Sham Transcranial Magnetic Stimulation Using Electrical Stimulation of the Scalp.

Abstract

BACKGROUND: Most methods of sham, repetitive transcranial magnetic stimulation (rTMS) fail to replicate the look, sound, and feel of active stimulation in the absence of a significant magnetic field. OBJECTIVE/HYPOTHESIS: To develop and validate a new method of sham rTMS appropriate for a double-blind, placebo-controlled study with subject crossover. METHODS: The look and sound of active rTMS was replicated using a matched, air-cooled sham TMS coil. Scalp muscle stimulation associated with rTMS was replicated using large rubber electrodes placed over selected muscles. The intensity and pulse width of electrical stimulation necessary to match 1-Hz rTMS was developed in one sample of normal subjects. The sham technique was validated in back-to-back comparisons with active rTMS in new samples of normal subjects who were either naïve or experienced with rTMS. RESULTS: Subjects naïve to TMS could not tell which type of stimulation was active or sham or which was electrical or magnetic. Naïve subjects incorrectly picked sham stimulation as active, when forced to choose, because electrical stimulation felt more focused than magnetic stimulation. Subjects experienced with TMS could correctly identify sham and active stimulation. Experimenters could detect subtle differences between conditions. CONCLUSIONS: This method of sham rTMS closely mimics the look, sound, and feel of active stimulation at 1Hz without creating a significant magnetic field. It is valid for use with naïve subjects and in crossover studies. It can accommodate differences in scalp muscle recruitment at different sites of stimulation, and it could potentially be used with higher frequency stimulation.

AI evidence extraction

Main findings

A sham rTMS method using a matched sham coil plus scalp electrical stimulation closely mimicked the look, sound, and feel of active 1-Hz rTMS without creating a significant magnetic field. Naïve subjects could not reliably distinguish active from sham (and often chose sham as active when forced), while subjects experienced with TMS could correctly identify sham vs active; experimenters could detect subtle differences.

Outcomes measured

• Ability of subjects to distinguish active vs sham stimulation
• Ability of subjects to distinguish electrical vs magnetic stimulation
• Ability of experimenters to distinguish conditions
• Development of electrical stimulation parameters (intensity, pulse width) to match 1-Hz rTMS sensation

Limitations

• Sample size not reported in the abstract
• Validation depended on participant TMS experience (naïve vs experienced)
• Experimenters could detect subtle differences between conditions

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "transcranial magnetic stimulation (rTMS) / sham rTMS",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Normal subjects (naïve or experienced with rTMS)",
    "sample_size": null,
    "outcomes": [
        "Ability of subjects to distinguish active vs sham stimulation",
        "Ability of subjects to distinguish electrical vs magnetic stimulation",
        "Ability of experimenters to distinguish conditions",
        "Development of electrical stimulation parameters (intensity, pulse width) to match 1-Hz rTMS sensation"
    ],
    "main_findings": "A sham rTMS method using a matched sham coil plus scalp electrical stimulation closely mimicked the look, sound, and feel of active 1-Hz rTMS without creating a significant magnetic field. Naïve subjects could not reliably distinguish active from sham (and often chose sham as active when forced), while subjects experienced with TMS could correctly identify sham vs active; experimenters could detect subtle differences.",
    "effect_direction": "unclear",
    "limitations": [
        "Sample size not reported in the abstract",
        "Validation depended on participant TMS experience (naïve vs experienced)",
        "Experimenters could detect subtle differences between conditions"
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "sham rTMS",
        "repetitive transcranial magnetic stimulation",
        "placebo control",
        "double-blind",
        "crossover",
        "scalp electrical stimulation",
        "sham coil",
        "1-Hz"
    ],
    "suggested_hubs": []
}

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