Question of the Week # 87

Q87) A 42 year old african-american man is admitted to hospital with acute seizures. Seizures were appropriately controlled in the ER and the patient currently, in post-ictal confusion. He is unable to give further history. However, a review of the old records reveal that the patient has history significant of Chronic HIV infection. He also has a history of IV drug use. As per his sister, the patient has been compliant with Highly active anti-retroviral therapy and prophylactic medications for Pneumocystis jiroveci and Mycobacterium Avium Complex for the past one year. His recent CD4 count 1 month ago was 45. On physical examination, he is afebrile with a blood pressure of 120/60.  He is confused. Reflexes are intact. Electrolytes and CBC are with in normal limits. Urine drug screen is negative. A non-contrast CT scan did not not reveal any bleed. A CT scan with IV contrast reveals a 4 cm ring – enhancing lesion in left cerberal hemisphere. A  subsequent MRI brain confirmed the findings on the CT. There is no mass effect. Next step in approaching this patient ?

A. Stereotactic Brain Biopsy

B. Start emperic Toxoplasma therapy.

C. Obtain Toxoplasma Serology ( IgM and IgG)

D. PCR for Papova Virus JC

E. Emperic therapy for CNS tuberculosis.

15 Responses

  1. bbbbbbbbbbbbbbbbbbb

  2. The answer is C. Anyone can explain why the ans is C and not B?

  3. OK
    you do that but you should start tx until the results come back.
    It doesnt hurt to tx and u can change your treatment if its not toxo.

  4. The patient has a ring-enhancing lesion. In developed countries such as the US, the most common causes include toxoplasma and CNS lymphoma. About 10% of general population has toxoplasma antibody; so a positive serology is not confirmatory. So, empiric treatment with sulfadiazine & pyrimethamine. After 10-14 days, a repeat CT/MRI is done. If the size of the lesion is reduced, then continue initial treatment; otherwise treat for CNS lymphoma.

    • very good clinical approach but old : (, The Lack of IgG and IgM may exclude infection–CDC: The sensitivities and specificities of the commercially available IgM and IgG tests vary substantially.-no need to wait 14 days to see if the mass decrease in size; this does not exclude that the parasite has resistant to medication and keeps on growing even though correct medication so you need a different non invasive method of Dx 1st Obtain Toxoplasma Serology ( IgM and IgG)–if negative its CNS lymphoma

      • the serology IgG and IgM tests are highly sensitive with high negative predictive value, but the test is NOt specific, so negative serology effectively R/O toxomasplosis , then can proceed with brain biopsy for lymphoma and subsequent treatment, you still need to do a brain biopsy with -ve serology to confirm diagnosis of lymphoma

  5. B. Treat x2wks then repeat CT head. If shrinking, continue Tx, if not shrinking, do brain lesion biopsy to r/o lymphoma.

  6. Dr red, please explain why you said c? We all think it is b. Treat first then get serology.

  7. PCP prophylaxis means he was already on TMP-SMX, which should have concurrently reduced his risk of developing Toxoplasmosis. Checking titers would help quickly decide if we want to continue treating for Toxoplasmosis or if serology is negative, maybe we should look into other etiologies (eg CNS lymphoma).

  8. Im not sure if there is a mistake in the answer to this questions, but I thought most people with TE are seropositive for anti-toxoplasma IgG antibodies and that is why we first treat empirically. Also, refer to uptodate.

  9. interesting question. It all revolves around pretest probability. I would argue that it is high % in this case given imaging and presentation, any side-effect of treatment outweighs the potential delay of obtaining the test (IgG)

    • Good thinking but missing a CNS lymphoma is not to be allowed either. A positive serology is not specific to active Toxoplasma but the negative predictive value of negative serology is very high. If Toxoplasma antibodies are negative –> go with biopsy. If Toxo serology is positive, this adds more weight to the presentation and clinical picture where you can start empiric antibiotics and can wait to see if the lesion regresses. If it does not after a few days, need stereotactic biopsy at that time.

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