Early presenting syndromes associated with PSP pathology. PSP clinical syndromes are first divided into the typical PSP syndrome and the atypical PSP syndromes. The typical PSP syndrome, or PSP-S, is also sometimes referred to as Richardson’s syndrome (PSP-RS) and is the most common presenting syndrome. The atypical PSP syndromes include PSP presenting as the corticobasal syndrome (PSP-CBS), as Parkinson’s disease-like (PSP-P), with progressive akinesia/gait freezing (PSP-PAGF), with cerebellar ataxia (PSP-C), as the behavioural variant of frontotemporal dementia (PSP-bvFTD) and with apraxia of speech with or without aphasia (PSP-AOS). Of note, PSP-AOS is sometimes incorrectly referred to as PSP-PNFA for non-fluent aphasia.