Purpose: To evaluate concordance of Arterial spin labeling (ASL) and FDG-PET findings in localization of epileptogenic focus for pre-surgical evaluation. 

Materials and Methods: Sixty consecutive pediatric patients with intractable epilepsy, underwent standardized evaluation with concurrent structural MRI including ASL and FDG – PET studies for pre-surgical evaluation.

Results: Out of the 60 patients (female: 28, male: 32, mean age: 8.5 years, SD: 5.7 years), 38 patients had structural abnormality on MRI, amongst which concordant ASL and PET findings were identified in 22 patients (58 %). Extremely high concordance was identified with structural abnormalities such as malformations of cortical development of 75% (6/8), tuberous sclerosis (4/4, 100 %), and arterial infarcts (5/5, 100 %).

Out of 22 patients with structurally normal MRIs, only 6 had ASL findings concordant with PET data (30.43%), amongst which 5 demonstrated normal perfusion and glucose metabolism, while one showed multifocal abnormalities on ASL and PET.

None of the 11 patients demonstrating hypometabolism in unilateral or bilateral temporal lobes demonstrated abnormal perfusion. Also, there was limited evaluation of cerebellum with only one (amongst 11 FDG-PET detected abnormal metabolism) demonstrated abnormal perfusion on ASL.

Overall the concordance between ASL and PET in our study is 47 % (28/60).

Conclusions: Arterial spin labelling perfusion imaging may be helpful in localization of epileptogenic focus in patients with structural abnormalities, but fares poorly in patients with no structural abnormality, in temporal lobe epilepsy and in depiction of posterior fossa abnormalities.