What’s Excessive Fragmentary Myoclonus (EFM)?

Understanding Fragmented Myoclonus (FM) | What is the Health Significance of EFM? |
The Effect of EFM on Sleep

Overview

Have you ever felt your muscles twitch abruptly and uncontrollably? This physiological event is known as myoclonus.

While seeing your muscles twitch uncontrollably may be disconcerting, these occurrences are usually harmless. However, doctors feel that sometimes these muscular occurrences may be latent symptoms of disorders such as epilepsy, nerve issues, and so on.

Studies have shown that many people experience small, involuntary muscle twitches during sleep, a phenomenon known as Fragmentary Myoclonus (FM).^[1]However, when these twitches become frequent and severe enough to disrupt the sleep cycle, the condition is classified as Excessive Fragmentary Myoclonus (EFM).

Understanding Fragmentary Myoclonus (FM)

FM is a relatively uncharted sleep event discovered incidentally during the polysomnographic study of several persons.

The American Academy of Sleep Medicine defines FM as abrupt, isolated, arrhythmic, asymmetric, and non-synchronous short twitches or twitch-like movements of muscles or muscle fibers affecting many body parts measured by surface electromyography (EMG) during polysomnography.^[2]

While muscle jerks can sometimes be physically observed, they are often not seen. Sleep experts generally do not view FM as a distinct disorder; instead, they list it among symptoms and a regular variation of sleep-related movement disorders.

According to the International Classification of Sleep Disorder, Third Edition, there are two (2) types of FM:

1) Physiologic Type

Some experts also call this Non-Excessive Fragmentary Myoclonus.^[3] Physiologic FM usually manifests as a sporadic condition during rapid eye movement sleep. It also occurs during non-REM sleep and awake, albeit less frequently.

2) Excessive/Pathologic Type

Excessive Fragmented Myoclonus (EFM) refers to an abnormal number of FM potentials that persist throughout all non-REM and REM sleep stages, unlike the Physiologic kind.

According to the most recent version of the AASM Manual for the Scoring of Sleep and Associated Events, EFM is clinically diagnosed when there are five potentials per minute during at least 20 minutes of recorded non-REM sleep.^[4]

In terms of demographics, several studies have revealed that EFM is more common in men and becomes more severe as people age. While it is generally agreed that EFM occurs primarily during sleep, a recent study of 98 patients found that EFM potentials can be seen while awake.^[5]

What's the Health Significance of EFM?

Scientists are not clear about the health implications of EFM. However, this condition has been observed in conjunction with many different diseases, including sleep problems like obstructive and central sleep apnea, insomnia, narcolepsy, and periodic limb movements.^[1]

Also, EFM was noticed among patients with neurodegenerative disorders and peripheral nerve damage. The fact that EFM is associated with these many diverse disorders lends credence to the notion that it is neither a particular sleep disorder nor a particular polysomnographic marker.

The Effects of EFM on Sleep

The impact of EFM on sleep is yet to be fully understood. However, some experts believe this sleep event can severely disrupt sleep and reduce overall well-being. Here are some ways EFM could negatively affect one's sleep, including:

Sleep Fragmentation: Recurrent myoclonic jerks cause repeated arousals, resulting in fragmented sleep. These arousals mean the individual may have several brief awakenings throughout the night, often without being completely aware.
Sleep Quality Decreased: Because of the frequent disturbances, people with EFM frequently spend less time in deeper stages of sleep, such as slow-wave sleep (SWS) and rapid eye movement (REM) sleep. These stages are essential for physical and emotional recovery.
Daytime Symptoms: The poor sleep quality associated with EFM can cause excessive daytime sleepiness, exhaustion, cognitive deficits, and mood swings. People may have trouble with attention, memory, and emotional regulation.

What's the Takeaway?

Optimal sleep is essential for healthy living. If you feel like you are not getting enough sleep or experiencing repeated muscle jerks. It may be time to see your doctor. A polysomnography will reveal if the cause of your sleep symptoms is EFM.

References:

Nepožitek, J., & Šonka, K. (2017). Excessive Fragmentary Myoclonus: What Do We Know?. Prague medical report, 118(1), 5–13. https://doi.org/10.14712/23362936.2017.1
Hoque, R., McCarty, D. E., & Chesson, A. L., Jr. (2013). Manual quantitative assessment of amplitude and sleep stage distribution of excessive fragmentary myoclonus. Journal of Clinical Sleep Medicine: JCSM: Official Publication of the American Academy of Sleep Medicine, 09(01), 39–45. https://doi.org/10.5664/jcsm.2336
Montagna, P., Liguori, R., Zucconi, M., Sforza, E., Lugaresi, A., Cirignotta, F., & Lugaresi, E. (1988). Physiological hypnic myoclonus. Electroencephalography and clinical neurophysiology, 70(2), 172–176. https://doi.org/10.1016/0013-4694(88)90116-2
Lins, O., Castonguay, M., Dunham, W., Nevsimalova, S., & Broughton, R. (1993). Excessive fragmentary myoclonus: Time of night and sleep stage distributions. The Canadian Journal of Neurological Sciences. Le Journal Canadien Des Sciences Neurologiques, 20(2), 142–146. https://doi.org/10.1017/s0317167100047715
Raccagni, C., Löscher, W. N., Stefani, A., Wanschitz, J., Kraemer, L., Heidbreder, A., & Högl, B. (2016). Peripheral nerve function in patients with excessive fragmentary myoclonus during sleep. Sleep medicine, 22, 61–64. https://doi.org/10.1016/j.sleep.2016.04.018