Diffuse bilateral thalamic astrocytomas as examined serially by MRI

Abstract

We report the case of a 13-year-old girl with diffuse bilateral thalamic astrocytomas. Incoordination was observed at the onset. Cranial computed tomography (CT) showed enlarged thalami, and magnetic resonance imaging (MRI) revealed these lesions to be symmetrically enlarged with high intensity on the T2-weighted image. Owing to these atypical findings in the neuroimaging studies, we had difficulty in making the correct diagnosis of a brain tumor. After the diagnosis of diffuse bilateral thalamic astrocytomas was obtained, we performed hyperfractionated radiotherapy followed by chemotherapy. Radiation therapy was effective for a while, but the girl's condition deteriorated again and she died 8 months after admission. Although diffuse bilateral thalamic astrocytomas are difficult to diagnose because they do not resemble most other neoplasms on neuroimaging studies, pediatricians should keep this entity in mind in order to arrive at a precise and prompt diagnosis.

Neuroimaging of thalamic tumors in children

“…When an abnormal tumor signal involves both thalami or extends from the thalamus to infiltrate the brainstem, the striatum, the capsules, or even the paraventricular white matter, the lesion should be regarded as malignant even when completely homogeneous and lacking contrast enhancement. In particular, bilateral thalamic astrocytomas represent an uncommon but easily recognized condition that implies a poor prognosis [25], as confirmed in another paper in the current volume of this journal.…”

“…Since multifocal/multicentric tumors are commonly encountered, contralateral thalamic and other basal ganglia lesions [25] should be excluded and CSF seeding should be ruled out (on contrast-enhanced images) in cases with infiltration of the third ventricle (i.e., in germ cell/primitive neuroectodermal tumors and lymphomas) (Fig. 15).…”

“…It is based on the application of different imaging sequences (essentially T1-and T2-weighted images), and on intravenous contrast medium administration. Computed tomography (CT) is still preferred in emergencies and for distinctly detecting intratumoral calcifications, while iodine-enhanced studies should no longer be considered useful [24,25]. When faced with a suspected thalamic tumor, Flow-Attenuated Inversion Recovery (FLAIR) and heavily T1-weighted Inversion Recovery (IR) sequences should be added to conventional Spin Echo (SE) and Turbo-Spin Echo (TSE) sequences; thin slice (3 mm) FLAIR and IR images can be acquired with short acquisition times using the TSE option, improving the definition of lesion margins with adjacent CSF spaces (FLAIR) and critical deep structures such as internal capsule, midbrain nuclei and tracts, and other basal ganglia (IR).…”

“…They are predominantly astrocytic neoplasms [4] and their deep location makes them difficult to treat, mainly because surgery is rarely feasible [3,4,6,7,13,14,22]; despite the introduction of modern computer/imaging-assisted procedures (neuronavigation/computer-assisted volumetric resection), [13] substantial tumor removal remains unfeasible in most instances, while radiation therapy -with or without adjuvant chemotherapy [1,18] -is still considered to be the basic treatment. Thalamic neoplasms are slightly more common in children [1,25] than in adults and involve significant diagnostic, prognostic, and therapeutic problems. Modern neuroimaging techniques have substantially improved the possibilities of correct noninvasive characterization and staging of these deep-seated lesions, and they have provided optimal assistance for guiding stereotactic biopsy [13], neuronavigation and surgical attempts [5,19,22], and allowing a reliable evaluation of the effects of the applied therapy.…”

Pathology of Diencephalic Astrocytomas

“…Clinically, patients with these bithalamic astrocytomas can present decrements at the level of motor function [8, 26], subtle sensory deficits, or mental changes such as confusion, loss of attention and emotional disturbance [26]. These tumors are generally low grade at presentation, and produce remarkably symmetric areas of radiographic abnormality, in some cases with extension, equally symmetric, to the adjacent basal ganglia and midbrain [8, 27, 28](fig. 7).…”