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Propriospinal Myoclonus
05 November 2004 Myoclonus: shock like muscle jerk Symmetrically or asymmetrically Rhythmically or arrhythmically Classified according to site of origin of generator Cortical myoclonus: discharges in sensorimotor cortex Conducted rapidly in the pyramidal tracts Focal or multifocal jerks Brainstem 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 jerks of flexion muscles in trunk & lower limbs INVESTIGATIONS MRI: looking for pathology as precipitant Usually in cervical region Back average EEG: eliminates cortical origin EMG: denervation at level of theoretical spinal injury PolyEMG: activation duration 40 – 1500 ms Frequency 0.3-0.7 Hz Diffusion speed 2 - 10 m/s Establishes the chronological order Usually focus in thoracic cord for flexion Usually focus in lumbar cord for extension Bereitschafts potential: eliminates a cortical origin C reflex: reflection of hyperexcitability of the nervous system ?utility Motor evoked potentials: ?utility SSEP: eliminates a cortical origin ?reliability ?utility |
