Secretory and nonsecretory pituitary adenomas are distinguishable by 1/T1 magnetic relaxation rates at very low magnetic fields in vitro.

RATIONALE AND OBJECTIVES: The authors investigated whether hormonally active and inactive pituitary adenomas can be discriminated in vitro by magnetic resonance (MR) imaging-related data. METHODS: 1/T1 nuclear magnetic relaxation dispersion profiles were measured for 39 fresh surgical specimens of secreting and nonsecreting adenomas, classified using clinical criteria or preoperative serum hormone levels. Nonsecreting adenomas were subdivided into hormone-producing and nonhormone-producing by immunostains. At five fields (0.00024 to 1.2 tesla [T]), mean 1/T1 was analyzed for statistically significant differences among these three tumor categories. RESULTS: Mean 1/T1 was significantly higher (P < 0.02) for hormone-secreting than for nonsecreting adenomas at fields below 0.24 T; no significant difference existed at typical MR imaging fields (0.5 to 1.5 T). Mean 1/T1 for hormone-producing and nonhormone-producing, nonsecreting adenomas were not significantly different at any field. CONCLUSIONS: Because 1/T1 at low fields is related to 1/T2 at imaging fields, it may be possible to detect hormone secretion of pituitary adenomas noninvasively by MR imaging.

Erdheim-Chester disease of the central nervous system. Report of two cases.

The authors report two cases of Erdheim-Chester disease (ECD), an illness of unknown pathogenesis. Generally, this disease process involves the metaphyseal and diaphyseal portions of the long bones, the lungs, and the retroperitoneum; however, other tissues may be involved including the central nervous system (CNS). To date only two cases of CNS-related ECD have been reported. The present report adds to the literature by documenting two more recent cases of ECD involving the CNS. The clinical presentations of these cases, their radiological findings with special reference to magnetic resonance imaging, pathological determination, and clinical management are briefly reviewed.

Pott's puffy tumor: the forgotten entity. Case report.

Pott's puffy tumor is a subperiosteal abscess of the frontal bone associated with underlying frontal osteomyelitis. The introduction of antibiotic medications has diminished the incidence of complications of frontal sinusitis. As a result, Pott's puffy tumor has become a rarity. In this communication a case of Pott's puffy tumor secondary to antecedent frontal sinusitis in an otherwise healthy adult man is described.

Resection of olfactory groove meningiomas: technical note revisited.

BACKGROUND: Although large olfactory groove meningiomas present in the midline, tumor volume is often unequally distributed to one side. Most surgeons favor a bifrontal craniotomy with retraction or partial resection of the frontal lobes to resect these tumors. However, frontal lobe retraction is not without complications. METHODS: We present a technical note regarding the resection of these large olfactory groove meningiomas. We describe the advantages of a unilateral frontal craniotomy complemented with orbital osteotomy. RESULTS: The orbital osteotomy has considerably reduced the need for frontal lobe retraction and avoids partial resection of the frontal lobe to uncap the tumor. Utilizing this approach we have been able to remove the tumor from one side, followed by an incision to the falx cerebri in order to remove the tumor from the other side. With this approach, we have gained excellent visualization of the tumor in its entirety. Moreover, this approach permits the surgeon to intercept the arteries emerging from the skull base during the initial stages of the procedure. CONCLUSIONS: Unilateral frontal craniotomy and orbital osteotomy has obviated the need to retract or resect the frontal lobe when resecting large olfactory groove meningiomas, which extend to either side of the falx. Because surgery is performed from one side, olfaction may also be preserved on the contralateral side.

Calcification can shorten T2, but not T1, at magnetic resonance imaging fields. Results of a relaxometry study of calcified human meningiomas.

RATIONALE AND OBJECTIVES: Water content and water-proton relaxation rates are reported for fresh, histologically characterized, surgical specimens of calcified human intracranial meningiomas and compared with results for noncalcified meningiomas from an earlier study and with calcium hydroxyapatite (CaHA) suspensions to elucidate the influence of calcification on magnetic resonance imaging (MRI) signal intensity of calcified meningiomas. METHODS: The magnetic field dependence of 1/T1 of water protons (nuclear magnetic relaxation dispersion profile) and dry weights are reported for 38 calcified nonhemorrhagic and 3 hemorrhagic specimens of known histologic subtype, a subset of the 67 specimens measured earlier. Calcification was considered mild or heavy when the dry weight was within or above the range for noncalcified meningiomas. Preliminary 1/T1 profiles for pure CaHA and a single high-field 1/T2 value also are reported. RESULTS: The ranges of dry weights and of low-field 1/T1 values were twice as large for calcified as for noncalcified meningiomas. No correlation was found between low-field 1/T1 and either histologic subtype or dry weight. Mild calcification produced the highest low-field 1/T1 values; the most heavily calcified tumor had slightly increased low-field 1/T1. Calcium hydroxyapatite increases low-field 1/T1 significantly but not high-field 1/T1; high-field 1/T2 is large. For calcified hemorrhagic meningiomas, increases in both low-field and high-field 1/T1 were seen. CONCLUSION: For mild calcification, MRI signal voids result from an increased high-field 1/T2; for heavier calcification, reduced proton density (from excluded water) becomes of increasing importance. Cellular CaHA appears to brighten the signal in T1-weighted MRI in the presence of hemorrhage.

Correlation of relaxometry and histopathology: the transplantable human glioblastoma SF295 grown in athymic nude mice.

Human glioblastomas of the brain are characterized by a wide range of proton relaxation rates in vitro (1/T1 and 1/T2) and heterogeneous appearance in magnetic resonance imaging. It was previously found that their 1/T1 values vary widely at magnetic field strengths much below imaging fields, even at the same water content. In the present study, we measure 1/T1 at different magnetic field strengths (NMRD profile) for a specific transplantable, human glioblastoma (SF295), grown subcutaneously in athymic nude mice, to search for histologic characteristics that might correlate with the variability of 1/T1 at low fields (1/T1L). Using a field-cycling relaxometer, NMRD profiles were obtained for 32 fresh, histologically characterized, tumor specimens, 7 to 24 days post implantation of cryopreserved SF295 fragments. Tumor volume, dry weight, and pH of specimens were determined, the extent of hemorrhage and necrosis rated, and specimen location within the tumor recorded. A statistically significant increase in the average 1/T1 was found with increasing level of necrosis at 0.0024 T and below, possibly reflecting progressive protein aggregation in samples with up to 40% necrosis. This correlation was not significant at imaging fields. Although pH was increased in central necrosis, neither pH, dry weight, sample location, nor fresh hemorrhage could explain the changes in 1/T1L. The variability of 1/T1L among SF295 samples is much reduced compared to that of fresh surgical specimens of human glioblastomas of the brain. The heterogeneous appearance of glioblastomas in MRI may have a histologic correlate which reflects molecular changes involved with induction of cell death and necrosis. Further investigations may identify the factors responsible for affecting 1/T1L (hypoxia, radiation, chemotherapy).

Relaxometry of noncalcified human meningiomas. Correlation with histology and solids content.

RATIONALE AND OBJECTIVES: Resected meningiomas were examined by relaxometry and light microscopy to evaluate the potential of magnetic resonance imaging (MRI) for identifying histologic subtypes and for discriminating among benign, radiation therapy-induced, and malignant meningiomas. METHODS: The magnetic field dependence of 1/T1 of water protons (nuclear magnetic relaxation dispersion [NMRD] profile) and the water content (dry weight) were measured for 67 specimens, and the data were compared with histology. Only noncalcified, nonhemorrhagic meningiomas are reported. RESULTS: No correlations were found between NMRD profiles, dry weight, and any histologic subtype, in contrast to an analogous study of astrocytomas. Rather, meningiomas have a broader variability of dry weight and 1/T1 than related parenchyma but a much narrower range than all grades of astrocytomas. The mean value of 1/T1, at all fields, is slightly higher in meningiomas--and the mean water content about the same--as adult cortical gray matter. CONCLUSION: Meningiomas are frequently isointense with cortex, and histologic subtypes cannot be differentiated at any magnetic field strength by MRI using only T1- or proton density-weighted MRI.

Correlation of intracranial pressure and transcranial Doppler resistive index after head trauma.

PURPOSE: To investigate the usefulness of transcranial Doppler ultrasonography in the evaluation of intracranial pressure changes after head injury. METHODS: Transcranial Doppler examinations and intracranial pressure measurements using intraparenchymal monitors were performed in 12 cases of closed head injury. Twenty-four sets of data, including the Glasgow Coma Scale, intracranial pressure, transcranial Doppler, and carbon dioxide pressure were compared. The side-to-side difference in the resistivity index was also assessed. RESULTS: There was a significant correlation between increased pressure values and resistivity index when comparing measurements from the same side. There was no correlation between carbon dioxide pressure and any transcranial Doppler parameter or intracranial pressure measurement. No significant correlation was found between the resistivity index and the Glasgow Coma Scale. End diastolic velocity was a stronger determinant of resistivity index than peak systolic velocity. CONCLUSION: The relationship of ipsilateral measurements of intracranial pressure to resistivity index is valid. The resistivity index must be analyzed within the context of the particular disease studied, especially with respect to the hemodynamic alterations. Initial findings suggest that intracranial pressure monitoring cannot be replaced by serial transcranial Doppler measurements in the treatment of the patient with acute head injury.

Variation of the magnetic relaxation rate 1/T1 of water protons with magnetic field strength (NMRD profile) of untreated, non-calcified, human astrocytomas: correlation with histology and solids content.

The magnetic relaxation rate 1/T1 of tissue water protons was measured over a wide range of magnetic field strengths (NMRD profile) for 92 fresh surgical specimens of astrocytomas to search for correlations of 1/T1 with tumor histology, as determined by light microscopy, and to assess the diagnostic potential of NMRD profiles for grading astrocytomas. A third goal was to elucidate the molecular determinants of 1/T1. Each specimen was histologically graded and inspected for evidence of mineral deposits (Ca, Fe); its dry weight was determined and expressed in % of original wet weight. To minimize variability not directly related to tumor grade, this initial report is limited to NMRD profiles of 47 non-calcified, non-hemorrhagic, untreated astrocytomas. For these, the mean value of 1/T1 at very low magnetic field strengths was found to increase with increasing grade of malignancy; no clear correlation could be demonstrated at high fields where most imaging is done. The spread of 1/T1 for different grades of malignancy is large, however, and the overlap significant, even at the lowest field, so that astrocytomas can not be graded by NMRD profiles alone. Average 1/T1 and average dry weight increase with grade of malignancy; but the variability of 1/T1 among specimens of the same dry weight is large, indicating that at least one other cellular parameter, not variable in normal tissue, influences 1/T1 strongly. We hypothesize that this parameter reflects changes at the molecular level in size distribution, mobility, or intermolecular interaction of cytoplasmic proteins. Which specific changes are induced by malignant transformation in astrocytomas remains to be investigated.

Cerebral blood flow velocity after head injury: transcranial Doppler evaluation. Work in progress.

To study blood flow velocity (BFV) changes, serial transcranial Doppler ultrasound (US) examinations of basal cerebral arteries were performed in 47 patients with head injury. Computed tomographic (CT) scans obtained at admission were analyzed for the presence of intracranial hemorrhages. Glasgow Coma Scale scores were obtained at admission in 46 patients. The prevalence of posttraumatic increased BFV was 77% (n = 36). Two groups of patients were identified according to the time of onset of increased BFV. They differed with respect to duration and severity of changes, Glasgow Coma Scale score, and evidence of intracranial hemorrhagic lesions. Low Glasgow Coma Scale scores were predictive of increased BFV within 72 hours after injury (P < .001). Patients with hemorrhages were significantly more prone to experience increased BFV within 72 hours (P < .05); 34% of patients who did not have hemorrhage, however, developed increased BFV. Increased BFV after head trauma is not uniformly found and cannot be explained by one pathologic mechanism.

Headache characteristics in aneurysmal subarachnoid hemorrhage.

To investigate the nature of the headache accompanying aneurysmal subarachnoid hemorrhage, a retrospective study was conducted. Fifty-four patients and 54 controls completed questionnaires regarding headache, medical history, and family history, in an attempt to derive further information regarding symptoms and factors that might be predictive of aneurysmal subarachnoid hemorrhage. Factors that appear to be of importance in evaluating headache caused by subarachnoid hemorrhage include ominously severe headache, a history of vigorous physical activity precipitating headache, syncope or transient lethargy accompanying headache, previous medical attention for headache, a family history of aneurysmal subarachnoid hemorrhage, or catastrophic central nervous system event at an early age. An algorithm for the management of serious headache is suggested.

Magnetic field dependence of 1/T1 of human brain tumors. Correlations with histology.

The authors have measured the magnetic field dependence of 1/T1 (nuclear magnetic relaxation dispersion, or NMRD profiles) of water protons of histologically characterized samples of astrocytomas, meningiomas, and lymphomas. The goal was to elucidate the determinants of 1/T1 of brain tumors at the cellular level and, in particular, to search for a possible correlation of the profiles with neoplastic properties, including degree of malignancy. Because of the recently demonstrated contribution of myelin to 1/T1 of white matter, careful histologic analyses were performed to correct for its presence. The range of magnitude of the profiles of differing types and grades of tumors correlates with the range of water content of these tumors; the correlation of water content with cellularity (density of cell nuclei in a histologic preparation), in turn, produces correlations of 1/T1 with tumor type. For all the tumors studied, 1/T1 is proportional to solids content; the constant of proportionality is relatively insensitive to tumor type and, for astrocytomas, grade of malignancy; and is about the same as that of normal gray matter. For low- and intermediate-grade astrocytomas that contain myelin, the myelin-specific contribution to 1/T1 has to be considered to make manifest the underlying correlations, which are best demonstrated at low fields, where the background contribution of water and dissolved oxygen is minimal. At high fields, where most imaging is done, a change in oxygen partial pressure, as for example from ischemia in very malignant tumors, is sufficient to alter 1/T1 significantly, reducing the intrinsic correlation between histology and 1/T1.

Occipitocervical fusion for reduction of traumatic periodontoid hypertrophic cicatrix. Case report.

Periodontoid hypertrophic cicatrix resulting from trauma, as demonstrated by magnetic resonance (MR) imaging, is essentially the same as that seen in rheumatoid arthritis. Recent reports suggest that, in rheumatoid arthritis, occipitocervical fusion without transoral decompression of the pannus is adequate for resolution of this anterior lesion. A case of traumatic periodontoid cicatrix is presented in which posterior fusion resulted in reduction of the anterior mass lesion, clearly demonstrated by MR imaging. The etiology of periodontoid hypertrophic scarring, both traumatic and rheumatoid, is discussed in light of MR findings, and treatment implications are considered.

Subdural empyema--an unusual presentation. A report on 2 cases.

Two cases of subdural empyema with unusual clinical features are described. Both had an undetermined primary source of infection, the onset was insidious and the course was rather indolent, and both cases occurred after steroid therapy. Subdural empyema is a potentially lethal condition if inappropriately managed. A high index of suspicion and prompt definitive treatment remain the cornerstones of successful management. The aetiology and pathogenesis of subdural empyema and the merits and demerits of various investigative procedures are discussed; the factors that influence prognosis are highlighted.

Giant pediatric aneurysm treated with ligation of the middle cerebral artery with the Drake tourniquet and extracranial-intracranial bypass.

Saccular intracranial aneurysms occur infrequently in children, and the incidence of pediatric giant aneurysms is statistically in the same proportion as in adults. The management of these giant aneurysms can be treacherous. This paper presents a case of a 9-year-old boy with a giant aneurysm of the right middle cerebral artery that was successfully managed by ligation of the middle cerebral artery using a Drake tourniquet with the patient awake and by augmentation of the middle cerebral artery circulation with superficial temporal artery-middle cerebral artery anastomosis without excision of the lesion.

Aggressive physiologic monitoring of pediatric head trauma patients with elevated intracranial pressure.

The management of pediatric patients with severe head trauma often requires aggressive physiologic monitoring and treatment. As intracranial pressure (ICP) increases, so does mortality. Yet attempts to decrease elevated ICP can cause physiologic and hemodynamic problems. In this retrospective analysis of 25 patients treated with ICP monitoring alone, ICP measurements plus mannitol, or ICP measurements plus pentobarbital (PB) induced coma/mannitol, survival rates were higher than predicted, particularly among the most severely injured. These results were apparently due to the intensive care and aggressive monitoring. Although barbiturates are known to decrease ICP, the adverse effects encountered, including hypotension, cardiovascular depression and arrhythmias, often outweigh the benefits. Hemodynamic abnormalities are unpredictable and monitoring with Swan-Ganz catheter is useful in managing patients with PB-induced comas. Many failures of PB therapy in pediatric patients may be related to undiagnosed decreases in cardiac output, resulting in decreased cerebral blood flow, even with well-controlled ICP.