Balloon test occlusion of the internal carotid artery with stable xenon/CT cerebral blood flow imaging

We describe a technique to predict preoperatively the safety of permanently occluding an internal carotid artery. The method was performed by imaging stable xenon cerebral blood flow (CBF) with the internal carotid artery both open and temporarily occluded with a nondetachable balloon on a double lumen Swan-Ganz catheter. Patients were those in whom we planned to sacrifice the internal carotid artery (those with giant or inaccessible aneurysms) or those in whom such a sacrifice was at least likely (those with skull base tumors). Patients were divided into three groups on the basis of a comparison of occluded and nonoccluded CBF values. Group-I patients had no significant change in CBF with internal carotid artery occlusion; group-II patients showed a symmetric decrease in CBF; and group-III patients had an asymmetric decrease in CBF, always greater on the occluded side. A fourth group clinically failed to tolerate even brief carotid occlusion. The internal carotid artery in one patients from group III was sacrificed at surgery: the size and shape of his postoperative infarct corresponded almost exactly to the area of asymmetrically decreased CBF on his occluded study. The data suggest that if surgery is likely to result in permanent occlusion of the internal carotid artery, then patients who are at risk for delayed neurologic injury due to a compromised cerebral blood flow should have arterial bypass grafts before such surgery is performed.

Effect of low concentration stable xenon on the EEG power spectrum

The effect on the central nervous system of inhaled stable xenon, at concentrations of 25%, 30% and 35%, was assessed by evaluating changes in power spectra computed on the electroencephalogram. Ten normal adult subjects were studied in a protocol designed as a repeated measures experiment. Synchronous changes in the EEG power spectra were observed with stable xenon inhalation. These changes were equivalent for symmetrical electrode pairs, but the time history of the changes differed depending on the cortical region being measure. This suggests regional effects of stable xenon inhalation on the mechanisms producing the EEG.

Thalamic and subcortical gliosis with dementia

We describe two cases of patients with "primary dementia" in whom autopsy showed marked astrocytosis in several subcortical nuclei, but chiefly in those of the thalamus. One patient had the onset of symptoms at 31 years of age and a subacute course. The second patient was an elderly man with a strong familial history of dementia. These cases offer further evidence that subcortical lesions, especially in the thalamus, may produce a dementia that is not always clinically distinguishable from Alzheimer's disease and other "cortical" dementias.

Xenon-enhanced computed tomography in brain death

The absence of cerebral blood flow is a valuable adjunct confirming clinical criteria of brain death. However, current methods to confirm absent cerebral blood flow have problems that limit their clinical use. We reviewed cerebral blood flow data obtained with xenon-enhanced computed tomography in nine patients who were being evaluated for brain death. In eight patients who met clinical criteria for brain death, mean cerebral blood flow was 1.6 +/- 2.0 mL X 100 g X min. This value was within the range of error inherent in the method, and therefore represented absent flow. In a patient with persistent respiratory efforts, flow values compatible with absent flow were obtained in the supratentorial compartment, while mean flows as high as 24 mL X 100 g X min were measured in selected regions of interest in the infratentorial compartment, correlating with the clinical evidence of residual function of the brain stem. Xenon-enhanced computed tomography may be a useful test to confirm the absence of cerebral blood flow in patients being evaluated for brain death.

Errors in cerebral blood flow determinations by xenon-enhanced computed tomography due to estimation of arterial xenon concentrations

Errors in the determination of xenon concentrations in arterial blood during inhalation of xenon-oxygen mixtures are used to assess errors in the derivation of regional cerebral blood flow by the xenon-enhanced computed tomography (CT) method. The results of this study indicate that approximating the arterial buildup by a single exponential introduces relatively small errors in estimated flow values. The most significant systematic error is introduced by errors in estimation of the xenon arrival time to the brain in relationship to sequential (CT) scanning times.

Brainstem death with persistent EEG activity: evaluation by xenon-enhanced computed tomography

A patient with brainstem infarction met the clinical criteria for brain death but had persistent EEG activity, complicating our decision to withdraw life support. We evaluated cerebral blood flow with xenon-enhanced computed tomography (Xe/CT), which documented the absence of posterior circulation flow and persistent, low, anterior circulation flow. This information led us to withdraw life support, despite the presence of EEG activity. The Xe/CT method noninvasively measures local cerebral blood flow and may enhance diagnostic certainty in complicated brain-death evaluations.

Adverse reactions to xenon-enhanced CT cerebral blood flow determination

Fourteen institutions performed 1,830 computed tomographic (CT) cerebral blood flow (CBF) examinations with 32% inhaled stable xenon. Respiratory rate delay greater than 10 seconds occurred in 3.6% of patients, with 83% of the delays lasting 10-15 seconds. There was no incident of prolonged respiratory difficulty. Headache (0.4%), seizures (0.2%), nausea and vomiting (0.2%), and change in neurologic status (0.1%) were uncommon, and there were no transient ischemic attacks. The CT CBF method with 32% inhaled stable xenon is thus associated with an acceptably low incidence of adverse reactions.

Relief of nonhemispheric symptoms in low flow states by anterior circulation revascularization: a physiologic approach

Operative intervention remains controversial for patients with transient nonhemispheric symptoms with occlusive disease of both the anterior and posterior cerebral circulations. In addition to the standard evaluation of these patients, we have used stable xenon-enhanced computed tomographic mapping of cerebral blood flow (Xe/CT CBF). This relatively new and potentially widely available CBF methodology, by measuring approximately 30,000 CBF values within each of three CT levels, provides a readily interpretable means of evaluating extremes of hemodynamic compromise within any or all vascular territories. In the past 30 months, Xe/CT CBF studies in 300 patients with occlusive vascular disease have identified nine patients with global low flow and nonhemispheric symptoms (vertigo, lightheadedness, and/or blurred vision). Blood pressures determined by ocular pneumoplethysmography of Gee were markedly abnormal with reduced ocular/brachial ratios. Each patient had a combination of both segmental carotid and vertebrobasilar occlusive disease. Each patient had a flow-augmenting procedure performed on the anterior circulation in an attempt to improve global flow: carotid endarterectomy (two patients), subclavian-external carotid bypass (one patient), and superficial temporal artery-middle cerebral artery bypass (six patients). In each case disabling transient symptoms were relieved. There were no operative deaths, but one stroke occurred, probably as a result of a brief period of postoperative hypotension. Postoperative Xe/CT CBF studies show a long-term improved global CBF in all patients.

Operative exposure and management of the petrous and upper cervical internal carotid artery

The exposure and operative management of the petrous and upper cervical internal carotid artery (ICA) in 29 patients is detailed. Twenty-seven of these patients had extensive cranial base neoplasms (benign or malignant), 1 had an inflammatory cholesteatoma, and 1 had an aneurysm of the upper cervical ICA immediately proximal to the carotid canal. Preoperative studies useful in the evaluation of these patients included computed tomography, magnetic resonance imaging, cerebral and cervical angiography, and a balloon occlusion test of the ICA with evaluation of neurological status and of cerebral blood flow. The exposure of the upper cervical and petrous ICA was useful to obtain proximal control of the cavernous ICA, aided in the operative approach to extensive petroclival, intracavernous, and parapharyngeal neoplasms, and enabled the total resection of 23 of 27 such tumors. A subtemporal and preauricular infratemporal fossa approach was most commonly used for the exposure of the artery. Intraoperative arterial management consisted of exposure and decompression only, dissection from encasing neoplasm, resection of the invaded arterial segment and vein graft reconstruction, or intentional arterial occlusion. Vascular complications included 1 stroke due to delayed arterial occlusion, 1 stroke and death due to infection spreading from the nasopharynx with bilateral ICA rupture, and 1 pseudoaneurysm formation secondary to wound infection necessitating postoperative balloon occlusion of the ICA. Nonvascular complications included facial nerve paralysis in 10 patients (usually temporary), glossopharyngeal and vagal paralysis in 13 patients requiring Teflon injection of the vocal cord in 9, temporary difficulties with mastication in 9 patients, and wound infection in 3. The surgical exposure and management of the upper cervical and petrous ICA may permit a total operative resection of extensive cranial base neoplasms and is also an alternative for the management of vascular lesions involving these segments of the artery. With malignant neoplasms extending from the nasopharynx, postoperative infection remains a problem and may best be resolved by the use of a vascularized rectus abdominis muscle flap to reconstruct defects of the nasopharynx. Bilateral ICA encasement by neoplasms is also a major problem to be solved. The value of such an aggressive approach to the management of malignant neoplasms remains to be proven.

Cerebral blood flow measured by xenon-enhanced computed tomography as a guide to management of patients with cerebrovascular disease

CT scanning performed before and sequentially during the inhalation of stable xenon (32%), coupled with end-tidal xenon measurements, has made possible the routine construction of regional cerebral blood flow (rCBF) maps with resolution that approximates that of the CT scanner. The capability of obtaining quantitative flow maps with direct anatomic correlation is now available with a commercial package of hardware and software adapted to the General Electric 9800 scanner. The ability to distinguish between normal and reduced rCBF in specific vascular territories has proved useful in the management of cerebrovascular disease. Specific clinical dilemmas that have been addressed with rCBF information from xenon-enhanced CT scanning include the following: In the patient with asymptomatic occlusive disease, is normal rCBF preserved? Is there adequate collateral flow? Are cerebrovascular symptoms a result of emboli or chronic regional low flow? In the patient with complex multivessel occlusive disease, which revascularization procedure is indicated first? Did operation improve rCBF? Should a further procedure be added? May a diffusely diseased but patent artery, which is the source of emboli, be sacrificed safely without compromising rCBF? On the basis of experience with 155 patients, the management and understanding of cerebrovascular disease has been aided substantially by the incorporation of rCBF mapping by xenon-enhanced CT scan in the evaluation of these patients.

Central herniation revealed by focal decrease in blood flow without elevation of intracranial pressure: a case report

Until recently, in standard hospital settings the tissue blood supply could be inferred only from indirect measures such as assessment of the clinical signs and intracranial pressure (ICP) monitoring. This critical parameter can now be imaged directly with stable xenon-enhanced computed tomographic (CT) imaging. The procedure requires only an additional 10 minutes after a standard head study, yet it provides potentially vital information about tissue perfusion. We describe here a patient in whom a frontal lobe hematoma produced a direct mass effect, causing an element of central herniation with relative sparing of lateral and posterior cortical regions. Although the ICP recordings remained unchanged, symptoms of brain stem compression became apparent. Xenon/CT cerebral blood flow (CBF) mapping demonstrated a flow decrease mainly within the left frontal lobe and throughout central ganglionic structures. After removal of the left frontal hematoma, both clinical status and local and central flow improved. Because the xenon/CT method combines direct anatomical information with blood flow information in one examination, it may be a valuable clinical tool in providing a better understanding of pathophysiology in patients with head injuries and other mass lesions.

Simultaneous measurements of cerebral blood flow by the xenon/CT method and the microsphere method. A comparison

Simultaneous measurements of cerebral blood flow have been performed in baboons to assess the correlation between the acute and invasive nondiffusible microsphere technique and the noninvasive xenon-enhanced CT method. Blood flows in small tissue volumes (approximately 1 cm3) were directly compared. The results of these studies demonstrate a statistically significant association between the two methods (P less than .001). Similar correlations were obtained by both the Kendall tau (tau) and the Spearman (r) methods. The problems and limitations of such correlations are discussed.

Measurement of cerebral blood flow during xenon inhalation as measured by the microspheres method

Measurements of cerebral blood flow (CBF) were performed using the microsphere technique in non-human primates (baboons) to assess the effect of non-radioactive xenon gas inhalation on CBF. Blood flows in small tissue volumes (approximately 1 cm3) were directly measured before and during the inhalation of xenon/oxygen gas mixtures. The results of these studies demonstrated that when inhaled in relatively high concentrations, xenon gas does increase CBF, but the changes are more global than tissue-specific. The problems and limitations of such evaluations are discussed.

Blood flow mapping in the human liver by the xenon/CT method

In the noninvasive, nonradioactive xenon/CT method of blood flow measurement, xenon gas is inhaled, and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential CT; time-dependent xenon concentration within various tissue segments is then used to derive local blood flow maps. The usefulness of the method in the assessment of local cerebral blood flow has been documented. In this paper we explore its application to blood flow measurement in the human liver. In our preliminary clinical studies, hepatic blood flow ranged from 50 to 120 ml/100 cc/min in normal and adequately supplied tissue, and lower flow values were observed in tissue with abnormal function. The advantages and limitations of the method in such applications are discussed.

Stable xenon CT blood flow mapping for evaluation of patients with extracranial-intracranial bypass surgery

Xenon computerized tomography (Xe CT) blood flow studies were conducted in 25 patients referred for a possible extracranial-intracranial bypass procedure for occlusive vascular disease in one or more extra- or intracranial vessels. These studies were helpful in selecting eight candidates for surgery. The Xe CT studies were performed at one or two brain levels using a prototype Xe CT system for measurement of cerebral blood flow which was designed in collaboration with the General Electric Co., and adapted for the GE 9800 scanner. In those patients selected to undergo operation, Xe CT demonstrated compromise of flow reserve regionally, globally, and/or in the watershed area. All eight patients who underwent the procedure showed a favorable clinical response postoperatively, and seven had a dramatic increase in flow. The 17 patients whose baseline CT studies showed no reduction of flow with the Xe CT method were not selected for surgery. All 25 patients have remained neurologically stable to date. Case studies of three of the eight patients undergoing bypass surgery are presented. This limited but consistent experience suggests that Xe CT blood flow mapping makes possible the recognition of brain regions in which flow reserves are compromised. This is due to the relatively high degree of spatial resolution that this technique provides and to the fact that mapping can be correlated directly with the anatomy. Used in combination with a careful clinical examination and an accurate medical history, this study method appears to be a useful guide in the selection of patients who are most at risk from hemodynamic instability and those who are most likely to benefit from flow-augmentation surgery.

Xenon/CT blood flow mapping of the kidney and liver

A noninvasive technique for measuring blood flow by xenon-enhanced X-ray transmission CT has been developed and reported quite extensively in recent years. In this method nonradioactive xenon gas is inhaled, and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential CT. Time-dependent xenon concentration within various tissue segments is used to derive local blood flow maps. The method has been amply discussed in relation to assessment of local cerebral blood flow. Its application to other body organs is explored in this paper, in which results from six preliminary blood flow studies in the liver and kidneys of nonhuman primates are reported. Blood flow in renal cortex ranged from 150 to 280 ml/100 cc/min and hepatic tissue perfusion from 80 to 120 ml/100 cc/min. The advantages and limitations of the method in such applications are discussed.

Local cerebral blood flow alterations (Xe-CT method) in an accident victim

Computed tomography was used before and during inhalation of nonradioactive xenon gas to measure and map local cerebral blood flow noninvasively at two PaCO2 levels in a 19-year-old accident victim. The technique demonstrated normal response to elevated PaCO2 with only a regional loss of autoregulation.

Mapping cerebral blood flow by xenon-enhanced computed tomography: clinical experience

Local cerebral blood flow was measured and mapped using xenon-enhanced x-ray transmission computed tomography. Studies involving 4-6 minutes of xenon-oxygen inhalation can be performed routinely in awake and anesthetized patients with acceptable patient tolerance and compliance. Several case studies of patients with acute and chronic ischemic injuries and other cerebral abnormalities are presented to illustrate characterization of flow pattern in normal and abnormal tissue, as well as the relevance of this flow information to clinical patient management.

Clinical experience with the use of xenon-enhanced CT blood flow mapping in cerebral vascular disease

Cerebral blood flow mapping with the xenon-enhanced/CT method has become a useful clinical tool in the management of patients with occlusive cerebral vascular disease. Studies involving 4-5 minutes of inhaling a xenon/oxygen mixture (less than or equal to 35%) can now be performed routinely with acceptable patient tolerance and compliance. Four cases with acute and chronic ischemic injuries are reported here to illustrate the manner in which this method has been used to characterize flow pattern in such patients and the relevance of this flow information to clinical patient management.

Measurement of local cerebral blood flow by xenon-enhanced computerized tomography imaging: a critique of an error assessment

A review of an error assessment of local cerebral blood flow values derived from xenon-enhanced computerized tomography imaging indicates that the authors have failed to consider the appropriate parameters, thereby yielding errors that are larger than the true errors.

Extreme pseudo-occlusion of the internal carotid artery

Angiographic criteria for the identification of patients with angiographic internal carotid artery occlusion but with anatomical patency are presented. The presence of retained contrast material in a caudal atherosclerotic internal carotid artery stump, especially when accompanied by visualization of the internal carotid artery at the base of the skull, suggests that the internal carotid artery may be patent. Two cases of "extreme" pseudo-occlusion are presented, and the indications for extracranial-intracranial bypass and caudal internal carotid artery stump resection are reviewed.

Progress in cerebrovascular disease: local cerebral blood flow by xenon enhanced CT

A noninvasive technique for measuring local cerebral blood flow (LCBF) by xenon enhanced x-ray transmission computed tomography (CT) has been developed an reported quite extensively in recent years. In this method, nonradioactive xenon gas in inhaled and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential computed tomography. Time dependent xenon concentrations within various tissue segments in the brain are used to derive both local partition coefficient (lambda) and LCBF. An assessment of this method reveals that although it provides functional mapping of blood flow with excellent anatomic specificity, there are distinct limitations. The assumptions underlying this methodology are examined and problems associated with various potential applications of this technique are discussed.

Errors associated with single-scan determinations of regional cerebral blood flow by xenon enhanced CT

Possible errors in the determination of xenon concentrations in arterial blood, and uncertainties in CT tissue enhancements during inhalation of xenon-oxygen mixtures, are used to assess errors in the determination of regional cerebral blood flow by the in vivo autoradiographic (single-scan) technique. The results of this study indicate that errors associated with the determination of xenon concentrations in arterial blood decrease rapidly as the time of scanning after the initiation of xenon inhalation is increased. Analysis of errors caused by statistical uncertainties in image enhancement indicate that time of scanning is optimal between 1.5 and 2.5 min for determination of fast flow, while errors in slow-flow determinations gradually decrease as the time of scanning increases.

In vivo mapping of local cerebral blood flow by xenon-enhanced computed tomography

A noninvasive technique has been developed to measure and display local cerebral blood flow (LCBF) in vivo. In this procedure, nonradioactive xenon gas is inhaled and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential computerized tomography. The time-dependent xenon concentrations in various anatomical units in the brain are used to derive both the local partition coefficient and the LCBF. Functional mapping of blood flow with excellent anatomical specificity has been obtained in the baboon brain. The response of LCBF to stimuli such as changes in carbon dioxide concentrations as well as the variability in LCBF in normal and diseased tissue can be easily demonstrated. This method is applicable to the study of human physiology and pathologic blood flow alterations.

Radiopaque silicone rubber and xeroradiography for the high-resolution visualization of the cerebral vasculature

Radiopaque silicone rubber provides uniquely high degree of vascular definition when combined with xeroradiography for visualization of the cerebral circulation. The method of tissue preparation is described and illustrated by xeroradiograms of coronal sections of brains from animals subjected to occlusion of the lenticulostriate artery.

Xenon and iodine enhanced cerebral CT: A closer look

Xenon and iodine enhanced dynamic computerized tomography (CT) have been used experimentally to obtain both qualitative and quantitative information on local cerebral blood flow in both normal and infarcted tissue. Direct comparisons between Xenon enhancement, iodine enhancement and pathological findings demonstrate significant differences between results derived from each of the 2 in vivo techniques. While iodine enhanced dynamic CT yields valuable information concerning the patency and density of vasculature, xenon enhanced studies can provide highly focal information on cerebral tissue perfusion.

Selective lenticulostriate occlusion in the primate. A highly focal cerebral ischemia model

A highly reliable model for the study of focal cerebral ischemia has been developed using a retro-orbital approach to occlude the lateral lenticulostriate arteries of the baboon. An infarction of the caudate, putamen and the anterior limb of the internal capsule has consistently been produced. Reliability has been attained because the anatomical variations of the lenticulostriate arteries of each animal can be fully appraised, permitting selective vessel occlusion. A well-defined clinical and radiographic lesion has also resulted from this procedure which was clinically well tolerated by all animals. Selective lenticulostriate occlusion provides a new approach to the study of focal cerebral ischemia in the sub-human primate, and serves for the evaluation of proposed therapies for treatment of focal cerebral ischemia.

Side effects of xenon inhalation

Short- and long-term side effects during and after inhalation of premixed xenon oxygen (28-47%) from 12 studies are reported. While all but one subject tolerated xenon inhalation without ill effects, that individual did experience unpleasantly severe dysesthesias and a brief period of unresponsiveness. We believe that further human studies with xenon inhalation should be conducted to explore possible early indicators for reduced tolerance of xenon by certain individuals.

Xenon enhanced dynamic computed tomography: multilevel cerebral blood flow studies

Xenon enhanced computed tomography with a fast scanning mode and interscan table incrementation was used to derive local cerebral blood flow in a nonhuman primate 19 days following infarction. The in vivo autoradiographic methodology was used to derive blood flow in normal and diseased tissue at four different brain levels (slices) during a single inhalation study.

The controlled delivery of thiopental and delayed cerebral revascularization

Sodium thiopental was administered to 10 dogs following embolization of the middle cerebral artery. Its effect on the "grace period" for revascularization was investigated by performing embolectomies 6 hours later. We observed a striking reduction in the size of infarction in the animals treated with thiopental at moderate and prolonged dosage levels. The control animals treated with pentobarbital received less protection against ischemia although blood levels were similar to those of the experimental groups during the period of vascular occlusion.

"True" traumatic aneurysm of the intracranial internal carotid artery: case report

This paper reports a case of a true aneurysm of the intracranial internal carotid artery that occurred after a closed head injury. The probable etiology of this unusual lesion is discussed in respect to other partial and complete vessel wall injuries. The diagnosis of a traumatic aneurysm must be suspected when a delayed intracranial hemorrhage occurs after a head injury. The treatment of most intracranial aneurysms should be early, direct operation. Traumatic aneurysms of the internal carotid artery, however, are uniquely treacherous, and they may warrant an indirect approach when discovered soon after injury.

Anterior spinal artery aneurysm. Case report

An anomaly of the anterior spinal artery in association with a berry aneurysm is reported. The embryological basis for this previously unreported combination is reviewed.

Abnormality of the xenon brain:blood partition coefficient and blood flow in cerebral infarction: an in vivo assessment using transmission computed tomography

Xenon-enhanced computed tomography (CT) was used to analyze, in vivo, the patterns of blood flow of cerebral infarction in a nonhuman primate model. Consistent and reproducible results were attained utilizing the numerical data from CT scans obtained during the inhalation of nonradioactive xenon. The spatial resolution of CT defined a morphophysiologic map of the variability in brain:blood partition coefficient and flow rate constant that exist within and around an infarct. Both the flow and the partition coefficient were significantly diminished in the ischemic focus in all animals studied. Although the partition coefficients were normal, the flow was decreased in the other locales sampled in the ipsilateral hemispheres. In the contralateral hemispheres, both flows and partition coefficients were within the range of normal for adolescent baboons.

Neurinoma of the trigeminal root and atypical trigeminal neuralgia: their commonality

Two cases of very small trigeminal neurinomas arising proximal to Meckel's cave are presented. We believe that the overlap of the symptoms and signs of these tumors with those of atypical trigeminal neuralgia strengthens the concept of the latter entity also being due to compression of the trigeminal nerve solely within the posterior fossa.

Acquired middle cranial fossa fistulas: normal pressure and nontraumatic in origin

To the accepted classification of three types of normal pressure, nontraumatic cerebrospinal fluid (CSF) fistulas, we would add "acquired." This type of CSF fistula tends to occur from the middle cranial fossa because of the enlargement of "pitholes" that are normally present in its anterior medial aspect. The enlargement of these bony defects is due to normal intracranial pressure variations that, not uncommonly, create meningoceles and meningoencephaloceles. A portion of the floor of this area is aerated in up to 10% of the normal population by the lateral recess of the sphenoid sinus, the pterygoid recess. Thus, this area has the potential to act as a pathway between the middle fossa and the paranasal sinuses, allowing cerebrospinal fluid to pass into the sinuses. Isotope and computerized tomographic studies are helpful in the localization of such a CSF leak. Tomography of the base of the skull, however, is essential for the ideal definition of possible routes of fistulization. If there is any question of the presence of a middle fossa fistula, these studies can show whether the floor of this area is pneumatized and whether there are any defects in the floor. The treatment of such a fistula should include generalized reinforcement of the floor of the anterior middle fossa by a middle fossa approach. If any doubt exists as to the site of leakage (anterior or middle fossa), the minimal surgical procedure should include exploration of both areas via a frontotemporal craniotomy.

The acute abdomen in patients with ventriculoperitoneal shunts

A rationale for management of the patient with an acute adbomen and a ventriculoperitoneal shunt is presented in relation to eight patients. In two patients peritonitis was due to perforation of an abdominal viscus, not shunt related, and six were due to infections of ventriculoperitoneal shunts. Resolution of abdominal symptomatology occurs within six hours after the distal end of the shunt catheter is removed from the abdomen and placed in a drainage bottle. In four of these six, infection was limited to the peritoneal end of the catheter. The ventricular fluid was sterile.

Pentothal protection for delay cerebral revascularization

Thiopentone (20 mg/kg/bolus and 20 mg/kg/three hours) was effective in preventing infarction in five dogs with six hours of middle cerebral occlusion. Nine control animals sustained massive to large infarctions. Utilizing this regime therapeutic blood levels were rapidly attained for over 12 hours without side effects. From the experimental and human experience with focal cerebral ischaemia, there appears to be a finite grace period in which cerebral revascularization can be undertaken. In canine and primate models this time has been about five hours, following which the infarction process may not be reversible (Sundt et al. 1977, Laha et al. 1978). Seeking to prolong this grace period, thiopentone was selected as an ideal drug for this purpose, and its effect on the revascularized canine middle cerebral distribution was evaluated at six hours following embolectomy.

Anterior choroidal artery aneurysms: their anatomy and surgical significance

The experience of the senior author was 16 anterior choroidal artery aneurysms is reviewed. The anatomic variations of the origin of the anterior choroidal artery are discussed, and the danger of sacrificing the artery in aneurysm surgery is stressed. The surgical procedure upon these aneurysms has frequently been difficult, requiring careful microdissection. This was due to variations of the origin of the aneurysm in respect to the artery and their frequent contiguity.

Dissecting intracranial aneurysms

The clinical, operative and pathological characteristics of a dissecting aneurysm of the vertebral artery are presented. A review of the literature suggests that this type of intracranial aneurysm is being recognized with increasing frequency and can be characterized by its symptomatology and radiological patterns. A set of guidelines for the management of dissecting intracranial aneurysms is proposed.

Hemangioma thrombocytopenia syndrome. A case masquerading as an encephalocele

The association of hemangioma and thrombocytopenia has been recognized since 1940. We cared for a newborn boy whose hemangioma resembled an occipital encephalocele. The true diagnosis was suspected only when his platelet count dropped to 3,000/cu mm with severe intestinal hemorrhage on the third day of life. The diagnosis was confirmed by arteriography. The hemangioma was excised surgically, and the platelet count returned quickly to normal. The baby has done well subsequently. When feasible, surgical excision of the platelet-trapping hemangioma is the treatment of choice in the hemangioma thrombocytopenia syndrome.