What is the role of MRI in a young to middle-aged adult from an area with poor sanitation, presenting with psychosis associated with typhoid fever, and recent travel history to endemic areas or exposure to contaminated food or water?

MRI Findings in Typhoid-Associated Psychosis

Primary Recommendation

In patients with psychosis associated with typhoid fever, MRI of the brain without and with IV contrast should be performed to evaluate for CNS infection, encephalitis, and other organic causes, as MRI has superior sensitivity for detecting subtle inflammatory changes, small infarcts, and infectious complications that may be missed on CT. 1

Imaging Approach

Initial Imaging Strategy

• MRI is preferred over CT as the initial neuroimaging modality when typhoid-associated psychosis is suspected, particularly in clinically stable patients where CNS infection or inflammatory complications are being considered 1

• MRI without and with IV contrast is the optimal protocol when intracranial infection, inflammatory lesions, or encephalitis are suspected in the context of typhoid fever 1

• MRI demonstrates higher sensitivity than CT for detecting encephalitis, small infarcts, and subtle cases of subarachnoid hemorrhage that may complicate typhoid fever 1

When CT May Be Used First

• Non-contrast head CT is appropriate as a first-line test only in unstable patients or when rapid exclusion of acute hemorrhage, mass effect, or hydrocephalus is needed before proceeding to MRI 1

• CT has limited sensitivity for detecting the subtle inflammatory changes and early infectious complications that can occur in typhoid-associated neuropsychiatric manifestations 1

Expected MRI Findings in Typhoid Psychosis

Common Patterns

While specific MRI findings in typhoid psychosis are not well-characterized in the guideline literature, the clinical context suggests:

• Normal MRI is possible in many cases of typhoid psychosis, as the condition may represent a toxic-metabolic encephalopathy without structural brain changes 2

• Nonspecific edema or inflammatory changes may be present when encephalitis complicates typhoid fever 1

• Temporal lobe involvement should prompt consideration of encephalitis, which is a recognized complication of typhoid fever 1

Specific Findings to Evaluate

• Basal ganglia and/or thalamic involvement may be seen in certain infectious encephalitides and should prompt consideration of systemic infection including typhoid 1

• Brainstem lesions can occur with infectious complications and may correlate with neurological deficits 1

• Space-occupying or ring-enhancing lesions would suggest abscess formation or other focal infectious complications requiring urgent intervention 1

Clinical Context and Diagnostic Algorithm

Key Clinical Features

• Psychotic symptoms in typhoid fever can present as confusional states, delirium, acute psychosis, or various psychiatric manifestations, with neuropsychiatric complications reported in up to 50% of cases in some series 3, 4

• Fever may appear late in the clinical course, with psychotic symptoms sometimes preceding obvious systemic signs of typhoid infection 4

• Level of consciousness is critical to assess: if consciousness is impaired or fluctuating, this represents delirium (a medical emergency) rather than primary psychosis, requiring urgent investigation for the underlying cause 5

Complementary Investigations

• Blood cultures remain the gold standard for diagnosing typhoid fever, with highest yield within the first week of symptoms 1

• CSF analysis should be performed if encephalitis or CNS infection is suspected, including opening pressure, cell count with differential, protein, glucose, Gram stain, and bacterial culture 1

• Serum testing should include routine blood cultures, and consideration of paired acute and convalescent serology 1

Critical Pitfalls to Avoid

Diagnostic Errors

• Do not assume primary psychiatric illness without excluding organic causes, as up to 46% of patients with psychiatric symptoms have an underlying medical disease that is causative or exacerbating 5

• Do not rely on CT alone when encephalitis or subtle infectious complications are suspected, as CT has poor sensitivity for these conditions 1

• Do not delay imaging in patients with focal neurological deficits, altered consciousness, or atypical features, as these suggest structural or infectious complications requiring urgent evaluation 1, 5

Management Considerations

• Visual hallucinations are the strongest indicator of a medical cause rather than primary psychiatric disorder and should prompt aggressive investigation for organic etiology 5

• Neurological examination findings such as reduced muscle tone, ataxia, or cerebellar signs may accompany typhoid psychosis and warrant neuroimaging 2, 6

• Treatment of the underlying typhoid infection with appropriate antibiotics (ceftriaxone preferred for empiric therapy given fluoroquinolone resistance) is the definitive management, with resolution of psychotic symptoms typically following successful antimicrobial therapy 1, 2