1. Spikes and Seizures: Remote Relatives
Jean Gotman, PhD
Montreal Neurological Institute
McGill University
Spikes are often not a good spatial indicator of the region of seizure onset and their temporal fluctuations tell us nothing about the likelihood of seizure occurrence.

2. Spikes and seizures do not always occur at the same place
It is common that spikes and seizures originate in the same place in focal epilepsy
It is frequent that spikes occur in the same general region but not exactly in the same place as seizures
It also occurs that spikes and seizures occur in very different regions (e.g. bitemporal spikes, unitemporal seizures).

3. Spikes primarily in hippocampus and first temporal gyrus (absent from amygdala)
Seizure primarily in hippocampus and amygdala

4. Spikes primarily left fronto-temporal
Seizure left occipital

5. Tyvaert et al, Brain, 2008 Interictal Ictal
BOLD increase involves the dysplastic lesion in the spikes and seizures. Activation during the seizure is larger in the dysplasia and spreads to connected areas.
Tyvaert et al, Brain, 2008

6. Interictal
Ictal
Nodular heterotopia is involved in the BOLD increase only during interictal events. Overlying cortex is involved at the time of seizure generation.

7. Spikes and seizures do not fluctuate in parallel over time
Reduction in antiepileptic medication
Increase in seizure frequency
No change in spiking rate
Increase in spiking rate following seizures; no change before seizures.

8. Spiking Rate and AED Withdrawal
Gotman and Marciani, Annals Neurology, 1985

9. Spiking Rate, AED Withdrawal and Seizure Occurrence

10. Spencer et al
Epilepsia, 2008

11. Conclusion There is abnormal brain tissue
This tissue generates seizures, the phenomenon we are primarily interested in
This tissue also generates spikes; just because we are interested in seizures does not imply that spikes should be a good indicator of seizure generation.
It appears that they are two phenomena, with a few links but many differences
(HFOs are more closely related to seizures than spikes are).

12. Left centroparietal spikes and brief electrical seizure recorded in a patient with a left parietal dysplasia.

13. Right posterior temporal spikes and brief electrical seizure recorded in a patient with a large right periventricular heterotopia.

14. Spiking Rate and AED Withdrawal