Parametric subtracted post-ictal diffusion tensor imaging for guiding direct neurostimulation therapy.

Area of Science:

• Neuroimaging
• Epilepsy Research
• Diffusion Tensor Imaging

Background:

• Partial-onset seizures can involve complex propagation pathways.
• Current pre-surgical evaluations may not fully capture white matter ictal changes.
• Responsive neurostimulation (RNS) therapy requires precise targeting of epileptogenic networks.

Purpose of the Study:

• To introduce and validate parametric subtracted post-ictal diffusion tensor imaging (pspiDTI) for visualizing ictal-associated white matter abnormalities.
• To assess the utility of pspiDTI in mapping seizure propagation in patients with refractory epilepsy.
• To evaluate the role of pspiDTI in guiding RNS therapy.

Main Methods:

• pspiDTI was developed to compare diffusion tensor imaging (DTI) volumes from early post-ictal and inter-ictal periods.
• The technique identifies statistically significant, transient changes in white matter water diffusivity.
• pspiDTI findings were compared with subtracted ictal SPECT co-registered to MRI (SISCOM) and RNS electrocorticography.

Main Results:

• pspiDTI detected significant global fractional anisotropy decreases and trace increases in white matter in all six patients.
• White matter diffusivity alterations were adjacent to gray matter hyper-perfusion in 83.33% of patients.
• pspiDTI guided RNS lead placement in 4/6 patients, correlating with early ictal propagation.

Conclusions:

• pspiDTI is a novel technique for visualizing transient, patient-specific, ictal-associated white matter abnormalities.
• pspiDTI provides crucial information on white matter ictal propagation pathways, complementing conventional pre-surgical evaluations.
• Incorporating pspiDTI into a multi-modality workflow can optimize RNS therapy by defining critical nodes within epileptogenic networks.