A longitudinal study of motor subtypes in delirium: relationship with other phenomenology, etiology, medication exposure and prognosis.

Objective: Motor subtypes have promise as a means of identifying clinically relevant delirium subgroups. Little is known about their relationship to etiologies, medication exposure, and outcomes.

Methods: Consecutive cases of DSM-IV delirium in palliative care patients were assessed twice-weekly throughout their delirium episodes using the Delirium Motor Subtype Scale (DMSS), Delirium Etiology Checklist (DEC) and Delirium Rating Scale Revised-98 (DRS-R98).

Results: 100 patients [mean age 70.2 ± 10.5] were assessed on 303 visits [range 2-9]. Over the entire episode, mean DRS-R98 Severity scores were 16.2 ± 5.7. The mean number of etiologies per case was 3.4 ± 1.2. Motor subtypes were no subtype throughout (6%), hypoactive subtype throughout (28%), mixed subtype throughout (18%), hyperactive subtype throughout (10%) and variable subtype (38%). DRS-R98 Total and Severity scales differed significantly across categories (highest in mixed) but only motor, sleep-wake cycle, perceptual and language disturbance items differed. The Generalized Estimating Equations (GEE) approach was used to explore the relationship between subtype profile and symptoms, medication exposure and etiology. This showed that apart from motor items, only delusions, affective lability, metabolic disturbance and CVA related to any subtype. Cross-sectional assessments indicated greater use of benzodiazepine and antipsychotics in hyperactive patients but GEE analyses did not identify major associations between motor subtype and medication exposure. Patients with sustained hypoactive subtype were significantly more likely to die within one month of study entry.

Conclusions: Motor profile in delirium is relatively consistent over episode course and relates more closely to delirium phenomenology than to etiology or medication exposure. Motor subtypes have comparable disturbance of key diagnostic features such as cognitive and thought process abnormalities. Although mixed subtype is the most phenomenologically intense, hypoactives have the poorest prognosis.