Adapted multiple point stimulation method : AMPS

(1)

(2)

•

The original The original McComasMcComas technique (1971) technique (1971) 10 S-MUAP are evoked at

10 S-MUAP are evoked at one singleone single point of stimulation point of stimulation ALTERNATION

ALTERNATION

•

The Multiple Point Stimulation method (The Multiple Point Stimulation method (Doherty & BrownDoherty & Brown, 1993), 1993) 10 S-MUAP are evoked at

10 S-MUAP are evoked at 10 distinct10 distinct stimulation points stimulation points

NO ALTERNATION, BUT NOT APPLICABLE TO ANY

SUBJECT OR PATIENT

(3)

• Incremental Stimulation (McComas 1971)

- percutaneous nerve stimulation

- short stimulation duration (50 µs)

- weak intensity gradually increased by increments

of 0.1 to 0.5 mA

Individual and sequential activation of motor axons

The Adapted Multiple Point Stimulation Method:

AMPS

(Kadrie

et al.

1976; Wang & Delwaide 1995)

(4)

The Adapted Multiple Point Stimulation Method:

AMPS

(Kadrie

et al.

1976; Wang & Delwaide 1995)

• The mean motor unit size is estimated by the evocation

The mean motor unit size is estimated by the evocation

of

10 S-MUAP

by using

incremental stimulation

in

distinct points

of the median nerve between the wrist

_{of the median nerve between the wrist}

and

_and

elbow.

• At each stimulation point,

At each stimulation point,

two or three S-MUAP

are

successively evoked and the compound motor response is

selected only if S-MUAP are

(5)

AMPS:S-MUAP selection criteria

• With distinct thresholds

With distinct thresholds

• In an all-or-nothing manner

In an all-or-nothing manner

• Without any fractionation of the compound motor

Without any fractionation of the compound motor

responses to successive suprathreshold stimuli

• In an orderly and reproducible manner

In an orderly and reproducible manner

(6)

AMPS advantages

•

AMPS minimises alternation AMPS minimises alternation

•

Incremental stimulation avoids any significant motor Incremental stimulation avoids any significant motor

unit selection bias

unit selection bias ? Erlanger and Gasser ?? Erlanger and Gasser ?

•

AMPS results are reproducible (CV = 10%) and fit well AMPS results are reproducible (CV = 10%) and fit well

with

with those obtained, in the same population, using an other those obtained, in the same population, using an other

estimation method: the F- response technique.

•

AMPS is non- invasive and painlessAMPS is non- invasive and painless

•

AMPS is a fast procedure AMPS is a fast procedure

(7)

•

AMPS minimises alternationAMPS minimises alternation

•

Incremental stimulation avoids any significant motor Incremental stimulation avoids any significant motor unit selection bias

•

with

•

No specific collection system or software is requiredNo specific collection system or software is required

(8)

•

unit selection bias

•

AMPS results are reproducible (CV = 10%) and fit well AMPS results are reproducible (CV = 10%) and fit well with

with those obtained, in the same population, using an other those obtained, in the same population, using an other estimation method: the F- response technique

estimation method: the F- response technique._.

•

(9)

AMPS advantages

TEST 1 TEST 1 T ES T 2 T ES T 2 40 40 100100 200200 40 40 100 100 200 200 r = 0.83 r = 0.83 CV = 9.5% CV = 9.5% µV.ms µV.ms µV.ms µV.ms 100 100 400400 r = 0.95 r = 0.95 CV = 10.4% CV = 10.4% MU MU 70 70 70 70 100 100 400 400 MU MU A. Thenar MUNE

(10)

AMPS advantages

1000 1000 1000 1000 r = 0.83 r = 0.83 P P < 0.001 < 0.001 A M PS A M PS 50 50 100100 50 50 100 100 MU MU MU MU

(11)

•

unit selection bias

•

with

•

(12)

•

unit selection bias

•

with

•

AMPS is a fast procedureAMPS is a fast procedure

•

(13)

•

unit selection bias

•

with

•

(14)

AMPS disadvantages

•

AMPS is not a hands - off techniqueAMPS is not a hands - off technique

•

The same S-MUAP recorded twice from two different The same S-MUAP recorded twice from two different

stimulation points

•

A subjective bias in recognition of new S-MUAP is A subjective bias in recognition of new S-MUAP is

possible

(15)

AMPS disadvantages

•

The same S-MUAP recorded twice from two different The same S-MUAP recorded twice from two different stimulation points

stimulation points

•

possible

(16)

AMPS disadvantages

•

stimulation points

•

A subjective bias in recognition of new S-MUAP is A subjective bias in recognition of new S-MUAP is possible

possible

(17)

AMPS disadvantages

•

stimulation points

•

possible

(18)

•

Techniques using the Techniques using the incremental stimulationincremental stimulation

Multiple Point Stimulation Multiple Point Stimulation McComas initial technique McComas initial technique

AMPS AMPS MOTOR MOTOR UNIT UNIT NUMBER NUMBER