Abstract
A 37-year-old man with underlying systemic lupus erythematosus and lupus nephritis presented with an episode of generalized tonic seizure. He complained of poor concentration and forgetfulness for 1 week. He suffered a relapse of lupus nephritis 4 months ago and received a course of intravenous methylprednisolone followed by oral prednisolone and mycophenolate mofetil. Clinically, there was no focal neurological deficit. Retroviral screening was negative. Magnetic resonance imaging (MRI) of the brain revealed eccentric and concentric signs which confirmed the diagnosis of cerebral toxoplasmosis.
Keywords: cerebral toxoplasmosis, concentric sign, eccentric sign
A 37-year-old man with underlying systemic lupus erythematosus and lupus nephritis presented with an episode of generalized tonic seizure. He complained of poor concentration and forgetfulness for 1 week. He suffered a relapse of lupus nephritis 4 months ago and received a course of intravenous methylprednisolone followed by oral prednisolone and mycophenolate mofetil. Clinically, there was no focal neurological deficit. Blood investigations revealed leucocytosis of 16.1 × 109/L with neutrophilia, normal erythrocyte sedimentation rate and negative retroviral screening. Lumbar puncture was not performed due to increased intracranial pressure. Toxoplasma gondii IgG was subsequently detected in the serum. Magnetic resonance imaging (MRI) of the brain showed eccentric and concentric signs which confirmed the diagnosis of cerebral toxoplasmosis. (Figure 1) There were marked clinical and radiological improvement following 6-week treatment of pyrimethamine and clindamycin.
Figure 1.
Axial view of MRI brain. (A) A ring-enhanced lesion with eccentric nodule was seen in the left occipital region on post-gadolinium T1 weighted sequence. (B) On T2 weighted sequence, the right parietal lesion showed concentric alternating zones of hypointensity and hyperintensity.
Cerebral toxoplasmosis is a common opportunistic infection in immunocompromised patients. The diagnosis can be challenging as the clinical features and neuroimaging often mimic other conditions such as cerebral abscess, tuberculoma or lymphoma. Brain MRI has become the key investigation as it may reveal certain characteristics of cerebral toxoplasmosis. The common locations affected are basal ganglia and corticomedullary junctions. Postcontrast T1 weighted “eccentric target sign” is highly suggestive of cerebral toxoplasmosis although it is found in less than 30% of cases. It has an eccentric enhancing nodule, surrounded by an intermediate hypointense zone and a peripheral hyperintense enhancing rim.1 Additionally, “concentric target sign” has been described as a more specific sign for cerebral toxoplasmosis.2 This focal lesion has 3 alternating zones of hypo- and hyperintensities on T2 weighted sequence.
Cerebral toxoplasmosis is commonly seen in patients with retroviral disease. However, it can occur in any immunocompromised individual. We demonstrate the importance of recognizing these characteristic signs in order to avoid unnecessary surgical procedures and initiate treatment early.
Footnotes
Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
ORCID iD: Chen Fei Ng 
https://orcid.org/0000-0003-2540-9905
References
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