Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-06-18
2001-11-06
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S063000
Reexamination Certificate
active
06314325
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electrically mediated pain relief and, in particular, to the use of electrical current to block sensory pathways associated with the medial branch of the spinal nerve root and its articular branches so as to relieve pain caused by painful zygopophysial joints.
BACKGROUND OF THE INVENTION
A large body of evidence now exists to support the fact that the zygopophysial joints (facet joints) can be pain-producing structures. In particular, it has been shown that the facet joints can be a source of chronic spinal pain in the cervical, thoracic and lumbosacral regions. This pain, which can be due to trauma to and/or degeneration of the facet joint, can be disabling in some patients.
Anatomical dissections reveal that the facet joint is innervated by the articular branches of the medial branch of the spinal nerve. Lesioning this nerve has been shown to relieve pain, but regrowth of the nerve is inevitable and pain returns.
Electrical stimulators of other neural structures has been proposed to provide pain relief. U.S. Pat. No. 5,041,974 to Walker et al, entitled MULTICHANNEL STIMULATOR FOR TUNED STIMULATION, includes a user interface enabling the selection of a channel and the creation of a stimulus wave signal. A slave circuit associated with the channel receives the wave building signal and generates a corresponding low-power stimulus. An output circuit coupled to the slave electronically isolates the stimulus from the other channels, amplifying and converting it to produce a high-fidelity stimulus wave signal.
There have also been developed neuro-type stimulators which are responsive to patient conditions, and adjust their function in accordance therewith. For example, in U.S. Pat. No. 5,031,618 to Mullett, entitled POSITION-RESPONSIVE NEURO STIMULATOR, a position sensor such as a mercury switch which may be used to determine whether a patient is erect or supine, is implanted in the patient. This position information is then used to vary stimulation intensity, in terms of pulse amplitude, pulse width, and a number of pulses per second and other factors. The output of the pulse generator is applied to the spinal cord, peripheral nerves and/or targets in the brain with leads in electrodes in a manner consistent with a given medical need.
To applicant's knowledge, however, no such neuro stimulators, whether adaptive or fixed in their operation, have been applied to the specific problem of pain relief relative to anodal blockade of the nervous system and specifically anodal blockade of the medial branches innervating the zygopophysial or facet joints. As the '
618
patent points out, stimulation of this type has so far been limited to the treatment of chronic intractable pain requiring spinal cord depolarization. Accordingly, one object of this invention is to provide novel apparatus specifically designed to block painful impulses transmitted by the medial branch of the spinal nerve through anodal blockade of electrical nerve impulses.
Another important object of this invention is to provide such apparatus in the form of an electrical nerve stimulator that is implantable as well as the accompanying electrodes.
It is a related object of this invention to create a pain-relief mechanism and accompanying methodology that is long lasting while being minimally invasive so as to reduce medical complications and provide improved pain relief as compared to temporary modalities.
SUMMARY OF THE INVENTION
The present invention resides in methods and apparatus for hyperpolarizing the medial branch of the spinal nerve associated with a painful spinal facet joint so as to block pain impulses from reaching the spinal cord. Broadly, according to an apparatus aspect, the invention is comprised of a neurostimulator and two or more electrodes placed adjacent to the target nerve or nerves. Hyperpolarization of the target nerve is achieved by placing the positive electrode (anode) adjacent to the target nerve. Multiple positive leads may be placed near multiple pain-generating medial and articular branch nerves. The negative electrode would be placed away from the target site. Once hyperpolarization of the nerve is achieved it would not reach threshold and therefore never depolarize, nor conduct an impulse.
In the preferred embodiment, the apparatus is capable of generating electrical impulses of sufficient intensity to cause hyperpolarization of a given medial branch and its articular branches.
Although the apparatus may be disposed externally of the individual, in the preferred embodiment the stimulator is physically small and battery operated, facilitating implantation underneath the skin. Accordingly, the components of the stimulator and electrodes would preferably be biocompatible and biostable so as not to cause tissue reactions.
The stimulator includes a controller and appropriate electronics operative to generate electrical impulses tailored to an individual's need for appropriate pain relief in terms of pulse frequency, pulse width, and pulse amplitude. In an alternative embodiment, the stimulator further includes electrodes and electrical circuitry operative to monitor myoelectrical activity generated by the surrounding muscles and modulate the impulses generated by the stimulator to meet the demands of the individual's activity and/or prolong battery life.
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Gifford Krass Groh Sprinkle Anderson & Citkowski PC
Layno Carl
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