|Year : 2006 | Volume
| Issue : 2 | Page : 66-69
Bilateral thalamic glioma: Report of four cases and review of literature
Girish Menon1, S Nair1, T Krishnamoorthy2, RN Bhattacharya1
1 Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
2 Department of Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
Department of Neurosurgery, SCTIMST, Trivandrum - 695 011
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Primary thalamic tumors are rare and bilateral thalamic tumors are even rarer. The incidence, clinical manifestations, natural history and prognosis of primary bilateral thalamic gliomas (PBTT) remain relatively obscure. In this article, four cases of bilateral thalamic gliomas are discussed and the available literature is reviewed. We conclude that primary bilateral thalamic tumors are distinct lesions, as proven by their specific neuroradiological and metabolic properties, unresponsiveness to radiotherapy and chemotherapy as well as a rapidly fatal clinical evolution. Early diagnosis and prompt therapy may delay the devastating effects of this tumor.
Keywords: Bilateral thalamic gliomas.
|How to cite this article:|
Menon G, Nair S, Krishnamoorthy T, Bhattacharya R N. Bilateral thalamic glioma: Report of four cases and review of literature. J Pediatr Neurosci 2006;1:66-9
| Introduction|| |
Primary thalamic tumors are rare and bilateral thalamic tumors are even rarer.,, Although the morphological features of primary bilateral thalamic tumors (PBTTs) are quite typical, characterized by the nearly symmetrical enlargement of both thalamic nuclei without any apparent interconnecting tumoral tissue, their incidence, clinical manifestations, natural history and prognosis remain relatively obscure. In this report, we describe four cases of bilateral thalamic tumors - three patients with PBTT and the fourth patient a case of unilateral thalamic tumor with secondary involvement of opposite thalamus - with the goal of studying the differences between the two patterns of bilateral thalamic involvement.
| Case Reports|| |
In the last 2 years, four cases of bilateral thalamic gliomas were surgically managed in our department. While three of them presented as primary bilateral thalamic tumors, in the fourth child the opposite thalamus got involved at a later stage of the disease. Age, sex, clinical presentation at admission, results of neuroimaging studies, modalities of treatment and outcomes of these four children are reported to analyze the difference between primary and secondary bilateral thalamic tumors.
A 23-year-old male presented with raised intracranial pressure symptoms of 1-month duration. He also gave a background history of having taken psychiatric treatment for manic-depressive psychosis (MDP) for the last 3 years. Soon after admission, he had a relapse of manic phase of MDP and required aggressive antipsychotic treatment before surgery. Examination revealed papilledema, bilateral abducens nerve palsy and gaze-evoked nystagmus. MRI [Figure - 1] showed a hyperintense infiltrative lesion with ill-defined borders on T2-weighted axial images, involving the medial aspects of bilateral thalami and bilateral pulvinar involvement was also noted. Left thalamus was more involved than the right, which was better appreciated on proton density (PD) weighted images. On T1-weighted images, the lesion appeared iso-intense to mildly hypointense to the adjacent brain parenchyma. No enhancement was seen on gadolinium administration. There was evidence of obstructive hydrocephalus. He underwent endoscopic third ventriculostomy with tumor biopsy and was referred for adjuvant radiotherapy. Follow-up MRI 18 months after treatment revealed slight increase in the size on the left side, but the size of the ventricular system had come down. Clinically the patient had remained static for the last 18 months.
This 17-year-old male presented with a 2-month history of raised intracranial pressure symptoms associated with left-sided weakness. Neurological examination revealed papilledema with UMN type of weakness of left half of the body and the face. MRI revealed diffuse infiltrating mass involving bilateral thalamus with extension into the thalamocapsular region on the right side.
Asymmetric hydrocephalus was observed. He underwent endoscopic biopsy of the lesion; and septostomy, followed by a right ventriculoperitoneal shunt. He is currently undergoing radiotherapy.
This 8-year-old girl presented with features of raised intracranial pressure of 2 months' duration. Neurological examination was normal except for papilledema. MRI brain revealed features of bilateral thalamic lesion, appearing hypointense on T1W, hyperintense on T2W and FLAIR. Contrast images showed lack of enhancement of the lesion. There was evidence of mild hydrocephalus. The girl underwent stereotactic biopsy of the lesion, which was reported as low-grade astrocytoma grade II. She was subsequently referred to radiotherapy.
This 15-year-old boy, a juvenile diabetic on human insulin, presented with features of raised ICT, gait unsteadiness and visual blurring in June 2003. On admission, neurological examination revealed papilledema, left lateral rectus palsy and left UMN facial paresis. A complete blood cell count, serum chemistries and other extensive laboratory tests were unremarkable. Subsequent MRI showed the presence of a mass involving the medial surface of right thalamus, showing heterogeneous, hypointense signals on T1 W I and hyperintense on T2 W and PD images [Figure - 2]. No contrast enhancement was observed.
He underwent decompression of the tumor through an interhemispheric transcallosal approach along with right ventriculoperitoneal shunt. Postoperative CT scan revealed evidence of residual lesion with decrease in hydrocephalus [Figure - 3]. Histopathological examination revealed a diagnosis of grade II fibrillary astrocytoma, following which he was advised to undergo radiotherapy. One year later, he was readmitted with features of hypoglycemic encephalopathy, which responded to correction of the metabolic parameters. He did reasonably well until June 2005, when he was readmitted again with features of altered sensorium, progressive gait unsteadiness and urinary incontinence. A repeat MRI [Figure - 4] showed the mass to have grown considerably in size and to have infiltrated the entire left thalamus. Anteriorly the mass was seen extending through bilateral hypothalamus to involve the optic chiasm, tracts and intracranial segments of the optic nerves. Inferiorly it was extending to the midbrain, bilateral superior and inferior cerebellar peduncles and the pons. Also, there was involvement of bilateral cerebellar white matter in continuity with involvement of the cerebral peduncles. Heterogeneous enhancement of the thalamic mass was seen on the post-contrast images. His level of consciousness continued to deteriorate. He was referred for further adjuvant therapy after explaining the guarded prognosis to his parents.
| Discussion|| |
Primary tumors of the thalamus account for only 1-1.5% of all intracranial tumors and approximately 25% of them arise in children aged 15 years or under. However, their actual incidence has not yet been established and two recent reports provide figures ranging from 0.84 to 5.2%, of all intracranial tumors. This broad discrepancy in incidence is mainly related to the difficulty in differentiating primary thalamic tumors from those lesions that only secondarily involve thalamic structures originating primarily from cerebral hemispheres, caudate nuclei, pineal gland and brain stem. On the other hand, PBTTs are considerably less common,,,,,,, and less than 50 case reports have been published so far in the literature.
Bilateral thalamic tumors have typical clinicoradiological features and are considered to be distinct from unilateral tumors. However, the existence of PBTTs, i.e., bilateral onset of a neoplastic process at the level of both thalami, is not widely accepted. Some authors consider bilateral involvement of thalamic nuclei to be the result of the spreading of a glioma from either of the sides to the other, a phenomenon seen in up to one-third of patients with unilateral thalamic tumors, especially in the late stages. Others attribute the bilaterality to the lateral sprouting of a tumor originating in the subependymal region of the third ventricle. With respect to the bilaterality of a tumor mass, Carter et al reported a connection across the midline through the posterior portion of corpus callosum and at the prerubral region of midbrain in their autopsy findings of diffuse bilateral thalamic astrocytomas. However, these hypotheses are more difficult to accept considering the topographic characteristics of these lesions, which remain bilaterally symmetrical, confined within the thalamic nuclei for a long time; and these lesions, unlike unilateral thalamic tumors, do not tend to violate the border between gray and white matter. Indeed in most cases of PBTT, the neuroradiological investigations do not detect any sign of tumor at the level of midbrain, pineal gland and midline basal subependymal region of III ventricle. Only in the late phases of their evolution may these tumors grow to infiltrate temporal lobe through connections with amygdaloid nuclei or brain stem. The two cases in this report, however, defy the findings reported in the literature and we are inclined to believe that bilaterality occurs in the later stages of progression of unilateral disease. Involvement of massa intermedia in our first three cases and the relative sparing of opposite thalamus in the initial stages in the last patient are suggestive of spread of gliomas from one side to the other.
The clinical picture of PBTTs is also quite typical: symptoms and signs may remain surprisingly mild even in patients with large tumors. Consequently, in the early stages of the disease, a correct clinical diagnosis is difficult and they are often misdiagnosed as brain stem encephalitis or acute narcotizing encephalopathy. Age distribution is similar to that of unilateral thalamic gliomas. Intracranial hypertension is not related to hydrocephalus, which may be moderate or absent, but it is secondary to the direct action of the neoplasm occupying space mass. However, in the first two cases reported here, raised ICT was associated with hydrocephalus. Other symptoms and signs may be protean and nonspecific because of the complex and various anatomical and functional connections of the thalamic structures. Hemiparesis, sensory disturbances, tremors, dysmetria and unsteady gait, torticollis and the nystagmus are justified by the involvement of the ventral anterior, ventral lateral nuclei and the cerebello-rubro-thalamic tracts. Some patients, more commonly adults, demonstrate personality changes rather than focal neurological signs. Severe dementia and personality modification observed in adults affected by PBTTs is attributed to the involvement of dorsomedial nuclei of thalami and their connections with temporal and frontal lobes., Memory dysfunction and disorientation are attributed to anterior thalamic nuclei and mammillothalamic tracts infiltration as described by Haut et al. Frontal lobe dysfunction is thought to result from tumor expansion to the nonspecific midline and intralaminar nuclei, which have been shown to connect with prefrontal cortex. Loss of psychic self-activation is due to striatal-ventral-pallidal-thalamic-frontomesial-limbic loop at different levels.
Diagnosis based on CT scan is at times difficult as these lesions appear as bilateral symmetrical isodense non-enhancing lesions. Absence of mass formation or mass effect renders CT scan insufficient in revealing these tumors. MRI is the best radiological examination for demonstrating these lesions, which appear as hyperintense on T2-weighted images and isointense on T1-weighted images without enhancement. Interestingly, PBTTs may show an increased creatine-phosphocreatine peak on MR spectroscopy, a pattern considered specific to these lesions, and one that is not present in unilateral thalamic gliomas; this may suggest that these tumors have a different metabolic pattern and may support the belief that they are a peculiar type of brain neoplasm. PBTTs are also characterized by the absence of tumor progression in serial MRIs, with tumors remaining within the thalamus respecting the border between gray and white matter.
Diffuse and bilateral involvement of thalamic nuclei by these tumors makes surgical therapy very difficult and no case of radical removal has been described in the literature. Consequently, the main role of surgery is to obtain a histological diagnosis. Generally, these gliomas are low-grade astrocytomas (grade II of WHO classification), but limited anaplastic areas may be encountered. Radiotherapy and chemotherapy are sometimes utilized as adjuvant therapy, but their role is questionable. Outcome is generally poor, independently of the therapy that is utilized. Rapid fatal evolution after diagnosis and the almost complete unresponsiveness of these tumors to radiotherapy make these rare tumors difficult to treat.
Bilateral thalamic gliomas are rare neoplasms. Probably they are not simply unilateral thalamic tumors that grow on both sides but are distinct lesions, as proven by their specific neuroradiological and metabolic properties, as well as a rapidly fatal clinical evolution. The unresponsiveness of these tumors to radiotherapy and chemotherapy treatment contributes further to distinguishing these extremely rare tumors from the relatively more common unilateral thalamic neoplasms. We wish to emphasize the importance that diffuse bilateral thalamic astrocytomas are a possible, although infrequent, cause of cerebellar symptoms and of cranial nerve and sensory deficits. Early diagnosis and prompt therapy may delay the devastating effects of these tumors.
| Acknowledgment|| |
Dr. Mohan Das, Director, SCTIMST, for permitting us to conduct this study and for his constant encouragement.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]
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