Hi all! Short-ish update today. We’re off for a long weekend in La Fortuna, so I’ll be focusing on work-related things for now, and then will have some cool pictures to share next week!
This week we mainly observed patient appointments instead of procedures, focusing on cases of neuromuscular disorders. One of the new things we learned was about the difference between muscle tone and muscle strength. Muscle tone refers to the ability of the muscle to resist gravity and keep the body in an upright posture. It can help maintain balance by reflexively responding to any sudden pull or stretch. Muscle tone is the default state of the muscles. Strength, on the other hand, is what we typically think of when we consider what our muscles do. It’s the ability of muscles to contract or extend. Tone and strength do not always correspond with each other. A person can have low tone but still have normal strength.
Dr. Bogantes also performed an electromyograph (EMG) on himself for us to observe. Typically, these procedures are performed using patch electrodes because it’s more comfortable, but you can get a clearer signal using a needle, which Dr. B subjected himself to in the name of our education. Very brave of him! We were able to see that when he only flexed his muscle a small amount, there was only a small potential from a single nerve. As he flexed harder though, the motor neuron recruited more and more fibers, and we were able to see the signal increasing in amplitude. We also saw a flat line at rest, when there was no muscle activation and therefor no electric potential. He compared this to a patient with nerve degradation who we had seen earlier. In that patient’s EMG, we could see small potentials firing at a regular interval. In a healthy patient, these potentials are suppressed, but with nerve damage, the brain does not suppress these properly.
Finally, Pablo and I continued working on our Doppler ultrasound project. We’ve tried out a few different materials for our ball and socket joint, and need to find the best one that will give the right amount of friction. If there’s too much friction, we won’t be able to angle the transducer easily, but if there is not enough, the transducer might fall out of place even when we’ve found the right position. We also need to make some modifications to the helmet so that the transducers can be in the right position. One of the big challenges we’re running into is with acquiring materials. The pieces we are using are so small that many of the hardware stores don’t carry them in the right size, and we won’t have enough time to ship screws and springs from the US before the summer is over. We’ll have to make do with the parts we do have, as well as some good old-fashioned glue. (It’s actually epoxy resin.) More to come soon!