Review Question - QID 104887

In a patient with HIV who is non-adherent to medical therapy, presenting with focal neurologic symptoms, and a contrast CT notable for a ring-enhancing lesion, raises suspicion for CNS toxoplasmosis. Given this patient's classic presentation and ring-enhancing lesion found on brain imaging, the next best step is to treat the toxoplasmosis with pyrimethamine-sulfadiazine.

CNS toxoplasmosis is caused by the intracellular protozoan, toxoplasmosis gondii. The parasite usually causes disease when an immunosuppressed person's CD4 cell count drops below 50 cells/mm3. Patients with toxoplasmosis encephalitis most commonly present with headache and fever, though focal neurologic findings are often present as well. The initial drug regimen of choice for active toxoplasmosis infections is sulfadiazine, pyrimethamine and leucovorin (to prevent drug-induced hematologic toxicity). There is a high probability that this patient has toxoplasmosis given this clinical scenario. A repeat non-contrast head CT would be used to track improvement. If there is no improvement after treatment, a biopsy would be needed to determine the etiology. If the patient were to not have HIV or immunosuppression, the next best step would be a biopsy.

Chu and Selwyn review complications of HIV, including CNS complications. They state that patients who have solitary lesions can present with headache or other focal deficits. Increased ICP from masses could result in visual disturbances, nausea, or altered consciousness. Moreover, patients with encephalitis generally present with fever, headache, altered mental status or seizure.

Luft and Chua reviewed CNS toxoplasmosis in HIV and found it to be the most common infectious cause of focal brain lesions. They emphasized the role of highly active antiretroviral therapy (HAART) and prophylaxis in preventing the infection, but also recommended empiric therapy with sulfadiazine and pyrimethamine for a presumptive diagnosis of toxoplasma gondii, though there may be a growing role for newer diagnostic tests, such as IgG titers and PCR.

Figure A is a CT with contrast showing a ring-enhancing lesion in the left frontal lobe - a radiographic finding highly suspicious for cerebral toxoplasmosis. Such a lesion would give upper motor neuron signs on the contralateral side. Also, the borderline midline shift may or may not give signs of altered consciousness.

Incorrect Answers:
Answer 1: Biopsy would be the next best step in management for a immunocompetent patient that does not have HIV since this lesion could be lymphoma, toxoplasmosis, malignancy or another cause such as neurocysticercosis. A lack of response to pyrimethamine-sulfadiazine in this patient raises suspicion for CNS lymphoma and a biopsy would be needed.
Answer 2: Though prion disease presents with altered mental status and personality changes, the abnormal findings on imaging are not consistent with prion disease. The 14-3-3 protein is a high yield association with Creutzfeldt-Jakob disease.
Answer 4: Brain imaging in neurocysticercosis reveals non-enhancing cysts and calcified lesions may also be present. That being said ring enhancing lesions can be seen and can look similar to neurocysticercosis. Seizure is common, as well as headache, visual complaints and changes in sensorium. Albendazole with steroids is the treatment for neurocystercycosis.
Answer 5: While always a concern in HIV patients, behavorial or personality changes would be more characteristic of HSV. An MRI will typically show diffuse edema with occasional necrosis of temporal and frontal lobes, along with a characteristic aseptic picture in CSF. Acyclovir is the best treatment for a CNS HSV infection.