Magnetic resonance imaging of interstitial laser photocoagulation in brain.

Magnetic resonance (MR) imaging can be used to monitor the development of thermal lesions induced in tissue using interstitial laser photocoagulation (ILP). A potential application for ILP is the treatment of surgically inaccessible brain tumors. For the successful clinical application of MR-monitored ILP, it is necessary to relate MR images of ILP lesions to the actual induced lesions. In this preliminary study we performed ILP in the normal brains of anesthetized cats by delivering interstitially 1.0, 1.5, and 2.0 W of continuous-wave Nd:YAG laser energy (1,064 nm) for 1,000 s via a plane-cut 400 microns core optical fiber. At 48 h post-irradiation the lesions consisted of four sharply demarcated concentric zones of thermal damage. Lesion diameter increased linearly with delivered power. T2-weighted proton spin-echo images acquired during ILP showed a region of complete or near signal loss that underestimated the actual lesion at 48 h. Gadolinium-enhanced T1-weighted spin-echo images acquired immediately post-irradiation showed the actual lesion precisely.     

Measurement of lesion area and volume by three-dimensional spoiled gradient-echo MR imaging in osteonecrosis of the femoral head.

The purpose of this investigation is to evaluate the diagnostic ability of three-dimensional spoiled gradient-echo (3D SPGR) magnetic resonance (MR) imaging in cases of osteonecrosis of the femoral head (ONFH), and to determine the accuracy of 3D SPGR imaging in area and volume measurement of ONFH. T1-weighted spin-echo (SE) and 3D SPGR imaging were performed on 20 femoral heads obtained from patients with ONFH. After MR imaging, the femoral heads were cut parallel to the imaging plane and were evaluated histologically. Areas and volumes of necrotic lesions were measured with a computer program and the deviation between MR images and anatomical measurements was evaluated. A low signal intensity band on 3D SPGR MR images was observed in all femoral heads and corresponded histologically to repaired marrow with viable fibrous mesenchymal tissue. The area proximate to the low band area coincided with the necrotic region. Both area and volume measurements by T1-weighted SE and 3D SPGR images showed a strong correlation to histological measurements. The discrepancies between histological and imaging results were minimal in 3D SPGR imaging, especially at the anterior and posterior portions of the femoral head. Three-dimensional SPGR imaging provides more accurate measurements of the area and volume of a necrotic lesion than T1-weighted SE imaging.     

Sequential magnetic resonance imaging following stereotactic radiofrequency ventralis lateralis thalamotomy

Serial postoperative magnetic resonance (MR) studies were obtained in 21 patients who underwent somatotopically placed stereotactic radiofrequency (rf) ventralis lateralis thalamotomy for the control of movement disorders. The MR studies were reviewed to determine the MR characteristics of early-phase (less than or equal to 7 days) and late-phase (8 days to 5 months) lesions. Surgery was performed for the control of parkinsonian tremor (14 cases), intention tremor (six cases), and essential tremor (one case). Single rf lesions were made with an electrode (1.6 mm in diameter, 3 mm in tip length) heated to 78 degrees C for 60 seconds. On MR images of the lesions, three distinct concentric zones were identified, described as follows (from the center outward). Zone 1 gives increased signal on long-relaxation time (TR) (T2-weighted) MR images in early- and late-phase lesions and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. Zone 2 gives decreased signal on long-TR (T2-weighted) images in early- and late-phase lesions; it gives isointense signal on short-TR (T1-weighted) images in early-phase lesions only. Zone 3 gives increased signal on long-TR (T2-weighted) images in early-phase lesions only and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. It is considered that in early-phase lesions, Zone 2, with a mean diameter of 7.3 mm on axial long-TR (T2-weighted) imaging, represents an area of hemorrhagic coagulation necrosis. In late-phase lesions, Zone 2, with a mean diameter of 5.0 mm on axial long-TR (T2-weighted) imaging, represents hemosiderin deposition. Zone 3 likely represents edema, and this zone disappears between the early and late periods. From regression analysis, lesion size began to stabilize at approximately 7 months with a mature lesion diameter of 3.3 mm. Long-term follow-up monitoring (median 16 months) showed good tremor control. Based on clinical and radiological findings, the authors conclude that forms of hemoglobin are suitable markers to assess the size of rf lesions. Serial MR imaging provides a noninvasive means of studying the evolution of rf thalamotomy lesions.     

0.23 T开放性磁共振实时引导下经皮激光热消融术 治疗肝脏恶性肿瘤

目的 评价肝脏肿瘤在磁共振介入激光治疗中的热消融变化及光学器械追踪系统对激光纤维的精确定位和实时监测激光治疗中热消融变化的能力，观察激光消融治疗肝脏恶性肿瘤的可行性与安全性。方法 对经病理学活检证实的14例恶性肝脏肿瘤患者(4例为肝细胞癌，10例为肝转移瘤，共22个肿瘤)进行0．23T开放性磁共振成像系统与介入引导下经皮激光热消融治疗术。结果 全部病灶均被成功定位、靶定并消融治疗。肿瘤形态、术后瞬间及3天后热消融形成的凝固坏死灶均在磁共振图像上显示。除1例有部分残余外，所有热消融灶均大于各自原始肿瘤大小；术后3天热消融凝固灶大于术后瞬间凝固灶。结论 磁共振引导经皮肝脏肿瘤激光热消融术是可行和安全的；光学追踪系统引导与磁共振温度监测对准确估计热治疗效果是有用且可信赖的工具。     

Interstitial laser photocoagulation: Evaluation of a 1320 nm Nd-YAG and an 805 nm diode laser: the significance of charring and the value of precharring the fibre tip

Interstitial laser photocoagulation (ILP) is a new percutaneous technique of thermal destruction (necrosis) of deep-seated tumours, using low power laser energy. Our purpose was to investigate: (i) the effects of different laser wavelengths on the extent of thermal damage produced; and (ii) the role of charring around the fibre tip during ILP. Forty-five normal Wistar rats (250–300 g) had ILP to their liver (exposed at laparotomy) by inserting a 400 μm optical fibre into the liver, and activating the laser at 1, 2 or 3W. This was performed at three laser wavelengths (1064 nm Nd-YAG, 1320 nm Nd-YAG, 805 nm diode) using a clean plane-cleaved fibre, and at two wavelengths (1064 nm and 1320 nm Nd-YAG) using a fibre with pre-charring at its tip. The 805 nm and 1320 nm laser wavelengths produced significantly greater necrosis than the 1064 nm, using a clean fibre tip (mean diameters at 2 W were 21.7 mm, 18.3 mm, 8 mm respectively). Pre-charring the fibre significantly increased the necrotic lesion size at 1064 nm (mean diameter at 2 W was 14.7 mm). Using more strongly absorbed wavelengths (805 nm and 1320 nm) and pre-charring the fibre tip give greater thermal damage during ILP, contrary to previously held views that the optimal wavelength for ILP was 1064 nm in the absence of charring.     

Colloid (enterogenous) cyst in the frontal lobe

A 60-year-old man presented with a left frontal mass lesion incidentally detected at a health check without apparent symptoms. Computed tomography revealed the lesion as homogeneous high density and magnetic resonance (MR) imaging showed the lesion as hyperintense on T(1)-weighted images, isointense on T(2)-weighted images, and hypointense on diffusion-weighted images. T(1)-weighted MR images with gadolinium showed no enhancement of the mass lesion. Cerebral angiography revealed an avascular area around the left frontal lesion. Total removal of the lesion was achieved through a craniotomy without complications. Histological, immunohistochemical, and electron microscopy examinations established the definite diagnosis of colloid cyst.     

磁共振观察宫颈癌放疗后盆部骨髓变化

目的分析宫颈癌放疗中与放疗后盆部骨髓MR改变。探讨MR成像对显示盆部骨髓损伤的临床价值。方法48例经病理证实的宫颈癌患者在放射治疗前及治疗中和治疗后不同时间段行盆腔的轴位SE T1WI，轴位及矢状位TSE T2WI，冠状位SPIR，以及Gd—DTPA增强后T1WI SE的轴位、冠状位、矢状位扫描。在MR图像上观察盆部骨髓在放疗前后的信号改变。结果骨髓信号最早出现改变是在外照射开始后第8天，患者受照剂量在12Gy时。放疗早期，骨髓在T1WI，T2WI及SPIR序列上信号升高，T1WI增强扫描见强化。放疗晚期，骨髓的T1WI，T2WI信号升高程度增加，SPIR序列出现信号降低，T1WI增强扫描，骨髓强化不明显。53％的患者在T1WI、T2WI上，18％的患者在SPIR序列上见照射野外骨髓信号有改变。结论宫颈癌外照射放疗可引起照射野内、外骨髓多种MR信号改变，并有一定规律性，对宫颈癌临床治疗有指导意义。     

Magnetic resonance imaging for assessment of radiofrequency lesions in kidney tissue immediately after ablation: an experimental study

BACKGROUND AND PURPOSE: Radiofrequency ablation (RFA) is an attractive minimally invasive treatment option for small renal masses. The purpose of this study was to investigate the morphologic imaging appearance of RF lesions immediately after the ablation of kidney tissue using standard clinical MR sequences, as well as to investigate the correlation between MR and gross lesion size. MATERIALS AND METHODS: Ablations were performed 17 times in a standardized model of ex-vivo perfused porcine kidneys using a resistance-controlled RF device (250 W, 470 kHz) and a nonexpandable bipolar applicator inserted into the center of healthy renal parenchyma. The RF current was applied for 9 minutes at 20 W. Imaging was performed after ablation using standard clinical MR sequences: morphologic T(1)/T(2)- weighted images and an isotropic post-contrast T(1) high-resolution measurement (VIBE). Maximum lesion diameters were measured in three directions and were compared with the measurements of the gross lesions. Histologic (hematoxylin + eosin and nicotinamide adenine dinucleotide staining) and statistical analyses were performed. RESULTS: The gross pathologic examination showed a firm, white-yellow ablation zone sharply demarcated from the untreated tissue. The histologic examination confirmed cellular viability outside but not in the treatment zone. The RF lesions were hyperintense on T(1)-weighted images and hypointense on T(2)-weighted images. The lesion size measured in the VIBE images correlated best with the macroscopic lesion size (N = 16). CONCLUSIONS: Morphologic MR T(1) and T(2) sequences of RF lesions immediately after ablation produce reliable and consistent imaging characteristics. The post-contrast, high-resolution sequence (VIBE) enables the extent of the lesion to be determined accurately. The potential uses of this imaging strategy in clinical practise warrant further investigation on human renal-cell carcinoma.     

A distinct phenotypic change in gliomas at the time of magnetic resonance imaging detection

OBJECT: Although gliomas remain refractory to treatment, it is not clear whether this characteristic is fixed at the time of its origin or develops later. The authors have been using a model of neurocarcinogenesis to determine whether a time exists during a glioma's evolution during which it is detectable but still curable, thus providing a justification for exploring the clinical merits of an early detection and treatment strategy. The authors recently reported the presence of 2 distinct cellular subsets, 1 expressing nestin and the other both glial fibrillary acidic protein (GFAP) and osteopontin (OPN), within all examined gliomas that developed after in utero exposure to ethylnitrosourea. METHODS: In this study, the authors used magnetic resonance (MR) imaging to assess when these 2 subpopulations appeared during glioma evolution. RESULTS: Using T2-weighted and diffusion-weighted MR imaging, the authors observed that gliomas grew exponentially once detected at rates that were location-dependent. Despite large differences in growth rates, however, they determined by correlating histochemistry with imaging in a second series of animals, that all lesions initially detected on T2-weighted images contained both subsets of cells. In contrast, lesions containing only nestin-positive cells, which appeared on average 40 days before detection on MR images, were not detected. CONCLUSIONS: The sequential appearance of first the nestin-positive cells followed several weeks later by those expressing GFAP/OPN suggests that all gliomas arise through common early steps in this model. Furthermore, the authors hypothesize that the expression of OPN, a molecule associated with cancer aggressiveness, at the time of T2-weighted detection signals a time during glioma development when the lesion becomes refractory to treatment.     

Prognostic relevance of the postoperative evolution of intramedullary spinal cord changes in signal intensity on magnetic resonance imaging after anterior decompression for cervical spondylotic myelopathy

OBJECT: Areas of intramedullary signal intensity changes (hypointensity on T1-weighted magnetic resonance [MR] images and hyperintensity on T2-weighted MR images) in patients with cervical spondylotic myelopathy (CSM) have been described by several investigators. The role of postoperative evolution of these alterations is still not well known. METHODS: A total of 47 patients underwent MR imaging before and at the end of the surgical procedure (intraoperative MR imaging [iMRI]) for cervical spine decompression and fusion using an anterior approach. Imaging was performed with a 1.5-tesla scanner integrated with the operative room (BrainSuite). Patients were followed clinically and evaluated using the Japanese Orthopaedic Association (JOA) and Nurick scales and also underwent MR imaging 3 and 6 months after surgery. RESULTS: Preoperative MR imaging showed an alteration (from the normal) of the intramedullary signal in 37 (78.7%) of 47 cases. In 23 cases, signal changes were altered on both T1- and T2-weighted images, and in 14 cases only on T2-weighted images. In 12 (52.2%) of the 23 cases, regression of hyperintensity on T2-weighted imaging was observed postoperatively. In 4 (17.4%) of these 23 cases, regression of hyperintensity was observed during the iMRI at the end of surgery. Residual compression on postoperative iMRI was not detected in any patients. A nonsignificant correlation was observed between postoperative expansion of the transverse diameter of the spinal cord at the level of maximal compression and the postoperative JOA score and Nurick grade. A statistically significant correlation was observed between the surgical result and the length of a patient's clinical history. A significant correlation was also observed according to the preoperative presence of intramedullary signal alteration. The best results were found in patients without spinal cord changes of signal, acceptable results were observed in the presence of changes on T2-weighted imaging only, and the worst results were observed in patients with spinal cord signal changes on both Tl- and T2-weighted imaging. Finally, a statistically significant correlation was observed between patients with postoperative spinal cord signal change regression and better outcomes. CONCLUSIONS: Intramedullary spinal cord changes in signal intensity in patients with CSM can be reversible (hyperintensity on T2-weighted imaging) or nonreversible (hypointensity on T1-weighted imaging). The regression of areas of hyperintensity on T2-weighted imaging is associated with a better prognosis, whereas the T1-weighted hypointensity is an expression of irreversible damage and, therefore, the worst prognosis. The preliminary experience with this patient series appears to exclude a relationship between the time of signal intensity recovery and outcome of CSM.     

Spontaneous regression of an asymptomatic meningioma associated with discontinuation of progesterone agonist administration

An 80-year-old male visited the hospital as an outpatient with a head injury sustained in a traffic accident. Brain computed tomography incidentally revealed a left frontal lobe tumor measuring 5 cm in a diameter. The patient had a history of taking chlormadinone acetate (a progesterone agonist) prescribed several years previously as treatment for benign prostatic hypertrophy. The tumor was seen as an isointense lesion on T(1)-weighted magnetic resonance (MR) images with enhancement by gadolinium, and as a heterogeneously hyperintense mass on T(2)-weighted MR images. The tentative diagnosis was left frontal meningioma attached to the sphenoid ridge or sphenoid plane. The patient was managed conservatively because of his advanced age and no symptoms or progression were observed during a 9-month follow-up period. The medication for benign prostatic hypertrophy was changed from chlormadinone acetate to naftopidil (an alpha-2-blocker) about 9 months after his first presentation. The patient presented again 2 years later complaining of dizziness. Computed tomography and MR imaging performed at this time revealed remarkable regression of the tumor. The signal intensity change with regression of the tumor on T(2)-weighted images was observed as a hypointense lesion. Thus, we wish to emphasize that treatment of meningiomas, especially those diagnosed incidentally, must be based on a thorough consideration of any history of hormonal therapy with prostate disease.     

Magnetic resonance imaging provides accurate and precise volume determination of the regenerating mouse liver

Direct and repetitive noninvasive determination of the time course and the strain-specific hepatic regenerative capacity after partial hepatectomy can extend our knowledge about the basic mechanisms of liver regeneration and repair. The aim of this study was to develop a magnetic resonance (MR)-based volumetric procedure to measure the hepatic volume in the regenerating mouse liver. In Balb-C mice (n = 14), varying amounts of liver tissue were resected and MR imaging was performed 24 hours later in a 1.5 TeslaMagnet Unit. Three dimensional (3D) T1- (volumetric interpolated breath-hold examination [VIBE] sequence) and T2-weighted images were acquired with continuous 1-mm thin slices. Animals with and without intravenous administration of paramagnetic contrast agents were compared. Immediately after MR examination, mice were euthanized and livers were weighted. The liver volume was determined on MR images using Cavalieri’s method and linear regression analysis was performed from the data obtained. Correlation coefficients between the liver volume measured by MR and the liver weight were 0.98 (T1) and 0.94 (T2) in the group without paramagnetic contrast injection and 0.70 (T1) and 0.96 (T2) after paramagnetic contrast application. We conclude that MR-based liver volumetry allows precise liver volume measurement during hepatic regeneration after partial hepatectomy in mice and can be a valuable tool with regard to experimental hepatology. Presented at the Forty-Fifth Annual Meeting of The Society for Surgery of the Alimentary Tract, New Orleans, Louisiana, May 15–19, 2004 (poster presentation).     

Monostotic fibrous dysplasia of the cranial vault: a case report

Fibrous dysplasia, when it occurs in the craniofacial region, mostly involves the skull base and is rarely localized in the cranial vault. Although there have been several reports on magnetic resonance imaging (MRI) findings of fibrous dysplasia involving the skull base, cases occurring in the cranial vault have seldom been reported. We describe here a rare case of monostotic fibrous dysplasia that occurred in the parietal bone and discuss the characteristics of the MRI findings. A 47-year-old female was admitted to our hospital with a complaint of vertigo. A computed tomography (CT) scan did not reveal any intraparenchymal lesions in either the infra- or supratentorium, and her vertigo improved immediately without any treatments. However, a solitary osteolytic lesion was found incidentally in the left parietal bone. MRI showed that the lesion demonstrated hypointensity on T1-weighted images and hyperintensity on T2-weighted images, and was enhanced heterogeneously following injection of Gadolinium-DTPA. Removal of the parietal bone containing the lesion was performed according to the patient's wishes. The histopathological findings of the removed tissues corresponded to fibrous dysplasia. Although it is well known that craniofacial fibrous dysplasia demonstrates iso- or hypointensity on T1- as well as T2-weighted images, in the present case, the lesion showed apparent hyperintensity on T2-weighted images. These findings suggest that fibrous dysplasia can display various MR intensities depending on its origin.     

Three-dimensional comparison of interventional MR radiofrequency ablation images with tissue response.

OBJECTIVE: Solid tumors are being treated using radiofrequency (RF) ablation under interventional magnetic resonance imaging (MRI) guidance. We are investigating the ability of MRI to monitor ablation treatments by comparing MR images of thermal lesions to histologically assayed tissue damage. MATERIAL AND METHODS: An open MRI system was used to guide an ablation electrode into five rabbit thigh muscles and acquire post-ablation MR image volumes. We developed a methodology using a 3D computer registration to make spatial correlations. After MR and histology images were registered with an accuracy of 1.32+/-0.39 mm (mean+/-SD), a boundary of necrosis identified in the histology was compared with the outer boundary of the hyperintense region in MR images. RESULTS: For 14 T2-weighted MR images, the absolute distance between boundaries was 0.96+/-0.34 mm (mean+/-SD). Since the small discrepancy between boundaries is comparable to our registration accuracy, the boundaries may match exactly. Similar correlations to histology were obtained with a deformable model segmentation method. CONCLUSIONS: This is good evidence that MR thermal lesion images can be used during RF ablation treatments to accurately localize the zone of necrosis at the lesion margin.     

Identification of brain tissue necrosis by MRI: validation by histomorphometry

The volume of an experimental necrotic lesion of the cortex expands up to 400% of its initial size within the first 24 h after the insult. Lesion expansion, a clinically well known phenomenon, is often accompanied by perifocal brain edema and consequently difficult to image and to analyze by magnetic resonance imaging (MRI). Therefore we aimed to validate a T(2)-weighted spin echo sequence upon its ability to distinguish necrotic from edematous brain tissue. Male Sprague-Dawley rats (n = 5 per group) were subjected to a cortical freezing lesion leading to immediate tissue necrosis with subsequent perifocal vasogenic brain edema. Immediately and 4, 12, and 24 h after the lesion the maximal area of necrosis was quantified longitudinally by coronal T(2)-weighted spin echo MRI-scans. After the last scan, animals were sacrificed for direct comparison of the lesion area obtained by MRI and histomorphometry. In parallel groups of animals, lesion expansion was quantified by histology. The acquired T(2)-maps clearly distinguish the cortical necrosis from perifocal edema and healthy brain. Focal freezing led to a cortical lesion of 5.24 +/- 0.36 mm(2) immediately after trauma (0 h; 100%) which expanded progressively to a maximum of 6.82 +/- 0.34 mm(2) after 24 h (131%; *p < 0.01 vs. 0 h). Lesion expansion quantified by histology was almost identical (132% within 24 h). Histological assessment resulted in smaller absolute lesion areas compared to MRI, most likely due to shrinking during tissue processing (4.72 +/- 0.26 mm(2) vs. 6.82 +/- 0.34 mm(2), p < 0.01). The current study shows that necrotic brain tissue can be distinguished from surrounding brain edema by T(2)-mapping. The technique is sensitive enough to detect small changes in necrosis expansion in vivo as validated by histology. The presented technique may be a useful future tool for the non-invasive identification of necrotic brain tissue following brain injury (e. g., from trauma or ischemia).     

Acquired lumbar epidermoid cyst in an adult

A 61-year-old female complained of low back pain, and had been treated by spinal anesthetic injection more than 70 times over 14 years. Magnetic resonance (MR) imaging, performed at the age of 47 years, revealed no abnormal lesion. However, she developed irritable hypesthetic pain in the left leg at 61 years of age. MR imaging revealed a round mass appearing isointense on the T1-weighted and slightly hyperintense on the T2-weighted images. Laminectomy revealed an epidermoid cyst, which was removed. This case clearly demonstrates that adults can acquire epidermoid tumor which very probably has an iatrogenic origin. The incidence of epidermoid tumor is low, but we should be aware of the potential adverse complications such as formation of epidermoid tumors after lumbar puncture.     

Cavernous angioma of the internal acoustic meatus--case report

A 39-year-old female presented with an intrameatal cavernous angioma manifesting as hearing loss and tinnitus in the right ear which progressed over 8 months. Magnetic resonance (MR) images revealed an intrameatal lesion as ultra-high intensity, nearly as bright as cerebrospinal fluid, on the T2-weighted images, and isointensity on the T1-weighted images. Computed tomography (CT) showed the mass accompanied by stippled patterns of calcification. The patient underwent surgery under a diagnosis of calcified acoustic neurinoma. Histological studies were compatible with cavernous angioma. Intrameatal cavernous angioma is a rare disease which requires differential diagnosis from the more common neurinoma or meningioma in this location. Intrameatal lesion with ultra-high intensity on T2-weighted MR imaging and stippled patterns of calcification on CT is more likely to be cavernous angioma than acoustic neurinoma. These neuroimaging features are important information in deciding the treatment strategy.     

Intracranial epidermoid tumor with changes in signal intensity on magnetic resonance imaging because of non-hemorrhagic pathology: case report

A 61-year-old woman presented an intracranial epidermoid tumor manifesting as dizziness and right facial hypesthesia. Magnetic resonance (MR) imaging revealed a well-defined lobulated mass in the right cerebellopontine angle as nearly isointense to the cerebrospinal fluid (CSF) on both T(1)- and T(2)-weighted images but inhomogeneously hyperintense on fluid-attenuated inversion recovery images. MR imaging performed 1 year later revealed that the tumor had significantly enlarged, and now appeared hyperintense to the CSF on T(1)- and T(2)-weighted images. The lesion was confirmed at surgery to be an epidermoid tumor filled with xanthochromic fluid. Histological examination found no evidence of hemorrhage in the resected tumor, so the changes in the MR imaging signal intensity were attributed to changes in the protein concentration of the intratumoral fluid, accumulation of debris, or some other non-hemorrhagic process.     

A Case of Intraosseous Microcystic Meningioma Without a Mass Lesion

Both intraosseous and microcystic meningiomas are rare tumor types. We report the case of a 66-year-old woman with intraosseous microcystic meningioma without a mass lesion. She presented with a rare intraosseous microcystic meningioma manifesting as pain. Radiological examination revealed an osteolytic lesion in the right parietal bone. Magnetic resonance (MR) images showed iso- to hypointensity on T₁-weighted images and hyperintensity on T₂-weighted images corresponding to the lesion. T₁-weighted MR imaging with gadolinium enhancement better defined the marginal area. The inner table of the skull was disrupted prominently, and both sides of the outer table were eroded. There was fluid leakage during surgery but no obvious tumor mass. Histological examination revealed microcystic meningioma in the inner part of the defective bone. A macroscopic lesion was not found, because most of the tumor comprised microcysts, and their contents leaked out during the surgical procedure. Intraosseous microcystic meningioma may be considered as one of the differential diagnoses when the intraosseous tumor in the skull has fluid leakage and does not have a mass lesion during the surgery.     

MR imaging as predictor of delayed posttraumatic cerebral hemorrhage

The occurrence of delayed traumatic intracerebral hemorrhage or hematomas was predicted in four patients by T2-weighted magnetic resonance (MR) imaging. From June, 1986, through February, 1987, 42 patients with head injury were admitted to the Neurosurgical Service of the Seirei Mikatabara General Hospital. Cerebral contusion was suspected in six of these patients. Although the initial computerized tomography (CT) scans showed no cerebral parenchymal lesion, the initial symptoms were more serious than might have been expected from the initial CT findings and/or because their initial CT scans showed intracranial extracerebral hemorrhage. In all six, the initial CT scans were obtained within 2 hours after the injury and were followed by MR imaging. In four patients, T2-weighted MR images revealed areas of increased signal intensity in the cerebral parenchyma, where hemorrhagic changes were subsequently demonstrated by follow-up CT scans. In the remaining two, T2-weighted MR images showed no parenchymal lesion and subsequent CT scans confirmed the absence of hemorrhagic change; these two patients were discharged from the hospital without neurological deficits. It is concluded that MR imaging is useful in predicting delayed hemorrhages.