Reader A, Tamè L, Holmes NP (unpublished) Two instances of presyncope during magnetic stimulation of the median nerve, and evaluation of resting motor threshold with transcranial magnetic stimulation (tms). , 0:0
Dear Editor: We report the following MS-related events that occurred at the Centre for Integrative Neuroscience and Neurodynamics, University of Reading, Reading, UK. The first participant was a healthy 21 year old man with a transannular patch on their pulmonary heart valve (following complete repair of Tetralogy of Fallot as a child), but no reported risk factors. On the day of the event, the participant had no additional risk factors (change in sleep pattern, sleep deprivation, change in medication, occult drug use, high doses of caffeine, etc.). MS was presented with a Mag&More PowerMag Research 100 stimulator via a 100mm diameter, flat, figure eight coil. The setting was a research lab. In this case we were stimulating the median nerve (MN, target) and the Extensor Digitorium Communis (EDC, as a control site). Coil orientation was with the handle parallel to the long axis of the arm. A biphasic MS pulse, double pulse stimulation with inter pulse interval of 50ms was used. In each trial of an experiment, there were a total of 4 pulses, as follows: pulse 1 - 50ms - pulse 2 - approx. 3s - pulse 3 - 50ms - pulse 4. We had two blocks per MS site (target and control), each with 48 trials, with two intervals per trial, each with 2 MS pulses (total=192 pulses). Intensity of the TMS pulse was set at 30% of machine output. The event happened in the second block of MS over the MN. The participant was comfortably sitting on a chair with his arm on the table. The participant was sweating, and experienced dizziness. Therefore, the session was terminated and the operator accompanied the participant out of the laboratory testing room and made him lie down with the legs raised. The presyncope self-terminated or stopped after 30 minutes after the intervention. LT and NPH were the investigators in this instance. The second participant was a healthy 20 year old woman with no reported risk factors. She was taking microgynon 30 contraceptive medication. On the day of the event, the participant had no additional risk factors. The setting was a research lab. The event occurred during the participant’s first session, whilst we were searching for the RMT using Rossini et al.'s (1994) method. BrainSight 2.2.6 frameless stereotaxy (Rogue Research Inc., Montreal, QC) was used for neuronavigation. A 100mm diameter, flat, figure eight coil was used, with output from a Powermag Research 100 stimulator. 125 monophasic pulses had been applied, at approximately 75% of machine intensity. The participant was sitting upright. The participant stated that they felt faint, and stimulation was stopped. Shortly after, they vomited. Following this, the participant was placed on the floor with legs raised to prevent syncope. She recovered within 10 minutes and reported no further illness (immediately following the event or later in the day). ATR and NPH were the investigators in this instance. The clinical diagnosis for both of these events was MS-related presyncope. The specific reasons for favouring this choice among the possible differential diagnoses were that the participants did not completely lose consciousness and muscle strength. In both instances, it was the first MS experience for the participants. Additionally, the ambient temperature of the lab was above normal room temperature (despite the use of a fan). We suspect that emotional components are quite a strong factor in these effects, or at least are involved. Neither participant was retreated with TMS. The events were reported to the University of Reading TMS committee and relevant Health and Safety bodies.