Surgery – Magnetic field applied to body for therapy
Reexamination Certificate
2001-11-12
2004-03-30
Winakur, Eric F. (Department: 3736)
Surgery
Magnetic field applied to body for therapy
C607S045000
Reexamination Certificate
active
06712753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of sensory stimulation through the exposure of neural tissue to electromagnetic fields, and producing sensory anesthesia.
2. Description of the Prior Art
At the present time, all methods of sensory stimulation involve stimulation of the end organ. It will be understood that reference to sensory stimulation in this patent application refers to stimulation of the sensory nerves for the senses of smell, taste, and touch. For example olfactory stimulation, senses of smell, is achieved with the chemicals of scent. Perfume, air freshener scented soaps and candles are examples of the means by which a consumer experiences scent.
Nerve impulses are transmitted in the body by the nervous system which includes the brain, spinal cord, nerves, ganglia and the receptor. Nerves are made up of axons and cell bodies together with their respective protective and supporting structures. The axon is the long extension of the nerve cell that conducts nerve impulses to the next neuron.
The propagation of the nerve impulse along the axon is associated with an electric potential and a flow of cations into and out of the axon. This electric potential is called the action potential. The typical human action potential has an advancing front of depolarization with a peak value of +40 mV. In order to continue to propagate, the action potential must trigger the depolarization of the neural tissue directly at the front of the advancing wave.
In order to produce depolarization, the interior of the axon must be depolarized from its resting potential of −70 mV (a typical resting voltage potential) to a potential of −60 mV. However, once −60 mV is reached, the sodium channels in the axon opens and causes sodium cations (Na+) to flow into the axon, thereby allowing the depolarization to proceed to +40 mV. Other ion channels then open and cause the potassium cations in the axon to flow out of the axon until the interior of the cell repolarizes to −70 mV.
Thus, all that is necessary to propagate the action potential is to have an external potential which can bring the interior of the cell to −60 mV. Since the action potential consists of an advancing wave of +40 mV, under normal conditions the interior of the cell will depolarize to −30 mV (−70 mV+40 Mv) which is more than enough to propagate the action potential. As is known, these potentials are externally induced transmembrane potentials which are measured across the wall of the axon.
Given the fact that the nerve impulse is transmitted along the axon due to an electrical potential (the action potential), there have been a number of studies into the artificial propagation of nerve impulses using various electrical devices. For example, electrodes have been inserted into a nerve and a current passed through the nerve to cause movement of muscles.
Direct application of electric current has also been used to effect neurostimulation. In this technique, electrodes were applied directly to the skin or to underlying structures in a way which created an electric current between the two electrodes in the tissue in which the target neuronal structure was located. This technique employed a constant voltage source and was intended to cause neuronal transmission and thereby produce stimulation both in peripheral nerves and in the brain.
The influence of an external electric field on neuronal tissue has also been studied. One model for this is the effect of a monopolar electrode in the proximity of a neuron. (Rattay F, J Theor. Biol (1987) 125,339-349). The model for electrical conduction in the neuron which has been widely accepted is the modified cable equation:
∂
V
∂
t
=
[
d
4
ρ
i
(
∂
V
∂
x
2
+
∂
V
e
∂
x
2
)
-
i
i
]
/
c
m
(
eqn
1
)
where:
V represents voltage,
i
i
is the total ionic current density,
&rgr;
i
=the resistivity of the axoplasm,
c
m
=capacitance of the membrane,
Ve=externally applied voltage,
the term:
∂
V
e
∂
X
2
(
eqn
2
)
is referred to the activating function by Rattay because it is responsible for activating an axon by external electrodes.
The activating function has two possible effects on an axon. If its magnitude is sufficient there is a superthreshold response. This leads to the generation of an action potential. If this occurs then the cable equation will predict the expected response. In order to calculate the equation however the ionic current term i
i
must be calculated.
In order to calculate the ionic current, an equation of membrane ionic current, as a function of the externally induced transmembrane potential, is used. For myelinated membranes the Hodgkin-Huxley equation can be used. For unmyelinated membranes the Huxley-Frankenhaeuser equation is used.
There are other equations which account for membrane temperature as well. The other possible effect on the axon is subthreshold stimulation.
If a subthreshold stimulus is applied, then the transmembrane voltage is directly related to the activating function. The voltage changes due the opening of voltage sensitive ionic channels can be ignored. The calculation of transmembrane voltage becomes simplified. It is the subthreshold stimulation of the neuron which is considered in this patent application.
SUMMARY OF THE INVENTION
The present invention produces sensory stimulation by exposing a patient to different spatially and temporally varying electromagnetic fields by means of a magnetic flux generator positioned external to the patient. More specifically, the invention produces areas of depolarization which lead to the propagation of nerve signals. Thus, this invention provides for an entirely new form of sensory stimulation. In addition to sensory stimulation this invention provides a means to block retrograde neural conduction that arises when sensory stimulation is produced. This same method of neural blockade can be used on its own to produce sensory anesthesia.
The term “electromagnetic sensory stimulation” will be used to refer to stimulating nerves with a varying electromagnetic field using a magnetic flux generator positioned external to a body in this specification. It also produces areas of hyperpolarization which act to prevent the transmission of action potentials down axons surrounding the target axon. Thus the axonal stimulation can be focused by using a combination of depolarization and hyperpolarization.
This invention also provides a localizing system. In the prior art of neurostimulation, it is usually administered in a manual way in which the neurophysiologist places a needle in close proximity to the targeted nerve by direct hand manipulation. The needle is manipulated to the endpoint of eliciting paresthesia or by muscle twitch when using a neurostimulator.
However, with manual needle manipulation, it is difficult to guarantee smooth progression from one point to another. It is also difficult to ensure that all points within a certain region have been probed with the needle. The present invention avoids these problems.
Broadly, the method of the present invention is a method for sensory stimulation or sensory blockade in a patient comprising the steps of creating a time varying magnetic field with a device positioned completely external to said patient, said time varying magnetic field resulting in an electric field which creates one or more regions of hyperpolarization or depolarization along neural tissue, for as long as required, said regions of depolarization causing the propagation of a sensory neural impulse and said regions of hyperpolarization being of sufficient magnitude to block the propagation of nerve impulses in said neural tissue preventing retrograde sensory conduction or producing sensory anesthesia.
Preferably, the device is a coil which can produce a time varying magnetic field. Also, preferably, the device consists of a resistor, capacito
LandOfFree
Electromagnetically induced anesthesia and sensory stimulation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electromagnetically induced anesthesia and sensory stimulation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electromagnetically induced anesthesia and sensory stimulation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3203666