Overlapping Clinical Presentations: PNES, Conversion Disorder (FND), Autism (ASD), PSH, BPD, and BDD
A clinician‑oriented, aurora‑glass guide for differential diagnosis. Built from the original brief by Bailey R. Gwyn (2025) with expanded red‑flags, work‑up, and communication tips.
At‑a‑Glance Core Features
| Condition | Key Characteristics |
|---|---|
| PNES | Seizure‑like events without ictal EEG change; often stress‑related; prolonged/onset-gradual; asynchronous or side‑to‑side movements; eyes closed; post‑event recall may be preserved; no true postictal confusion. |
| Conversion Disorder (FND) | Positive functional signs (e.g., Hoover’s sign), internal inconsistency, incongruent with neuroanatomy; symptoms include non‑epileptic seizures, weakness, tremor, gait, vision, speech. |
| ASD | Early‑onset social‑communication differences; restricted/repetitive behaviors; sensory hyper/hypo‑reactivity; alexithymia; shutdowns/meltdowns can mimic catatonia‑like or non‑epileptic events. |
| PSH | Post‑brain‑injury paroxysms of sympathetic surge: tachycardia, hypertension, hyperthermia, diaphoresis, dystonic/ridig posturing; stimulus‑triggered. |
| BPD | Affective instability, fear of abandonment, dissociation under stress; self‑harm/somatic complaints; transient stress‑related psychotic/dissociative symptoms. |
| BDD (ICD‑11) | Persistent bodily distress with multi‑system physical symptoms not fully explained medically; high utilization; emphasis on symptom distress/impact more than anxiety per se. |
This table distills the original brief and expands phrasing for clinical quick‑use.
Overlap Hot‑Spots
Dissociation & Emotional Dysregulation
PNES, FND, and BPD frequently include dissociation. ASD can show shutdowns/meltdowns that look similar but arise from sensory overload and neurodevelopmental differences rather than trauma‑linked dissociation.
Motor & Autonomic Phenotypes
PSH, PNES, and FND can all present with abnormal movements or posturing. PSH requires a history of brain injury and shows paroxysmal sympathetic signs (T, HR, BP, diaphoresis). FND favors positive functional signs and internal inconsistency. PNES lacks ictal EEG change.
Somatic & Sensory Focus
BDD features diffuse bodily symptoms and distress; FND shows focal functional deficits; ASD includes atypical sensory processing that can be misconstrued as “somatic focus.”
Decision Guide (Clinic Triage)
- Time‑course & Onset: Lifelong traits → consider ASD. Acute/change after trauma → consider PNES/FND/BPD. After moderate–severe TBI/hypoxia/stroke → consider PSH.
- Vital Signs During Events: Sympathetic surge (↑HR/↑BP/↑T/diaphoresis) with stimulus‑triggered paroxysms → PSH work‑up.
- Neurological Examination: Look for positive functional signs (e.g., Hoover’s). Incongruent exam → FND likelihood ↑.
- EEG Strategy: If seizure suspected → video‑EEG. PNES shows no epileptiform activity during typical events.
- Phenomenology: Asynchronous thrashing, side‑to‑side head movements, eyelids closed, long duration, fluctuating responsiveness → PNES more likely.
- Developmental History: Early social‑communication differences, RRBs, sensory profile → ASD assessment (ADOS‑2, developmental history).
- Psychiatric Patterning: Rapidly shifting relationships, identity disturbance, recurrent self‑harm, dissociation under stress → evaluate for BPD.
- Symptom Breadth: Multisystem, persistent bodily symptoms with high distress/utilization → consider BDD (ICD‑11).
Red Flags & Helpful Clues
| Scenario | Lean Toward | Why |
|---|---|---|
| No ictal EEG change during typical event on video‑EEG | PNES | By definition non‑epileptic; capture typical spell to confirm. |
| Paroxysms after TBI with ↑HR/↑BP/↑T and dystonic posturing | PSH | Sympathetic storms in acquired brain injury. |
| Inconsistent weakness, positive Hoover’s sign | FND | Positive signs define functional weakness. |
| Early childhood social‑communication differences + sensory profile | ASD | Neurodevelopmental onset; not episodic. |
| Self‑harm, unstable relationships, dissociation under stress | BPD | Pattern across contexts with affective lability. |
| Multiple chronic bodily symptoms with high distress/utilization | BDD | ICD‑11 construct emphasizing bodily distress. |
Minimal Work‑Up Checklist
- Careful timeline + collateral (onset, triggers, developmental and trauma history, TBI/ICU course).
- Video‑EEG to differentiate PNES vs epileptic seizures when events are disabling/unclear.
- Vitals during events (HR/BP/T, diaphoresis), consider autonomic capture for PSH.
- Focused neuro exam with functional signs (Hoover’s, entrainment for tremor, distraction tasks).
- Psychometrics: dissociation scales, BSL‑23 features for BPD, autism instruments (e.g., AQ, SRS‑2, ADOS‑2 by specialists).
- Imaging (if red flags): MRI for suspected structural lesions/brain injury; labs as indicated.
Care Pathways (Brief)
PNES / FND
Psychoeducation with a non‑stigmatizing explanation of functional symptoms; FND‑informed PT/OT/SLP; CBT‑informed approaches; trauma‑focused therapies when appropriate; coordinated neurology‑psychiatry follow‑up.
ASD
Neuroaffirming supports: sensory accommodations, communication supports, structured routines; address co‑occurring anxiety, catatonia‑like states with specialist input.
PSH
Trigger minimization; pharmacologic regimens may include agents used in PSH protocols (institution‑specific); management within neurorehab/ICU pathways; monitor autonomic burden.
BPD
Dialectical Behavior Therapy (DBT), safety planning, skills for emotion regulation/distress tolerance; coordinate with trauma‑informed care; avoid iatrogenic invalidation.
BDD
Collaborative, validating approach; goal‑oriented functional rehab; CBT‑informed strategies; careful avoidance of unnecessary investigations once red flags excluded.
Clinician Script (Delivering a PNES/FND Diagnosis)
“Your episodes are real and not your fault. Our tests show they’re not epileptic seizures. They’re functional—meaning the brain’s ‘software’ is glitching under stress or sensory overload, not that you’re making them up. With the right rehab and strategies, many people improve. Here’s how we’ll help…”
Printable Handoff (One‑Page)
Include: diagnosis working list, key risks, triggers, preferred de‑escalation steps, and who to call. Provide QR linking to this page for full context.
Educational only. Not a substitute for individualized medical judgment.