Abstracts

Rationale: Cortical electrical stimulation (CES) may produce different motor responses according to the brain area stimulated. In this study, we describe a new motor response obtained from high frequency CES characterized by finger movements, such as a person playing piano, which we named the Piano Player Hand (PPH) sign. This sign—which differs from tremor—was anecdotally observed, in our patients’ cohort throughout the years, which led us to better describe it clinically and define its anatomical origins.

Methods: We revised the effect of low (1 Hz, 1 msec pulse width, 40 sec) and high (50 Hz, 1 msec pulse width, 5 sec) frequency CES on patients who underwent SEEG for drug-resistant epilepsy between January 2005 and December 2019, at the Epilepsy Unit of the Grenoble-Alpes University Hospital. We retrospectively reviewed the CES results of 252 consecutive pediatric and adult patients, on whom CES were performed with the aim to induce seizures and perform brain mapping. We screened CES results for hand movements of any sorts and then watched videos searching for the PPH sign. The general clinical patients’ characteristics, SEEG findings, and CES parameters of the patients from whom we retrieved the clinical sign were extracted to find common clinical and anatomical features.

Results: The PPH sign was identified twenty times, from 16 different electrode contacts out of twelve patients (9 females and 3 males, age at SEEG from 16 to 52 years). The PPH sign was observed only from 50 Hz CES, with intensity ranging from 0,7 to 3 mA. In six patients, the PPH sign was part of their ictal semiology. In all but one patient, the PPH sign was contralateral to the stimulation side. Other features were sometimes present: hand pronation (1/20), hand supination (2/20) or wrist flexion (6/20). Two patients did not realize the occurrence for the fingers’ movements. An afterdischarge was observed in 4-5 of the 20 relevant CES, either local (n=1), regional (n=1) or extended (n=3). Most of the CES were lateralized on the right side (17/20) and the PPH sign was obtained with stimulation of either the supplementary motor area (SMA, BA 6; 10 CES) (Figure), anterior cingulate gyrus (ACG, BA 24 & 32; 4 CES), pre-supplementary motor area (pre-SMA, BA 8; 3 CES), middle frontal gyrus (2 CES) and anterior insula (1 CES).

Conclusions: To our knowledge, the PPH sign is a novel clinical sign, that differs from tremor and looks like a normal movement of strumming, without any intent to move. It was obtained mainly, but not exclusively, with CES of a small vicinity encompassing the SMA, pre-SMA and ACG. Not only are these regions anatomically closely related but they share dense connections. This sign has not been described with CES of the SMA and pre-SMA regions which rather induce proximal tonic movement mainly of the contralateral limb. CES of the cingulate cortex produces various motor responses, including hand twitches and tremors but no finger movements similar to the PPH sign. The PPH sign, when occurring ictally, may thus point to the premotor mesial frontal surface of the brain.

Funding: Please list any funding that was received in support of this abstract.: None.