Clinical and imaging characteristics of toxoplasmic encephalitis in patients with HIV/AIDS with different immune statuses

Abstract

Background: Toxoplasmic encephalitis (TE) is one of the most common opportunistic central nervous system infections in patients with acquired immunodeficiency syndrome (AIDS) and a major cause of death. Magnetic resonance imaging (MRI) serves as a key adjunct in the clinical diagnosis of TE. This study aimed to identify the MRI characteristics of TE in patients with human immunodeficiency virus (HIV)/AIDS across different immune statuses.

Methods: A retrospective analysis was conducted on the clinical and imaging data of hospitalized patients with AIDS and concurrent TE treated at two centers between January 2019 and December 2023. Patients were divided into three groups based on CD4⁺ T-cell count levels (<50, 50-100, and >100 cells/µL). The differences in MRI imaging features between patients with varying immune statuses were analyzed.

Results: A total of 41 patients were included, 82.9% had multiple lesions on MRI, and 203 lesions larger than 2 mm were identified. The lesions predominantly presented with nodular and ring-enhancing patterns, mainly distributed at the gray-white matter junction and the thalamus-basal ganglia region. In the comparison of MRI features between the three groups, patients with >100 CD4⁺ T cells/µL had a higher prevalence of nodular lesions and eccentric target lesions (both P<0.05). For patients with <50 CD4⁺ T cells/µL, larger lesions (>2 cm) were more frequently observed on MRI (P<0.05). Additionally, the <50 CD4⁺ T cells/µL group showed significantly elevated cerebrospinal fluid protein levels as compared to the other two groups (P<0.05).

Conclusions: In patients with HIV/AIDS with secondary TE, MRI findings varied in terms of lesion size and enhancement patterns according to the immune status of the patient. These imaging characteristics provide valuable guidance for the clinical diagnosis and treatment of TE.

Keywords: Toxoplasmosis; acquired immunodeficiency syndrome (AIDS); brain; human immunodeficiency virus (HIV); magnetic resonance imaging (MRI).

Figure 1

Neuroimaging findings in four patients with AIDS with confirmed cerebral toxoplasmosis. (A1-A4) Case 1: a 34-year-old male with right-sided limb movement disorder (25 CD4⁺ T cells/µL). (A1) Axial FLAIR: slightly hyperintense lesion (15 mm × 12 mm) in the right occipital lobe (white arrow). (A2) Axial T1WI: patchy hypointense signal in the same region. (A3) Axial T2WI: hyperintense signal with perilesional edema (FLAIR hyperintensity, arrow). (A4) Postcontrast T1WI: target-like enhancement (central hypointensity + eccentric nodular enhancement, arrow). (B1-B4) Case 2: a 35-year-old male with chronic headache (88 CD4⁺ T cells/µL). (B1) Axial FLAIR: slightly hyperintense lesion (18 mm × 14 mm) in the left frontal lobe with mass effect (arrow). (B2) Axial T1WI: patchy hypointense signal in the same region. (B3) Axial T2WI: heterogeneous hyperintensity (arrow). (B4) Postcontrast T1WI: classic target enhancement (arrow). (C1-C4) Case 3: the same patient as in Case 2 after treatment. A 35-year-old male with chronic headache (88 CD4⁺ T cells/µL). (C1) Axial FLAIR: markedly reduced lesion (8 mm × 6 mm) in the left frontal lobe with resolution of perilesional edema (arrow). (C2) Axial T1WI: hypointense signal at the lesion site. (C3) Axial T2WI: residual hyperintensity within the lesion (arrow). (C4) Postcontrast T1WI: thin-walled peripheral enhancement (arrow), indicating treatment response. (D1-D4) Case 4: a 31-year-old male with left hemiparesis (1 CD4⁺ T cell/µL). (D1) Axial FLAIR: large hyperintense lesion (27.2 mm × 23.5 mm) in the right temporal lobe with surrounding edema and midline shift (arrow). (D2) Axial T1WI: hypointense signal in the same region. (D3) Axial T2WI: high signal intensity within the lesion (arrow). (D4) Postcontrast T1WI: irregular ring enhancement with a wall thickness of 2–4 mm (arrow). (E1-E4) Case 5: a 42-year-old female with speech dysfunction (132 CD4⁺ T cells/µL). (E1) Axial FLAIR: hyperintense lesion (10 mm × 8 mm) in the left basal ganglia with surrounding edema (arrow). (E2) Axial T1WI: hypointense lesion with subtle marginal hyperintensity, suggesting possible focal hemorrhage within the toxoplasmic lesion (arrow). (E3) Axial T2WI: high signal intensity in the lesion (arrow). (E4) Postcontrast T1WI: dual enhancement patterns—target-like enhancement on the left and punctate foci on the right (arrows). AIDS, acquired immunodeficiency syndrome; CD4⁺ T, CD4-positive T lymphocytes; FLAIR, fluid-attenuated inversion recovery; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging.