Developmental regression and neurodegeneration — branching viva

Opening branch — the regressing adolescent

A previously well fourteen-year-old presents over ten days with insomnia, agitation, hallucinations, a seizure, and orofacial dyskinesia, with a fluctuating conscious level. The candidate must first recognise this as developmental regression in its subacute form - loss of previously acquired cognitive and behavioural function - and distinguish it from a primary psychiatric disorder. The candidate states that the combination of psychiatric onset, seizures, a movement disorder, and altered consciousness is the phenotype of autoimmune encephalitis, a treatable mimic of neurodegeneration, and that the cardinal error is dismissing the early phase as psychiatric. ^[3]

The examiner probes the framework. The candidate gives the Graus diagnostic approach, which permits a diagnosis of probable autoimmune encephalitis on the phenotype - subacute onset of psychiatric symptoms, seizures, a movement disorder, autonomic instability, and a decreased level of consciousness - supported by EEG, CSF, or imaging, before the antibody panel confirms it. The teaching point is that the framework exists so that empirical immunotherapy is justified while the panel returns, because the outcome is better the earlier treatment begins. ^{[3] [4]}