Objective: To investigate the pattern of paracervical muscle activity in cervical dystonia CD patien

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Patterns of Nuchal Muscle Overactivity in
Cervical Dystonia as Determined by EMG of
Multiple Muscle Pairs Preceding and Subsequent to
Botulinum Toxin Therapy Does the Pattern
Change? Drake D. Duane and Glenn
Heimburger Arizona Dystonia Institute / Arizona
State UniversityScottsdale / Tempe, Arizona,
U.S.A.
Objective To investigate the pattern of
paracervical muscle activity in cervical dystonia
(CD) patients by dual-channel, multiple muscle
pair EMG just prior to and several months post
botulinum toxin (bot tox) therapy and observe
what change occurs in the muscle activity
pattern. Background We have employed EMG of
multiple pairs of paracervical muscles to guide
bot tox administration in CD. This investigation
contrasts the recorded dystonic muscle pattern
preceding and3 to 6 months post bot tox
treatment and its correlation with clinical
postural pattern. Methods 10 CD patients (8
female, 2 male mean age 60 years /- 8.5) with gt
3 year histories (mean9 years) of CD were
randomly selected from a database of 123 CD
patients evaluated by dual-channel, multiple
muscle pair EMG used in our laboratory to
ascertain which muscles and dosage/muscle to be
injected. Examinations were performed with
patients in a seated upright position during
involuntary and voluntary muscle contraction.
Recordings utilized intramuscular bipolar
electrodes with a TECA NeuroStar instrument.
Muscle pairs included at least splenius capitis
(Sp Cap), oblique capitis inferior (OCI),
trapezius (Trap), levator scapulae (Lev Scap),
scalene (Scal) and sternocleidomastoid (SCM) in
all subjects. Records were stored on graph paper
and graded on a scale of 0 to 3 activity units in
0.5 increments of dystonic muscle contraction.
Compared were recordings just before initial
treatment and3 to 6 months later,
pre-retreatment (mean 4 months). Results In 8
of the 10 patients, the pattern of muscle
activity remained similar, although occasional
severity of activity within individual muscles
varied by .5 to 1 units between examinations. In
2 patients, the pattern showed new muscle
overactivity with reduction in some previously
injected muscles by gt1 unit, although resting
head posture and TWSTRS severity scores were
similar between examinations.In rotational CD,
ipsilateral OCI, Sp Cap and contralateral SCM
overactivity was most common. However, in 3
patients ipsilateral SCM and Scal muscle
overactivity accompanied ipsilateral latero-
and/or anterocollis. Toxin dosages averaged
212.5 IU Botox (range 125-300) with individual
muscle dosages varying from 12.5 to 50 IU. The
average number of muscles injected was 6 (range
4-8). All10 patients were clinical responders
to bot tox. Conclusion Although clinical gross
muscle overactivity patterns in CD are commonly
predictable, multichannel EMG sometimes reveals
unanticipated muscle involvement apparently not
compensatory. In the majority of treated
patients, the pattern returns to pretreatment
levels once toxin effect has wornoff with minor
changes in relative activity within individual
muscles. However, occasionally patients
demonstrate new muscle involvement warranting a
change in the bot tox injection pattern. This
pre-injection multiple bilateral paired muscle
EMG approach optimizes clinical benefit,
demonstrates physiologic patterns within CD and
the extent to which these are modified by bot
tox. Poster Presentation, 8th International
Congress of Parkinson's Disease and Movement
Disorders, June 14, 2004, Rome, Italy. Duane DD,
Heimburger GE. Movement Disorders 19(Supplement
9) S84, 2004.