The thumb sign is defined as the stretched abduction of the thumb and is localized in the contralateral temporal lobe [14]. After the classification of the observed phenomenology of hand postures by Holl et al. [11], two further groups were defined by their predominant muscle reactions: sustained muscle contractions (Type I) and myoclonic jerks (Type II).

Type I involves sustained muscle contractions with (a) abduction of the thumb, (b) flexion of the wrist, or (c) extension of all fingers.

Type II consists of myoclonic dystonia with (a) abduction of the thumb, (b) flexion of the wrist and fist closure, or (c) extension of all fingers.

These groupings were used to correlate ictal phenomena with either the mesial or lateral temporal lobe origin. Although the difference in location was not statistically significant [11], a comparison of the mean latencies of contralateral sustained dystonic posturing, including flexion of the wrist and fist closure (Type IB), between seizures resulting from mesial temporal lobe epilepsy (MTLE) and those from neocortical temporal lobe epilepsy (NTLE) resulted in a statistically significant difference (mean latencies: 19 and 7 s, respectively; p = 0.001). The pathophysiological considerations differentiated between striatopallidal and thalamic dystonia [15]. A clinical analysis of flexion of the wrist hand posturing showed a significant earlier occurrence of the “striatopallidal” type in NTLE compared to MTLE seizures, suggesting rapid seizure propagation from the neocortical focus to the striatopallidal complex compared to the “delayed” spread of ictal discharges from mesial temporal structures.

Different hand signs are presented in Fig. 1, including their lateralization and localization values. The predominant lateralization and localization information of ictal hand signs has been presented in various studies [11, 13, 14, 16]. Our video EEG monitoring analysis of 145 patients revealed six patients with ictal fist, six with ictal hand extension, five with ictal cup, three with RINCH, two with ictal thumb-up, two with ictal pincer, and one each with ictal index pointers.

Ictal hand sign lateralization and/or localization values from different studies. (Concurrence with the results described by Ferando et al. [13] is indicated by the letters i–iii: i, study by Vilaseca et al. [14]; ii, study by Ferando et al. [13]; iii, our study). Cup sign points to temporal lobe (in study ii) in study c to fronto-temporal, extended hand to contralateral fronto-temporal (in study ii, iii); claw to fronto-temporal (study iii); fist to frontal (in studies ii, iii), index pointer to frontal (in studies ii, iii); thumb-up, pincer and politician’s fist to temporal (study i, iii); a the “cup” sign, contralateral fronto-temporal (ii, iii), b the thumb sign, contralateral temporal (i, iii), c the “claw” sign, contralateral, fronto-temporal (iii), d the extended hand sign, contralateral (ii, iii), e the closed fist sign, contralateral, frontal (ii, iii), f the “pincer” sign, contralateral temporal (ii), g the index pointer sign, frontal (ii, iii), h the Politician’s fist to temporal (ii)

Ictal hand signs were found in 54.5% of patients with temporal lobe seizures and 72.5% of those with frontal epilepsies by Ferando et al. [13]. The signs identified were cup, fist, pincer, politician’s fist, index pointer, and extended hand, which corresponded to some of the signs observed in this study as shown in Fig. 1. The index pointer sign in our case was combined with a fist posture of the other fingers, whereas in the report by Ferando et al., the index finger and thumb were extended while the other fingers were less flexed, resulting in a more open hand. The results of that study [13] identified a significant correlation between ictal hand posture and epileptogenic zone localization (p = 0.00001). Only seizures with temporal onsets were associated with the cup or pincer sign, while the fist, extended hand, and pointer signs were only present in frontal seizure onsets.

The ictal thumb-up sign was observed by Vilaseca et al. [14] in 5% of temporal lobe seizures. The latency to the seizure onset was 3–25 s and ipsilateral automatism was not featured in these cases.

Bleasel et al. [2] recognized that dystonic posturing occurred in 35.3% of TLE patients (κ: 0.78, positive predictive value [PPV] for the sign being contralateral to seizure onset: 92%), while tonic limb posturing occurred in 17.7% (κ: 0.36, PPV 40%) and unilateral immobile limb was present in 11.8% of the patients (κ: 0.23, PPV: 100%). In patients with extratemporal epilepsy, dystonic posturing was observed in 20.0% (κ: 0.31, PPV: 100%) of the cases and tonic limb posturing occurred in 15.0% (κ: 0.08, PPV: 67%). The higher kappa indexes were significant for dystonic posturing (p < 0.001) and tonic limb posturing (p = 0.032) in TLE patients. Dystonic posturing (p = 0.034), tonic posturing (p = 0.07), and version (p = 0.0038) was reported to occur earlier in extratemporal seizures than in temporal seizures. Marashly et al. [17] stated that ictal dystonia only included dystonic posturing of the hand. These authors suggested that the rotatory component of the hand (into extreme pronation or supination), which is the hallmark of increased tonic flexion or extension in ictal dystonia, was previously included as a tonic seizure component. During the tonic phase of a focal-to-bilateral tonic–clonic seizure, a posture similar to the dystonic posture can exist. Marashly et al. [17] stressed that the similarity of these postures may cause confusion leading to the reporting of a higher prevalence of ictal dystonia in some studies: “Moreover, despite a strict definition of dystonia, this sign had the least interrater reliability, further limiting the utility of this sign. It is important to stress, however, that in this study we analyzed ictal dystonia as presence of dystonia at any point before the generalization irrespective of its association with an `automotor or dialeptic´ phase of the seizure. Because previous studies analyzed ictal dystonia specifically in association with these features, this difference may explain the discrepancy (up to 67% difference; annotation by the authors of this manuscript) of the positive predictive value of ictal dystonia between the reports in the literature and the present study.”