The Value of Hg203Brain Scans in Patients with Intracranial Hematomas

Abstract

Brain scanning with radioactive isotopes has become sufficiently reliable to be employed in many medical centers in the detection and localization of intracranial mass lesions. Most reports indicate that certain intracranial neoplasms, i.e., meningiomas, malignant gliomas, and metastatic tumors, can usually be detected by the scan. The mechanisms of the selective localization of tracer substance in or around intracranial neoplasms are not yet fully known, nor is there evidence that a single etiological condition is operative in all instances. Among the factors that appear to be related to the increased uptake of various unstable nuclides in the brain are : (a) selective breakdown of the blood-brain and/or blood-tumor barrier, (b) increased vascularity of neoplastic tissue, (c) increased mitotic activity of neoplastic tissue, and (d) selective acquisition of a specific colloid or crystalloid by a particular tumor. If the selective accumulation of an isotope in the region of a brain tumor is not related exclusively to the neoplastic nature of the tissue per se, but rather to various alterations in the type and pattern of vascularization as well as local changes of capillary and glial permeability, it can be expected that other pathologic entities exhibiting similar vascular or membranous changes might also be characterized by increased localized tracer concentration. In practice, this appears to be true: positive brain scans have been reported in entities as diverse as cerebral contusions (9), subdural hematomas (3, 7, 12), brain abscesses (1, 2, 6), vascular anomalies of the brain (6, 9, 11), encephalomyelitis (10), and cerebral vascular accidents (1, 2, 7). Since many of these represent clinical conditions which are not always subjected to surgical or pathologic verification, the finite diagnosis of a positive scan in such circumstances must often rest on circumstantial evidence. This is especially true of the positive brain scan associated with cerebrovascular disease. Although numerous references are found in the literature to positive brain scans in “cerebral vascular disease,” it is far from clear whether the author is dealing with arterial or venous occlusive disease, cerebral edema, subarachnoid hemorrhage, intracerebral hematomas, or various combinations of these pathologic entities. The present report is concerned with 7 cases in which positive mercury-203 Neohydrin brain scans were associated with well defined intracranial hematomas. The precise location, configuration, and size of the blood clot could in each instance be mapped out at the time of surgery. Observations were also made relative to the degree of hematoma encapsulation and the nature and extent of surrounding brain edema and vascularity. A review of the pertinent data in these 7 cases has allowed us to advance certain speculations relating to the specific origins of the positive brain scan associated with intracranial hematomas.