Ictal SPECT statistical parametric mapping in temporal lobe epilepsy surgery.

OBJECTIVE: Although subtraction ictal SPECT coregistered to MRI (SISCOM) is clinically useful in epilepsy surgery evaluation, it does not determine whether the ictal-interictal subtraction difference is statistically different from the expected random variation between 2 SPECT studies. We developed a statistical parametric mapping and MRI voxel-based method of analyzing ictal-interictal SPECT difference data (statistical ictal SPECT coregistered to MRI [STATISCOM]) and compared it with SISCOM. METHODS: Two serial SPECT studies were performed in 11 healthy volunteers without epilepsy (control subjects) to measure random variation between serial studies from individuals. STATISCOM and SISCOM images from 87 consecutive patients who had ictal SPECT studies and subsequent temporal lobectomy were assessed by reviewers blinded to clinical data and outcome. RESULTS: Interobserver agreement between blinded reviewers was higher for STATISCOM images than for SISCOM images (kappa = 0.81 vs kappa = 0.36). STATISCOM identified a hyperperfusion focus in 84% of patients, SISCOM in 66% (p < 0.05). STATISCOM correctly localized the temporal lobe epilepsy (TLE) subtypes (mesial vs lateral neocortical) in 68% of patients compared with 24% by SISCOM (p = 0.02); subgroup analysis of patients without lesions (as determined by MRI) showed superiority of STATISCOM (80% vs 47%; p = 0.04). Moreover, the probability of seizure-free outcome was higher when STATISCOM correctly localized the TLE subtype than when it was indeterminate (81% vs 53%; p = 0.03). CONCLUSION: Statistical ictal SPECT coregistered to MRI (STATISCOM) was superior to subtraction ictal SPECT coregistered to MRI for seizure localization before temporal lobe epilepsy (TLE) surgery. STATISCOM localization to the correct TLE subtype was prognostically important for postsurgical seizure freedom.

Mistaken identity: a case of false positive on CT angiography.

We describe the case of a 42-year-old female presenting with subarachnoid haemorrhage from a posterior inferior cerebellar artery (PICA) aneurysm rupture on intracranial digital subtraction angiography (DSA). One year postoperatively, the patient was followed with CT angiography and was reported to show a de novo aneurysm at the bifurcation of the left inferior cerebellar artery (ICA). Subsequent DSA revealed an aberrant vein crossing over the ICA bifurcation on mask phase images. This is the first reported case of a such a reason for a 'false positive' on CT angiography (CTA). The case demonstrates that although CTA has a reported high specificity, careful interpretation of multiple views is required to diagnose intracranial aneurysms when compared to the 'gold' standard of CTA.

Resection of frontal encephalomalacias for intractable epilepsy: outcome and prognostic factors.

PURPOSE: Because focal encephalomalacia is an important cause of medically intractable partial epilepsy and few studies have evaluated the efficacy and the safety of resecting focal-encephalomalacias to improve seizure control, we studied a cohort of 17 consecutive patients who underwent resection of encephalomalacias in the frontal lobes as a treatment of their intractable epilepsy. METHODS: We evaluated several factors for their value in predicting postsurgical seizure control. Pre- and postsurgical magnetic resonance imaging (MRI) scans were reviewed independently by 2 blinded investigators. RESULTS: At a median of 3 years of follow-up (range 0.6-7.5 years), 12 patients (70%) were seizure-free or had only rare seizures. The presence of a focal fast frequency discharge (focal ictal beta pattern) at the beginning of seizures on scalp EEG was predictive of seizure-free outcome (p = 0.017), even among patients who had complete resection of their encephalomalacias (p = 0.016). There was no significant differences in outcome with regard to age at the time of the injury that caused encephalomalacia, interval between injury and onset of seizures, duration of presurgical seizure history, presurgical seizure frequency, age at surgery, or the completeness of encephalomalacia resection. The analysis regarding completeness of encephalomalacia resection almost reached significance, suggesting that it may also be an important predictive factor (p = 0.051). CONCLUSIONS: We conclude that surgery is a very effective treatment for intractable frontal lobe epilepsy (FLE) secondary to encephalomalacias. Patients are more likely to become seizure-free if they have a focal ictal beta discharge on their scalp EEG. Complete resection of the encephalomalacia should be attempted, since our results suggest that this may be a favorable predictive factor. Moreover, the operative strategy for our patients entailed, whenever possible, complete resection of the encephalomalacias and of the adjacent electrophysiologically abnormal tissues.