Incidental Thalamic Lesions Identified on Brain MRI in Pediatric and Young Adult Patients: Imaging Features and Natural History

Abstract

Background and purpose: Nonspecific, localized thalamic signal abnormalities of uncertain significance are occasionally found on pediatric brain MR imaging. The goal of this study is to describe the MR imaging appearance and natural history of these lesions in children and young adults.

Materials and methods: This retrospective study evaluated clinically acquired brain MR imaging examinations obtained from February 1995 to March 2022 at a large, tertiary care pediatric hospital. Examinations with non-mass-like and nonenhancing thalamic lesions were identified based on term search of MR imaging reports. A total of 221 patients formed the initial group for imaging assessment. Additional exclusions during imaging review resulted in 171 patients. Imaging appearance and size changes were assessed at baseline and at follow-up examinations.

Results: A total of 171 patients (102 male) at a median age of 11 years (range: 1-23 years), 568 MR imaging examinations, and 180 thalamic lesions were included. Median time from baseline to the last follow-up MR imaging was 542 days (range: 46-5730 days). No lesion enhanced at any time point. On imaging follow-up, 11% of lesions (18/161) became smaller, 10% (16/161) resolved, 73% (118/161) remained stable, and 6% (9/161) increased in size at some point during evaluation. Median time interval from baseline to enlargement was 430 days (range: 136-1074 days).

Conclusions: Most incidental, non-mass-like thalamic signal abnormalities were stable, decreased in size, or resolved on follow-up imaging and are likely of no clinical significance. Surveillance strategies with longer follow-up intervals may be adequate in the management of such findings.

FIG 1.

Flow chart of study participant selection process. Conditions on right denote exclusion criteria.

FIG 2.

Example cases of incidental thalamic lesions identified in this study. A, Axial T2-weighted images of a 13-year-old adolescent girl with headache show a focal thalamic lesion (arrow) within the anterior lateral right thalamus on baseline MR imaging. The lesion was stable on the 3-month follow-up and resolved at 22-month follow-up. B, Axial T2-weighted images of a 9-year-old girl with headache show ill-defined thalamic signal (arrow) in the posterior right thalamus on baseline MR imaging. At 1-year follow-up, the lesion was slightly less defined and smaller. At 9-year follow-up, the lesion was smaller and less defined. This patient had 12 follow-up scans for this lesion over a 9-year period. C, Axial T2 FLAIR images of a 5-year-old girl after a single seizure episode. Baseline MR imaging shows a small focal signal abnormality in the right thalamus (arrow). This lesion slightly enlarged at 1-year follow-up and resolved at 18-month follow-up imaging.

FIG 3.

Example cases of enlarging incidental thalamic lesions identified in this study. A, Axial T2 FLAIR images of a 6-year-old boy with headache show a focal thalamic lesion (arrow) within the posterior left thalamus on baseline MR imaging. At 13 month follow-up, the lesion was enlarged. At 46-month follow-up, the lesion was more ill-defined and slightly decreased posteriorly. B, Axial T2 FLAIR images part of routine follow-up of a 4-year-old boy with history of right cerebellar complex developmental venous anomaly. Baseline MR imaging shows a small focus of increased signal in the posterior right thalamus, enlarged at 13-month follow-up, then stable 52 months after baseline MRI. C, Axial T2-weighted images of an 8-year-old girl with history of head trauma and headache showing a focal lesion within the left medial thalamus (7 × 5 mm). There was slow interval enlargement over 5 MR imaging studies for 19 months, at which point the lesion was classified as presumed low-grade glioma, and was treated with a total of 50.4 Gy fractionated radiation therapy over 8 weeks. Following therapy, there was a decrease in the site over subsequent 34 months.

FIG 4.

Growth trajectories of 9 thalamic lesions that enlarged at any time during follow-up MR imaging. Patient D, an 8-year-old girl with history of head trauma and headache, was treated with radiation therapy 19 months after initial lesion identification after growth identified with a subsequent decrease in size. Patient B, a 14-year-old adolescent boy with history of fetal alcohol syndrome and tethered cord, had additional stable follow-up examinations at 138 and 190 months (not shown).