Transcranial Magnetic Stimulation and
Epilepsy
Epilepsy is
a neurological condition resulting in abnormal behavior such as seizures, loss
of sensation or alternation of mental status. Epilepsy, unfortunately, can
happen to anyone and the cause of this condition remains unknown. Undoubtedly,
whatever defects our mental health as well as our life quality must be
inhibited.
One of the
most common treatments for epilepsy is taking anti-seizure medications, which can
stop seizure right away… but not to everyone. Also, as you might guess, they always
have side effects such like thinning bones, dizziness, trouble talking etc.
Another option is deep brain stimulation which basically implants electrodes in
several specific regions of your brains. Apparently, those are the ones having
abnormal activities which will be adjusted by electrodes. The good thing is this
treatment has been approved by FDA which can also applied to treat depression,
stroke recovery, addiction. On the other hand, no one would like anything inserted
into their body, especially the brain. Moreover, this procedure is usually
expensive and of course risky. On the same token, Transcranial Magnetic
Stimulation (TMS) is another advanced brain-stimulating method which is non-invasive
because it utilizes the magnetic field generated by an external mini coil,
followed by the induction of electrical currents in target region within the
brain. It is considered a consistent stimulating technique since the intensity
of magnetic field is less attenuating.
Back to
2014, the first attempt to implement TMS in investigating the mechanism of
epilepsy was conducted by Dr Jancke from Ruhr-Universitaet-Bochum in
Germany. They administered
voltage-sensitive dyes on the cell membrane. Under electrical stimulation
induced by high-frequency TMS, the fluorescent signal would be detected
inferring whether the neurons of interest are activated or inhibited.
Those
previous studies, when the neuron is considered to be polarized by electrical
stimulation, it is one-way direction. In contrast, Dr. Hui Ye at Loyola
University Chicago, who have been studying external-applied electric field to
enhance therapeutic benefits of TMS, believes that the interaction between
neuronal tissues and electrical field is bilateral. “A direct consequence of
the counter-effects of the cell to the electric field is that electric field
alteration by one individual cell may cause secondary effects on neighboring
cells during electric stimulation, particularly in the scenario that two or
more cells are located in close proximity and in a high-density cell medium” is
one of his major findings. In addition, he also found that some features of
magnetic field applied to induce transmembrane potentials of the hippocampal
tissues include orientation, magnitude, frequency. On the same token, several
neuronal properties such as the neuronal density and spatial organization within
the tissues determine how strongly induced transmembrane potential (ITP) within
a single neuron.
In order to improve
the future study on ITP, Dr. Ye and his co-author suggest that the neuronal
shape, radius, orientation and geometrical properties should be examined
thoroughly. They believe that those properties could re-distribute the external
field and determine the neuronal activity of electrically-targeted tissues. Dr.
Ye suggests these parameters are important to build biophysics-engineering
model of behavior of inhomogeneous tissues under the presence of external field,
which might one day help us explain the mechanism of epilepsy.
Source:
Ye and
Steiger Journal of NeuroEngineering and
Rehabilitation (2015) 12:65
No comments:
Post a Comment