Psychosis Due to Neurologic Conditions.

Psychosis arises with considerable frequency in a number of neurologic conditions. The treatment of such patients is often challenging, as many of the treatments for psychosis pose some risk of worsening the underlying neurologic condition. Although psychosis may emerge in the context of any neurologic condition that sufficiently disrupts the functioning of or connections between limbic, paralimbic, frontal, subcortical areas mediating complex sensory perception, interpretation, and thought or language organization, secondary psychoses are most often encountered in patients with Alzheimer's disease (Parkinson's disease receives dopaminomimetic therapies) and epilepsy. Psychosis, and particularly delusions and visual hallucinations, may arise in Alzheimer's disease. Based on the available literature, the first-line therapy for this problem is risperidone 0.5 to 3 mg per day. If this treatment proves unsuccessful, low-dose haloperidol or olanzapine should be considered next. If these treatments prove unsuccessful, quetiapine should then be considered. Finally, clozapine may be useful for treatment-refractory psychosis due to Alzheimer's disease, but due caution is warranted given its considerable anticholinergic properties and potential for worsening cognition in these patients. Although disease-emergent psychosis (paranoid delusions and visual hallucinations) may develop in patients with Parkinson's disease, psychosis due to dopaminomimetic therapy is much more common. When such symptoms develop, the accepted first step is to taper anti-parkinsonian medications were possible. Anticholinergic medications, amantadine, selegiline, and dopamine receptor agonists should be reduced or discontinued, provided that the patient can tolerate changes in motor symptoms attendant to such reductions. When these reductions are not feasible or fail to improve treatment-emergent psychosis, low-dose quetiapine or clozapine may be useful. The greatest body of evidence supports the effectiveness of these treatments and their relative lack of adverse effects on motor function. When psychosis develops in the context of epilepsy, the generally accepted first step is to maximize anticonvulsant therapy in an effort to reduce the possible contribution of electrophysiologic disturbances in the described areas to psychotic symptoms. When interictal psychosis persists despite such adjustments, initiation with low-dose atypical antipsychotics carries the least risk of lowering seizure threshold and should be considered.