Joseph M.K. Lam

The role of computed tomographic angiography in the diagnosis of intracranial aneurysms and emergent aneurysm clipping.

Conventional cerebral angiography has always been regarded as the gold standard for intracranial aneurysm detection. However, conventional angiography has the disadvantages of being invasive and time consuming. We present here 30 patients who underwent computed tomographic angiography (CTA) with three-dimensional reconstruction for the detection of intracranial aneurysms. All of these patients had subarachnoid hemorrhage or suspected intracranial aneurysms. CTA was performed in all patients with the use of a General Electric Hispeed Advantage helical scanner. Iohexol, 135 ml, was used as the contrast agent. Twenty-five patients also underwent conventional angiography for comparison. The five patients who underwent CTA only did not have conventional angiography because of poor clinical condition, and four of them subsequently died. Five patients had subarachnoid hemorrhage, but the results of both CTA and conventional angiography were negative for aneurysms. One patient had an incidental finding of a 3-mm left posterior communicating artery aneurysm on CTA, which was confirmed by conventional angiography. In the remaining 19 patients, 19 saccular aneurysms and 1 fusiform aneurysm were detected by CTA. Locations and sizes were confirmed by conventional angiography in all except two. The first exception was a patient who had a 2.5-mm anterior communicating artery aneurysm detected by CTA but not by conventional angiography. Surgical exploration confirmed the CTA diagnosis. The other exception was a patient in whom a 2-mm right posterior communicating artery aneurysm was detected by CTA but in whom conventional angiography showed a 2-mm left posterior communicating artery aneurysm. Unfortunately, there was no surgical confirmation in this case because the family of the patient refused surgery. Our results have demonstrated that CTA is a quick, reliable, and relatively simple diagnostic tool for intracranial aneurysms. In an emergent situation, such as a deteriorating patient with a hematoma, it is superior to either empiric exploration or infusion computed tomographic scans because it delineates the orientation and configuration of the aneurysm and its associated vascular anatomy.

The surgical treatment of intracranial aneurysms based on computer Tomographic angiography alone – streamlining the acute mananagement of symptomatic aneurysms

Summary. Background: We aimed to prospectively assess the usefulness of computer tomographic angiography (CTA) in streamlining the management of symptomatic intracranial aneurysms in a tertiary neurosurgical unit, from admission to surgery. Methods: We performed a prospective evaluation over a 2-year period of all symptomatic intracranial aneurysms managed according to a standardized departmental protocol, to assess how CTA has impacted the decision-making process pertaining to the suitability of this investigation to proceed directly to surgery. Findings: A total of 90 patients with intracranial aneurysms were treated over the 2-year period. 23 (26%) underwent endovascular occlusion while 67 (74%) patients underwent a surgical clipping procedure. In the surgical group, 22 (33%) patients had their aneurysms clipped based on CTA alone, while 45 (67%) required additional conventional angiography prior to surgery. Thus around one quarter of all patients treated for symptomatic intracranial aneurysms in our unit had their aneurysm secured surgically based solely on CTA. Interpretation: CTA significantly influences the acute management of symptomatic intracranial aneurysms by streamlining the decision-making process during the early and acute management of these lesions.

Aneurysm recurrence after treatment of paraclinoid/ophthalmic segment aneurysms - A treatment-modality assessment

SummaryObject. The treatment of 21 paraclinoid/ophthalmic segment internal carotid artery aneurysms (PCOSAs) over a seven year period in a regional neurosurgical center was reviewed to assess the degree of obliteration and recurrence rate of these aneurysms after treatment by surgical and endovascular methods.Method and result. An assessment of the clinical notes, operation records and cerebral angiograms was made to evaluate the rate of residual and recurrent aneurysms after treatment and at follow-up. In the coiling group, the aneurysm recurrence rate was eight out of fifteen aneurysms (53%). Four recurrences were from previously totally occluded aneurysms. Out of the six surgical cases, five had follow-up angiography performed. All had stable occlusions of their aneurysms including one with subtotal occlusion. Two clipping procedures after previous coiling achieved total occlusion of aneurysm on follow-up angiography.Conclusion. Based on our case series we conclude that PCOSAs frequently recur after primary treatment. GDC coiling was associated with a higher rate of recurrent aneurysms when compared with surgical treatment. A review of the literature on the surgical and endovascular treatment of PCOSAs support this observation.

Pre- and postoperative fMRI and clinical memory performance in temporal lobe epilepsy.

Objective: The present study aimed to examine and compare memory processing in patients with unilateral temporal lobe epilepsy (TLE) before and after surgery using functional magnetic resonance imaging (fMRI). Methods: Seventeen preoperative patients with unilateral TLE (nine left, eight right) and eight healthy controls were recruited. They performed a complex visual scene-encoding task during fMRI to measure memory activation in the mesial temporal lobe. Their memory performance was evaluated using standardised neuropsychological tests. After unilateral temporal lobe resection (either temporal lobectomy, selective amygdalohippocampectomy or lesionectomy), the same fMRI paradigm and neuropsychological tests were administered to the patient group. Results: Left-TLE patients demonstrated a decline in verbal memory after left temporal lobe resection. Their postoperative verbal and visual memory performance was positively associated with postoperative functional activation in the right mesial temporal lobe, whereas the postoperative memory performance of right-TLE patients was positively associated with postoperative functional activation in the left mesial temporal lobe, contralateral to their respective side of resection. Conclusion: Postoperative memory performance was significantly associated with functional activation contralateral to the side of resection in patients with unilateral TLE, and the function of the contralateral mesial temporal lobe might play an important role in supporting memory performance after temporal lobe resection.

An anterior intradural neurenteric cyst of the cervical spine: complete excision through central corpectomy approach--case report.

The case of a cervical intraspinal neurenteric cyst in a 6-year-old boy is reported. The anterior intradural location of the cyst was confirmed by preoperative magnetic resonance imaging. Complete excision of the cyst was achieved through the anterior central corpectomy approach. The vertebral defect was reconstructed with autogenous fibular graft. The child made a complete neurological recovery without a mechanical problem either at the neck or at the graft donor site.

Cerebral venous oxygen saturation monitoring: is dominant jugular bulb cannulation good enough?

Venous oxygen saturation at the clinically dominant jugular bulb (SjO2) and that at the confluence of the cerebral sinuses (SccsO2) were compared by direct simultaneous blood sampling of 13 severely head injured patients. The side of dominant jugular bulb (JB) was determined by neck compression test. The right side was chosen if the test was equivocal. In effect, the right side was cannulated in all cases. Subsequent angiography showed that two of the 13 cases were left side dominant. In all, 176 pairs of blood samples were analysed. Correspondence rates (the difference between each pair of blood samples being less than 4% of oxygen saturation) for individual case were good (80-100%) in nine cases including one case with left side dominance. Correspondence rates were moderate in two cases (50 and 56%); the differences were not clinically significant. In the remaining two cases, including one with left side dominance, the correspondence rates were poor (0 and 4%, respectively); SccsO2 was always lower than SjO2; median differences were 13.4 and 23.1%. Ischemia in the cerebral hemispheres would have been underestimated if management were based on SjO2. Monitoring at the dominant JB accurately reflected the global and hemispheric cerebral oxygenation in 11/13 of cases. Monitoring at the non-dominant JB is not recommended.

Effects of Illness Duration on Memory Processing of Patients with Temporal Lobe Epilepsy

Summary:  Purpose: To examine the effects of illness duration on the neural processing of memory in patients with temporal lobe epilepsy (TLE) by using functional MRI.

Re-defining the ischemic threshold for jugular venous oxygen saturation--a microdialysis study in patients with severe head injury.

Neurological change is more likely to occur when jugular venous oxygen saturation (SjvO2) is less than 50%. However, the value indicating cellular damage has not been clearly defined. We determined the critical SjvO2 value below which intracerebral extracellular metabolic abnormalities occurred in 25 patients with severe head injury. All patients received standard treatment with normoventilation and maintenance of intracranial pressure < 20 mmHg. SjvO2 was measured from the dominant jugular bulb using a calibrated fibreoptic catheter. Intracerebral metabolic monitoring was performed by collecting perfusate from a microdialysis probe placed in the frontal lobe anterior to the intracranial catheter. Excitotoxin (glutamate) and other extracellular metabolites (lactate, glucose and glycerol) were measured frequently using enzymatic and colorimetric methods. We observed biphasic relationships between SjvO2 and all intracerebral metabolites. Analysis of variance showed that there were rapid increases in glutamate, glycerol and lactate when SjvO2 dropped below 40, 43 and 45% respectively. Extracellular glucose decreased when SjvO2 dropped below 42%. Our findings suggested that the ischemic threshold for SjvO2 in patients with severe head injury is 45%, below which secondary brain damage occurred.

Cerebral blood flow (CBF)-directed management of ventilated head-injured patients

OBJECTIVE Ischaemic brain damage has been shown to be an important contributing factor causing head injury fatality. Maintenance of an adequate cerebral perfusion pressure is difficult in patients with elevated intracranial pressure (ICP) and deranged cerebral vasoreactivity. Thirty-five cases of ventilated moderate-to-severe head-injured patients were prospectively studied, correlating their cerebral haemodynamic abnormalities, neurochemical disturbances (using microdialysis methodology) and clinical outcome. METHODS Cerebral haemodynamic abnormalities were defined and classified by transcranial Doppler ultrasonography (TCD) and stable xenon-CT cerebral blood flow measurements (XeCT) into their status of CO2 reactivity, pressure autoregulation, hyperaemia or non-hyperaemia. Two-hour episodes of these abnormalities with and without haemodynamic intervention were followed in their changes in ICP, CPP, intracerebral metabolites and finally their clinical outcome. RESULTS Loss of CO2 reactivity was associated with a significantly higher ICP, increasing intracerebral metabolites (lactate, glutamate and glycerol) and invariably a fatal outcome. Impaired pressure autoregulation was also associated with an elevated ICP, but no significant difference in intracerebral metabolites and incidence of favourable clinical outcome. Patients with intact CO2 reactivity and impaired pressure autoregulation were treated with an elevated CPP in 32 episodes, resulting in a significant reduction in ICP, intracerebral glutamate and glycerol and non-survival. In patients with intact CO2 reactivity and impaired pressure autoregulation, eleven episodes of hyperaemia were identified by XeCT. A modest 20%, blood pressure reduction resulted in a trend towards a reduction of ICP, intracerebral glutamate and glycerol and non-survival. CONCLUSIONS The need for haemodynamic intervention in this group of ventilated patients with moderate-to-severe head inury can be made logical when these abnormalities are identified daily. The success of management was reflected by a stable or improved ICP, CPP, intracerebral metabolic deranagement and survival.

Language lateralization of chinese-english bilingual patients with temporal lobe epilepsy : A functional MRI study

Functional MRI was used to examine language lateralization of Chinese characters and English words associated with temporal lobe epilepsy (TLE) in Chinese-English bilinguals with left or right TLE. The results suggest that the neural basis of processing Chinese and English seems to be different, as normal controls demonstrated left hemispheric lateralization in reading English words but bi-hemispheric lateralization in reading Chinese characters. This difference in the neural bases of Chinese and English processing was found to affect the patterns in change-of-language processing associated with TLE. That is, whereas left-TLE patients were more likely than right-TLE patients to demonstrate a bi-hemispheric language involvement in reading English, both left- and right-TLE patients demonstrated primarily bilateral hemispheric involvement for reading Chinese characters.