Biomedical subjects
Publications and source records attributed to R R Smith.
The various modifications and variations of the cranio-orbital approach have been recently described; the author uses different modifications according to the location, size and extent of the lesion. Some of the prime indications for these modifications are presented herein.
Radiation therapy plays an integral part in managing intracranial tumors. While the risk:benefit ratio is considered acceptable for treating malignant tumors, risks of long-term complications of radiotherapy need thorough assessment in adults treated for benign tumors. Many previously reported delayed complications of radiotherapy can be attributed to inappropriate treatment or to the sensitivity of a developing child's brain to radiation. Medical records, radiological studies, autopsy findings, and follow-up information were reviewed for 58 adult patients (31 men and 27 women) treated between 1958 and 1987 with radiotherapy for benign intracranial tumors. Patient ages at the time of irradiation ranged from 21 to 87 years (mean 47.7 years). The pathology included 46 pituitary adenomas, five meningiomas, four glomus jugulare tumors, two pineal area tumors, and one craniopharyngioma. Average radiation dosage was 4984 cGy (range 3100 to 7012 cGy), given in an average of 27.2 fractions (range 15 to 45 fractions), over a period averaging 46.6 days. The follow-up period ranged from 3 to 31 years (mean 8.1 years). Findings related to tumor recurrence or surgery were excluded. Twenty-two patients had complications considered to be delayed side effects of radiotherapy. Two patients had visual deterioration developing 3 and 6 years after treatment; six had pituitary dysfunction; and 17 had varying degrees of parenchymal changes of the brain, occurring mostly in the temporal lobes and relating to the frequent presentation of pituitary tumors (two of these also had pituitary dysfunction). One clival tumor with the radiographic appearance of a meningioma, developed 30 years post-irradiation for acromegaly. This study unveils considerable delayed sequelae of radiotherapy in a series of adult patients receiving what is considered "safe" treatment for benign brain tumors.
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Transcranial Doppler ultrasonography was used to evaluate 2 patients who developed hyperperfusion syndromes after carotid endarterectomy. During the initial postoperative period, each patient had symptoms that were associated with elevated flow velocities in the ipsilateral cerebral vasculature. In addition, vascular resistance of these vessels was found to be abnormally low, as reflected by the Gosling pulsatility index. As the patients' symptoms improved, flow velocities decreased to normal levels and pulsatilities were noted to increase proportionately.
Trisporic acids are end products of the sex-specific pheromones in mucoraceous fungi. We have found three new trisporic acids in cultures of Blakeslea trispora in which (+) and (-) mating types were separated by a membrane with 0.45-microns pores. Two of the trisporic acids were new compounds; the structure of the third [previously described by Miller and Sutter [(1984) J. Biol. Chem. 259, 6420] as methyl trisporate-E with a hydroxyl group at C-2] was revised. Trisporic acid-E(3R), trisporic acid-E(3S), and trisporic acid-D(2S) were in a 1:1:2 ratio, accounted for 9% of the total trisporic acids, and differed by the position and configuration of a hydroxyl group on the ring at C-2 or C-3, the conformation of the ring, the extent of rotation of the side chain relative to the ring, and either a carbonyl or hydroxyl group on the side chain at C-13. These three compounds accounted for only 0.5% of the total trisporic acids in combined mating type cultures. Since the combined cultures did not metabolize trisporic acid-E(3R), its biosynthesis apparently ceases when opposing mating types contact each other physically. We speculate that B. trispora and Phycomyces blakesleeanus utilize different pheromones to regulate an early event (possibly zygotropism) in sexual development.
A conceptual and empirical analysis of the strategic vulnerability of HMOs shows that they are strategically vulnerable on the social dimension of stakeholder supportiveness. One of the major implications of this finding is that HMOs' cost leadership strategy cannot be sustained, given the competition from such substitutes as PPAs.
Transcranial Doppler (TCD) was used to assess collateral flow and to quantitate perfusion velocity changes in a group of 18 patients requiring temporary or permanent surgical occlusion of the internal carotid artery for treatment of their cerebrovascular lesions. Velocity measurements were correlated with times of occlusion and neurological outcome in order to assess safe vessel occlusion times and the need for an intraoperative shunt. These data were used to calculate a perfusion velocity index (PVi), which indicated that values greater than 2 were well tolerated, and values of less than 1 were associated with ischemic signs. In addition, preoperative TCD examinations were combined with compressive maneuvers of the carotid artery in the neck to evaluate the feasibility of carotid clamp ligation for the treatment of giant intracranial aneurysms deemed unsuitable for direct clipping. When maintenance of neurological function and intracranial vessel flow velocities were found to be normal, with aneurysmal flow velocities of zero, ligation of the carotid artery could safely be undertaken. Finally, TCD allowed continuous surveillance of cerebral hemodynamics, which gave immediate assurance of postoperative ICA patency, as well as the ability to identify high velocity states associated with hyperperfusion syndromes, which occurred in two patients.
A surgical approach to the skull base was developed in cadavers and then used in the treatment of patients with complex aneurysms of the anterior circulation. The operative method involves removal of portions of the orbital rim, orbital roof, and sphenoid bone. By removing the orbital rim and a portion of the orbital roof, multidirectional viewing is possible. This is important when dealing with the anterior aspect of the cavernous sinus and anterior clinoid process, as must frequently be done when isolating the neck of an ophthalmic aneurysm. The optic canal is opened wide and the optic nerve mobilized, allowing resection of the dura propria covering the cavernous carotid artery. Clip placement is performed in an anteroposterior plane, thus lessening the chance for compromise of the internal carotid artery. The low approach alleviates brain retraction and the small flap minimizes brain exposure. The approach also allows preservation of the arterial and neural supply to the frontalis and temporalis muscles, thereby preventing postoperative cosmetic deficits. During the past year and a half, this approach has been employed in 25 patients with difficult aneurysms of the anterior circulation. The difficulties of these cases stemmed from their odd location, size, or complex anatomy. Although periorbital edema may have been more severe during the first postoperative week, overall improved cosmesis was achieved.
Intimal accumulation of indium-111-labeled platelets in the middle cerebral arteries was examined in two different models of experimental subarachnoid hemorrhage (SAH) in the cat. SAH was produced in 7 subjects by a transorbital rupture of the right middle cerebral artery (RMCA) and in 10 subjects by the transorbital cisternal injection of 2 ml of autologous arterial blood around the RMCA. Animals in both experimental groups were sacrificed at 2, 4, 24, and 48 hours after SAH. The radioactivity (in counts per minute) of the RMCA segment was divided by that of the left middle cerebral artery (LMCA) to produce a radioactivity ratio (RMCA/LMCA). This radioactivity ratio was determined for each animal and was scored as positive if it was 1.25 or greater, and as negative if it was less than 1.25. The scores derived from the radioactivity ratios in both experimental SAH groups were mostly positive (86 and 70%, respectively) and were significantly different (P less than 0.05) from those of intact controls (n = 7) or sham-operated controls (n = 5; n = 4). There was, however, no significant difference (P = 0.35) between the scores of the two experimental groups in the first 48 hours after SAH. The results indicate that subarachnoid blood placed upon the adventitial surface of intact cerebral arteries activates platelet aggregation to a degree comparable to that which occurs after mechanical vessel rupture in the acute stages of SAH. We suggest that the noxious agents responsible for arterial injury and subsequent intimal platelet aggregation after SAH exert their influence primarily from the abluminal surface of the cerebral artery.
Intraventricular and intra-axial lesions can be reached through a transsulcal approach, avoiding the more extensive cerebral tissue damage that may result from a conventional cortical incision. The sulci of five cadaver brains fixed in formalin solution were dissected using the operating microscope. The brains were photographed for surface mapping and x-rays to demonstrate underlying ventricular relationships were taken. The brains were then coronally sectioned to characterize anatomical relationships between sulci and deep brain structures. Three important sulci were identified and thoroughly characterized with respect to surface relationships, average depth, and underlying structures that can be readily approached. Surgical application of these findings is discussed.
Transcranial Doppler (TCD) ultrasonography was used to perform multiple examinations of 24 patients who sustained cranial injuries, 23 of whom progressed to death. In the 20 of these 23 patients for whom an adequate TCD signal could be obtained, a characteristic reverberating wave form pattern was observed, with an associated net flow velocity of less than 10 cm/sec in all cases. In the last patient in our study group, a reverberating pattern was also identified, however, a net flow velocity of greater than 20 cm/sec was associated with functional recovery. Correlations of neurological function, TCD tracings, and net flow velocities permitted identification of characteristic hemodynamic changes that preceded cerebral circulatory arrest. Early changes included decreased flow velocity as well as an increase in pulse pressure. Late changes consisted of a persistent increase of pulse pressure with the appearance of retrograde flow velocities during diastole. In the end stage, complete diastolic retrograde flow velocities were found. These gave rise to the characteristic reverberating pattern mentioned earlier. Identification of flow velocity reversal alone, however, proved to be inadequate for making the diagnosis of brain death. Evaluation of net flow velocity (calculated at bedside) was found to be a more sensitive determinant of brain death and closely paralleled the patients' neurological function.
Transcranial Doppler (TCD) evaluation of the intracranial vessels was performed in sixty-six patients, 51 of whom received conventional angiography either prior to or subsequent to the ultrasonic arteriogram. Of the 14 patients evaluated for arteriovenous malformations (AVMs), TCD indicated the existence of the AVM in 10 cases. Of those 10 cases, 9 correlated with angiography. Twenty-one patients with aneurysms were evaluated with TCD and only 2 were detected. Twenty-three patients suspected of having ischemic disease were evaluated with TCD, which indicated the presence of stenosis in 21 patients. Twenty of those patients received conventional angiography, with 18 demonstrating significant stenosis.
White matter disease is imaged with great sensitivity and poor specificity on MRI. Congenital, vascular, infectious, and autoimmune diseases as well as those with many other causes, may create similar-appearing lesions on MR. A knowledge of disease patterns and pulse sequences may improve the diagnostic specificity, but there is no substitute for an adequate clinical history.
The role of blood platelets in producing early intimal changes in cerebral arteries following subarachnoid hemorrhage (SAH) was examined by using 18 cats. Experimental SAH was produced by a rupture of the proximal portion of the right middle cerebral artery. Following SAH, the scanning electron microscope revealed that structural alterations in the intimal layer of major cerebral arteries occurred as early as 2 hours and became more severe by 48 hours. Vascular alterations, which were predominantly detected in the ruptured vessel, consisted of endothelial cell corrugation, detachment, crater formation, intimal adhesion of platelets and red blood cells, intimal thrombi, and reendothelialization. When cats were pretreated prior to SAH with an anti-platelet-aggregating agent, OKY-1581, the intimal blood elements and thrombi were clearly reduced, and reendothelialization was not observed. However, endothelial cell changes in the OKY-1581-treated group were very similar to those occurring in the nontreated group. While these results suggest that bioactive substances contained within blood platelets, such as growth factors, serotonin, and norepinephrine, have little effect on producing endothelial cell injury, platelets may be important in the initiation of reendothelialization following vessel injury.
An 8-year old patient with Coffin-Siris syndrome is presented, who was found to have a medulloblastoma during the evaluation of apnea and ventilator dependency. Although several cases of Dandy Walker cysts and one case of brain-stem heterotopia have been described in this rare syndrome, this is the first report of medulloblastoma in a patient with Coffin-Siris syndrome. Possible pathogenetic mechanisms are briefly discussed.
Isovolemic hemodilution has been reported to increase cerebral perfusion in humans and has been advocated as a treatment for acute cerebral infarction. This study examines the effect of isovolemic hemodilution with low-molecular-weight dextran on mortality and the incidence of neurological deficit in gerbils after internal carotid ligation. Sixty-four Mongolian gerbils were anesthetized with pentobarbital and the left internal carotid artery was ligated in both control and experimental animals. In the experimental group, blood was removed and an equal volume of dextran was injected to reestablish normal blood volume and lower hematocrit to a mean of 30.5. Control animals were not so treated. Animals were observed for neurological deficits for 24 hours after carotid ligation. The incidence of neurological deficit in control animals was 67%; it was 64% in the experimental group. Mortality within the first 24 hours was 28% in the controls and 75% in animals that were treated by hemodilution (p less than 0.001). Isovolemic hemodilution with dextran did not reduce the incidence of neurological deficit after carotid ligation in gerbils and was associated with a significant increase in mortality during the first 24 hours.