A longitudinal study of motor subtypes in delirium: frequency and stability during episodes.

Objective: Motor-defined subtypes are a promising means of identifying clinically relevant patient subgroups but little is known about their course and stability during a delirium episode.

Methods: We assessed 100 consecutive adult palliative care patients with DSM-IV delirium twice weekly during their episodes using the Delirium Motor Subtype Scale (DMSS), Delirium Rating Scale-Revised-98 (DRS-R98) and Cognitive Test for Delirium (CTD). DMSS subtypes were assigned for each assessment and analysed for stability within patients during episodes.

Results: Across all assessments (n=303; mean 3 per patient, range 2-9), subtype occurrence was hypoactive (35%), mixed (26%), hyperactive (15%) and no subtype (24%). "No subtype" was associated with significantly lower DRS-R98 severity scores, of which 80% were subsyndromal, whereas mixed subtype assessments were the most impaired on the DRS-R98 and CTD. Subtypes were stable within delirium episodes in 62% of patients: 29% hypoactive, 18% mixed, 10% hyperactive and 6% no-subtype. The DRS-R98 noncognitive subscale scores differed across groups whereas cognitive subscale scores did not (p<0.001).

Conclusions: We conclude that motor subtypes occur in nearly all patients with full syndromal delirium and are often stable during an episode. Subtypes exhibited comparable levels of cognitive impairment but differed in non-cognitive symptoms, supporting the importance of cognitive testing to detect delirium in less overt cases.