NeurologyTier 2Disease (DEADMAN)

Psychogenic neurological disorders

Description

Functional neurological disorder (FND) - genuine neurological symptoms (weakness, seizures, movement disorder, sensory loss) without a structural/organic cause, arising from abnormal nervous system functioning rather than being consciously feigned
Distinct from malingering (conscious feigning for external gain) and factitious disorder (conscious feigning for the sick role) - in FND, symptoms are not under voluntary control

Common - among the most frequent presentations to neurology outpatients; functional seizures (PNES) account for a substantial minority of patients referred for "refractory epilepsy"

The modern model is a disorder of the brain's predictive/attentional processing, not "hysteria" or pure psychological conversion - though psychological stressors, trauma, and comorbid anxiety/depression are common contributors
Positive clinical signs (not just exclusion of organic disease) support diagnosis - reflects genuine, reproducible neurophysiological inconsistency rather than "normal" findings

Functional weakness: Hoover's sign (weak hip extension normalises with contralateral hip flexion against resistance), collapsing/give-way weakness
Functional (non-epileptic) seizures: video-EEG showing no ictal epileptiform activity during a typical event is the gold standard; clinical clues include long duration, fluctuating course, closed eyes with resistance to opening, pelvic thrusting, and preserved awareness during bilateral limb movement
Functional tremor: entrainment (tremor frequency matches an examiner-imposed rhythmic movement of the unaffected limb) and distractibility
Diagnosis is made on positive features, not simply after excluding organic disease

Clear, non-judgemental explanation of the diagnosis is itself therapeutic - explicitly frame it as genuine, common, and potentially reversible, not "nothing wrong" or "all in the mind"
Specialist physiotherapy for functional motor symptoms; CBT and psychology input particularly for functional seizures
Avoid unnecessary further investigation once confidently diagnosed - repeated normal tests can reinforce illness anxiety and delay engagement with treatment

Anxiety, depression, prior trauma (though a specific psychological trigger is not required for diagnosis), comorbid epilepsy (dual diagnosis of epilepsy + PNES is not uncommon)

Prognosis is better with early diagnosis, clear communication, and engagement with specialist rehabilitation; longstanding symptoms before diagnosis predict a poorer outcome
Misdiagnosis as "organic" disease, or dismissal as "not real," both worsen outcomes and delay appropriate treatment

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