Biomedical subjects
Publications and source records attributed to R D Tien.
The limbic system has a pivotal role in attention, memory, and the emotions. The limbic lobe comprises four C-shaped arches stretching from the medial surface of the frontal lobe to the temporal pole. The anatomic relationships are elegantly demonstrated by MR imaging. This article provides an overview of the development and complex anatomy of the limbic system.
MR imaging sections of the hippocampus in different orthogonal planes are illustrated. Matching coronal slices in T2-weighted and gradient echo sequences allow a comparative evaluation of the intricate structure of the hippocampus and its relationship with adjacent structures. Techniques in volumetric assessment of the hippocampus are discussed in light of recent advancement in MR imaging.
Medial temporal sclerosis of the hippocampus and other lesions in the adjacent temporal lobe that can cause epilepsy are discussed in this article. The technical factors to consider to optimally image the hippocampus and criteria to diagnose medial temporal sclerosis are emphasized.
Comprising the septal area and the subcortical nuclei, the septal region is gray matter structures with widespread projection systems and different neurotransmitters. Although their function is poorly understood, lesions of the septal nuclei result in a syndrome of hyper-reactivity, amnesia, and hypersexuality. The pathologic processes affecting the septal region are discussed.
The limbic system seems to be involved in the pathophysiology of neuropsychiatric disorders, including dementia, schizophrenia, affective disorders, and amnestic disorders. These findings are subtle and largely went undetected until the advent of modern neuroimaging. This article discusses some of the neuroimaging findings in these disorders.
Syphilis has become much more prevalent because of the dramatic increase in immunocompromised patients. The increase in immunocompromised patients is mainly secondary to AIDS. This article is put forth to refamiliarize the reader with syphilis, specifically neurosyphilis. The neurologic symptomatology and neuroimaging characteristics are presented so that one can recognize the findings and consider the diagnosis of neurosyphilis when confronted with a patient with AIDS.
OBJECTIVE: Malignant neoplasms exhibiting mixed populations of neuronal and glial cells occurring in the cerebral hemispheres of young adults and children are well recognized, but rare. A confusing array of diagnostic terms has arisen. We describe two patients with such tumors and review the literature concerning these interesting cases. PATIENTS: A 21-year-old man and a 5-year-old girl presented with large, cystic, intracerebral lesions on magnetic resonance images, which proved to be composite neoplasms exhibiting malignant neurons and astrocytes. RESULTS: The 21-year-old man had a frontal lobe mass with enhancing and nonenhancing regions, which corresponded to cerebral neuroblastoma and anaplastic astrocytoma, respectively. The presence of occasional microtubules and rare primitive presynaptic processes, accompanied by antisynaptophysin immunoreactivity, established the neuronal nature of the cells in the enhancing region. The nonenhancing region was composed of a moderately cellular neoplasm of fibrillar astrocytes that were mitotically active. The 5-year-old girl presented with a left parietal lobe neoplasm, which histologically was composed of lobular proliferations of neuroblasts and glia. The neuroblastic populations exhibited evidence of maturation with small anaplastic cells, spindle-shaped cells, and large dysmorphic ganglion cells. The glial tumor showed both well-differentiated fibrillary astrocytes with microcysts and anaplastic populations with central necrosis and pseudopalisading. CONCLUSIONS: Present classification systems devised to describe mixed neuronal and glial tumors do not adequately encompass the diversity of morphologies presented by these two cases. We conclude that the terms cerebral neuroblastoma-anaplastic astrocytoma for case 1 and cerebral ganglioneuroblastoma-glioblastoma for case 2 are preferred because they convey useful clinical information by reflecting concepts already encompassed by the World Health Organization's classification system of tumors of the central nervous system.
Gliomatosis cerebri is a rare form of astrocytoma characterized by extreme infiltration of the brain structure in conjunction with a relative paucity of clinical findings. We describe the MRI findings in a patient with gliomatosis cerebri widely infiltrating the brain who presented with symptoms related to involvement of the optic nerves and chiasm. Contrast-enhanced MRI showed enlargement of the optic nerves and chiasm with pathological enhancement; T2-weighted images showed extensive infiltration of the brain by tumor. Histopathologic examination of the biopsy specimen showed anaplastic astrocytoma with gemistocytic predominance and a diagnosis of gliomatosis cerebri was reached.
OBJECTIVE: The Single-Voxel Proton Brain Exam (PROBE/SV) is an automated MR spectroscopic technique. The purpose of this study was to investigate the use of PROBE/SV as a diagnostic tool in patients with primary brain tumors and to compare our findings with the known information obtained from conventional nonautomated MR spectroscopic techniques. SUBJECTS AND METHODS: We used PROBE/SV to image 10 normal adults and 46 patients with primary brain tumors: 29 glioblastoma multiformes (GBMs), five anaplastic astrocytomas, and 12 low-grade astrocytomas. All studied were performed on a 1.5-T Signa unit. Average voxel sizes were 6-8 cm3. A corresponding point-resolved spectroscopy spectrum was obtained from normal-appearing brain parenchyma in each patient for comparison with the spectra from known areas of pathology. RESULTS: In patients with low-grade gliomas (grades 1 and 2), we observed decreased N-acetylaspartate (12 of 12) and slightly increased choline (11 of 12) when we compared these metabolites with those in the spectra of patients' normal brains. This comparison in patients with GBM yielded markedly decreased N-acetylaspartate (29 of 29) and prominently increased choline (27 of 29). In the short TE spectra, we frequently saw lipid signal in high-grade tumors, especially in GBMs (12 of 20). We identified lactate peaks in high-grade tumors (anaplastic astrocytoma and GBM, 29 of 34) and also in low-grade tumors (four of 12). The creatine signal in all gliomas was slightly less than that of healthy brain tissue. The lowest N-acetylaspartate, choline, and creatinine levels in conjunction with the highest lactate levels were usually found in necrotic portions of high-grade tumors. CONCLUSION: PROBE/SV is a simplified MR spectroscopy technique that reduces setup time and provides automatic on-line data processing and display. The voxel location can be selected to focus on the area of interest and to minimize voxel contamination from unwanted tissue. The results from our experimentation with PROBE/SV in patients with brain tumors generally concur with published reports of tumor spectra obtained by conventional MR spectroscopic techniques. The ease and accuracy of this new technique make it a useful clinical tool in differentiating human brain tumor grades.
We aimed to determine the maximum tolerated dose (MTD) of 131I-labeled 81C6 in patients with leptomeningeal neoplasms or brain tumor resection cavities with subarachnoid communication and to identify any objective responses. 81C6 is a murine IgG monoclonal antibody that reacts with tenascin in gliomas/carcinomas but does not react with normal adult brain. 131I-labeled 81C6 delivers intrathecal (IT) radiation to these neoplasms. This study was a Phase I trial in which patients were treated with a single IT dose of 131I-labeled 81C6. Cohorts of three to six patients were treated with escalating doses of 131I (starting dose, 40 mCi; 20 mCi escalations) on 10 mg 81C6. MTD is defined as the highest dose resulting in serious toxicity in no more than two of six patients. Serious toxicity is defined as grade III/IV nonhematological toxicity or major hematological toxicity. We treated 31 patients (8 pediatric and 23 adult). Eighteen had glioblastoma multiforme. Patients were treated with 131I doses from 40 to 100 mCi. Hematological toxicity was dose limiting and correlated with the administered 131I dose. No grade III/IV nonhematological toxicities were encountered. A partial response occurred in 1 patient and disease stabilization occurred in 13 (42%) of 31 patients. Twelve patients are alive (median follow-up, > 320 days); five are progression free >409 days median posttreatment. The MTD of a single IT administration of 131I-labeled 81C6 in adults is 80 mCi 131I-labeled 81C6. The MTD in pediatric patients was not reached at 131I doses up to 40 mCi normalized for body surface area.
We evaluated the utility of MR imaging in pediatric patients with acute and subacute spinal cord injuries. MR imaging of 22 pediatric patients with suspected traumatic spinal cord injuries was reviewed. MR findings were correlated with physical examination and compared to available radiographs and CT examinations performed at time of presentation. Twelve patients had abnormalities on MR imaging. Seven had spinal cord contusions; five contusions were hemorrhagic. Five of seven patients with cord contusion had normal radiographs and CT exams. Six patients with normal radiographs and CT examinations had abnormal MR studies revealing cord contusion, ligamentous injury, disc herniation, and epidural hematoma. MR is useful in initial evaluation of pediatric patients with spinal cord injuries and in prognosis of future neurologic function. In the setting of spinal cord symptomatology and negative radiographic studies, MR imaging should be performed. Surgically correctable causes of cord compression demonstrated by MR imaging include disc herniation, epidural hematoma, and retropulsed fracture fragments. The entity of spinal cord injury without radiographic abnormality is a diagnosis of exclusion which should only be made after radiologic investigation with radiographs, high-resolution thin-section CT, and MR imaging.
To assess the value of magnetic resonance imaging (MRI)-measured hippocampal volume in the detection of hippocampal sclerosis, we studied 28 patients undergoing anterior temporal lobectomy for medically intractable mesial temporal lobe epilepsy. Hippocampal volumetry and visual analysis of T2 signal change were performed using fast spin-echo T2-weighed MRI. Quantitative neuronal density measurements were performed in the resected hippocampal specimens. There was a significant correlation between MRI-measured absolute hippocampal volume (AHV) and neuronal density in CA1, CA2, and CA3 subfields (p < 0.0001, p < 0.01, and p < 0.05, respectively). Differential hippocampal volume (side-to-side volume difference) failed to detect bilateral atrophy in three patients, but the bilateral hippocampal atrophy was recognized by considering AHV in these patients. This study suggests that MRI-measured AHV can be of value in elevating patients with mesial temporal lobe epilepsy, especially when there is no side-to-side difference in hippocampal volumetry.
PURPOSE: To describe imaging findings in the hippocampus in status epilepticus with fast spin-echo (SE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Five patients with status epilepticus were examined with fast SE MR imaging, and the findings were correlated with neuropathologic observations of status epilepticus. RESULTS: One patient with diffuse bilateral hippocampal and amygdalal abnormal hyperintensity died. In three patients with hippocampal abnormal hyperintensity and enlargement, hyperintensity and enlargement, follow-up fast SE MR images depicted decreased hyperintensity and swelling; one patient has remained seizure free at 6 months follow-up; a complex partial seizure disorder developed in two, and repeat images demonstrated hippocampal atrophy. CONCLUSION: T2-weighted fast SE MR images demonstrate reversible abnormal hyperintensity and swelling of the hippocampus and amygdala in patients with status epilepticus. Sequential fast SE MR imaging allows differentiation of this process from neoplasia and is useful in documentation of post-status epilepticus developments such as mesial temporal sclerosis.
Brainstem gliomas are an important oncologic problem in the pediatric age group, constituting between 10 and 15% of childhood central nervous system neoplasms. A new classification scheme based on magnetic resonance imaging (MRI) has recently been proposed leading to speculation that gadolinium-DTPA-enhanced MRI may prove useful in defining the prognosis of subsets of patients with these tumors. We retrospectively reviewed gadolinium-DTPA-enhanced MRIs in 26 consecutive newly diagnosed pediatric patients (11 males, 15 females) from our institution between June 1988 and June 1994 with the diagnosis of diffuse brainstem glioma. The site, extent of invasion, T1 and T2 signals, and the pattern and the degree of contrast enhancement of the tumors were evaluated. We correlated the image features, clinical symptoms, and survival period in each patient. Seventeen tumors demonstrated contrast enhancement and 9 did not. The survival in the whole group ranged between 3 months and > 5 years with a median of 9 months. There was no statistical difference in the median survival between patients with or without contrast enhancement (11 versus 8 months).
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