Diffusion-weighted magnetic resonance imaging of intracranial epidermoid tumours

CT cisternography to visualize epidermoid tumors for stereotactic radiosurgery treatment planning

The visualization of intracranial epidermoid tumors is often limited by difficulties associated with distinguishing the tumor from the surrounding cerebrospinal fluid using traditional computed tomography (CT) or magnetic resonance imaging (MRI) modalities. This report describes our experience using CT cisternography to visualize intracranial epidermoid tumors in three illustrative cases. CT cisternography of the epidermoid tumor provides more clarity and precision compared to traditional neuroimaging modalities. We demonstrate the feasibility of using CT cisternography to produce high-resolution images with well-defined tumor margins that can be used effectively for precise SRS treatment planning.

Intracranial epidermoid tumor; microneurosurgical management: An experience of 23 cases

OBJECTIVES

An intracranial epidermoid tumor is relatively a rare tumor, accounting for approximately 0.1% of all intracranial space occupying lesions. These are also known as pearly tumor due to their pearl like appearance. In this series, the localization of the tumor, presenting age and symptoms, imaging criteria for diagnosis, surgical management strategy with completeness of excision and overall outcome were studied prospectively. Here, we report our short experience of intracranial epidermoid as a whole.

MATERIALS AND METHODS

Between January 2006 to December 2010, 23 cases of intracranial epidermoid were diagnosed preoperatively with almost certainty by computed tomography (CT) and magnetic resonance imaging (MRI) of brain in plain, contrast and other relevant studies. All of them underwent operation in Dhaka Medical College Hospital and in some Private Hospital in Dhaka, Bangladesh. All patients were followed-up routinely by clinical examination and neuroimaging. Average follow-up was 39 (range-71-11months) months. Patients of the series were prospectively studied.

RESULTS

Supratentorial epidermoids were 04 cases and infratemporal epidermoids were 19 cases. Clinical features and surgical strategy varies according to the location and extension of the tumors. Age range was 19-71 years (37.46 years). Common clinical features were headache, cerebellar features, seizure, vertigo, hearing impairment and features of raised intracranial pressure (ICP). Investigation was CT scan or/+ MRI of brain in all cases. Pre-operative complete excision was 20 cases, but post-operative images showed complete excision in 17 cases. Content of tumor was pearly white/white material in all cases except one, where content was putty material. Re-operation for residual/recurrent tumor was nil. Complications included pre-operative mortality one case, persisted sixth nerve palsy in one case, transient memory disturbance one case, and extra dural hematoma one case. One senior patient expired three months after the operation from spontaneous intracerebral hemorrhage. Rest of the patients were stable and symptom/s free till last follow-up.

CONCLUSION

In the management of such tumors, one should keep in mind that an aggressive radical surgery carrying a high morbidity and mortality and a conservative subtotal tumor excision is associated with a higher rate of recurrence, but earlier diagnosis and complete excision or near total excision of this benign tumor can cure the patient with the expectation of normal life.

Differentiation between pediatric spinal arachnoid and epidermoid-dermoid cysts: is diffusion-weighted MRI useful?

BACKGROUND

Appropriate differentiation between epidermoid-dermoid and arachnoid cysts is important for patient management. MRI has had limitations in differentiating these two types of cysts, especially in the region of the spinal cord.

OBJECTIVE

To evaluate the role of diffusion-weighted (DW) MRI for differentiation between spinal arachnoid and epidermoid-dermoid cysts.

MATERIALS AND METHODS

Four children underwent conventional and DW MRI. Turbo spin-echo imaging was used to obtain DW images.

RESULTS

On conventional MRI, low T1-W and high T2-W signal was present in all lesions. DW imaging showed restricted diffusion in two patients with epidermoid-dermoid cysts and no water restriction in two patients with arachnoid cysts. Three of four children had extramedullary lesions and one patient had an intramedullary lesion. Three children had surgery, two with epidermoid-dermoid cysts and one with arachnoid cyst. Diagnosis was confirmed by histopathology. One child with a thoracic arachnoid cyst had stable clinical imaging findings during a follow-up of 21 months.

CONCLUSION

On conventional MRI, epidermoid-dermoid and arachnoid cysts have similar signal characteristics. Initial experience with spine DW imaging shows promise in differentiating epidermoid-dermoid cysts from arachnoid cysts. Preoperative differentiation is important because it changes management and surgical approach.

The role of diffusion-weighted magnetic resonance imaging in pediatric brain tumors

OBJECTIVES

Diffusion-weighted imaging (DWI) may enhance the radiographic diagnosis of pediatric brain tumors. This study reviews the DWI properties of pediatric brain tumors at our institution and examines their relationship to tumor grade and type.

MATERIALS AND METHODS

The preoperative DWI and apparent diffusion coefficient (ADC) characteristics of brain tumors in 41 children were compared with histologic diagnosis. Signal characteristics on DWI and ADC maps correlated well with tumor grade. High-grade lesions were hyperintense on DWI and hypointense on ADC maps. Sensitivity, specificity, positive predictive value, and negative predictive value were 70, 100, 100, and 91%, respectively. Signal characteristics did not differ among different tumors of the same grade. All primitive neuroectodermal tumors showed diffusion restriction whereas none of the ependymomas did.

CONCLUSIONS

The signal characteristics on DWI and ADC maps appeared to be strongly correlated to grade in pediatric brain tumors and they may assist with preoperative diagnostic predictions.

Diffusion Tensor Magnetic Resonance Imaging of Brain Tumors

DTI seems to offer the possibility of adding important information to presurgical planning. Although experience is limited, DTI seems to provide useful local information about the structures near the tumor, and this seems to be useful in planning. In the future, DTI may provide an improved way to monitor intraoperative surgical procedures as well as their complications. Furthermore, evaluation of the response to treatment with chemotherapy and radiation therapy might also be possible. Although DTI has some limitations, its active investigation and further study are clearly warranted.

Intracranial epidermoid cysts: diffusion-weighted, FLAIR and conventional MR findings

PURPOSE

To compare diffusion-weighted echo-planar imaging (DW) with spin-echo (SE), and fluid-attenuated inversion recovery (FLAIR) sequences in the evaluation of epidermoid cysts (ECs), and to evaluate T2 shine-through effect.

MATERIALS AND METHODS

Fifteen patients were imaged prospectively in two different 1.5 T magnetic resonance (MR) units with standard head coils with SE, FLAIR and DW echo planar imaging sequences. The qualitative and quantitative assessments were performed by two radiologists in consensus. Apparent diffusion coefficient (ADC) values were obtained from all ECs. Exponential DW images are obtained in 11 cases to eliminate T2 shine-through effects. The results are analyzed with variance analysis (ANOVA) and Bonferroni t method.

RESULTS

FLAIR sequence was superior to T1- and T2-weighted sequences in showing ECs. In 13 cases, the borders of the lesions could be delineated from the surrounding structures with only DW imaging where ECs were markedly hyperintense. The ADC values of ECs are significantly lower than CSF (P < 0.001), and significantly higher than deep white matter (P < 0.01). On exponential DW images, ECs had similar intensity with brain parenchyma showing that the real cause of the hyperintensity of the lesions on trace images is the enhanced T2 effect of the tissue.

CONCLUSION

FLAIR sequence is superior to the conventional MR sequences in demonstrating the ECs and DW imaging is superior to other MR sequences in delineating the borders of the ECs. Exponential DW images had shown that the hyperintensity in the trace images are caused by increased T2 effect of the lesion rather than the decrease in ADC values.

Diffusion tensor magnetic resonance imaging of brain tumors

DTI seems to offer the possibility of adding important information to presurgical planning. Although experience is limited, DTI seems to provide useful local information about the structures near the tumor, and this seems to be useful in planning. In the future, DTI may provide an improved way to monitor intraoperative surgical procedures as well as their complications. Furthermore, evaluation of the response to treatment with chemotherapy and radiation therapy might also be possible. Although DTI has some limitations, its active investigation and further study are clearly warranted.

Reflexions about imaging technique and examination protocol 2. MR-examination protocol

Adequate imaging protocol is crucial for any imaging technique. As MR is a time consuming examination, the physician serves the patient best, when he/she makes the best choice of sequences, which answer the question of the clinician and provide a definite diagnosis. Although any patient requires an individual protocol, some general rules should be known.

Epidermoid of the lateral ventricle: evaluation with diffusion-weighted and diffusion tensor imaging

We report of a large epidermoid tumor of the lateral ventricle in a 67-year-old man. Conventional imaging (CT, T1/T2, MRI) could not differentiate the tumor from the surrounding cerebral spinal fluid (CSF). On diffusion-weighted and diffusion anisotropy images the tumor was clearly seen as a hyperintense mass surrounded by hypointense CSF, highly suspected for epidermoid. Diffusion-tensor imaging (DTI) accentuated its lobulated structure and clearly demonstrated its relationship to neighboring white matter tracts. We suggest that in case of the suspicion of a space-occupying lesion in CSF containing areas, not distinguishable from CSF by conventional MR imaging, diffusion-weighted and diffusion-tensor MR imaging should be added.

Diffusion-weighted MRI of cholesteatomas of the petrous bone

PURPOSE

To investigate if primary cholesteatomas of the petrous bone show high signal in diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

In this blinded study, we compared 15 patients with clinically certain cases and later surgically proven cholesteatomas vs. 12 patients with clinically acute otitis of the middle ear and 20 volunteers without petrous bone disease. Two blinded readers without knowledge of the clinical data decided in consensus agreement whether there was a pathologic signal increase in the petrous bone in an anisotropic single-shot echo-planar imaging (EPI) DWI sequence, an artifact, or no signal increase.

RESULTS

Thirteen of 15 patients with cholesteatomas showed bright signal in EPI DWI, whereas 10 of 12 patients with acute otitis media and all volunteers presented the usual low signal of petrous bone.

CONCLUSION

EPI DWI is a fast diagnostic method that may be an additional valuable tool in the workup of suspected cholesteatomas. The ability of this technique to differentiate between cholesteatomas and granulomas or chronic otitis is not yet available.

Huge craniopharyngioma: diffusion MRI and contrast-enhanced FLAIR imaging

Craniopharyngiomas are most commonly located extraaxially in the suprasellar area. They are benign but aggressive neoplasms. An adult patient is reported to have a huge craniopharyngioma with gross extensions to the surroundings. In diffusion MRI, it had high signal for b=1000 mm(2)/s (true diffusion) images, and at the same time, high ADC values (=2.12 and 2.27 x 10(-3)mm(2)/s, compared to that of normal cerebellar parenchyma 0.85 x 10(-3)mm(2)/s). In FLAIR images, obtained after administration of intravenous contrast medium, an intense, diffuse enhancement pattern was seen involving the viable tumor portions as well as the intratumoral fluid.

Evaluating pediatric brain tumor cellularity with diffusion-tensor imaging

OBJECTIVE

MR imaging of central nervous system (CNS) malignancies falls short of a definitive evaluation. Tissue diagnosis remains the gold standard. Diffusion-tensor MR imaging measures the apparent diffusion coefficient and diffusion anisotropy of water in tissue. The purpose of this study was to test the hypothesis that the apparent diffusion coefficient may improve the MR imaging evaluation of newly diagnosed CNS neoplasms. We examined the relationship between the apparent diffusion coefficient, anisotropy, and tumor cellularity in 12 pediatric patients.

MATERIALS AND METHODS

On the basis of histopathologic evaluation, tumors in this case series were segregated into three types: low-grade gliomas, embryonal tumors, and nonembryonal high-grade tumors. Mean apparent diffusion coefficient and anisotropy values obtained from the solid components of each tumor were compared with cellularity, total cellular area, and total nuclear area derived from biopsy material.

RESULTS

The apparent diffusion coefficient ratio (tumor to normal brain) correlated well with tumor classification (p = 0.001). Anisotropy was decreased similarly in all tumor classifications. The absolute apparent diffusion coefficient correlated well with cellularity (p = 0.014) and total nuclear area (p = 0.005) per high-power field. The correlation between apparent diffusion coefficient and total cellular area per high-power field was not statistically significant.

CONCLUSION

The apparent diffusion coefficient may be predictive of tumor classification and may be a useful tool in characterizing tumor cellularity and total nuclear area. These parameters are not available in standard MR imaging. Therefore, diffusion-tensor imaging may enhance the diagnostic process in pediatric CNS malignancies.