Thermosensitive/thermochromic silicone and infrared thermography mapping in 60 consecutive cases of epilepsy surgery

Abstract

Background: Epilepsy surgery represents a therapeutic opportunity for those patients who do not respond to drug therapy. However, an important challenge is the precise identification of the epileptogenic area during surgery. Since it can be hard to delineate, it makes it necessary to use auxiliary tools as a guide during the surgical procedure. Electrocorticography (ECoG), despite having shown favorable results in terms of reducing post-surgical seizures, have certain limitations. Brain mapping using infrared thermography mapping and a new thermosensitive/thermochromic silicone (TTS) in epilepsy surgery has introduced a new resource of noninvasive and real-time devices that allow the localization of irritative zones.

Methods: Sixty consecutive patients with drug-resistant epilepsy with surgical indications who decided to participate voluntarily in the study were included in the study. We measured brain temperature using two quantitative methods and a qualitative method: the TTS sheet. In all cases, we used ECoG as the gold standard to identify irritative areas, and all brain tissue samples obtained were sent to pathology for diagnosis.

Results: In the subgroup in which the ECoG detected irritative areas (n = 51), adding the results in which there was a correlation with the different methods, the efficiency obtained to detect irritative areas is 94.11% (n = 48/51, P ≤ 0.0001) while the infrared thermography mapping method independently has an efficiency of 91.66% (P ≤ 0.0001). The TTS has a sensitivity of 95.71% and a specificity of 97.9% (P ≤ 0.0001) to detect hypothermic areas that correlate with the irritative zones detected by ECoG. No postoperative infections or wound dehiscence were documented, so the different methodologies used do not represent an additional risk for the surgical proceedings.

Conclusion: We consider that the infrared thermography mapping using high-resolution infrared thermography cameras and the TTS are both accurate and safe methods to identify irritative areas in epilepsy surgeries.

Keywords: Electrocorticography; Epilepsy surgery; Infrared thermography mapping; Thermochromic silicone; Thermosensitive silicone.

Figure 1:

Examples of the three methods described. Method 1: Graph of brain’s surface temperatures recorded using the infrared thermometer with laser pointer, where color gradients were added, being red for the warmest point and blue for the coldest point of the recording. Method 2: Example of thermal gradients obtained by the high-resolution thermography camera (capable of taking photos and videos). Method 3: Example of the color contrast achieved by the thermosensitive/thermochromic silicone when in contact with the brain surface. Note that the purple basal color corresponds to the coldest part of the cerebral cortex and pink to the warmest areas, generating a thermal imprint that allows differentiating temperatures with the naked eye, without the need of filters, dyes, contrasts, or special lights.

Graph 1:

Error bars for pathology result versus age.

Graph 2:

Correlation between methodology 1, 2, and 3 and electrocorticography (ECoG) trivariate graphic. (A) Correlation between method 1, method 2, and ECoG; (B) correlation in two hypothermic regions detected with method 1 and 2 with irritative zones detected by ECoG regions; (C) correlation between method 1, 2, and 3 without irritative zones detected by ECoG; (D) only method 2 was used; and (E) correlation between method 1 and 2 in functional hemispherectomy cases. In selected cases, we added contralateral electroencephalography (EEG) in order to document electrical changes after interhemispheric disconnections.

Graph 3:

Error bars for thermographic pattern, gender, and chronicity.

Graph 4:

Dispersion graphic for age, chronicity, and thermographic pattern.