizing seizure foci in TLE.
- IDEX SPECT demonstrates superiority over HMPAO SPECT and complements MRI in the preoperative assessment of TLE.
