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Myoclonus Workup
05 November 2004
| Myoclonus: |
shock
like muscle jerk
symmetrically
or asymmetrically
Rhythmically
or arrhythmically
Classified
according to site of origin of generator
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| Cortical myoclonus: |
discharges
in sensorimotor cortex
Conducted
rapidly in the pyramidal tracts
Focal
or multifocal jerks
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| Brainstem (reticular) myoclonus: |
reticular
firing causing more generalized axial jerks
Rostral
& caudal spread of activity in reticulospinal pathways
|
| Spinal myoclonus: |
focal
& segmental
Little
spread of activity from spinal generator sites
Longer
and more variable duration jerks.
|
| Propriospinal myoclonus: |
form
of spinal myoclonus
Spinal
generator recruits axial muscles via slowly conducting propriospinal
pathways
more
extensive jerks
typically,
slow, rhythmic bilateral synchronous jerksof flexion muscles in trunk
& lower limbs
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INVESTIGATIONS
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Metabolic
workup
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FBE,
UCE, Ca, Mg, PO4, LFT, TFT
NH3
|
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MRI:
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looking
for pathology as precipitant
brain
for cortical myoclonus, brainstem for reticular etc
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Back
average EEG:
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eliminates
cortical origin
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Bereitschafts
potential:
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eliminates
a cortical origin
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EMG:
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denervation
at level of theoretical spinal injury
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PolyEMG:
(Surface
activation order EMG)
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Establishes
the chronological order and localises lesion in spine
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C
reflex:
|
reflection
of hyperexcitability of the nervous system
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Motor
evoked potentials:
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localises
lesion
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SSEP:
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eliminates
a cortical origin (look for giant cortical waves)
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