In a woman with opioid dependence who has recurrent seizure-like episodes accompanied by self-mutilation, head-banging, screaming, marked hypersomnia, and a normal neurologic work-up, what is the most likely diagnosis?

Functional Neurological Disorder (Conversion Disorder) with Possible Opioid Withdrawal

The most likely diagnosis in this patient is functional neurological disorder (conversion disorder) manifesting as psychogenic non-epileptic seizures (PNES), potentially complicated by opioid withdrawal syndrome. The combination of seizure-like episodes with self-mutilation, head-banging, screaming, marked hypersomnia, and negative neurologic workup in a patient with opioid use history strongly suggests a functional disorder rather than true epileptic seizures.

Key Diagnostic Features Supporting Functional Neurological Disorder

The clinical presentation is classic for psychogenic non-epileptic seizures rather than true epilepsy:

• The dramatic behavioral manifestations (head-banging, screaming, self-mutilation) are atypical for epileptic seizures and more consistent with PNES 1
• Normal neurologic workup effectively rules out structural or metabolic causes of true seizures 2
• The combination of violent motor behaviors with preserved consciousness during episodes suggests non-epileptic events 1

Critical Consideration: Opioid Withdrawal as Contributing Factor

While true epileptic seizures from opioid withdrawal are rare, withdrawal can present with complex behavioral manifestations:

• Opioid withdrawal primarily manifests as CNS irritability, autonomic overreactivity, and gastrointestinal dysfunction—not typically seizures 1
• When withdrawal-associated seizures do occur, they are primarily myoclonic, respond to opiates, and carry no increased long-term risk 1
• However, complicated opioid withdrawal can rarely present with convulsions and delirium, though this is unpredictable and uncommon 3
• The hypersomnia could represent either withdrawal symptoms or a separate somatoform manifestation 1

Differential Diagnosis Considerations

The negative neurologic workup is crucial for narrowing the diagnosis:

• True epileptic seizures would typically show EEG abnormalities or other objective findings 1, 2
• REM behavior disorder presents with violent dream enactment but occurs during sleep, not wakefulness, and is more common in older adults 1
• Nocturnal seizures would be captured on polysomnography if present 1
• Substance withdrawal seizures (when they occur) typically manifest within 24-72 hours of last use and are generalized tonic-clonic, not the complex behavioral pattern described 1, 2

Management Approach

Treatment should address both the functional disorder and potential opioid dependence:

• For the functional symptoms: Psychotherapy (particularly cognitive-behavioral therapy) is first-line treatment for conversion disorder, not anticonvulsants 2
• For opioid dependence: If withdrawal is contributing, stabilization with medication-assisted treatment (methadone or buprenorphine) is indicated rather than acute detoxification 1, 4, 5
• Environmental safety: Remove dangerous objects, pad surfaces around the patient to prevent injury during episodes 1
• Avoid reinforcing behaviors: Do not treat with anticonvulsants if EEG is normal, as this reinforces the sick role 2

Critical Pitfalls to Avoid

• Do not assume all seizure-like activity in opioid users is withdrawal-related—most opioid withdrawal does NOT cause seizures 1, 3
• Do not prescribe long-term anticonvulsants when the sole cause is functional or withdrawal-related 2
• Do not abruptly discontinue opioids if the patient has been on chronic therapy, as this can worsen symptoms 1, 6
• Do not miss coexisting psychiatric comorbidities (trauma history, mood disorders) that commonly accompany both opioid use disorder and conversion disorders 1, 5

The diagnosis of functional neurological disorder (conversion disorder) should be made positively based on the characteristic clinical features, not merely as a diagnosis of exclusion after negative testing.