J Neurosurg (5 Suppl Pediatrics) 106:354–362, 2007

354 J. Neurosurg: Pediatrics / Volume 106 / May, 2007

P to 5% of pediatric intracranial tumors occur in thethalamic region.6,28 The management regimen forchildren with tumors in this region is not clear-cut.

The existing literature is sparse and difficult to interpret be-cause many series combine both adult and pediatric popu-lations,2,16,22,27,32,34 or they include tumors arising in the basalganglia and other diencephalic structures.12,18–23,30 In the fewseries in which purely thalamic tumors in children are ad-dressed, the cases are often confined to one histologicalgroup, usually astrocytic tumors.1,6,8,14,17,28,35

A clear anatomical picture of these deeply seated lesions

is now possible because of the recent improvements in im-aging modalities. Although these advances make more ag-gressive surgery technically feasible, it is uncertain whichchildren might benefit from a more radical surgical proce-dure.1 In most pediatric tumors the interpretation of the clin-ical and neuroimaging features observed at presentationpredicts the likely pathological findings and outcome. Un-fortunately, the histological features of tumors in this regionare diverse; hence a wide variation in clinical behavior andoutcome is experienced. Questions remain whether surgeryis necessary, feasible, or even safe in these children.

In this series we retrospectively reviewed the childrenpresenting to our institution with thalamic tumors over a14-year period. The aims were to identify prognostic fac-tors and to clarify the behavior and response to treatment ofthis diverse group of tumors.

Thalamic tumors in children: a reappraisal

STEPHANIE PUGET, M.D.,1 DARACH W. CRIMMINS, F.R.C.S.I.,5

MATTHEW R. GARNETT, F.R.C.S.,1 JACQUES GRILL, M.D.,4 RICARDO OLIVEIRA, M.D.,1

NATHALIE BODDAERT, M.D.,2 ALISON WRAY, F.R.A.C.S.,6

ARIELLE LELOUCH-TUBIANA, M.D.,3 THOMAS ROUJEAU, M.D.,1 FEDERICO DI ROCCO, M.D.,1

MICHEL ZERAH, M.D.,1 AND CHRISTIAN SAINTE-ROSE, M.D.1

Departments of Pediatric 1Neurosurgery, 2Neuroradiology, and 3Neuropathology, Hôpital Necker-Enfants Malades, and 4Department of Pediatric and Adolescent Oncology, Gustave Roussy Institute,Paris, France; 5Department of Neurosurgery, Leeds General Infirmary, Leeds, United Kingdom; and 6Royal Children’s Hospital, Melbourne, Australia

Object. Two to five percent of pediatric brain tumors are located in the thalamus. The optimal management for thesetumors remains unclear. The aim of this study was to determine whether clinical and neuroimaging features could guidetreatment, and to what extent these features, together with histological diagnosis and treatment modalities, influencedsurvival.

Methods. The records of 69 children who presented with a thalamic tumor between 1989 and 2003 were retrospec-tively reviewed. Three groups of tumors were analyzed separately: 1) unilateral thalamic tumors (54 lesions); 2) thala-mopeduncular tumors (six); and 3) bilateral thalamic tumors (nine).

In the patients in whom a unilateral thalamic tumor was diagnosed, 33 had an astrocytic tumor. Of the 54 patients,32 had a low-grade and 22 had a high-grade tumor. The survival rate was significantly better for patients with the fol-lowing characteristics: symptom duration longer than 2 months (p , 0.001), lesions with low-grade histological fea-tures (p = 0.003), and tumor excision greater than 90% at surgery (p = 0.04). The perioperative morbidity and mortal-ity rates were 37 and 4%, respectively. Fifty-four percent of the patients in this group had a long-term and independentsurvival. The thalamopeduncular tumors were mostly pilocytic astrocytomas, which had a good prognosis followingsurgery. The bilateral thalamic tumors in this series were mainly low-grade astrocytic lesions, and more than half ofthe children attained long-term survival (mean follow-up duration 4.5 years).

Conclusions. The majority of tumors arising in the thalamus are astrocytic, of which less than half are high-gradelesions. Histological evaluations should be performed in all patients in whom resection is being considered for discretelesions. Long-term survival is possible in patients with these tumors.

KEY WORDS • thalamic tumor • glioma • pediatric neurosurgery

Abbreviations used in this paper: CT = computed tomography;ETV = endoscopic third ventriculostomy; ICP = intracranial pres-sure; MR = magnetic resonance; VP = ventriculoperitoneal.

U

Clinical Material and Methods

Patient Population

Case notes and imaging studies were reviewed for all chil-dren presenting between 1989 and 2003 to Hôpital Necker-Enfants Malades with lesions in the thalamic region. Tumorsarising from adjacent structures (basal ganglia, hypothal-amus, optic pathways, pineal region, brainstem, and ventri-cles) were excluded. In addition, patients were excludedfrom the study if the greater part of their treatment had beenperformed elsewhere.

Clinical and Neuroimaging Data

Clinical data, including age at presentation, duration andtype of symptoms, treatment received, and status at the endof the follow-up period were recorded. The patients whowere still alive were categorized as having complete remis-sion with no residual tumor, stable disease, or progressivedisease at the last follow-up visit. All patients underwentneuraxis MR imaging prior to treatment and during the fol-low-up period, and in addition, most children had under-gone a preoperative head CT scan. Heterogeneity, cysticnature of the lesions, presence of calcification, edema, andcontrast enhancement were noted, as were features on T1-and T2-weighted MR imaging. The presence of hydroceph-alus was noted, and tumor extension to other structures, ifapplicable, was carefully documented. All the neuroimagesand histological specimens were interpreted by a single pe-diatric neuroradiologist and a pediatric neuropathologist,respectively.

Treatment Regimens

In patients who underwent surgery, the degree of resec-tion was defined as partial (# 90%), subtotal (. 90%), ortotal on postoperative imaging. Various surgical approach-es (anterior interhemispheric, posterior interhemispheric,transcortical, and transinsular) were used; the approach wasdetermined according to the location of the tumor in thethalamus and surrounding structures.

Statistical Analysis

The chi-square test was used to compare survival statuswith age at presentation, duration of symptoms, tumor size,and extent of surgery. Overall survival was correlated withsymptom duration, pathological findings (benign or malig-nant), and extent of resection (total/subtotal compared withpartial/biopsy/none). These correlations were made usingunivariate analysis according to the Kaplan–Meier method;the power of the predicting factors was evaluated in a Coxmodel. Probability values of less than 0.05 were consideredstatistically significant. Statistical analysis was performedusing commercially available software (SPSS, Inc.). Valuesare given as the mean 6 standard deviation.

Results

Between 1989 and 2003, 1725 children presented to Hô-pital Necker-Enfants Malades with new intracranial tumors;69 of them (4%) had thalamic tumors and satisfied the entrycriteria for the study. When reviewed as a series, it becameapparent that from a surgical point of view these tumors fell

into three categories, as follows: 1) unilateral thalamic tu-mors, originating from one thalamus with possible extensionto adjacent structures; 2) thalamopeduncular tumors, arisingat the junction of these two structures with symmetricalsupra- and infratentorial extension; and 3) bilateral thalamictumors, originating from both thalami as opposed to tumorswith contralateral extension. In our series, 54 children (78%)had unilateral thalamic tumors, six (9%) had thalamopedun-cular tumors, and nine (13%) had tumors arising from boththalami.

Unilateral Thalamic Tumors

In this group of 54 patients there were 29 boys, and in 30of the children the tumor was on the left side. The meanage at presentation was 9.5 6 4.4 years (range 0–16 years),and the mean duration of symptoms was 147 6 238 days(range 2–1093 days). Thirty-one children (57%) experi-enced symptoms for fewer than 2 months prior to presen-tation. The types of symptoms and neuroimaging featuresseen on MR and CT studies are shown in Tables 1 and 2.The most common presentation of children with this tumorwas with symptoms of increased ICP and/or motor deficits.Presentation with sensory deficits was unusual. The meantumor volumes, which were calculated based on the MRimages, were 32 6 31 ml (range 2–131 ml). In this sub-group, 34 patients (63%) required cerebrospinal fluid di-version (VP shunts in 24 and ETV in 10).

The treatment strategy for this subgroup is shown in Ta-ble 3. Forty-nine patients (91%) underwent surgery for thetumor, and in 25 of them a greater than 90% excision wasachieved. Two examples of discrete unilateral thalamic tu-mors before and after complete resection are shown in Figs.1 and 2, and an example of a diffuse unilateral thalamic tu-mor for which only a biopsy was performed is shown inFig. 3. Of the 49 patients who underwent surgery, 31 expe-rienced either improvement or no change neurologically, 16were neurologically worse, and two died in the periopera-tive period. The histological results, which are summarizedin Table 4, confirm that 33 (61%) of the 54 lesions were as-trocytic. Twenty-four (44%) were low-grade and 22 (41%)were high-grade tumors. There were eight patients with nohistological diagnosis; in three of them biopsy results werenondiagnostic, three were referred directly for radiotherapyat the beginning of the series without undergoing biopsysampling, and for two a policy of observation was adopted.Postoperative radiotherapy and/or chemotherapy were usedin patients with malignant tumors and in those with pro-gressive low-grade tumors.

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TABLE 1Clinical features in 69 children with thalamic tumors

No. w/ Tumor Type (%)

Clinical Feature Unilat Thalamopeduncular Bithalamic

total patients 54 6 9increased ICP 33 (61) 3 (50) 4 (44)motor deficits 35 (65) 4 (67) 6 (67)sensory deficits 4 (7) 1 (17) 1 (11)visual problems 23 (43) 3 (50) 5 (56)other* 21 (39) 4 (67) 2 (22)

* Other symptoms consisted of involuntary movement, spasticity, seizures,behavioral problems, and central pain.

Of these 54 children, 37 remain alive and 17 have died(mean follow-up duration 4.9 years, median 3.6 years). TheKaplan–Meier curve (Fig. 4A) shows that the probability ofa 5-year survival for children in this group was 66 6 7%.When patients with low- and high-grade tumors were con-sidered separately, the probability of a 5-year survival was86 6 7% and 41 6 11%, respectively (Fig. 4B). Similarly,when the patients who underwent a total or subtotal resec-tion were considered separately from the ones with a par-tial resection or biopsy, the 5-year survival rates were 83 66% and 48 6 9%, respectively (Fig. 4C). Of the 37 sur-vivors, 11 are in complete remission, 21 are alive with sta-ble disease, and five have evidence of ongoing disease pro-gression. Of these 37 patients, 29 are living independently.No patient was lost to follow up.

There was no correlation between age at presentation andsurvival, but presentation at a younger age was significant-ly associated with a higher incidence of benign tumors (p =0.03). As shown in Table 5, patients with a low-grade tumorand with symptoms that had lasted for more than 2 monthshad a statistically significantly prolonged survival com-pared with patients who had a high-grade tumor (p = 0.003

for comparison of tumor grade, and p , 0.001 for durationof symptoms). In addition, the survival was significantlylonger (p = 0.04) in those who underwent total or subtotalresection, compared with those in whom only a partial re-section or biopsy procedure was performed. Furthermore,the patients with a tumor volume of 30 ml or less had a sta-tistically significantly longer survival (p = 0.03) comparedwith those who had a tumor volume of greater than 30 ml.No significant differences in survival duration were foundwhen comparing patients who had received radiotherapyand/or chemotherapy with those who had not.

A Cox regression analysis was performed using the vari-ables that individually had an effect on survival (histologicalfindings, duration of symptoms, tumor volume, and extentof resection). The two variables that remained significantprognostic factors after this analysis were the extent of sur-gery (total or subtotal resection compared with partial resec-tion or biopsy sampling, p = 0.002) and the pathological type(low-grade compared with high-grade tumors, p = 0.03).

Thalamopeduncular Tumors

There was no gender predilection (three boys and threegirls) for this subgroup of patients, and the mean age was9.3 years (range 3–13 years). Motor deficits were the mostcommon form of presentation (Table 1).

The MR images revealed that these were typically con-trast enhancing, heterogeneous lesions with little surround-ing edema (Table 6). All were hyperintense on T2-weightedMR imaging. Half of the lesions were cystic, and in five of

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356 J. Neurosurg: Pediatrics / Volume 106 / May, 2007

TABLE 2Imaging features in 54 children with unilateralthalamic tumors on CT and MR imaging studies

Imaging Feature No. (%)

homogeneous 26 (48)heterogeneous 28 (52)calcification 12 (22)surrounding edema 12 (22)contrast enhancement 40 (74)cystic 20 (37)hydrocephalus 34 (63)confined to thalamus 20 (37)extension

to brainstem 17 (32)contralat 2 (4)diffuse 15 (28)

total 54 (100)

TABLE 3Management of disease in 54 children

presenting with unilateral thalamic tumors*

Treatment No. (%)

treatment of hydrocephalusETV 10 (19)shunt placement 24 (44)

tumor opbiopsy sampling 17 (32)excision

partial 7 (13)subtotal 20 (37)total 5 (9)

overall treatmentnone 2 (4)biopsy only 3 (6)excision only 8 (15)op & chemo 13 (24)op & RT (w/ or w/o chemo) 25 (46)RT (w/o histo evaluation) 3 (6)

* chemo = chemotherapy; histo = histological; RT = radiotherapy.

FIG. 1. Left thalamic pilocytic astrocytoma demonstrated onMR images obtained in a 12-year-old girl. A: Sagittal T1-weight-ed image demonstrating a partially cystic lesion. B: Axial T1-weighted image obtained after addition of contrast agent demon-strating enhancement of the solid component of the tumor. C:Coronal T2-weighted image demonstrating hyperintensity of thesolid component of the tumor. D: Axial T1-weighted image ob-tained after complete excision via a transfrontal approach, and afteraddition of contrast material.

six patients associated hydrocephalus was found at presen-tation. The tumors varied in volume from 1 to 78 ml. Exam-ples of pre- and postoperative MR images of a cystic, en-hancing, thalamopeduncular tumor are shown in Fig. 5.

All children with this tumor type required cerebrospinalfluid diversion; in five cases it was the first procedure and inone case it was done during the follow-up period (in threean ETV was performed and in the other three placement ofa VP shunt was done). Five patients underwent surgery; twofor biopsy sampling, one for a partial excision, and two fora subtotal, staged excision. The sixth patient did not undergooperation because of the surgeon’s clinical decision to ob-serve expectantly. The predominant histological finding (infour of the five specimens) was pilocytic astrocytoma, witha malignant astrocytoma diagnosed in the remaining patient(Table 4). Radiotherapy was used postoperatively in threepatients.

The child with the malignant astrocytoma has died, one

child has progressive disease, and four have stable residualdisease (mean follow-up duration, 4.9 years).

Bithalamic Tumors

In this subgroup the mean age was 9.6 years, and five ofthe nine patients were girls. The main clinical feature atpresentation was motor disturbances, as in the other groups(Table 1).

The features demonstrated on MR images are shown inTable 6. These tumors tended to be homogeneous (seven ofnine), and fewer than half (four of nine) enhanced with addi-tion of contrast material. Six of the patients had hydroceph-alus. Examples of neuroimages obtained in a patient with abilateral thalamic tumor are shown in Fig. 6.

All nine patients underwent surgery; in eight of them bi-opsy sampling was performed and one had a partial exci-sion. Five patients required a VP shunt insertion to controlhydrocephalus. The histological analysis of the tumors isshown in Table 4; seven patients had low-grade lesions, of

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FIG. 2. Low-grade mixed glioma demonstrated on MR images obtained in a 15-year-old girl. A: Axial T1-weightedimage obtained after addition of contrast material, demonstrating a nonenhancing left-sided thalamic tumor that was re-moved in a staged procedure because of poorly defined tumor margins at surgery. B: Axial image demonstrating appear-ance of the lesion before the second procedure. C: Final MR image demonstrating a complete excision.

FIG. 3. High-grade astrocytoma demonstrated on MR imagesobtained in an 11-year-old girl. Coronal (left) and axial (right)T1-weighted images obtained after administration of contrast agent,demonstrating an enhancing and infiltrative right-sided thalamic tu-mor. The patient’s disease was managed by performing a stereotac-tic biopsy procedure to confirm the diagnosis, followed by chemo-therapy and radiotherapy.

TABLE 4Histological types observed in thalamic

tumors evaluated in 69 pediatric patients*

No. w/ Tumor Type (%)

Histo Finding Unilat Thalamic Thalamopeduncular Bithalamic

astrocytomapilocytic 9 (17) 4 (67) 1 (11)low-grade 7 (13) 5 (56)malignant† 17 (31) 1 (17) 1 (11)

oligodendrogliomalow-grade 2 (4)anaplastic† 3 (6) 1 (11)oligoastrocytoma 4 (7) 1 (11)

PNET 2 (4)neurocytoma 1 (2)ganglioglioma 1 (2)no histo assessment 8 (15) 1 (17)total 54 (100) 6 (100) 9 (100)

* PNET = primitive neuroectodermal tumor.† Designates the 22 high-grade tumors.

which five were fibrillary astrocytomas, and two had high-grade tumors. Radiotherapy was used postoperatively infour patients.

In this subgroup five patients remain alive with disease(mean follow-up duration 4.5 years), four of whom are in-dependent, whereas four have died (including the two pa-tients with malignant tumors). Two of the children withlow-grade tumors died (both of them had received radio-therapy).

Discussion

Thalamic tumors account for 2 to 5% of all intracranialtumors in pediatric series.5,6,14,35 Despite the fact that this in-cidence is higher than that of, for example, craniopharyn-giomas or pinealomas (2 and , 1%, respectively), there isa comparative paucity of published literature concerning thetreatment of these lesions. In this series we have reviewedthe patients presenting to our institution over a 14-year peri-od with a newly diagnosed thalamic tumor. In total, 1725patients with intracranial tumors were treated during thisperiod, of whom 69 (4%) had a newly diagnosed thalamictumor, which is in keeping with the previous reports in theliterature.5,6,14,35 The previously published series of thalamictumors are shown in Table 7.

The children in the current series generally presentedwith symptoms of increased ICP and, on examination, werefound to have a motor deficit, which is in keeping with pre-vious studies.1,15,25 Based on the MR images obtained inthese 69 patients, we were able to divide the thalamic tu-mors into three groups, which included bilateral thalamic,unilateral thalamic, and thalamopeduncular lesions. In thecurrent series, all of the bilateral thalamic tumors had a sim-ilar appearance on neuroimaging, with both thalami beingsymmetrically enlarged. These lesions were normally ho-mogeneous on MR images, with minimal mass effect andoften no surrounding edema, which is in keeping with pre-vious descriptions.7,28 The unilateral thalamic tumors were,however, a more mixed group, with an almost equal distri-bution of lesions demonstrating homogeneous and hetero-geneous signals on MR imaging. Fewer than half of thesetumors were confined to the thalamus, with the remainderextending to the surrounding structures.

A subgroup of these unilateral tumors was identified thatwas called thalamopeduncular. These tumors probably

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FIG. 4. Kaplan–Meier survival curves showing results for 54unilateral thalamic tumors. A: Results for the 54 tumors com-bined. B: Results for the 54 tumors, distinguishing between be-nign and malignant tumors. C: Results for the 54 tumors, distin-guishing between the two main categories for extent of surgery(total/subtotal resection [. 90%], and partial resection [# 90%] orbiopsy). Cum = cumulative; ext = extent.

TABLE 5Univariate analysis of prognostic factors in the

54 patients with unilateral thalamic tumors*

Prognostic Factor 5-Yr OS (%) Mean OS p Value

histo findinglow-grade 87.5 .60 mos 0.003high-grade 45.5 21 mos

symptom duration$2 mos 95.7 .60 mos ,0.001,2 mos 48.4 22 mos

tumor vol#30 ml 84.0 .60 mos 0.03.30 ml 40.0 23 mos

extent of resectiontotal/subtotal 85.0 .47 mos 0.04other 47.1 24 mos

* OS = overall survival.

arose at the junction of the thalamus and cerebral peduncleand invariably extended inferiorly into the cerebral peduncleand superiorly into the thalamus. These thalamopedunculartumors were all high-signal lesions on T2-weighted MR im-ages and normally enhanced after injection of contrast mate-rial. When the imaging appearances were reviewed for thesethree groups, there was no individual or even a set of fea-tures that could be used to predict either the type or grade ofthe tumor. Indeed, in the patients with unilateral pilocytic as-trocytomas, only half of the tumors demonstrated the typicalappearance of a cystic lesion, with an enhancing mural nod-ule and no surrounding edema.

Unilateral Thalamic Tumors

This group of tumors accounted for 78% of the patients

in the current series. In this group, two factors were shownto influence outcome in a multivariate analysis, namely thegrade of the tumor and the extent of resection. The patientsin whom more than 90% of the tumor was resected had asignificantly improved survival duration compared with theones in whom 90% or less of the tumor was resected. In ad-dition, the patients in whom low-grade tumors were foundhad a significantly improved survival duration comparedwith the ones who had a high-grade lesion. The effect thattumor grade may have on outcome has been described pre-viously;1,3,4,18,28,35 however, the effect that extent of resectionmay have on outcome has not been described previously inpatients with thalamic lesions.

In the patients with a unilateral thalamic tumor, 22 (41%)had a high-grade lesion, and all of these patients receivedadjuvant therapy after surgery. In this group the expected 5-year survival rate was 41%. This prolonged survival is incontrast to findings in previously reported series in whichthe survival duration after surgery in patients with a malig-nant tumor was approximately 1 to 2 years.1,6 It is possiblethat this improvement in outcome is related to the extent ofsurgery, in keeping with a report from the Children’s Can-cer Group, which confirmed that, in patients with an intra-cranial malignant tumor, survival improved if the extent oftumor resection was greater than 90%.36

In our series the larger extent of resection, whether it wasin patients with a low- or high-grade lesion, improved prog-nosis. This implies that, if possible, a child with a symptom-atic unilateral thalamic tumor should undergo a radical re-section. Survival with severe disability would clearly not bethe aim of radical surgery, however, and indeed in the cur-rent series 29 of the 37 long-term survivors were indepen-dent. There are several surgical routes that can be used toapproach thalamic tumors. The particular approach shouldbe selected based on the location of the tumor in the thala-mus to minimize resection of unaffected brain.1 Moreover,because radical resection of these tumors has been reportedto be difficult and the complication rate high,1 their excisionin a staged procedure should be considered (Fig. 2). The useof a staged procedure is recommended either for the largertumors in which highly functional tissue (pyramidal tract,basal ganglia, remaining thalamus) is stretched around thelesion and can easily be injured when attempting a one-stageremoval, or for lesions with poorly defined boundaries. In

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TABLE 6Imaging features of thalamopeduncular andbithalamic tumors on CT and MR imaging

No. w/ Tumor Type (%)

Imaging Feature Thalamopeduncular Bithalamic

homogeneous 1 (17) 7 (78)heterogeneous 5 (83) 2 (22)calcification 1 (17) 2 (22)surrounding edema 1 (17) 1 (11)contrast enhancement 5 (83) 4 (44)cystic 3 (50) 1 (11)hydrocephalus 5 (83) 6 (67)total 6 (100) 9 (100)

FIG. 5. Left thalamopeduncular pilocytic astrocytoma demon-strated on MR images obtained in a 3-year-old girl. A: CoronalT1-weighted image obtained after addition of contrast agent dem-onstrating an enhancing tumor. B: Coronal T2-weighted imagedemonstrating the cystic component of the tumor. C and D: Fol-low-up T1-weighted images obtained after subtotal excision via asubtemporal route, and after addition of contrast agent.

FIG. 6. Bilateral thalamic tumor demonstrated on neuroimagesobtained in a 9-year-old girl. Left: Axial CT scan revealing a par-tially calcified bithalamic tumor. Right: Enlarged T1-weightedMR image demonstrating the symmetrically enlarged thalami withsome contrast enhancement.

patients with diffusely infiltrating tumor, only stereotacticbiopsy sampling was undertaken.

Administration of radiotherapy to histologically uncon-firmed thalamic tumors has previously been advocated.There were three patients who received radiotherapy at thestart of the series despite the lack of a histological diagnosis.This is now considered unacceptable, however.3,4,10,30,31 In aseries of thalamic mass lesions in which stereotactic biopsysampling was performed, eight (18%) of 44 were nonneo-plastic, highlighting the need for tumor confirmation beforeinstituting potentially harmful adjuvant therapies.10 In thecurrent series, 25 of 54 patients underwent radiotherapy af-ter surgery for their unilateral thalamic tumors. This adju-vant therapy was reserved, with the exceptions mentionedearlier, for patients with high-grade lesions or for those withtumors that showed clinical and neuroimaging evidence ofprogression.

Patients with a smaller tumor volume and a longer histo-ry of symptoms had a significantly better outcome com-pared with those who had a larger volume and a shorter his-tory of symptoms. These findings are likely to reflect thetumor grade, in that a patient with a malignant tumor oftenpresents with a short clinical history and on neuroimagingis often found to have a large lesion. This finding is in keep-ing with a previous report.6 Other clinical findings, for ex-ample symptoms of raised ICP, have also been associatedwith a worse outcome.6,11,24 In our study no other clinical (orindeed neuroimaging) finding correlated with outcome.

Thalamopeduncular Tumors

This subset of unilateral thalamic tumors is quite distinctfrom the thalamic tumors that extend into the midbrain. Inthe current series of 69 patients who presented with a thalam-

ic tumor, there were six children with this type of lesion.These tumors were all hyperintense on T2-weighted MR im-ages and appeared to arise at the junction of the thalamus andthe cerebral peduncle. Five of the six patients underwentsurgery, with debulking of the tumor, including the cerebralpeduncle component, achieved in three via a staged subtem-poral approach that resulted in no deterioration in neuro-logical function. This is in contrast to previous reports on at-tempts at resection of the midbrain portion of a tumor thathave resulted in significant postoperative complications andneurological dysfunction.1,16 Nevertheless, outcomes in thissubgroup of patients with thalamopeduncular tumors aresimilar to those in seven patients who were previously re-ported.33 In that earlier study, all seven patients underwent re-sective surgery via a subtemporal approach, with no perma-nent deterioration in neurological function.

In our series, four of the five patients in this subgroupwho underwent surgery had a benign astrocytoma and thefifth child had a malignant astrocytoma. The child with amalignant astrocytoma has died, whereas the remaining fiveare alive after a mean follow-up duration of 4.9 years; fourof these children have stable disease. This is similar to a pre-vious study in which all the patients with a tumor in this re-gion had a benign astrocytoma, with only one recurrence af-ter a follow-up duration of 3.8 years.33

Bilateral Thalamic Tumors

This group was quite distinct from the patients who hada unilateral thalamic tumor, and indeed from the patientswho had a unilateral tumor with diffuse spread bilaterally.The tumors in these nine patients were normally homoge-neous on MR images, with bilaterally, often symmetricallyenlarged thalami. Biopsy sampling was performed in all pa-

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TABLE 7Literature review of series of resected thalamic tumors treated between 1958 and the present*

No. of PeriopAuthors & Year Patients Ages Lesions Included Extent of Op Deaths (%)

Arseni, 1958 10 all thalamic tumors PR 4 (40)Tovi et al., 1961 15 all thalamic tumors open exploration 7 (47)Cheek & Taveras, 1966 9 all thalamic tumors resection 7 (78)Greenwood, 1973 20 all midline diencephalic tumors PR, 4; radical excision, 16 5 (25)Hirose et al., 1975 11 children thalamic astrocytomas STR, 9; GTR, 2 1 (9)Bernstein et al., 1984 41 children thalamic or basal ganglia astrocytomas open biopsy, 20; PR, 20; GTR, 1 0Prakash, 1985 15 ,30 thalamic gliomas open resection 1 (7)Beks et al., 1987 9 all thalamic tumors open biopsy, 5; PR, 4 0McGirr et al., 1987 6 ,30 thalamic & basal ganglia pilocytic GTR, 3; STR, 3 0

astrocytomasKelly, 1989 28 all thalamic astrocytomas GTR, 17; $90% resection, 9; 1 (4)

,90% resection, 2Drake et al., 1991 6 children thalamic low-grade astrocytomas 95% excision, 4; total excision, 2 0Lyons & Kelly, 1992 19 all thalamic pilocytic astrocytomas GTR, 14; $95% resection, 5 1 (5)Hoffman et al., 1993 13 children thalamic low-grade astrocytomas .50% resection, 4; #50% resec- 0

tion, 9Villarejo et al., 1994 8 children thalamic astrocytomas GTR, 7; STR, 1 0Matsumoto et al., 1995 5 all thalamic gliomas stereotactic resection 0Cuccia & Monges, 1997 19 children thalamic astrocytomas GTR, 9; PR (40–90%), 10 2 (11)Steiger et al., 2000 14 all thalamic astrocytomas GTR, 5; $90% resection, 5; 0

,90% resection, 4Martinez-Lage et al., 2002 11 children thalamus & basal ganglia craniotomies for tumor removal 0Ozek & Ture, 2002 18 children thalamic tumors GTR, 16; STR, 2 0Albright, 2004 19 children thalamic gliomas GTR, 6; .90% resection, 10; 1 (5)

,90% resection, 3

* GTR = gross-total resection; PR = partial resection; STR = subtotal resection.

tients, with one proceeding to a partial excision. Althoughin this series all patients had a glial tumor, it is important toexclude other medical causes of bilateral enlargement of thethalami; for example, encephalitis and metabolic disorders.9Most of the lesions were astrocytic, and seven of nine werelow-grade tumors, which is in keeping with a previous se-ries.28 In our series five of the nine patients were still aliveafter a mean follow-up duration of 4.5 years. This is con-trary to previous studies in which patients with a bilateralthalamic tumor, even those with a low-grade lesion, did nottend to survive beyond 2 years (Table 8). Although only twopatients in this subgroup had a high-grade tumor, the diseasein these two progressed rapidly, even with radiotherapy andchemotherapy. There were two other patients in this group(both of whom have died) who received radiotherapy aftertheir biopsy procedure, which raises the question whetherirradiation may stimulate tumor transformation. The fivepatients who have survived to date have received no furthertreatment, other than to confirm the diagnosis and to treatthe hydrocephalus. In our series there was no obvious ben-efit of adjuvant therapy, which is in keeping with findings inprevious series.7,28

The number of patients in our series who had a bithalam-ic tumor was small, and although there were some long-term survivors, the identification of these patients at thetime of diagnosis was not possible. Therefore, the progno-sis in children with this diagnosis remains uncertain.

Conclusions

Thalamic tumors in pediatric patients are generally astro-cytic, and more than half are benign. In patients with unitha-lamic tumors, a short duration of symptoms, large tumors,incomplete resection, and high-grade histological type areall poor prognostic factors. There were no specific imagingfeatures that were predictive of the histological type. Neu-roimaging could be used to determine resectability, howev-er, particularly in well-defined lesions with no extension in-to adjacent structures. Total or subtotal resection is the goal;this extent of resection is associated with improved overall

survival and can be achieved with minimal occurrences ofmorbidity and mortality. Tumors that are not safe to resectshould be investigated using biopsy sampling to excludenonneoplastic pathological entities and to direct future ad-juvant therapies based on histological tumor types. Radio-therapy and chemotherapy should be reserved for patientswith malignant lesions or tumor progression. Adjuvant ther-apies should not be considered without a histological diag-nosis.

There are two subgroups of thalamic tumors. The firstincludes the thalamopeduncular tumors, which are general-ly benign pilocytic astrocytomas. These can be macroscop-ically excised and potentially have a good prognosis. Thesecond subgroup includes the bithalamic tumors, which areoften low-grade astrocytomas. Following biopsy samplingto confirm the histological type, these lesions can be ob-served expectantly, with more than half of the patients withtumors in this subgroup attaining a long-term survival.

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TABLE 8Literature review of reports of pediatric bithalamic tumors*

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Manuscript submitted December 11, 2006.Accepted February 6, 2007.Address reprint requests to: Christian Sainte-Rose, M.D., Service

de Neurochirurgie Pédiatrique, Hôpital des Enfants Malades, 149 ruede Sèvres, 75743 Paris Cedex 15, France. email: christian.sainte-rose@nck.aphp.fr.

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