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Q1: What is the differential diagnosis in this patient?
The differential diagnosis of HIV patients presenting with focal neurological deficits should include disorders such as toxoplasmosis, primary central nervous system lymphoma, cerebral Chagas’ disease, progressive multifocal leucoencephalopathy (PML), central nervous system tuberculosis, and cryptococcosis.1
Q2: What are the computed tomography and mri findings?
Computed tomography of the head (fig 1; see p356) shows well defined hypodense areas in the white matter in bilateral posterior parietal regions and in the right temporoparietofrontal region without areas of enhancement or mass effect. Figure 2A (see p356) shows the gadolinium enhanced T1 sagittal MRI of the brain showing non-enhancing white matter changes. Figure 2B (see p356) shows the T2 weighted coronal MRI showing white matter changes without mass effect. The findings of non-enhancing white matter lesions with typical increased T2 and decreased T1 signals on MRI head are highly suggestive of PML.2
Q3: How is the diagnosis confirmed?
Though the definitive diagnosis of PML depends on identification of characteristic neuropathological abnormalities on brain biopsy, it is not necessary to confirm the diagnosis.3 Neuroimaging is most helpful in diagnosis with typical computed tomography and MRI findings as described above, MRI being more sensitive than computed tomography. Recently polymerase chain reaction amplification of JC virus DNA from the cerebrospinal fluid has become the favoured diagnostic modality to confirm the diagnosis.4
The neurological infections commonly presenting in HIV1 are toxoplasmosis, cryptococcal meningitis, PML, while the less common ones are central nervous system tuberculosis, syphilis, cytomegalovirus, HTLV, acanthamoeba, or naeglaria. Among the neoplasms, primary central nervous system lymphoma is the more common entity in HIV positive individuals.
Toxoplasmosis is one of the most common secondary central nervous system infections in AIDS presenting late at CD4+ counts <200/μl. The most common clinical presentation is fever, headache, with focal neurological deficits. The diagnosis is suspected on finding multiple ring enhancing lesions on MRI head and positive serology for Toxoplasma gondii. Definite diagnosis is by brain biopsy. Trypanosomiasis or Chagas’ disease may present in HIV patients as acute meningoencephalitis with fever, vomiting, seizures, and focal neurological signs. Lesions appear on MRI as single or multiple hypodense ring enhancing lesions mainly in the subcortical areas. Cryptococcal meningitis is one of the leading neurological complications in HIV patients and generally occurs in patients with CD4+ T cell counts <100/μl. The diagnosis is confirmed by identifying organisms in the cerebrospinal fluid on India ink examination or by detection of cryptococcal antigen. Central nervous system tuberculosis in the form of tubercular meningitis or tuberculomas is common in HIV patients and may present with focal deficits. Computed tomography findings show prominent leptomeningeal and basal cistern enhancement or rim enhancing granulomas. Cerebrospinal fluid analysis often helps in establishing the diagnosis.
PML, caused by JC virus, a human papilloma virus, is an important neurological manifestation in patients with AIDS. It is a subacute demyelinating disease of the central nervous system and is caused by reactivation of the latent JC virus in presence of underlying immunosupression. Since the onset of AIDS epidemic, HIV infection has become, by far, the most common risk factor for the disease and currently more than 60% cases of PML occur in patients with AIDS. It commonly occurs in the setting of advanced immunosuppression and only infrequently heralds AIDS.5–7 However in this patient, PML was the initial and the only manifestation of AIDS.
Patients most often present with visual deficits, motor weakness, or other focal neurological deficits with or without changes in sensorium. Neuroimaging is most helpful in diagnosis with MRI typically revealing multiple non-enhancing white matter lesions, predominantly in the occipitoparietal areas. Yan Geisen et al have laid down diagnostic criteria on the basis of epidemiological, neuroradiological, and cerebrospinal fluid parameters to make the clinical diagnosis of PML.3 Recently polymerase chain reaction amplification of JC virus DNA from the cerebrospinal fluid has become the favoured diagnostic modality to confirm the diagnosis.4
Currently, outlook for patients with PML is poor and there is no effective treatment. Few authors have reported promising results with HAART treatment.8,9 Recently treatment with cidofovir has been tried in such patients with varying results.10 Mean survival time after diagnosis is about six months.
Progressive multifocal leucoencephalopathy in AIDS.