Welcome to NMES for CP.com! The aim of
this blog is to provide physiotherapists and students an overview of the use of
NMES in children with cerebral palsy. Over the next few weeks, we will be
posting information regarding clinically important treatment parameters,
precautions and contraindications, as well as research and support for it’s
use. But to start off with, here’s some information about what NMES is, what it’s
used for and how to differentiate it from other electrical stimulation
modalities.
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Figure 1. Photograph taken the first time
NMES was used
on the forearm of a child for wrist extension and finger
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Neuromuscular Electrical Stimulation (NMES)
describes the application of electrical stimulation to weakened, but otherwise
normally innervated muscles. Treatments are performed transcutaneously, using
surface electrodes over motor points within a target muscle/group of muscles.
Percutaneous electrodes are available but are generally reserved for
experimental conditions. Most researchers use biphasic rectangular pulses that
are symmetrical to avoid accumulation of charge within the tissue, thereby
decreasing risk of injury to the patient [1].
Stimulation can be applied while performing
functional tasks (for example walking or reaching), and this is termed
Functional Electrical Stimulation (FES) [1].
The two main types of electrical
stimulation used in children with cerebral palsy (CP) are:
1) Neuromuscular electrical
stimulation (NMES) – this is a high intensity, short duration stimulation which
elicits a muscle contraction. NMES is predominantly based on the principle of
overload, as well as its’ selective recruitment of Type II muscle fibres.
2) Threshold electrical
stimulation (TES) – a low level sub-contraction stimulation generally applied
during sleep. TES is thought to increase blood flow to the target musculature
causing heightened trophic hormone secretion, thereby increasing the bulk of
the muscle [2].
Kerr,
McDowell [2]
compared the effects of NMES and TES in children with CP. The following
parameters were used:
Table
1 - Stimulation Parameters [2]
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NMES
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TES
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Intensity (mA)
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Max
tolerated with muscle
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Sensory
Threshold
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contraction
elicited
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<10mA
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Freqency (Hz)
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35
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35
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Pulse Duration (µs)
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300
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300
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On:Off (s)
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7:12
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7:12
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Ramp Up (s)
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2
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2
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Ramp Down (s)
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1
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1
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Daily Session Time (Hr)
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1
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8
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Treatments Per Week (Days)
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5
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5
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Total Duration Of Treatment (Wks)
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16
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16
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As seen in the table above, the only
difference between NMES and TES is the intensity and daily session time. There
is a much lower intensity required for TES as there is no muscle contraction
elicited, but rather a sensory stimulation, where as NMES requires a larger
amplitude to achieve a muscle contraction. Due to the lower intensity of TES,
it requires a longer application time, hence the TES is applied overnight for 8
hours, five nights per week.
Note that in contrast to microcurrent
modalities, NMES has an amplitude measured in milliamps (mA), and low frequency
values are used in comparison to modalities used for treatment of pain (such as
traditional transcutaneous electrical nerve stimulation).
References:
Good opening contrast to set the scene Anika. Microcurrent can't cause muscle contractions so i think that the contrast you made there is a little bit of overkill. No matter. I know you'll focus on the rather obvious questions of how you get children to tolerate NMES and the additional safety considerations. cheers CY
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