From the Guidelines
Diagnosis of neurotoxoplasmosis typically involves a combination of clinical symptoms, serologic evidence of infection, and imaging studies of the brain.
Key Diagnostic Tests
- Serum IgG may define those at risk for reactivation disease 1
- CSF PCR has a lack of sensitivity and standardization, but can be used in some cases 1
- MRI shows multiple ring-enhancing lesions in patients with AIDS, and can confirm basal ganglia lesions in the majority of patients 1
- CT scan may indicate multiple, bilateral, ring-enhancing lesions in CNS toxoplasmosis, especially in the basal ganglia and cerebral corticomedullary junction 1
- Brain biopsy can provide a definitive diagnosis, but is typically reserved for cases where empiric treatment has failed or there is early neurologic deterioration 1
Additional Diagnostic Considerations
- A presumptive diagnosis of CNS toxoplasmosis can be made based on clinical symptoms, serologic evidence of infection, and the presence of a space-occupying lesion on imaging studies of the brain 1
- Negative serology does not exclude the diagnosis, as cases of Toxoplasma encephalitis have been reported in persons without Toxoplasma-specific IgG antibodies 1
- F-fluoro-2-deoxyglucose-positive emission tomography can be helpful in distinguishing Toxoplasma abscesses from primary CNS lymphoma, but the accuracy is not high and this test is not widely available 1
From the Research
Diagnostic Tests for Neurotoxoplasmosis
The diagnosis of neurotoxoplasmosis can be achieved through various tests, including:
- Magnetic Resonance Imaging (MRI) to detect brain lesions and evaluate treatment response 2
- Computerized Tomography (CT) scans to identify brain lesions, although CT scans may not be as sensitive as MRI 3
- Susceptibility-weighted imaging (SWI) to detect intralesional susceptibility signal (ISS) foci, which are present in the vast majority of neurotoxoplasmosis patients 4
- Real-time PCR of cerebrospinal fluid to detect Toxoplasma gondii DNA, which has high specificity and good sensitivity 5
- Intrathecal synthesis of specific IgG antibodies against Toxoplasma gondii, which can be detected in the cerebrospinal fluid and has high specificity for the diagnosis of neurotoxoplasmosis in AIDS patients 6
Laboratory Tests
Laboratory tests that can aid in the diagnosis of neurotoxoplasmosis include:
- Serum tests for Toxoplasma gondii IgG antibodies, which can indicate past or present infection 2, 6
- Cerebrospinal fluid analysis for Toxoplasma gondii IgG antibodies, which can indicate local production of antibodies in the central nervous system 6
- Real-time PCR of cerebrospinal fluid to detect Toxoplasma gondii DNA, which can confirm the diagnosis of neurotoxoplasmosis 5
Imaging Characteristics
Imaging characteristics of neurotoxoplasmosis include:
- Ring-enhancing lesions on MRI, which are characteristic of neurotoxoplasmosis 2, 4
- Intralesional susceptibility signal (ISS) foci on SWI, which are present in the vast majority of neurotoxoplasmosis patients 4
- Hyperintense FLAIR foci, which are common in neurotoxoplasmosis patients 4
- Enhancing foci on CE-T1WI, which are also common in neurotoxoplasmosis patients 4