Sham for transcranial magnetic stimulator

Surgery – Magnetic field applied to body for therapy

Reexamination Certificate

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C600S015000

Reexamination Certificate

active

06491620

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an apparatus and a method for simulating the sounds and vibrations of a genuine magnetic nerve stimulator, in the preferred version, a transcranial magnetic stimulator (“TMS”), while reducing the induced current for the device from reaching the patient. The present invention relates to a sham TMS which presents the appearance, noise, apparatus, etc. of a genuine TMS, but which, in fact, may be used as a placebo in clinical studies to determine the therapeutic effectiveness of the genuine magnetic nerve stimulator or TMS.
BACKGROUND OF THE INVENTION
TMS is well known in the art. Magnetic stimulation realizes the electric fields necessary for the charge transfer by induction. Magnetic stimulation may be used to induce electric fields in biologic tissue. Rapidly changing magnetic fields induce electric fields in biologic tissue, and when the proper rates, intensity, depth of penetration are achieved, the magnetically induced electric field accomplishes transferring charge directly into the neuron to be excited. TMS involves the magnetic stimulation of neurons in the brain and has been used in the localization, characterization and treatment of brain function. TMS is known to non-invasively alter the function of the cerebral cortex. (See e.g. George M S, Wasserman E M, Post Rm, Transcranial magnetic stimulation: A neuropsychiatric tool for the 21
st
century,
J. Neuropsychiatry,
1996 8:373-382
, the disclosure of which is fully incorporated herein by reference). The magnetic fields used in transcranial magnetic stimulation are generally generated by large, rapidly-changing currents passing through a wire coil on the scalp. Use of a coil with a ferro magnetic core of a material with a saturability of at least 0.5 tesla has been found to be very effective.
Two recent studies have suggested that rapid rate transcranial magnetic stimulation (rTMS) may be used for exploring the functional neuroanatomy of emotions: emotionally healthy volunteers who received left pre-frontal stimulation reported an increase in self-rated sadness, while, in contrast, right pre-frontal stimulation to similarly healthy volunteers caused an increase in happiness. (See, Pascual-Leone A., Catala M D, Pascual A P, Lateralized effect of rapid rate transcranial magnetic stimulation of the prefrontal cortex on mood,
Neurology,
1996; 46: 499-502; and, George M S, Wasserman E M, Williams W., et al., Changes in mood and hormone levels after rapid-rate transcranial magnetic stimulation of the prefrontal cortex,
J. Neuropsychiatry Clin. Neurosci.
1996; 8: 172-180, the disclosures of which are also fully incorporated herein by reference.)
Other reports have begun to delineate the therapeutic use of rTMS in depression. The earliest such studies used round, non-focal coils centered at the cranial vertex, with stimulation rates well under 1 Hertz (Hz). Results were promising but not always statistically significant. (See, Hoflich G., Kasper S. Hufnagel A. et al., Application of transcranial magnetic stimulation in treatment of drug-resistant major depression: a report of two cases,
Human Psychopharmacology,
1993; 8: 361-365; Grisaru N., Yarovslavsky U., Abarbanel J., et al., Transcranial magnetic stimulation in depression and schizophrenia,
Eur. Neuropsychopharmacol.
1994; 4: 287-288; and, Kilbinger H M, Hofilich G., Hufnagel A., et al., Transcranial magnetic stimulation (TMS) in the treatment of major depression: A pilot study,
Human Psychopharmacology,
1995; 10: 305-310, the disclosures of which are fully incorporated herein by reference.)
Subsequently, George et al., described a striking improvement in some depressed patients from the treatment with rTMS over the left pre-frontal cortex. (See, George M S, Wasserman E M, Williams W A, et al., Daily repetitive transcranial magnetic stimulation (rTMS) improves mood in depression,
NeuroReport,
1995; 6: 1853-1856; and, George M S, Wasserman E M, Williams W E, Kimbrell T A, Little J T, Halleft M., Post R M, Daily left prefrontal rTMS improves mood in outpatient depression: a double blind placebo-controlled crossover trial,
Am. J. Psychiatry,
1997 (in press), the disclosures of which are fully incorporated herein by reference). A large study was reported by Pascual-Leone et al., who used a five-month double blind placebo-controlled cross-over design with five different treatment conditions. (See, Pascual-Leone A., Rubio B., Pallardo F. Catala M D, Rapid-rate transcranial magnetic stimulation of left dorsolateral prefrontal cortex in drug-resistant depression,
The Lancet,
1996; 348: 233-237, the disclosure of which is fully incorporated herein by reference.) Left pre-frontal rTMS was uniquely effective in 11 of 17 young (less than 60 years of age) psychotically depressed and medication resistant patients.
A recently developed TMS was disclosed by the present applicant and Charles M. Epstein in the PCT International Application NO. PCT/US97/14826, filed Aug. 15, 1997. That disclosure is therefore specifically incorporated herein by reference.
The TMS studies have demonstrated a need for a sham TMS, which may be used as a placebo, to provide a control to determine the effectiveness of a device genuinely providing TMS. There is a need for a sham TMS which can be effectively used in placebo-controlled TMS blind studies. Accordingly, it is a goal of the present invention to provide a sham apparatus for transcranial magnetic stimulation, which may be used in placebo-controlled blind studies to further investigate the uses and effectiveness of TMS in the treatment of patients. Such a sham device must simulate, as much as practicable, the apparatus under investigation, while shielding the induced current of the device from reaching the patient, especially since the studies are related to ephemeral concepts, e.g., self-perception, depression, etc. concepts which are difficult to accurately measure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus for imitating the external appearance, sounds and vibration of a genuine TMS while keeping low the induced current which is actually transmitted to the patient.
It is a further object of the present invention to provide a sham TMS which may be used as a placebo in studies to determine the effectiveness of a TMS apparatus and/or procedural protocol under investigation.
A further object of the present invention is to provide a method and an apparatus for realistically simulating a TMS, to be used as a control in legitimate and verifiable medical studies.
As disclosed more fully hereafter, a method and an apparatus is described for realistically simulating a TMS wherein the induced current reaching the patient is kept to a very small percentage of the functioning core which is not provided with the sham shroud. The apparatus placebo comprises the genuine TMS device, modified however, such that an aluminum shroud is situated over the core's end faces. The aluminum plate absorbs a significant amount of the transmitted energy from the TMS, thus substantially keeping the induced current from penetrating to the patient who is receiving the TMS placebo treatment and/or device.


REFERENCES:
patent: 4940453 (1990-07-01), Cadwell
patent: 5116304 (1992-05-01), Cadwell
patent: 5197940 (1993-03-01), Sievert et al.
patent: 5441495 (1995-08-01), Liboff et al.
patent: 6203486 (2001-03-01), Miller et al.
patent: 2008946 (1994-03-01), None
K. Davey and Lanbo Luo, Toward Functional Magnetic Stimulation Theory (FMS) and Experiment, submitted to IEEE Transactions on Biomedical Engineering (submitted in Jul. 1993).

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