Which of the following statements regarding transcranial magnetic stimulation (TMS) is true?
a.It doses not require general anestheisa
b.Seizures do not apperar to be required for therapeutic effects
c.it is a noninvasive central nervous system stimulant
d.All of the above
ans:
a. In neurology, TMS has been developed as a way to stimulate the CNS noninvasively by application of a focal magnetic field over regions of the cortex. Refinements of magnetic stimulators, including the development of stimulators capable of discharging at frequencies up to 60 Hz (referred to as rapid-rate TMS [rTMS]) have allowed focal stimulation of the CNS to estimate motor thresholds and determine hemispheric language dominance. Interestingly, rTMS was found to benefit some patients with Parkinson’s disease, and some patients with Parkinson’s disease exhibited improved mood after rTMS. Additionally, subjects exposed to rTMS for purposes of determining hemispheric language dominance exhibited affective responses after stimulation of the left frontal cortex.
b. These observations suggest that rTMS may have therapeutic potential in psychiatry and may allow focal stimulation of areas most involved in affective states. Although experience with rTMS in psychiatry is limited, some evidence suggests that depending on the placement of the magnetic coil, rTMS can improve or worsen affective state. In one of the best studies to date, left dorsolateral prefrontal cortex stimulation significantly improved depression ratings in 11 of 17 patients with psychotic major depression. rTMS appears to be well tolerated and does not require general anesthesia.
c. Seizures may be a side effect in some patients but do not appear to be required for therapeutic effects. TMS is performed using a high-speed magnetic stimulator that generates a 1.5- to 2.5-Tesla field for brief periods.
This field is similar to that used for nuclear magnetic resonance imaging. rTMS stimulus is delivered at frequencies of 10 to 60 Hz using a figure 8- shaped coil that is placed over the desired region of the skull and cooled continuously with water to prevent overheating. Patients and staff usually wear earplugs because of the noise generated by the stimulator. Stimulation is typically given several times per session and is repeated over several days to weeks.
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