General Discussionscerebral toxoplasmosis and primary CNS lymphoma

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cerebral toxoplasmosis and primary CNS lymphoma

Unread post by thuraiaibrahim » 28 Dec 2012, 00:47

A 44-year-old man who is known to have HIV is admitted to the Emergency Department following a seizure. He has been taking antiretroviral therapy for the past two years. A CT scan (without contrast) shows a solitary lesion in the basal ganglia. What is the most effective method to help differentiate between lymphoma and toxoplasmosis?

A. MR spectroscopy
B. CT with contrast
C. Thallium SPECT
D. Peripheral blood film
E. Lumbar puncture
Answer: C.
Differentiating between toxoplasmosis and lymphoma is an important aspect of managing neurocomplications relating to HIV. Given the more limited availablity of SPECT compared to CT many patients are treated empirically on the basis of scoring systems, for example there is a 90% likelihood of toxoplasmosis if all of the following criteria are met:

* toxoplasmosis IgG in the serum.
* CD4 < 100 and not receiving prophylaxis for toxoplasmosis.
* multiple ring enhancing lesions on CT or MRI.
Features that favour primary CNS lymphoma include:

single lesion
subependymal spread
solid enhancement
Thallium SPECT positive
MRS : increased choline (Cho)
MR perfusion : increased rCBV=cerebral blood volume

Features that favour cerebral toxoplasmosis include:

multiple lesions
scattered though basal ganglia an corticomedullary junction
ring or nodular enhancement
Thallium SPECT negative
MRS : decreased choline (Cho)
MR perfusion : decreased rCBV
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