Burton P. Drayer

Xenon enhanced CT for analysis of cerebral integrity, perfusion, and blood flow

Enhancement of the brain substance for CT evaluation using inhaled Xenon is confirmed. This technique was applied to the study of the normal and the embolized adolescent baboon. Healthy cerebral tissue enhances symmetrically, while abnormal areas show significantly diminished enhancement. At maximal enhancement, an indication of gross comparative cerebral perfusion is obtained. By obtaining serial CT scans over a 10 minute time interval, the clearance rate of Xenon (cerebral blood flow) may be evaluated. Xenon-enhanced CT enables a visual and numerical analysis of both brain morphology and physiology.

Computed tomography in white-matter disease.

CT scans of 11 patients with proved white-matter disease were reviewed and divided into three categories. The demyelinating (secondary) and diffuse sclerosis groups frequently exhibited abnormal intravenous enhancement and mass shift. This made differentiation from inflammatory and neoplastic processes difficult. In the dysmyelinating disorders, pathologically noted diffuse loss of white matter and absence of inflammatory response appeared on the scans as areas of diffuse and decreased density in the centrum semiovale. There was no evidence of abnormal contrast enhancement.

Transverse atlantal ligament disruption associated with odontoid fractures.

Objectives. The authors evaluated transverse atlantal ligament integrity in patients with fractures of the odontoid process of the axis. Summary of Background Data. Injuries of the transverse atlantal ligament can result in atlantoaxial instability after fractures of the atlas or axis, even if osseous healing occurs. Methods. The clinical histories and follow‐up examinations and radiographic data of 30 patients with odontoid fractures were reviewed, using a combination of magnetic resonance (MR) imaging, thin‐cut computed tomography (CT), and plain radiographs to evaluate osseous and ligamentous injuries. Results and Conclusions. Osteoperiosteal ligamentous avulsion injuries were identified on MR imaging in three patients and were associated with acute and delayed instability and nonunion. The combination of MR imaging, CT, and plain radiographs is useful in evaluating unstable odontoid fractures to facilitate rational treatment planning. Odontoid fractures with transverse ligament injuries should be considered for early surgical stabilization because this combination of injuries is unlikely to heal nonoperatively. Anterior odontoid screw fixation should be avoided when the ligament is injured. [Key words: cervical spine injury, magnetic resonance imaging, odontoid fracture, transverse atlantal ligament] Spine 1994;19:2307‐2314

Tethered Spinal Cord Following Meningomyelocele Repair

Of 16 consecutive patients with tethered spinal cord studied, most had undergone repair of a meningomyelocele. All were evaluated using somatosensory evoked potentials at 6 to 12-month intervals. Other possibilities include tethered filum terminale, lipomeningocele, membrana reuniens, and miscellaneous conditions (diastematomyelia, neurenteric cysts, etc.). Metrizamide myelography with polytomography was superior to gas myelography in showing a low-lying cord, obtuse nerve root angles, and a thin subarachnoid space between the cord and the dorsal meninges cephalad to the tether. Surgery is generally helpful in these patients.

Pharmacokinetics of Nitroxide Nmr Contrast Agents

Pharmacokinetics of the nitroxide stable free radical functionality of compounds containing this moiety were evaluated in the rat. The agents were injected i.v. at either high (1.75 mmoles/kg) or low (10 mumoles/kg) dose, and timed blood samples were drawn and assayed for nitroxide concentration by EPR spectrometry. Similarly, various organs and tissues were removed at specified times after injection and homogenized for determination of nitroxide concentration. Urine was collected by catheter for estimation of urinary excretion of the intact nitroxide free radical. At high doses, the various nitroxides exhibited an initial rapid disposition phase, followed by a terminal disposition phase with disappearance from the blood showing apparent log-linear half-lives of about 5 to 30 minutes. Generally, 20 to 60% of the dose was recovered in the urine. At low doses, dissimilar results were obtained. Blood levels again showed biphasic decay; however, blood concentrations at all times were much lower than those predicted by the high dose kinetics, indicating probably nonlinear pharmacokinetic behavior. Tissue homogenate studies showed low or nondetectable levels of nitroxide signal, demonstrating that the low blood concentrations could not be accounted for by a rapid uptake into specific tissues. Moreover, only 2 to 6% of the nitroxide could be recovered in the urine. Additional studies demonstrated that at the low dose a rapid in vivo bioreduction occurred which appeared to be saturable at the higher dose.

Tortuous vertebrobasilar arteries causing cranial nerve syndromes: screening by computed tomography.

Considerable concern with cranial nerve syndromes has often required detailed information of the relationship between the vertebrobasilar system and the brainstem. The obvious invasiveness of conventional vertebral angiography poses the question of whether computed tomography (CT) might serve as a satisfactory technique or even as a sufficient diagnostic method. During a 12 month period, 12 of 250 patients with cranial nerve syndromes were diagnosed by CT as having vertebrobasilar ectasia. This communication correlates the clinical symptomatology with angiography and CT and presents evidence that CT alone can prove satisfactory.

MR characteristics of meningioma subtypes at 1.5 tesla

Analysis of MR signal characteristics and histopathologic findings confirms the strong correlation between meningioma subtype and observed signal intensity (SI) changes in 24 patients imaged at 1.5 T. On T2-weighted images, 90% of fibroblastic and transitional tumors were hypointense relative to cerebral cortex (SI intermediate greater than SI T2-weighted images); conversely, 66% of meningothelial subtypes displayed persistent hyperintensity (SI intermediate less than or equal to SI T2-weighted images), and the remaining one-third demonstrated mixed high-signal changes. Subtype specific differences in collagen distribution and cellularity, i.e., tumor geometry, appeared to account for these signal trends. Based solely on SI characteristics, correct histologic subgrouping of tumors as either fibroblastic/transitional or meningothelial/angioblastic was possible in 80% (19 of 24) of patients. Utilization of adjunctive imaging features (i.e., mass effect, peritumoral edema, intratumoral cyst formation) in conjunction with signal changes permitted a correct histologic pattern in 96% (23 of 24) of patients.

Magnetic resonance imaging in pathologically proven Hallervorden‐Spatz disease

We present an 11-year-old girl in whom high field strength MRI performed 2 1/2 years and 6 months before her death showed prominent hypointensity in the globus pallidus and substantia nigra consistent with iron deposition. This finding suggested Hallervorden-Spatz disease, which was confirmed at autopsy.

Computed Tomographic Diagnosis of Suprasellar Masses by Intrathecal Enhancement

Ten suspected suprasellar mass lesions were evaluated by CT cisternography (CTC). In each case the cisterns could be defined. Suprasellar mass lesions were found in six. Precise assessment of the anterior, lateral, posterior, and superior extent, made by metrizamide CTC, was verified at surgery. In two masses the intravenously enhanced scan was not diagnostic, while a lesion was visualized by intrathecal (metrizamide) CT. The major diagnostic entity was an enlarged third ventricle. When a chiasmic lesion is suspected and the conventional scan is negative, metrizamide CTC is the examination of choice.

Transient Cerebral Ischemia as a Manifestation of Ruptured Intracranial Dermoid Cyst

Transient cerebral ischemia was the initial manifestation of a ruptured intracranial dermoid cyst in a young adult male. The ischemia could have resulted from vasospasm caused by release of the contents of the dermoid cyst into the subarachnoid space or from other local effects of the tumor. The role of computed tomography in the evaluation of patients with transient cerebral ischemia is discussed.