Surgery – Magnetic field applied to body for therapy
Reexamination Certificate
2002-04-29
2004-12-14
Winakur, Eric F. (Department: 3736)
Surgery
Magnetic field applied to body for therapy
C600S300000, C607S045000
Reexamination Certificate
active
06830544
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods and devices for transcranial magnetic stimulation (TMS), preferably for navigated TMS, in particular for non-invasively localizing and/or positionally determining particular areas of a brain, such as for example so-called primary or secondary areas of the brain. In this way, for example, brain functions may be mapped, i.e. assigned to certain areas of the brain, which is also referred to as cortical cartography. Equally, it is possible to establish which area of the brain or of a brain convolution (gyrus) fulfils a particular function.
DESCRIPTION OF RELATED ART
In various areas of medicine, such as for example neurology, psychiatry or brain surgery, it is desirable to be able to localize certain functional areas of the brain, in order to map brain functions. If, for example, a brain tumor is to be removed by surgery, then the tumor should be removed as much as possible, while so-called primary areas of the brain above all, which play a decisive role with respect to a person's motor systems, sensory systems, language or visual capacities, should if possible not be injured. In surgery, these areas should if possible not be injured at all or only to an exceedingly minor extent.
SUMMARY OF THE INVENTION
Locating these particular areas of the brain has been performed intra-operatively according to a known direct method, wherein direct cortical stimulation (DCS) was performed on an exposed cranium by means of electrodes. In this way, an electrode was introduced into a particular area of the brain and an electrical impulse applied, the consequent response of the person being examined to the electrical impulse, for example the twitching of a muscle or the perception of visual impressions, being observed. The particular areas of the brain located by direct cortical stimulation were marked by means of small, attached plates which in a subsequent brain operation represents an orientation aid for the surgeon with respect to the areas of the brain which are as far as possible not to be injured. To date, direct cortical stimulation represents the most precise method of mapping brain functions and enables a precision in the range of a few millimeters in locating particular areas of the brain. However, this method can only be performed intra-operatively, the person being examined having to be fully conscious. This, however, can lead to problems when using this method, as this state is unpleasant for the person being examined and, if complications should arise, the person cannot simply be laid down and made to relax, due to their exposed cranium.
Furthermore, various indirect methods for mapping brain functions are known, using which however only a considerably lower precision can be achieved in locating specific areas of the brain. Thus, for example, in functional nuclear spin tomography (fMRI) a person being examined has to perform certain actions, such as for example a sweep of the hand, which promotes blood flow in the areas of the brain assigned to these actions. Due to the decoupling of blood flow and oxygen consumption during neuronal activity, this change in blood flow in particular areas of the brain can be measured, since this causes hyperoxygenation and thus a drop in the concentration of paramagnetic deoxyhaemoglobin (BOLD effect), which can then be measured as a so-called “endogenic contrast medium” by means of suitable sequences, using nuclear spin tomography. However, as mentioned above, this method is relatively imprecise and only provides a spatial resolution in the range of about 0.5 cm to 1.0 cm.
A method is known from Neurosurgery 1992-1998, December 1997, Volume 41, Number 6, 1319 “Stereotactic Transcranial Magnetic Stimulation: Correlation with Direct Electrical Cortical Stimulation”, in which stereotactic transcranial magnetic stimulation (TMS) is used for pre-operative functional mapping of the motor cortex. Thus, the head of a patient is securely and immovably connected to a headrest, wherein a rotating arm is provided to which a figure-eight coil is attached such that the tip of the arm is under the intersecting point of the coil. The arm is thus aligned such that the tip under the intersecting point of the two coils points to a particular area in which a current is to be induced.
A method is known from U.S. Pat. No. 5,738,625 for magnetically stimulating nerve cells.
U.S. Pat. No. 5,644,234 described a nuclear spin resonance (MR) method in which the position of a micro-coil in an object is to be determined.
A method and a device for transcranial magnetic stimulation of the brain are known from WO 98/06342, in which a broadly hemispherical magnetic core wound with coils is used to generate a stimulation signal. The described device and method are intended localize the speech function.
It is an object of the present invention to propose methods and devices for stimulating particular areas of a brain, by which the spatial precision of stimulating and localizing particular areas of the brain can be improved.
This object is solved in the way defined in the independent claims. Advantageous embodiments follow from the sub-claims.
Stimulation in the sense of the invention means not only actually, actively stimulating a particular area or point of the brain, but also applying or generating signals which cause certain areas of the brain to be functionally suppressed, also often referred to as functional lesion. The term “stimulate” is accordingly to be understood such that certain stimulation signals can also cause brain functions to be blocked or inhibited. An area of the brain is stimulated or inhibited by applying or generating signals in the brain using a stimulation device such as for example a coil attached to the head and through which current flows, to generate electrical signals in the brain by induction, wherein the signals can be a particular impulse shape or a succession of impulses having particular impulse shapes and one or more predetermined frequencies. It has been shown that certain areas of the brain can be blocked or inhibited using higher frequencies, for example in the range of 50 Hz, such that the functions to be fulfilled by the areas of the brain in question, such as for example perceiving an external stimulus, can no longer be performed. In this respect, stimulation is preferably carried out using a single magnetic or so induced electrical impulse.
In accordance with a first aspect of the invention, in a method for stimulating and/or inhibiting a particular area of a brain, for example, an individual point or a cluster or grid of a number of points, using for example an induction device as the stimulation device, the spatial structure of the head or brain to be examined in firstly recorded, for example using nuclear spin resonance (MRI) methods, computer tomography (CT), ultrasound, x-ray, video imaging with subsequent reconstruction of the surface of the brain, or other known examination methods. Based on the spatial structure of the head or brain thus obtained, a simulation model of the surface of the brain is generated. Here the fact is utilized, in accordance with the invention, that sensory, motor, visual, auditory and olfactory functions are realized by areas on the surface if the brain. Since the brain exhibits an irregular surface, an attempt is made in accordance with the invention to simulate this surface as precisely as possible, in order to perform stimulation based on a stimulation model generated in this way as far as possible orthogonal or vertical with respect to the surface of an area to be stimulated. If a stimulation device, such as for example a coil for generating a stimulation signal, such as is common in the prior art, is arranged relative to the surface of the head such that the magnetic field generated by the coil is as vertical with respect to the surface of the head as possible, then the irregular surface of the brain could result in an area of the surface of the brain being stimulated by a magnetic field which is not vertical with respect to the surface of the b
BrainLAB AG
Veniaminov Nikita R
Winakur Eric F.
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