What could be causing my nocturnal leg convulsions, considering I've been taking Magnesium (magnesium) supplements at a dose of 288mg before bed for 2 weeks, and I have no known medical history of sleep disorders or neurological conditions?

Nocturnal Leg Convulsions: Differential Diagnosis and Management

Direct Answer

Your single episode of violent nocturnal leg convulsions lasting several hours most likely represents periodic limb movements of sleep (PLMS), nocturnal frontal lobe epilepsy, or REM sleep behavior disorder (RBD), and requires clinical evaluation to differentiate these conditions—magnesium supplementation at 288mg nightly is unlikely to be causative and should not be discontinued based solely on this isolated event. 1, 2

Key Diagnostic Considerations

Most Likely Diagnoses Based on Your Description

Periodic Limb Movements of Sleep (PLMS)

• PLMS consists of rhythmic, stereotyped extensions of the big toe and dorsiflexions of the ankle, occasionally with knee and hip flexions, lasting approximately 2-4 seconds with a frequency of about 1 every 20-40 seconds 1
• Critically, you would be completely unaware of these movements during sleep, which matches your description 2
• Your bed partner may report "twitchy legs" or kicking movements, which aligns with the "violent convulsing" observation 2
• These movements may cause brief awakenings or arousals that you wouldn't consciously remember 1

Nocturnal Frontal Lobe Epilepsy

• Can present with paroxysmal leg symptoms including cramps and paresthesias that occur during sleep 3
• Often mistaken for other sleep disorders and requires careful observation of clinical symptoms and frequency 4
• Typically involves more frequent episodes per night rather than a single prolonged event 4

REM Sleep Behavior Disorder (RBD)

• Involves complex, often violent motor activity during REM sleep due to loss of normal muscle atonia 5
• Patients typically don't recall the episodes, similar to your experience 2
• However, RBD usually involves more whole-body movements rather than isolated leg activity 5

Magnesium Supplementation Analysis

Your magnesium supplement is unlikely to be the culprit:

• At 288mg before bed for 2 weeks, you're within typical supplemental dosing ranges 6
• Magnesium is actually studied for potential benefits in sleep-related conditions, not as a cause of nocturnal movement disorders 6
• The FDA label for magnesium warns about kidney disease, gastrointestinal issues, and drug interactions—but not nocturnal leg movements 7
• No evidence in the literature links magnesium supplementation to PLMS, nocturnal seizures, or RBD 8, 6

Essential Clinical Questions You Should Answer

To differentiate between conditions, consider:

1. "Do you have an uncomfortable urge to move your legs when awake, especially in the evening?" - If yes, this suggests restless legs syndrome (RLS), which is associated with PLMS in up to 90% of cases 1, 9

2. "Have you experienced any daytime leg cramps or painful muscle tightening?" - Nocturnal leg cramps involve painful, involuntary contractions with no urge to move, relieved specifically by stretching 9

3. "Have you had any other unusual movements, behaviors, or dream enactment during sleep?" - This would suggest RBD 2

4. "Has this happened on any other nights, even mildly?" - A truly isolated single episode is unusual for PLMS, which tends to be chronic 1

Recommended Evaluation Pathway

Initial Assessment:

• Perform a thorough neurological examination looking for signs of peripheral neuropathy 9
• Check serum ferritin level—if below 50-75 ng/mL, iron supplementation is indicated as low iron is strongly associated with RLS and PLMS 5, 1
• Review all current medications, as SSRIs, tricyclic antidepressants, and dopamine antagonists can induce or exacerbate movement disorders 5, 8

When to Pursue Polysomnography:

• The American Geriatrics Society recommends polysomnography only if PLMD is suspected based on sleep disturbance not explained by other causes 1
• Given this was a single isolated episode with no ongoing sleep disturbance or daytime symptoms, immediate polysomnography is not indicated 1, 2
• However, if episodes recur or you develop daytime fatigue/sleepiness, polysomnography with video-audio recording becomes essential 2

Red Flags Requiring Urgent Neurological Referral:

• New-onset severe symptoms, numbness, weakness, speech disturbance, gait disturbance, or memory loss would necessitate direct neurology referral 5
• Recurrent violent movements with potential for injury warrant sleep specialist evaluation 5, 2

Management Approach

Watchful Waiting is Appropriate:

• Since this was a single isolated episode without recurrence over 3 weeks, and you have no daytime symptoms or sleep disturbance, observation is reasonable 1, 2
• PLMS treatment is only indicated if causing significant sleep disturbance or daytime symptoms, which you don't currently have 2

If Episodes Recur:

• First-line treatment for PLMS includes gabapentin, pregabalin, or levodopa compounds, though no FDA-approved agents exist specifically for PLMD 1
• For RBD, melatonin 3-15mg at bedtime is first-line treatment 2
• Environmental safety measures should be implemented if violent movements recur (padding sharp surfaces, removing dangerous objects from bedroom) 5

Critical Pitfall to Avoid

Do not assume this is simply "restless legs" or "leg cramps":

• The violent, prolonged nature lasting "a couple of hours" and your complete unawareness distinguishes this from typical nocturnal leg cramps, which are painful and would wake you 9
• This also differs from RLS, which involves an uncomfortable urge to move that you would consciously experience 9
• The duration and intensity warrant proper evaluation if recurrent, as misdiagnosis could delay treatment of an underlying neurological condition 5, 3

Continue your magnesium supplementation unless other contraindications arise—there is no evidence linking it to your symptoms, and discontinuing it based on temporal association alone would be premature 7, 6