Seizure Onset Patterns, Histological Types Predict Surgical Outcomes for Resection
Predicting which patients will achieve the best outcomes in surgical resection has remained challenging.
Researchers in France recently identified important markers for outcomes of surgical resection to eliminate epileptic seizure activity associated with the 2 most prevalent types of malformation of cortical development (MCD): focal cortical dysplasia (FCD) and neurodevelopmental tumors (NDT), according to a study published in Epilepsia.
Surgical resection is effective in achieving freedom from seizures (Engel class I) in 65% of patients with FCD seizures and as many as 80% of patients with NDT seizures, although predicting which patients will achieve the best outcomes has remained challenging.1-3
Graduate Epileptologist Stanislas Lagarde and colleagues at the Timone Hospital in Marseille, France, were able to define 6 specific types of seizure patterns that occurred in 53 patients with pathologically confirmed MCD that were either due to FCD or NDTs and that were predictive of surgical outcomes. Engel classifications were used to measure outcomes in all patients with a mean follow up of 4.9 years after surgery. Results showed that 29 patients (54%) were Engel class I, 8 (15%) were Engel class II, 6 (5%) were Engel class III, and 10 (18%) were Engel class IV.
Seizure Onset Patterns
Using stereo-electroencephalographic (SEEG) recordings to perform blind analyses of seizure onset pattern (SOP) activity, the researchers analyzed a total of 222 seizures from the cohort. They found a high prevalence of low-voltage fast activity (LVFA) patterns among the study patients, including LFVA (pattern 1, 32.1%) pre-ictal spiking followed by LVFA (pattern 2, 17%), burst of polyspikes followed by LVFA (pattern 3, 18.9%) and slow-wave DC shift followed by LVFA (pattern 4, 15.1%). A surprising amount of SOP activity was also generated by slower patterns, including rhythmic spikes/spike waves (pattern 5, 5.7%) and theta/alpha sharp waves (pattern 6, 11.3%) . The LVFA patterns were evident in majority of patients (44/53 or 83%), but not all seizure types.
The investigators found that the epileptogenic zone (EZ) affected multiple areas of the brain, with greater activity in the frontal, temporal and parietal regions (n=23, 16, and 11, respectively) compared with lesser occipital activity (n=3). Frontal lobe localization was more likely in FCD type II seizures, while NDT seizures had greater association with the temporal region.
Four of the patients demonstrated insular involvement. The group also divided in terms of type of EZ organization, as 20 had only focal involvement, while 33 demonstrated network events.
A second pattern emerged that was associated with histological type, with a much higher prevalence in FCD subtype I of SOP pattern 4 (slow wave DC shift followed by LVFA) and pattern 1 (LVFA). In FCD subtype II, patterns 1-3 (LVFA, pre-ictal spiking followed by LVFA, and burst of polyspikes followed by LVFA) dominated. NDT seizures were associated predominantly with pattern 1 (LVFA).
Seizure onset patterns identify outcomes to surgical resection in cases of FCD and NDT seizures. In this study, SOP patterns that included LVFA were most likely to be associated with Engel class I outcomes to surgery. Specific combinations of SOPs and histological type also pointed to significantly better postsurgical outcomes, information that could be useful in identifying candidates for surgery. The authors noted, however, that complete and accurate resection remains the single best predictor of a favorable surgical outcome.
1. Lagarde S, Bonini F, McGonigal A, et al. Seizure-onset patterns in focal cortical dysplasia and neurodevelopmental tumors: Relationship with surgical prognosis and neuropathologic subtypes. Epilepsia. 2016; doi:10.1111/epi.13464.
2. Guerrini R, Duchowny M, Jayakar P, et al. Diagnostic methods and treatment options for focal cortical dysplasia. Epilepsia. 2015;56:1669–1686.
3. Englot DJ, Berger MS, Barbaro NM, et al. Factors associated with seizure freedom in the surgical resection of glioneuronal tumors. Epilepsia. 2012;53:51–57.
4. Rowland NC, Englot DJ, Cage TA, et al. A meta-analysis of predictors of seizure freedom in the surgical management of focal cortical dysplasia. J Neurosurg. 2012;116:1035–1041.