[P3-81] A case of abdominal functional myoclonus in a 16-year-old male −About the availability of MRCP (movement related cortical potentials)−
We here report a case with functional (psychogenic) myoclonus of abdominal muscles showing unique findings in movement related cortical potentials (MRCP).
The patient is 16-year-old male with glycogenosis type 9 followed-up without treatment. He has a history of possible pervasive development disorder and functional bowel syndrome, and transient gait disturbance at the age of 12. This time, persistent abdominal jerk had appeared. The abdominal jerk was like hiccup, appeared once a few seconds and reduced its amplitude and frequency with distraction. Surface electromyogram with EEG excluded epileptic spasms. MRCP, setting contraction of rectus abdominis as a trigger, showed slowly rising negative waves from 0.6 seconds prior to the trigger (Bereitschaftpotentials, BP). Based on his past history, social environment and MRCP findings, we diagnosed his involuntary jerks as functional (psychogenic) abdominal myoclonus.
In a voluntary movement, after the drive to move from frontal and limbic regions, the discharges from bilateral supplementary motor area (SMA), and pre-SMA transfer to the primary motor cortex. At this moment, MRCP shows the slow negative waves originated from pre-SMA and SMA etc (BP). The sense of agency is also generated in this process. While in patients with tic, BP was absent in MRCP, despite they have urge to move without sense of agency.
The myoclonus in our case is similar to tic, because of the lack of sense of agency, but is generated, at least in part, in the pathway of voluntary movement since BP in MRCP was detected.
The patient is 16-year-old male with glycogenosis type 9 followed-up without treatment. He has a history of possible pervasive development disorder and functional bowel syndrome, and transient gait disturbance at the age of 12. This time, persistent abdominal jerk had appeared. The abdominal jerk was like hiccup, appeared once a few seconds and reduced its amplitude and frequency with distraction. Surface electromyogram with EEG excluded epileptic spasms. MRCP, setting contraction of rectus abdominis as a trigger, showed slowly rising negative waves from 0.6 seconds prior to the trigger (Bereitschaftpotentials, BP). Based on his past history, social environment and MRCP findings, we diagnosed his involuntary jerks as functional (psychogenic) abdominal myoclonus.
In a voluntary movement, after the drive to move from frontal and limbic regions, the discharges from bilateral supplementary motor area (SMA), and pre-SMA transfer to the primary motor cortex. At this moment, MRCP shows the slow negative waves originated from pre-SMA and SMA etc (BP). The sense of agency is also generated in this process. While in patients with tic, BP was absent in MRCP, despite they have urge to move without sense of agency.
The myoclonus in our case is similar to tic, because of the lack of sense of agency, but is generated, at least in part, in the pathway of voluntary movement since BP in MRCP was detected.