Have you evaluated an elderly patient with a history of sudden, unprovoked jerk movements lasting several seconds and not been sure what to make of it? It's easy to disregard this information because it doesn't fit into one category but perhaps, we shouldn't.
Myoclonic "jerks" can occur as a part of an epileptic syndrome (myoclonic epilepsy) or as a separate movement disorder. As a movement disorder, they may arise from neuromuscular, spinal, cortical or subcortical origin and therefore may have many different etiology. A report in Cavalier King Charles Spaniels came out recently (https://doi.org/10.1111/jvim.16404) which detailed myoclonic jerks in older CKCS. This study was not conclusive about the origin of the jerk, but suggested a cortical or subcortical origin. Several of the dogs in this group had idiopathic epilepsy, diagnosed with MRI/CSF/blood work prior to the onset of the myoclonic jerk so it is possible this is simply a manifestation of their epileptic syndrome. However, several of the dogs were on treatment with primary anticonvulsant drugs (imepitoin and phenobarbital) and the seizures improved but the myoclonic jerk worsened! This suggests a more likely non-epileptic origin. This study was SMALL so it is much too early to draw conclusions about the cause but it does provoke thought.
Here is what I took away:
1. Older adult or geriatric onset myoclonic jerks may be seizure, or non-seizure in origin
2. Phenobarbital (and imepitoin) didn't help
3. Levetiracetam helped in 3 or 6 cases. This could mean it is epileptic or non-epileptic in origin, remember!
4. If non-epileptic in origin, myoclonic jerks do not warrant treatment as they are unlikely to result in progressive neurologic disease (but knowing if they are non-epileptic is difficult)
5. Myoclonic jerks are seen as rapid movements of the face, head or thoracic limbs that are several seconds in duration and do not have a pre or post ictal period associated with the signs. Not sure what I'm talking about? Follow the link to the article and scroll to the supplementary material. There are two videos attached to help you visualize what is being noted.
So what do I do?
1. If the neurologic examination is ABnormal - suggest diagnostic imaging of the brain or spinal cord to determine if pathology is present to account for the jerk motion.
2. If the neurologic examination is normal, consider non-epileptic jerks and either start levetiracetam or monitor if infrequent.
Thanks for reading and have a great week! Stay cool out there and watch out for jerks!