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| CASE REPORT |
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| Year : 2015 | Volume
: 2
| Issue : 1 | Page : 50-52 |
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Bilateral thalamic glioma
Nisar A Wani1, Parvez Nazir2, Parveen A Lone3, Sheikh Hilal4
1 Department of Radiodiagnosis and Imaging, Government Medical College, Srinagar, Jammu and Kashmir, India
2 Department of Radiology, Realscan Diagnostic Centre, Srinagar, Jammu and Kashmir, India
3 Department of OMF Surgery, GDC, Jammu, Jammu and Kashmir, India
4 Department of Neurology, JLNM Hospital, Srinagar, Jammu and Kashmir, India
| Date of Web Publication | 23-Jul-2015 |
Correspondence Address:
Dr. Nisar A Wani
Department of Radiodiagnosis and Imaging, Government Medical College, Srinagar - 190 011, Jammu and Kashmir
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2348-9995.161384
Bilateral thalamic glioma is a rare type of primary thalamic tumor. It presents clinically with personality changes and dementia rather than mass effect or focal neurological deficit. Imaging findings are somewhat characteristic with the diffuse homogenous enlargement of bilateral thalami with altered attenuation or signal intensity on computerized tomography and magnetic resonance imaging, respectively. This tumor is refractory to radiotherapy and chemotherapy and survival beyond 2 years after diagnosis is rare. This report emphasizes the need of neuroimaging in a patient with dementia to identify this rare devastating tumor early. Keywords: Dementia, magnetic resonance imaging, thalamic glioma
How to cite this article:
Wani NA, Nazir P, Lone PA, Hilal S. Bilateral thalamic glioma. J Geriatr Ment Health 2015;2:50-2 |
| Introduction | |  |
Within the spectrum of primary gliomas in the thalamic region, an unusual type called bilateral thalamic glioma (BTG) has been identified. [1] This glioma is characterized by large tumor involving both thalami diffusely and symmetrically. BTG is accompanied by behavioral impairment varying from personality changes to dementia. [1],[2] Tumor originates from subependymal glia of third ventricle and then spreads leading to symmetric thalamic masses. BTG preferentially involves intralaminar and dorsomedial nuclei of thalamus causing cognitive impairment. [1],[2],[3],[4],[5] In this report, we present a case who clinically presented with features suggestive of dementia and on magnetic resonance imaging (MRI) was found to have BTGs.
| Case Report | | |
A 53-year-old, nondiabetic, nonhypertensive male presented with subacute onset of cognitive decline in the form of memory impairment for the last 5-6 months. There was no history of any other significant medical disease or substance abuse. There was no family history of dementia. There were no behavioral abnormalities or psychological symptoms. On examination, the patient was conscious and oriented to time and place; there was evidence of memory impairment. There was no focal neurological deficit or any other systemic abnormality. A brief neuropsychiatric assessment revealed a mini-mental state examination score of 23/30 with impairment of recent memory and recall. Language comprehension, expression and calculation abilities were grossly intact. A provisional diagnosis of rapidly progressive dementia was made, and the patient worked up. Routine blood counts, renal, liver function tests, and cerebrospinal fluid analysis were unremarkable. MRI brain was performed using a 1.5 tesla magnetic resonance (MR) scanner to look for any underlying brain disorder. MRI demonstrated swelling and enlargement of bilateral thalami slightly more prominent on the left side [Figure 1] and [Figure 2]. There was a distortion of lateral ventricles with slight dilatation of left lateral ventricle [Figure 1] and [Figure 2]. The bilateral thalamic lesions were homogenous and appeared hypointense on T1-weighted (T1-W) [Figure 1] and hyperintense on T2-W [Figure 2] and fluid-attenuated inversion recovery images. There was no significant contrast enhancement of the thalamic lesions on postgadolinium enhanced T1-W MRI. Magnetic resonance spectroscopy (MRS) showed slight elevated choline and creatine peaks with reduced N-acetyl-aspartate peak in the thalamic lesions. There was no diffusion restriction or any arterial or venous obstruction. MRI findings were suggestive of BTG. Stereotactic brain biopsy confirmed the diagnosis of World Health Organization (WHO) grade II astrocytoma and the patient was referred for radiotherapy. | Figure 1: T1-weighted axial magnetic resonance imaging at the level of basal ganglia shows enlarged and swollen thalami (bilateral) with homogenous hypointense signal intensity
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 | Figure 2: T2-weighted axial magnetic resonance imaging at the level of basal ganglia shows enlargement of bilateral basal ganglia (left more than right) with homogenous hyperintense signal intensity. Left lateral ventricle is mildly enlarged
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| Discussion | | |
Primary thalamic tumors account for 1-1.5% of all brain tumors and are usually unilateral in location. BTG is a distinct and rare type of the thalamic tumor which can be seen both in children and adults. [1],[2],[3],[4] The BTG is clinically different from the unilateral thalamic tumor and is characterized by poor prognosis despite aggressive treatment. [1],[2],[3],[4] Two patterns of presentation of thalamic gliomas are differentiated that reflect the specific anatomic location. Intrinsic thalamic gliomas originate in the subependymal glia in the third ventricle. These tumors spread and expand from the medial nuclei and laterally involving the frontal and temporal lobe connections and causing early mental deterioration. The capsulothalamic and peduncular tumors invade the lateral or ventrolateral thalami and result in a sensory disturbance in the early stages. [5] The origin of BTG has been explained by two views. According to first, BTG is supposed to arise on one side in thalamus and then spread to other side over time, while according to second view BTG arises by spread of tumors from the subependymal region around the third ventricle. BTG is commonly confined to the thalamic region and does not violate the border between gray and white matter sparing midbrain and pineal gland. [4],[5],[6],[7]
The BTG may present from 1 year to up to 70 years of age and is more commonly reported in adults. Patients with BTG present with mild symptoms and signs, even though, the tumors are large. Tumor bulk of BTG may itself cause mass effect and raised intracranial pressure which is not generally related to hydrocephalus, as hydrocephalus is usually absent or mild if present. In children, hemiparesis, sensory disturbances, dysmetria, and unsteady gait are the common presenting features. [4],[5],[6],[7],[8] In adults personality changes, confusion, memory loss, apathy, emotional lability, and dementia are the principal symptoms and more common in comparison to the focal neurological deficit. The presence of cognitive decline and personality changes with sparing of sensory and motor functions is a distinctive feature of BTG in adults. [4],[5] Various clinical presentations seen in patients with BTG can be explained by the involvement of different thalamic nuclei or tracts related to them. Anatomical structures and pathways involved in case of dementia and personality changes are dorsomedial nuclei of the thalamus and their connections with frontal and temporal lobes of the brain. Memory dysfunction and disorientation are explained by the involvement of anterior thalamic nuclei and mammillothalamic tracts. Frontal lobe dysfunction results when there is infiltration of midline and intralaminar nuclei, which connect with the prefrontal cortex. The anatomic substrate thought to be responsible for loss of psychic self-activation is the involvement of ventral pallidal thalamic fronto mesial limbic loop at various levels. Sensory dysfunction sometimes encountered in case of BTG is attributable to the involvement of ventral thalamic nuclei. [4],[5],[6],[7],[8]
On imaging, BTG is characterized by diffuse swelling of bilateral thalami with homogenously hypodense attenuation on computerized tomography (CT) scan. On MRI enlarged bilateral thalami show homogenous hypointense or isointense signal intensity on T1-W and hyperintense signal intensity on T2-W images. No contrast enhancement is seen on postcontrast enhanced CT or MRI. [1],[8],[9] These features are characteristic of a diffuse low-grade astrocytoma. Histological higher grade tumors (anaplastic type) may show some enhancement on contrast-enhanced CT/MRI. There may or may not be any dilatation of lateral ventricles. MR spectroscopy shows reduced N-acetylaspartate peak in the tumor with variably elevated choline and myoinositol peaks. MR spectroscopy in case of BTG may show classic elevated creatine/phosphocreatine peak which might be typical for a glioma at the thalamic location. [9] Radiological differential diagnosis of bilateral thalamic lesions includes Wernicke's encephalopathy (WE), basilar artery occlusion or artery of Percheron infarction, deep vein thrombosis, Flavivirus encephalitis, and Creutzfeldt-Jakob disease More Details (CJD). [10] Of these WE, CJD, and rarely encephalitis may present with rapidly progressive dementia as was seen with BTG in our case. WE is usually seen in alcoholics and on MRI involves mammillary bodies and periaqueductal gray matter in addition to medial thalami. CJD classically involves basal ganglia and cerebral cortex besides thalami. Diffusion-weighted MRI, MR angiography and MR venography can clinch the diagnosis of arterial or venous infarction as the cause of bilateral thalamic lesions. [10] BTG may be of low (WHO grade I/II) or high grade (WHO grade III/IV) type on histology. There is no relationship of the age of patient with the histologic grade of the tumor. [1],[2],[4] Though, imaging may suggest the grade of the tumor on the basis of contrast enhancement, definitive grading needs a histopathologic examination of the excised tissue. Stereotactic biopsy is the preferred mode of tissue retrieval for definitive diagnosis of BTG. [1],[5],[6],[7] There is no definitive treatment of BTG as of now. Due to diffuse and bilateral involvement, surgical excision is difficult, and there is not any report of radical removal. The role of surgery at present is limited to get tissue for histological diagnosis. [4],[6] Access to the tumor can be obtained by open surgery via interhemispheric (transcallosal), infratentorial (supracerebellar), or trans-sylvian (transinsular) approaches. The tumor can be reached and sampled endoscopically or under stereotactic guidance. Besides biopsy, in case of a large tumor causing significant mass effect, debulking should be tried surgically. Biventricular shunt may be placed in case of hydrocephalus. [4],[6],[7],[8] The role of adjuvant radiotherapy and chemotherapy is not established. Radiotherapy is the preferred mode of attempted treatment and has not been reported to be curative. Chemotherapy is also not effective. The outcome is poor irrespective of treatment. Prognosis is universally dismal even after surgical debulking of the tumor and radiotherapy. [1],[2],[4],[6]
To conclude, this case report suggests that BTG may present with rapidly progressive dementia and hence the need of neuroimaging in case of cognitive decline to identify this devastating condition early. Imaging findings are distinct with bilateral, symmetric enlargement of the thalami with no contrast enhancement and with elevated creatine peak on MRS.
| References | | |
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[Figure 1], [Figure 2]
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