Sequential Semiology of Seizures and Brain Perfusion Patterns in Patients with Drug-Resistant Focal Epilepsies: A Perspective from Neural Networks

The authors of this manuscript appreciate all your comments and suggestions. QUESTIONS, COMMENTS AND SUGGESTIONS

ANSWER FROM AUTHORS

Given that the authors use several tables with abbreviated text, it would be convenient to avoid using abbreviations in the manuscript as much as possible, in order to facilitate the understanding of the study:

For example, Temporal lobe epilepsy (TLE), Frontal lobe epilepsy (FLE), Perfusion indexes (PI), Posterior Quadrant Epilepsy (PQE) are the most used abbreviations in the manuscript.

However, drug-resistant focal epilepsies (DRFE), Cortical Developmental Disorders (CDD), epileptogenic zone (EZ), ictal onset zone (IOZ), extratemporal epilepsies (Ex E), regions of interest (ROIs), etc, could be avoided.

We replaced almost all abbreviations (except in tables) for full words in order to facilitate the understanding of the study (for example, TLE for temporal lobe epilepsy, FLE for frontal lobe epilepsy, PI for perfusion indexes, etc.).

Line 120: authors mention “number of ES and radiopharmaceutical injection times (ictal SPECT). What is “number of ES”?

In line 120 we mentioned ``number of ES´´. Number of ES (epileptic seizures) is the amount of epileptic seizures registered by patient in the Video-EEG unit in both states (awake and sleep). You also can see Table 2.

Authors mention “For ictal SPECT, the radiopharmaceutical was injected when the EEG seizures onset was identified.” How long does it take to identify the focus and administer the radiopharmaceutical?

We should clarify in case of ictal SPECT the radiopharmaceutical delivery must be as soon as possible, in terms of few seconds (< 15 seconds). This is crucial for achieving a correct localization of the epileptic zone. If the radiopharmaceutical is delivered belatedly, then we will obtain the seizure spreading, no the ictal onset itself. In our study the mean of radiopharmaceutical injection time was 12 seconds (temporal lobe epilepsy), 5.8 seconds (frontal lobe epilepsy) and 4.5 seconds (posterior quadrant epilepsy).

Is the number of patients studied (n=15) enough to conclude that there are no differences between the three groups of

About your last question authors know the number of patients evaluated (n=15) isn´t enough probably, but in our study we

 The authors of this manuscript appreciate all your comments and suggestions. QUESTIONS, COMMENTS AND SUGGESTIONS

ANSWER FROM AUTHORS

I want the authors to mention clearly that the observed groups are TLE, FLE, and PQE with the abstract.

This was checked in the abstract

Also, on page 7, line 183, the SD "deviation standard" should be corrected to be "deviation."

All your suggestions were reflected in the manuscript.

The authors of this manuscript appreciate all your comments and suggestions. QUESTIONS, COMMENTS AND SUGGESTIONS

ANSWER FROM AUTHORS

How many patients underwent ictal SPECT? Line 90: Each patient underwent ictal and interictal studies... But (line 225) In TLE, the ictal SPECT was successfully performed in 2 patients... There are no data (in the text) for FLE and PQE, but from table 4 there are no data for FLE patients 4, 5 and 6, and PQE patient 1.

In this study we include a total of 15 patients, divided as follow: 4 patients with temporal lobe epilepsy, 8 subjects with frontal lobe epilepsy and 3 patients with posterior quadrant epilepsy. The ictal SPECT was successfully performed just for 9 patients: patient 3 and 4 (TLE); patients 1, 2, 3, 7 and 8 (FLE) and patient 1 and 2 for PQE. This occurred because of the SPECT couldn´t be done, was useless for diagnosis and it was impossible an adequate quantitative processing. We did changes in paragraph d) (page 3).

In table 1 there are discrepancies between epilepsy duration and age of seizures onset and age at evaluation (e.g. TLE patient 1: duration 18 y, but onset 34 y and evaluation at 35 y; FLE patient 8: 18 y, 3 y and 28 y, respectively).

In table 1 the epilepsy duration was reviewed and corrected.

Laterality. Line 161: 9 patients with left laterality of EZ; but in table 2: laterality of EZ 9 R and 6 L.

In line 161 (page 5) we wrote ``9 patients with right laterality of EZ´´, it was a writing mistake. All data about laterality of EZ in table 2 are correct.

Again in table 2; if the global mean are for 15 patients, it is unclear why the data are presented for 9 patients, and not for the other 6 patients as well.

Also, in table 2 we didn´t present any data of 6 patients related to ``duration of electrographic seizure´´ and `` time between behavioral pattern onset and electrographic seizure onset´´ because these subjects couldn´t be evaluated neither with ictal EEG nor ictal SPECT.

The paper presents a good description of the sequential semiology of various types of focal seizures. But it is not clear the relevance of this for a comparison with a functional neuroimaging method, which is not sequential, but refers to a single time window, and which - moreover - is not available in all 15 patients.

In our paper we used the SPECT for obtaining quantitative information about brain perfusion in different brain regions from perfusion index (epileptogenic zone or ictal onset zone). From these data we suggest those cortical and subcortical areas which were parts of the epileptogenic network in each state (interictal and ictal)

QUESTIONS, COMMENTS AND SUGGESTIONS

ANSWER FROM AUTHORS

I learn from the cover letter (answer # 4) that 6 patients couldn’t be evaluated neither with ictal EEG nor ictal SPECT. It is therefore appropriate to specify how many - of the total 248 seizures - were recorded in video-EEG. In fact, the assertion at line 175 “a total of 248 seizures were analyzed” suggests that all 248 seizures were recorded in video-EEG.

About this point we should point out that all 248 seizures were evaluated from a semiological point of view. When we write that ``that 6 patients couldn’t be evaluated neither with ictal EEG nor ictal SPECT´´ we just want to clarify they couldn´t be evaluated with ictal EEG at the same time that ictal SPECT (the subject remained monitored by electroencephalography during the intravenous radiopharmaceutical delivery in ictal SPECT, also in interictal SPECT). This situation didn´t interfere with the clinical semiological description of all seizures in the Video-EEG unit.

The statement (answer from authors # 6) "the images of SPECT are a picture of brain perfusion at the exactly moment when the radiopharmaceutical is delivered" does not take into account the fact that there is a pharmacokinetic arm-brain circulation time, estimated at approximately 30 seconds from W. Van Paesschen, Epilepsia 2004 [After injection in an arm vein, the tracer takes ∼30 s to reach the brain. The postictal switch (i.e., switch from ictal hyperperfusion to postictal hypoperfusion) occurs ∼1–2 min postictally in temporal lobe seizures, but is shorter in extratemporal seizures. It has been estimated that extratemporal seizures should last ≥10–15 s after ictal SPECT injection to give localizing information] and even greater by Lauro Wichert-Ana et al, J Epilepsy Clin Neurophysiol 2005 [the ictal SPECT is a "photograph" of the perfusion status of the brain in a temporal window of 30 to 60 seconds after tracer injection]. The sum "injection time" and "circulation time" therefore has a longer duration than the seizures of patients F3 and F7 (minutes 0.19 and 0.35 = seconds 11.4 and 21.0), so that in these patients the fixation of the radiopharmaceutical is already post-critical. Also in the other patients the uptake occurs in an advanced seizure phase and certainly not in an initial phase. All this in the hypothesis that the fixation of the radiopharmaceutical requires only one arm-brain circulation time, and that the fixation following "only one arm-brain time", which cannot be excluded, does not overlap the initial fixation.

The authors took into account the fact that there is a pharmacokinetic arm-brain circulation time, estimated at approximately 15 - 30 seconds for extratemporal epilepsies and temporal lobe epilepsies respectively, which is relevant especially in ictal SPECT (paragraph d, page 3). In ictal SPECT the patient 3 and 7 (frontal lobe epilepsy) were also ruled out due to the brain uptake of the radiopharmaceutical occurred in the postictal period (table 4).

It was add a row in table 4 with ``Injection times (sec) of radiopharmaceutical (ictal SPECT)´´ for better understanding of data.

It was done a critical revision of the manuscript having in count all the suggestions and comments (paragraph 3 page 6 and paragraph 5 page 18).