FWD:RSD World News-Repetitive Transcranial Magnetic Stimulation

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From: byrd45 (Original Message) Sent: 6/10/2005 4:17 PM
June 3, 2005 - Repetitive transcranial magnetic stimulation (rTMS) is
effective for neuropathic pain, specifically for trigeminal neuralgia
(TGN) and post-stroke pain (PSP), according to the results of a
randomized study published in the June issue of the Journal of
Neurology, Neurosurgery, and Psychiatry.

"A single session of repetitive transcranial magnetic stimulation
(rTMS) over motor cortex had been reported to produce short term
relief of some types of chronic pain," write E.M. Khedr, from Assiut
University Hospital in Egypt, and colleagues. "The present study
investigated whether five consecutive days of rTMS would lead to
longer lasting pain relief in unilateral chronic intractable
neuropathic pain."

Of 48 patients enrolled in this study, 24 had TGN and 24 had PSP. Of
the 24 patients in each group, 14 were randomized to receive 10
minutes of real rTMS over the hand area of the motor cortex (20 Hz,
10×10 s trains, intensity 80% of motor threshold) every day for five
consecutive days, and the other 10 patients were randomized to receive
sham stimulation. Using a visual analogue scale (VAS) and the Leeds
assessment of neuropathic symptoms and signs (LANSS) scale, pain was
assessed before the sessions; after the first, fourth, and fifth
sessions; and two weeks after the last session. Patients receiving
real rTMS vs sham rTMS had no significant differences in basal pain
ratings.

Real and sham rTMS had different effects on the VAS and LANSS scales,
based on a two-factor analysis of variance revealing a significant
"±TMS'' × ''time'' interaction. In both groups of patients, post hoc
testing revealed that real rTMS led to a greater improvement in scores
than sham rTMS, even two weeks after the end of the treatment. No
adverse effects were reported.

"These results confirm that five daily sessions of rTMS over motor
cortex can produce long lasting pain relief in patients with TGN or
PSP," the authors write. "The mechanisms responsible for the effect of
MCS [motor cortex stimulation] on pain are still unknown. Several
authors have observed an increase of cerebral blood flow in the
ipsilateral thalamus, orbitofrontal and cingulate gyri, and in the
upper brain stem during MCS."

The authors report no conflicts of interest.

In an accompanying editorial, S.L.F. Owen and T.Z. Aziz, from the
University of Oxford, United Kingdom, call these findings significant.

"This may well establish higher frequency TMS as an effective
methodology of screening patients for implantation of motor cortex
stimulation and since the effects are rather prolonged, may even prove
to be a methodology that may be useful as an outpatient treatment for
certain pain patients," they conclude.

J Neurol Neurosurg Psychiatry 2005;76:761; 833-838
Clinical Context

Intractable neuropathic pain caused by central PSP and TGN have been
successfully treated in the short term by chronic epidural MCS in some
studies. However, in up to 30% of patients, pain fails to respond,
according to the authors of the current study. The application of
rTMS, a noninvasive technique, over the motor cortex may also relieve
pain in a way similar to epidural stimulation. The proposed mechanism
is unknown, and the authors of the current study suggest that the
effect may be due to improved cerebral blood flow to the brain or
activation of the corticothalamic projections, entailing a cascade of
synaptic events.

This study conducted at the chronic pain unit of a neurology
department compared the use of 200 pulses of rTMS, at 20 Hz per
session at daily intervals for five days, with sham rTMS to examine
the effect on the relief of unilateral neuropathic TGN and PSP.
Study Highlights

* Participants were 48 patients with unilateral chronic
neuropathic pain, 24 with TGN and 24 with PSP. In all, medications had
failed, including anticonvulsants, narcotic and non-narcotic
analgesics, and antidepressants. None had experienced rTMS previously.
* Clinical diagnosis of TGN was based on criteria of the
International Association for the Study of Pain. Mean age was 51.5
years, and mean duration of illness was 39 months. Facial pain was
evoked by trivial stimuli and also occurred spontaneously.
* The diagnosis of PSP was based on a history of cerebrovascular
stroke with minor motor deficits. Pain in the face, upper limb, or
trunk was described as burning, tearing, or deep-boring. Mean age was
52.3 years, and mean duration of illness was 18 months.
* Exclusion criteria were the presence of intracranial metal
devices or pacemaker, epilepsy, and significant myocardial ischemia.
* Baseline evaluation included history and complete physical
examination and VAS and LANSS pain scale ratings. The 2 groups had
similar baseline pain scores.
* Patients were randomized according to the day recruited to
receive either rTMS (n = 28; Sunday to Monday) or sham rTMS (n = 20;
Tuesday to Thursday) treatment daily for 5 days.
* Patients were prepared using electromyelographic recordings from
the abductor digit minimi muscle with a ground electrode on the wrist.
* Optimal scalp location for rTMS evoked motor potential of the
greatest magnitude was determined and a figure-8 coil was used to
induce electrical currents perpendicular to the central sulcus at 45°
from the midsagittal line.
* The resting motor threshold (RMT) was defined as the minimal
intensity required to elicit motor evoked potentials of 50 μV
peak-to-peak amplitude in 5 of 10 consecutive trials. The same scalp
location was used for the 5 days of treatment.
* rTMS consisted of a train of 200 pulses per minute for 10
minutes at 80% RMT over the identified motor cortex contralateral to
the affected side of the body. The sham-rTMS group had the same
procedure but did not receive current induction.
* Pain evaluations were conducted at the first, fourth, and fifth
rTMS sessions and 15 days after baseline by an evaluator blinded to
treatment allocation.
* Primary outcome was reduction in pain as indicated by VAS and
LANSS scores at 2 weeks after the baseline. Individual pain responses
were classified as good (reduction </= 70%), satisfactory (reduction
of 40% - 69%), and poor (reduction < 40%).
* In both the TGN and PSP groups, there was a significant
interaction between time and rTMS response in pain. Patients who
received rTMS had significantly greater pain reduction over time at
each time point assessed vs those who received sham rTMS (P < .05).
* There was no change in LANSS ratings after sham rTMS in the PSP
group.
* Reductions in pain ratings in the rTMS group vs baseline were
40% at day 5 and 45% at 2 weeks. Corresponding reductions in the sham
rTMS group were 5% and 2%, respectively (P < .001).
* No patient experienced adverse effects.
* The authors suggest that this method be used to screen for
patients who may benefit from implantation of a chronic stimulating
device for intractable pain.

Pearls for Practice

* rTMS for the treatment of neuropathic pain in this study
consists of a train of 200 pulses per minute at 20 Hz for 10 minutes
over the identified motor cortex contralateral to the affected side of
the body.
* rTMS vs sham rTMS daily for 5 days is efficacious at reducing
intractable pain for up to 2 weeks in patients with unilateral TGN and
PSP.