Cell surface antigens of murine leukemias induced by radiation leukemia virus. Recognition of individually distinct cell surface antigens by cytotoxic T cells on leukemias expressing crossreactive transplantation antigens.

The specificity of transplantation immunity and T cell cytotoxicity against leukemias induced by RadLV was examined. Subcutaneous inoculation of two RadLV leukemias induced in BALB/c mice, BALBRVB and BALBRVD, resulted in initial tumor growth in CB6F1 mice, followed by complete tumor regression. Mice that had rejected leukemias BALBRVB or BALBRVD were subsequently challenged with various tumors of BALB/c origin. The growth of all five RadLV leukemias tested, and of one radiation-induced leukemia, was significantly inhibited. Another radiation-induced leukemia, a methylcholanthrene-induced sarcoma, and a leukemia induced by the Moloney leukemia virus, were not inhibited. The results indicate that RadLV leukemias share cell surface antigens that induce transplantation immunity in vivo. Cytotoxic lymphocytes were generated by coculturing spleen cells from mice that had rejected leukemia BALBRVB or BALBRVD with the corresponding leukemia cells. Direct tests and inhibition tests showed that such cytotoxic cells recognized individually specific antigens on leukemias BALBRVB and BALBRVD, distinct from the shared antigens detected in transplantation experiments. The effector cells in cytotoxicity assays were Thy-1+, Lyt-1+,-, Lyt-2+, and Lyt-3+ T cells.

Outcome of risk-based therapy for infant acute lymphoblastic leukemia with or without an MLL gene rearrangement, with emphasis on late effects: a final report of two consecutive studies, MLL96 and MLL98, of the Japan Infant Leukemia Study Group.

We evaluated the efficacy of a treatment strategy in which infants with acute lymphoblastic leukemia (ALL) were stratified by their MLL gene status and then assigned to different risk-based therapies. A total of 102 patients were registered on two consecutive multicenter trials, designated MLL96 and MLL98, between 1995 and 2001. Those with a rearranged MLL gene (MLL-R, n=80) were assigned to receive intensive chemotherapy followed by hematopoietic stem cell transplantation (HSCT), while those with germline MLL (MLL-G, n=22) were treated with chemotherapy alone. The 5-year event-free survival (EFS) rate for all 102 infants was 50.9% (95% confidence interval, 41.0-60.8%). The most prominent late effect was growth impairment, observed in 58.9% of all evaluable patients in the MLL-R group. This plan of risk-based therapy appears to have improved the overall prognosis for infants with ALL, compared with previously reported results. However, over half the events in patients with MLL rearrangement occurred before the instigation of HSCT, and that HSCT-related toxic events comprised 36.3% (8/22) of post-transplantation events, suggesting that further stratification within the MLL-R group and the development of more effective early-phase intensification chemotherapy will be needed before the full potential of this strategy is realized.

Characterization of the immunoglobulin heavy chain complementarity determining region (CDR)-III sequences from human B cell precursor acute lymphoblastic leukemia cells.

Sequence analysis of the immunoglobulin heavy chain complementarity determining region (CDR)-III of B-lineage cells at various stages has provided important insights concerning B cell maturation and selection. Knowledge of human CDR-III sequences has been relatively limited compared with that of the murine system. We analyzed the CDR-III sequences of B cell precursor acute lymphoblastic leukemia (pre-B ALL) cells in 23 newly diagnosed and 10 relapsed patients, in order to elucidate the organization of CDR-III in B cell precursors. We found a very low frequency of somatic mutations in D and JH regions, preferential use of DLR, DXP, DHQ52, and DN elements, and of 3' side JH segments, and no predominant usage of D coding frames. Unusual joinings such as VH-D-D-JH and VH-JH were observed in three, and one sequences, respectively. We compared the CDR-III sequences derived from 10 patients between diagnosis and relapse. Two of them had three spots of mutated nucleotides at relapse, all of which were found in the N region near the D segments. Our data showed the possibility of somatic mutation at relapse, in addition to developmentally regulated rearrangement of the immunoglobulin gene at the stage of B cell precursors.

The seventh international childhood acute lymphoblastic leukemia workshop report: Palermo, Italy, January 29--30, 2005.

Between 1995 and 2004, six International Childhood Acute Lymphoblastic Leukemia (ALL) Workshop have been held, and the completion of several collaborative projects has established the clinical relevance and treatment options for several specific genetic subtypes of ALL. This meeting report summarizes the data presented in the seventh meeting and the discussion.

High expression of ganglioside alpha-2,8-sialyltransferase (GD3 synthase) gene in adult T-cell leukemia cells unrelated to the gene expression of human T-lymphotropic virus type I.

Expression of ganglioside alpha-2,8-sialyltransferase (GD3 synthetase; EC 2.4.99.8) gene and gangliosides in human leukemia cells were analyzed. Flow cytometric analysis of various types of leukemia cells using monoclonal antibodies revealed that GD3 was expressed at a moderate level on adult T-cell leukemia (ATL) cells and weakly on T-cell acute lymphocytic leukemia cells. Accordingly, high levels of GD3 synthase mRNA in ATL and low levels in T-cell acute lymphocytic leukemia were demonstrated by semiquantitative reverse transcription-PCR analysis. High-level expression of the GD3 synthase gene in ATL cells was detected in the uncultured state, and was not changed during short-term culture in vitro. This was in contrast with the rapid up-regulation of GM2/GD2 synthase gene, which was observed within 24 h after start of culture after the emergence of human T-lymphotropic virus type I (HTLV-I) gene expression in cultured normal T lymphocytes with or without HTLV-I p40tax protein, GD3 synthase gene was almost equally expressed, whereas GM2/GD2 synthase gene was much more strongly expressed in the p40tax-positive T cells. These findings indicated that the GD3 synthase gene was highly expressed in ATL cells unrelated to HTLV-I genome expression.

Characterization of pediatric Philadelphia-negative B-cell precursor acute lymphoblastic leukemia with kinase fusions in Japan.

Recent studies revealed that a substantial proportion of patients with high-risk B-cell precursor acute lymphoblastic leukemia (BCP-ALL) harbor fusions involving tyrosine kinase and cytokine receptors, such as ABL1, PDGFRB, JAK2 and CRLF2, which are targeted by tyrosine kinase inhibitors (TKIs). In the present study, transcriptome analysis or multiplex reverse transcriptase-PCR analysis of 373 BCP-ALL patients without recurrent genetic abnormalities identified 29 patients with kinase fusions. Clinically, male predominance (male/female: 22/7), older age at onset (mean age at onset: 8.8 years) and a high white blood cell count at diagnosis (mean: 94 200/µl) reflected the predominance of National Cancer Institute high-risk (NCI-HR) patients (NCI-standard risk/HR: 8/21). Genetic analysis identified three patients with ABL1 rearrangements, eight with PDGFRB rearrangements, two with JAK2 rearrangements, three with IgH-EPOR and one with NCOR1-LYN. Of the 14 patients with CRLF2 rearrangements, two harbored IgH-EPOR and PDGFRB rearrangements. IKZF1 deletion was present in 16 of the 22 patients. The 5-year event-free and overall survival rates were 48.6±9.7% and 73.5±8.6%, respectively. The outcome was not satisfactory without sophisticated minimal residual disease-based stratification. Furthermore, the efficacy of TKIs combined with conventional chemotherapy without allogeneic hematopoietic stem cell transplantation in this cohort should be determined.

Calcium-dependent Ret activation by GDNF and neurturin.

Glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) define a new family of neurotrophic factors that play crucial roles in survival and differentiation of various neurons. Recent studies demonstrated that GDNF and NTN use a multicomponent receptor system in which glycosyl-phosphatidylinositol (GPI)-linked cell surface proteins and Ret receptor tyrosine kinase function as the ligand-binding and signalling components, respectively. In the present study, we investigated the role of Ca2+ ions for biochemical and biological activities of Ret because Ret has a unique structure of the extracellular domain with the cadherin-like motif. The results demonstrated that Ca2+ ions might be required for the complex formation of Ret and GDNF or NTN that induces Ret oligomerization and autophosphorylation. Full morphological differentiation of neuroblastoma cells by these neurotrophic factors was also Ca2+-dependent. These findings thus suggested that, in addition to GPI-linked cell surface proteins, Ca2+ ions are components of the signal transducing complex formed by Ret and GDNF protein family.

Clinicopathologic characteristics of leukemia in Japanese children and young adults.

The aim of this study is to clarify the clinicopathologic characteristics of adolescent leukemia in Japan by retrospective analysis. Patients with acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), chronic myelogenous leukemia (CML), and myelodysplastic syndrome (MDS), consecutively diagnosed from 1986 to 1999, were enrolled. A total of 3,856 patients from 1 to 15 years of age and 1,803 patients from 15 to 29 years of age were eligible for this study. Demographically, the frequency of AML found was almost constant during the teenage years, whereas the frequency of ALL gradually decreased. The relative frequency of CML and MDS apparently started to increase in patients in their late teens. The relative frequency of M3 and t(15;17) gradually increased during adolescence. Among patients aged 1 to 4 years, M7 was the most frequent FAB subtype. Among patients aged 5 to 9 years, M2 and t(8;21) was the most frequent subtype. The percentage of T cell ALL increased in patients 5 to 9 years old, reaching 31.2% in the 20- to 24-year-old age group. The percentage of patients with hyperdiploidy over 50 chromosomes was highest (17.0%) in patients aged 1 to 4 and decreased to 3.9% in the older teens. The percentage of patients with the Ph1 chromosome increased from 9.9% in teens to 30.0% in patients in their late twenties. When comparing event-free survival (EFS) rates for ALL according to age, the estimated 7-year EFS rate was highest for patients aged 1 to 9 years (65.9%) and intermediate for patients aged 10 to 15 years (48.4%). However, the EFS rate was significantly worse for patients aged 15 to 19 years (19.4%) and 20 to 29 years (17.0%) (P = 0.024). On the other hand, the EFS rate for AML decreased with increasing age, although without statistical significance. The overall survival rates are approximate among all age groups. The results of the study indicate that there are considerable variations in biologic features of leukemia between children and young adults. The prognosis for adolescent leukemia may be improved by introducing pediatric trials, which take into account the prognostic biological features.

New E2A/PBX1 fusion transcript in a patient with t(1;19)(q23;p13) acute lymphoblastic leukemia.

About 25% of the children with pre-B cell acute lymphoblastic leukemia (ALL) have a chromosomal translocation of t(1;19)(q23;p13). This translocation juxtaposes the E2A gene on chromosome 19 to the PBX1 gene on chromosome 1, leading to production of a fusion transcript. The fusion sites of the E2A and PBX1 coding sequence have been identical among all cases of t(1;19) ALL studied so far. Here we described a new fusion site of the E2A and PBX1 genes, which was detected in the leukemic blasts of a child with t(1;19) pre-B ALL using the reverse transcriptase polymerase chain reaction and direct sequencing. The fusion site was located just upstream of the DNA binding domain of the E2A gene, and was close to a homeodomain of the PBX1 gene.

Comparison of the immunoglobulin gene transcripts between immature B lineage acute lymphoblastic leukemia and the normal phenotypic counterparts in the bone marrow.

Immature B lineage acute lymphoblastic leukemia (ALL) is divided into two subtypes, 'pre-B' and 'early pre-B' ALL, by the presence or absence of cytoplasmic immunoglobulin (cIg). To study their clonal origin, we compared mu-chain transcripts in six cIg+ and eight cIg- ALL samples (CD10+/- CD19+ surface Ig-) with those in the normal phenotypic counterparts (CD10+ CD19+ surface Ig-) sorted from the bone marrow (BM). Northern blot analysis showed that the cIg+ ALL samples expressed greater amounts of mu-chain transcripts than the cIg- ALL samples. In the ALL samples and their counterparts, sequence analysis of mu-chain transcripts revealed infrequent somatic mutations of the V(H) genes and the similar usage of D and J(H) gene segments, but the length of complementarity determining region (CDR)-3 in the ALL samples was longer than that in the counterparts (50.0 +/- 15.5 vs 40.8 +/- 12.7 bp, P = 0.01). The mu-chain transcripts in the six cIg+ ALL samples and the counterparts (119/120 clones) had productive sequences, whereas those in the eight cIg- ALL samples had nonsense codons and/or frame shifts in their CDR-3. Our data suggest that a phenotype of ALL, 'pre-B' or 'early pre-B', is associated with V(H)-D-J(H) gene recombinatorial events, and that the CD10+ CD19+ surface Ig- population in the BM is not simply the cellular origin of ALL.

Molecular analysis of the t(15;17) translocation in de novo and secondary acute promyelocytic leukemia.

To study mechanism of chromosomal translocation, we analyzed the breakpoints (b/p) of the PML and RARA genes in 120 and 5 patients with de novo and secondary (therapy-related) acute promyelocytic leukemia (APL), respectively. In de novo APL, the b/p in the PML gene were clustered in introns 3 (bcr 3; 30%) and around intron 6 (bcr 1 and 2: 70%). The b/p of the RARA gene were widely distributed in intron 2. In studied 8 de novo APL patients, no consensus sequence-motif was found around the b/p, but there were identical stretches of one to seven nucleotides between the PML and RARA genes in the joining regions, suggesting non-selective DNA double strand cleavage followed by single strand base-pairing within identical short stretches as a molecular mechanism of the translocation. In 4 secondary APL patients after chemotherapy including etoposide against Langerhans cell histiocytosis, the b/p of the PML gene were located in intron 6, and those of the RARA gene were in a restricted region within intron 2, 1 kb EcoRI-BamHI fragment, while in an APL patient after chemotherapy without etoposide against breast cancer, the b/p of the PML and RARA genes were located in intron 6 and another region within intron 2, respectively. These data suggest that a different mechanism was associated with the t(15;17) translocation in etoposide-related APL.

Etoposide-related acute promyelocytic leukemia.

The development of therapy-related acute myeloid leukemia (t-AML) has become a growing concern over the past decade, because of the increase in the percentage of long-term survivors of primary malignancy. We reviewed 17 cases with etoposide-related acute promyelocytic leukemia (APL) reported in the literature. The close association between treatment with etoposide for Langerhans cell histiocytosis (LCH) and the development of etoposide-related APL was demonstrated among Japanese and Italians. Our data on the breakpoints (b/ps) of the PML and RARalpha genes are presented. It is suggested that chromatin structure might be more important than specific consensus sequence in the distribution of b/ps in etoposide-related APL.

Homozygous deletions of p16/MTS1 and p15/MTS2 genes are frequent in t(1;19)-negative but not in t(1;19)-positive B precursor acute lymphoblastic leukemia in childhood.

We analyzed 60 B precursor acute lymphoblastic leukemia (ALL) primary samples and 15 cell lines for homozygous deletions of p16 and p15 genes and mutations of p16 gene. These included five cell lines and 13 primary samples with the t(1;19)(q23;pl3), and eight primary samples with the t(9;22)(q34;qll). Of 10 cell lines without t(1;19), homozygous deletion of both p16 and p15 genes was found in eight cell lines (80%), and a rearrangement of p16 in one cell line (10%). In contrast, only one (20%) of the five cell lines with t(1;19) showed homozygous deletion or rearrangement of p16/p15 gene. Thirteen of 60 (22%) primary samples demonstrated p16 gene homozygous deletion. No case with t(1;19) showed homozygous deletion of p16 gene (0/13, 0%), while cases without t(1;19) showed considerable incidence of p16 gene homozygous deletion (13/47, 28%). These results suggest that the incidence of deletions of p16 gene differs according to the subtypes of B precursor ALL. We also compared the frequency of p16 gene homozygous deletion between the patients at diagnosis and at relapse. Nine of 45 (20%) samples at diagnosis and four of 22 (18%) samples at relapse showed p16 homozygous deletions. The similarity of the rate in these two groups raises the question of the role of p16 gene in progression of B precursor ALL. Mutations were found in three of the primary cases (5%); the mutations included two nonsense mutations at codon 72 and one missense mutation at codon 98. All the mutations found in this study were heterozygous, and the clinical relevance of p16 gene mutation is yet to be determined in these case

High expression of EVI1 and MEL1 is a compelling poor prognostic marker of pediatric AML.

EVI1 and MEL1 are homolog genes whose transcriptional activations by chromosomal translocations are known in small subsets of leukemia. From gene expression profiling data of 130 Japanese pediatric acute myeloid leukemia (AML) patients, we found that EVI1 and MEL1 were overexpressed in ~30% of patients without obvious translocations of these gene loci, and that their high expression was significantly associated with inferior survival. High EVI1 expression was detected mainly in myelomonocytic-lineage (designated as e-M4/M5 subtype) leukemia with MLL rearrangements and in megakaryocytic-lineage (designated as e-M7 subtype) leukemia, and its prognostic association was observed in the e-M4/M5 subtype but not in the e-M7 subtype. On the other hand, high MEL1 expression was detected in myelocytic-lineage (designated as e-M0/M1/M2 subtype) and e-M4/M5 subtype leukemia without MLL rearrangements, and its prognostic association was independent from the subtypes. Because of their subtype-dependent and mutually exclusive expression, a combined evaluation of their high expression enabled a clear distinction of patients with inferior survival (P<0.00001 in event-free survival (EFS) and overall survival (OS)). This association was confirmed by quantitative reverse transcription PCR analysis of an independent cohort of 81 patients (P=0.00017 in EFS, P=0.00028 in OS). We propose that the combined estimation of EVI1 and MEL1 expression will be an effective method to predict the prognosis of pediatric AML.

Early use of allogeneic hematopoietic stem cell transplantation for infants with MLL gene-rearrangement-positive acute lymphoblastic leukemia.

Sixty-two infants with MLL gene-rearrangement-positive acute lymphoblastic leukemia (MLL-r ALL) were treated with the MLL03 protocol of the Japanese Pediatric Leukemia/Lymphoma Study Group: short-course intensive chemotherapy followed by early allogeneic hematopoietic stem cell transplantation (HSCT) within 4 months of the initial induction. The 4-year event-free survival and overall survival rates were 43.2% (95% confidence interval (CI)=30.7-55.1%) and 67.2% (53.8-77.4%), respectively. A univariate analysis showed younger age (<90 days at diagnosis), central nervous system disease and poor response to initial prednisolone therapy significantly associated with poor prognosis (P<0.05). In a multivariate analysis, younger age at diagnosis tended to be associated with poor outcome (hazard ratio=1.969; 95% CI=0.903-4.291; P=0.088). Although the strategy of early use of HSCT effectively prevented early relapse and was feasible for infants with MLL-r ALL, the fact that substantial number of patients still relapsed even though transplanted in their first remission indicates the limited efficacy of allogeneic HSCT for infants with MLL-r ALL. Considering the risk of severe late effects, indications for HSCT should be restricted to specific subgroups with poor risk factors. An alternative approach incorporating molecular-targeted drugs should be established.

Bone marrow transplantation for children with acute myelogenous leukaemia in the first complete remission.

Of 52 children aged 9 months to 16 years old with acute myelogenous leukaemia (AML) in first complete remission undergoing bone marrow transplantation at our institution, 31 received allogeneic transplants (allo-BMT) and 21 received autologous transplants (ABMT). Initial induction and consolidation chemotherapy were not uniform. BMT was performed at a median of 7 months (range: 2.5 to 22.5 months) from the diagnosis. Conditioning included chemotherapy (n=43: 4 x 4 mg/kg of busulfan and 3 x 60 to 70 mg/m(2) of melphalan) or total body irradiation (12 Gy) plus chemotherapy (n=9). Graft-versus-host disease (GVHD) prophylaxis in allo-BMT cases consisted of methotrexate +/- cyclosporin A. Unpurged marrow was used in ABMT cases. All patients showed sustained engraftment. Amongst allograft cases, acute or chronic GVHD developed in 7 patients each (23%). 8 patients (15%) died (5 with allo-BMT, 3 with ABMT), including transplant-related mortality in 3 of the allo-BMT patients. 7 patients had relapses (3 with allo-BMT, 4 with ABMT). As of June 1999, 43 patients are alive and well 13 to 160 months after BMT (median, 71), with 5-year disease-free survival rates after BMT of 84% for allo-BMT, 81% for ABMT and 83% altogether. Although the presented data are based on a retrospective evaluation, we consider BMT for childhood AML during first complete remission an effective treatment for eradicating leukaemia.

A randomised dose-comparison trial of granisetron in preventing emesis in children with leukaemia receiving emetogenic chemotherapy.

This randomised study was performed to assess the anti-emetic efficacy and tolerability of two-dose regimens of granisetron in children with leukaemia. 49 children with leukaemia were treated with three consecutive courses of high-dose methotrexate or cytarabine regimen. During the first course, patients were evaluated regarding the emetogenicity of each regimen. They were randomised in a crossover manner to receive 20 or 40 micrograms/kg of granisetron before the second and third course of chemotherapy. Neither emesis nor severe appetite loss were observed in over 80% of patients within the first 24 h in all treatment groups. There was no significant difference in the anti-emetic efficacy between the two-dose regimens of granisetron. However, complete protection was achieved less frequently on days 2 and 3. Older children and girls appeared to be less well protected. No adverse events attributable to granisetron were observed. Granisetron dose regimens of 20 and 40 micrograms/kg are, comparably, well tolerated and effective in controlling chemotherapy-induced emesis in the first 24 h, though this protection fails thereafter, particularly in older patients and girls.

Pathology review for paediatric non-Hodgkin's lymphoma patients in Japan; a report from the Japan association of childhood leukaemia study (JACLS).

A central pathology review system with an immunophenotyping laboratory was established in Japan to support the clinical trial, the Japan Association of Childhood Leukaemia Study (JACLS) NHL-98, for patients with paediatric non-Hodgkin's lymphoma (NHL). Pathology samples from 155 clinically-suspected NHL cases were evaluated centrally initially using the Revised European-American Lymphoma (REAL) classification in a rapid review (within 2 weeks after surgery/biopsy) and then later at the consensus review (once a year). The samples were subsequently re-classified according to the new World Health Organisation (WHO) classification. After the pathology review, 96 (62%) patients were eligible for the study, and 58 of them (60%) had extra-nodal primaries. These NHL cases included B-cell lymphomas (precursor B-cell, 11; Burkitt, 18; diffuse large B-cell, 18; not otherwise specified, 3) and T/Natural Killer (NK)-cell lymphomas (precursor T-cell, 23; anaplastic large cell, 20; others, 3). There was excellent concordance in making the diagnoses (95/96, 99%) and typing (93/96, 97%) of NHL between the rapid and consensus reviews. Five cases, initially diagnosed as diffuse large B-cell lymphoma by the review, were re-classified as Burkitt lymphoma according to the immunocytochemical criteria by the WHO classification. A total of 59 (38%) cases were excluded from the study: they were Hodgkin lymphoma (7), leukaemias (11), reactive lymphoid hyperplasia (20), necrotizing lymphadenitis (7), no consensus diagnosis (1), insufficient materials (2), and others (11). This is the first report of the central pathology review from the paediatric NHL group study in Japan. Because various diseases, either neoplastic or reactive, mimicked NHL, clinically and histopathologically, the central pathology review system was critical and essential for patient enrollment and protocol assignment in our clinical trial. Through the two-step review system, highly reliable data were generated to support this study.

Flow cytometric determination of intracytoplasmic Wiskott-Aldrich syndrome protein in peripheral blood lymphocyte subpopulations.

We have produced a novel monoclonal antibody (mAb) directed against Wiskott-Aldrich syndrome protein (WASP) by immunizing mice with the recombinant protein. The mAb designated 5A5 is highly specific to WASP and suitable for Western blot analysis and immunoprecipitation. A flow cytometric assay using the 5A5 mAb identifies expression of intracytoplasmic WASP in lymphocytes from normal individuals. Double staining analysis with cell surface CD3, CD19, and CD56, and intracytoplasmic molecules revealed WASP expression in each subpopulation. With regard to WASP expression in patients with Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT), peripheral blood mononuclear cells (PBMCs) from nine patients and Epstein-Barr virus-transformed B-lymphoblastoid cell lines from seven patients examined did not show WASP expression by flow cytometric analysis. These results were confirmed by Western blot analysis. We conclude that WASP expression in lymphocyte subpopulations from patients with WAS and XLT can be more precisely evaluated by flow cytometry as compared with Western blot analysis. This flow cytometry method is important as a supplement to Western blots, but even more important as an alternative and powerful assay that can contribute to research on WASP as well as diagnosis in a clinical setting.

Cerebral blood flow imaging with technetium-99m-HMPAO SPECT in a patient with chronic subdural hematoma: relationship with neuropsychological test.

We report the relationship between cerebral blood flow (CBF) and neuropsychologic tests in a patient with a chronic subdural hematoma suffering from severe dementia and left hemiparesis. Regional CBF was quantified using 99mTc-HMPAO SPECT and 133Xe-CBF. CBF-SPECT could detect the hematoma which was isodense by CT scan and the neuropsychological test improved remarkably with the increase in CBF after surgery. We conclude that if there is a strong clinical suspicion of subdural hematoma and CT scan is not diagnostic then CBF-SPECT may be valuable in localizing the hematoma and monitoring the effect of operation.