Unawareness of illness in neuropsychiatric disorders: phenomenological certainty versus etiopathogenic vagueness

Awareness of illness is a form of self-knowledge concerning information about the pathological state, its functional consequence, and the way it affects the patient and his interaction with the environment. Unawareness of illness has raised much interest for its consequences on compliance with treatment, prognosis, and the patient's quality of life. This review highlights the great complexity of this phenomenon both at phenomenological and etiopathogenic levels in stroke, traumatic brain injury, psychosis, dementias, and mood disorders. In particular, the clinical expression is characterized by failure to acknowledge being ill, misattribution of symptoms, and noncompliance with treatment. Unawareness of illness may also be linked with characteristics that are peculiar to each individual disturbance, such as symptom duration and cognitive impairment. Despite a long-lasting interest in the clinical characteristics of unawareness, only recently has the focus of research investigated pathogenic mechanisms, with sometimes controversial results. The vast majority of studies have pointed out a remarkable involvement of the right hemisphere. Specifically, functional and structural changes of the dorso-lateral prefrontal cortex and some other frontal areas have often been found to be associated with awareness deficit, as well as parieto-temporal areas and the thalamus, although to a lesser extent. These data indicate the present difficulty of localizing a specific cerebral area involved in unawareness and suggest the existence of possible brain circuits responsible for awareness. In conclusion, phenomenological manifestations of poor awareness are well outlined in their complexity, whereas neuroanatomic and neuropsychological findings are still too vague and sparse and need further, greater efforts to be clarified.