Aetiologies of altered states of consciousness: a prospective hospital-based study in a series of 464 patients of northern Tanzania.

BACKGROUND: Empirical knowledge suggests that altered states of consciousness are common in sub-Saharan Africa. However, to date prevalence studies are scarce.
METHODS: The study was conducted at the Haydom Lutheran Hospital in northern Tanzania. Over a period of eight months all patients with altered states of consciousness were seen prospectively by a neurologist. The study population was subdivided into patients with acute confusional states (ACS) and those with impairment of consciousness (IOC).
RESULTS: Out of 768 patients with neurological/psychiatric diagnoses 464 patients (60.4%) with altered states of consciousness were admitted. 159 patients had ACS (20.7%) and 447 IOC (58.2%). The diagnoses were not mutually exclusive. The most frequent aetiologies were of non-infectious origin. In patients with ACS, non-infectious encephalopathy, psychiatric disorder and dementia made up for 13.8%, 7.6% and 6.9%, respectively. In 25.2% of the cases with ACS, the reason remained obscure. In patients with IOC, the leading causes were epileptic seizures (febrile seizures 20.6% and epilepsy 13.9%) and head trauma 13.9%. Both ACS and IOC carried a bleak prognosis with 26% and 27% in-hospital mortality, respectively.
INTERPRETATION: The above data emphasize that altered states of consciousness contribute substantially to morbidity and mortality in a rural African hospital. In our study sample, non-infectious causes represented the leading aetiologies although HIV testing was not available at the time of the study.