How should I manage a patient with upper-body myoclonus who is taking clonazepam and sertraline and has a normal brain CT scan?

Management of Upper-Body Myoclonus in a Patient on Clonazepam and Sertraline

First, discontinue sertraline immediately as it is a known cause of drug-induced myoclonus, particularly with prolonged use, and continue clonazepam which is actually the appropriate treatment for myoclonus. 1, 2, 3

Immediate Action: Address Drug-Induced Myoclonus

Your patient's jerky movements are likely drug-induced myoclonus from sertraline, an SSRI with level A evidence for causing this condition 3. This is particularly concerning given:

• Sertraline is documented to cause myoclonus, especially with prolonged treatment 2, 3
• The FDA label explicitly warns about myoclonus as part of serotonin syndrome 1
• SSRIs including sertraline (citalopram, escitalopram, paroxetine, sertraline) have the highest level of evidence for causing myoclonus 3

Critical pitfall: The patient is already on clonazepam, which is actually the correct treatment for myoclonus 4, 5, 6. This suggests the sertraline-induced myoclonus may be overwhelming the therapeutic effect of clonazepam.

Diagnostic Workup Required

Before adjusting treatment, obtain:

• EEG (electroencephalogram) - Essential to determine if this is epileptic myoclonus with time-locked discharges or non-epileptic myoclonus 4
• Look specifically for: cortical discharges, burst-suppression patterns, or rhythmic/periodic activity 4
• Electromyography (EMG) if needed to classify the neurophysiological subtype 5, 7

The normal CT scan rules out structural causes but does not exclude epileptic myoclonus 4.

Treatment Algorithm

Step 1: Discontinue Sertraline

• Taper gradually over 10-14 days to avoid withdrawal symptoms (which can include myoclonus) 8
• Monitor for serotonin discontinuation syndrome: irritability, mood changes, electric shock sensations, confusion 1

Step 2: Optimize Clonazepam Dosing

Clonazepam is the established first-line treatment for most types of myoclonus 4, 9, 5, 6, 7, 10:

• Typical dosing: 0.5-1 mg at bedtime initially 4, 11
• Can increase to higher doses if tolerated and needed 11
• Effective in 90% of myoclonus cases 12, 11
• Works across multiple myoclonus subtypes (cortical, subcortical, segmental) 5, 6, 7, 10

Important caveat: Clonazepam causes sedation 4, which may have been why sertraline was added initially. However, the sedation typically improves with continued use 11.

Step 3: If Myoclonus Persists After Sertraline Discontinuation

Add levetiracetam or valproic acid as these are the most effective agents for cortical myoclonus (the most common type) 4, 5, 6, 7, 10:

• Levetiracetam: Suggested as first-line for cortical myoclonus 10, well-tolerated
• Valproic acid: Highly effective, particularly if EEG shows epileptiform activity 4, 5, 6
• These can be used in combination with clonazepam 4

Step 4: Based on EEG Results

If EEG shows epileptiform discharges or time-locked activity:

• Treat as epileptic myoclonus with valproic acid as primary agent 4
• Add levetiracetam if monotherapy insufficient 4
• Consider propofol or benzodiazepines for refractory cases 4

If EEG is normal (non-epileptic myoclonus):

• Continue clonazepam optimization 5, 6, 7
• Consider adding levetiracetam for additional benefit 5, 10

Key Clinical Considerations

Avoid these common errors:

• Do not add phenytoin - it is often ineffective for myoclonus 9
• Do not use prophylactic antiepileptics without documented seizures 4
• Do not assume all jerking movements are seizures - many are non-epileptic 4, 9

Monitor for:

• Sedation from clonazepam (may need dose timing adjustment - give 1-2 hours before bedtime if morning drowsiness occurs) 11
• Tolerance to clonazepam is rare in clinical practice 11
• Recurrence of myoclonus if sertraline is reintroduced 2

Alternative Antidepressant if Needed

If depression treatment is still required after sertraline discontinuation, consider:

• Bupropion - does not cause myoclonus and is activating 8
• Mirtazapine - less likely to cause movement disorders 8
• Avoid other SSRIs as they share the same risk profile 3

The most likely scenario is that discontinuing sertraline while maintaining clonazepam will resolve the myoclonus within days to weeks 2, 3. The normal brain imaging supports a drug-induced rather than structural etiology.