Organic Psychosis

Always consider an organic cause for psychosis, especially on first presentation.

Suspecting an organic cause

• Cognitive dysfunction is present.
• A general medical disorder is present (e.g. SLE).
• The presentation is atypical for a primary psychiatric illness (age of onset, clinical features).
• Resistance to standard treatment.

Neuropsychiatric assessment

Psychiatric and cognitive assessment; medical history (past and family); detailed mental state exam; physical/neurological examination. Investigations as indicated: haematology, chemistry, immunology (e.g. ANA, ENA, anti-CCP), endocrine work-up, electrophysiology (EEG, evoked potentials), neuroimaging (CT, MRI, PET, SPECT).

Differential diagnosis

Short list: brain tumour/cyst; dementia (including Alzheimer’s); degenerative brain disease (Parkinson’s, Huntington’s) or a chromosomal disorder; HIV or another CNS infection; some epilepsies; stroke; delirium.

By presenting symptom:

Presentation	Causes to consider
Delusions	CNS disease (cerebrovascular disease, Parkinson’s, MS, temporal lobe epilepsy, neoplasm, HIV); drugs (stimulants, corticosteroids, dopaminergic agents, cannabis); endocrine (Cushing’s, hypo-/hypercalcaemia, thyroid disease, hypopituitarism); connective tissue disease (SLE, temporal arteritis); porphyria; heavy metal toxicity
Visual hallucinosis	Ocular pathology (cataracts, macular degeneration); optic neuritis; brainstem or cerebral hemispheric lesions (incl. epilepsy); migraine; narcolepsy; delirium; toxins/hallucinogens; schizophrenia/mood disorder; normal variants (hypnagogic states, sensory/sleep deprivation, imaginary companions, autoscopy)
Auditory hallucinations	Deafness; brainstem or cerebral (temporal neocortex, epilepsy) pathology; alcohol withdrawal; schizophrenia/mood disorder; normal variants (hypnagogic, deprivation)
Depression	Drugs (antihypertensives, corticosteroids, stimulant withdrawal); CNS disease (cerebrovascular disease, Parkinson’s); endocrine (hypothyroidism, Cushing’s); viral illness (hepatitis, influenza); malignancy (pancreatic, chest, lymphoma); B12 deficiency; SLE
Mania	Drugs (stimulants, corticosteroids, antidepressants, ECT, dopamine agonists, sympathomimetics); CNS disease (temporal lobe epilepsy, MS, neoplasm, neurosyphilis, trauma); hyperthyroidism
Generalised anxiety	Endocrine/metabolic (hyperthyroidism, phaeochromocytoma, fasting hypoglycaemia, hypercortisolism); intoxication (caffeine, stimulants) or withdrawal (alcohol, sedatives); CNS disease (tumour, trauma, cerebrovascular/Parkinson’s/Huntington’s disease, MS, epilepsy); cardiopulmonary (PE, COPD, AMI); aspirin toxicity; brucellosis