Microsurgical anatomy of the anterior perforating arteries

Flow diversion for anterior choroidal artery (AChA) aneurysms: a multi-institutional experience

BACKGROUND

Anterior choroidal artery (AChA) aneurysms represent a small subset of cerebral aneurysms. The Pipeline Embolization Device (PED) has been successfully applied to various aneurysms of the supraclinoid internal carotid artery (ICA). The treatment of these aneurysms requires special attention due to the eloquent territory supplied by the AChA. We report the largest and first dedicated series of flow diversion treatment of AChA aneurysms.

METHODS

Four institutional neurointerventional databases were reviewed for cases of intracranial aneurysms treated with PED. Patient and aneurysm data as well as angiographic imaging were reviewed for all cases of AChA aneurysms treated with PED. AChA aneurysms were defined as aneurysms distal to the AChA and proximal to the ICA terminus, with or without the incorporation of the AChA.

RESULTS

Eighteen AChA aneurysms were treated during the study period. All aneurysms were successfully treated with a mean follow-up of 19.1 months. The large majority of aneurysms (15/18, 83.3%) were completely obliterated. No patients suffered from intra- or post-procedural complications. A1 stenosis was a common occurrence, seen in 10 of 16 (62.5%) covered anterior cerebral arteries (ACAs), although all were asymptomatic. All AChAs remained patent at last follow-up.

CONCLUSIONS

The PED can be used successfully in AChA aneurysms with a good safety and efficacy profile. All AChAs remained patent. Collateral flow networks, especially for the ACA, affect long-term branch vessel patency. Treatment with PED for AChA aneurysms appears to be a reasonable option to consider and should be evaluated in a larger cohort.

The Clinical Importance of Perforator Preservation in Intracranial Aneurysm Surgery: An Overview with a Review of the Literature

Clipping for intracranial aneurysms is done to achieve complete occlusion of the aneurysm without a remnant sac. Despite modern advancements of neurosurgical techniques, morbidity related to the clipping of intracranial aneurysms still exists. Clip occlusion of a parent artery or small hidden perforators commonly leads to permanent neurological deficits, and is a serious and unwanted complication. Thus, preserving blood flow in the branches and perforators of a parent artery is very important for successful surgery without postoperative morbidity and mortality. The aim of this review article is to discuss the consequences of perforator injury and how to avoid this phenomenon in aneurysm surgeries using intraoperative monitoring devices.

Perfusion-weighted imaging and dynamic 4D angiograms for the estimation of collateral blood flow in lacunar infarction

Although lacunar infarction accounts for approximately 25% of ischemic strokes, collateral blood flow through anastomoses is not well evaluated in lacunar infarction. In 111 lacunar infarction patients, we analyzed diffusion-weighted images, perfusion-weighted images, and blood flow on dynamic four-dimensional angiograms generated by use of Signal Processing In NMR-Software. Blood flow was classified as absent (type 1), from periphery to center (type 2), from center to periphery (type 3), and combination of type 2 and 3 (type 4). On diffusion-weighted images, lacunar infarction was found in the basal ganglia (11.7%), internal capsule (24.3%), corona radiata (30.6%), thalamus (24.3%), and brainstem (9.0%). In 58 (52.2%) patients, perfusion-weighted image showed a circumscribed hypoperfusion, in one (0.9%) a circumscribed hyperperfusion, whereas the remainder was normal. In 36 (62.1%) patients, a larger perfusion deficit (>7 mm) was observed. In these, blood flow was classified type 1 in four (11.1%), 2 in 17 (47.2%), 3 in 9 (25.0%), and 4 in six (16.7%) patients. Patients with lacunar infarction in the posterior circulation more often demonstrated blood flow type 2 and less often type 3 (p = 0.01). Detailed examination and graduation of blood flow in lacunar infarction by use of dynamic four-dimensional angiograms is feasible and may serve for a better characterization of this stroke subtype.

Arteries and Veins of the Sylvian Fissure and Insula: Microsurgical Anatomy

We present a vascular anatomical study of the arteries and veins of the sylvian fissure and insula.A good knowledge of the sylvian fissure, the insula, and their vascular relationship would seem mandatory before performing surgery in this area, whatever the type of surgery (aneurysms, arteriovenous malformations, insular tumors).We start with the sylvian fissure and insula morphology, followed by the MCA description and its perforators, with special attention paid to the insular perforators. We demonstrate that the long insular perforators penetrating in the superior part of the posterior short gyrus and long gyri vascularize, respectively, the corticonuclear and corticospinal fasciculi. We particularly insist too on three anatomical constants regarding the vascularization of the insula, already described in the literature: The superior periinsular sulcus is the only sulcus on the lateral surface of the brain without an artery along its axis; the superior branch of the MCA supplies the anterior insular pole and both the anterior and middle short gyri in 100 % of cases; in at least 90 % of cases, the artery that supplied the central insular sulcus continued on to become the central artery.We end with the anatomical study of the veins and cisterns.

Surgical Treatment of Middle Cerebral Artery Aneurysms Without Using Indocyanine Green Videoangiography Assistance: Retrospective Monocentric Study of 263 Clipped Aneurysms

INTRODUCTION

Middle cerebral artery (MCA) aneurysms represent 20% of intracranial aneurysms. Most (80%) of them are located on the sylvian bifurcation, the seat of hemodynamic turbulence flow. Morbidity and mortality related to surgery of MCA aneurysms are not negligible. MCA vascularization areas are important eloquence functional territorial of Brain tissue. Indocyanine green videoangiography assistance (ICG-VA) is an emergent tool for intraoperative assessment of aneurysmal occlusion and for checking a possible stenosant clip in vascular area. The purposes of this study were to evaluate the safety of clipping procedure in terms of morbidity, mortality, and efficiency of aneurysm occlusion without using ICG-VA, recurrence and bleeding/rebleeding at short and long terms, and angiographic and clinical follow-ups.

MATERIAL AND METHODS

This study is a monocentric retrospective study performed at Pitié-Salpêtrière-Charles Foix Hospital Center, reporting clinical and angiographic follow-up of consecutive patients treated for MCA aneurysms (ruptured and unruptured) by clipping procedures. From 2002-2012, 251 consecutive patients were admitted at the author's institution for treatment of 263 MCA aneurysms (163 ruptured and 100 unruptured). Procedure-related death and complications were systematically assessed without video-angiography availability. The degree of aneurysms exclusion was evaluated according to the Raymond-Roy scale after the procedure and at long-term angiographic follow-up (mean delay = 36 months).

RESULTS

The death rate related to aneurysmal exclusion procedure was 1.2%. The major complication rate related to surgery was 5.3%. Postprocedure, an aneurysm occlusion rate Raymond-Roy grade A or B was 95.6%. Neither recanalization controlled clipped aneurysms nor re-aneurysmal rupture was observed in the long-term clinical follow-up (mean time = 83.5 months). The institution's series of surgical outcomes reported 95.6% of complete exclusion and 4.5% incomplete procedures without ICG-VA. A clip of repositioning rate was estimated at 15% when ICG-VA was used.

CONCLUSION

Surgical management is relatively safe for patients, with an acceptable complication rate in the era when ICG-VA was not yet available. Indeed, the main source of procedural ischemia microsurgery is stenosant clip. To limit the occurrence of malposition, the author's center began using ICG-VA a few months ago and expects to reduce its rate of incomplete occlusion.

Common features of the cerebral perforating arteries and their clinical significance

BACKGROUND

The perforating vessels supply very important regions of the brain stem and diencephalon, as well as the basal ganglia and internal capsule. Some of their micro-anatomical characteristics are still not well known. The aim of this study was to examine and evaluate the features of all the perforating vessels.

METHODS

The arteries of 24-32 cerebral hemispheres, diencephalons and halves of the brain stem were injected with India ink mixture or methylmethacrylate, and microdissection was performed or the vascular casts were produced and examined under the sterescopic microscope.

RESULTS

It was noticed that the perforators ranged from 0 to 14 in number, with the smallest mean value (1.1) for the diencephalic perforators and the largest one (8.1) for the lenticulostriate arteries. The smallest mean diameter (175 μm) was found in the group of the perforators of the anterior communicating artery, whereas the largest one is related to the Heubner's artery (668 μm), the diencephalic thalamoperforating vessels (562 μm), the premamillary vessel (489 μm) and the lenticulostriate arteries (469 μm). The perforators most frequently originated from the pial branches of the basilar artery (91.7 %) and of the posterior cerebral artery (59.4 %). The common stems were most often formed by the perforators of the basilar (79.2 %), posterior cerebral (75.0 %) and middle cerebral arteries (40.6 %). Some perforators arose close to or from the terminal divisions, the branching sites or the junctions of the parent arteries, where the saccular aneurysms most often develop. The anastomoses among the perforators were present in a range from 6.3 % to 53.2 %.

CONCLUSIONS

The micro-anatomical data obtained may be useful for neurosurgeons when operating at the base of the brain, as well as for a neurological and radiological evaluation of the perforators in the occlusive cerebrovascular disease, or in the cases of an aneurysm, arteriovenous malformation (AVM) or tumour presence.

Head positioning for anterior circulation aneurysms microsurgery

Objective To study the ideal patient's head positioning for the anterior circulation aneurysms microsurgery. Method We divided the study in two parts. Firstly, 10 fresh cadaveric heads were positioned and dissected in order to ideally expose the anterior circulation aneurysm sites. Afterwards, 110 patients were submitted to anterior circulation aneurysms microsurgery. During the surgery, the patient's head was positioned accordingly to the aneurysm location and the results from the cadaveric study. The effectiveness of the position was noted. Results We could determine mainly two patterns for head positioning for the anterior circulation aneurysms. Conclusion The best surgical exposure is related to specific head positions. The proper angle of microscopic view may minimize neurovascular injury and brain retraction.

Microsurgical anatomy of the cisternal anterior choroidal artery with special emphasis on the preoptic and postoptic subdivisions

Object

The object of this study was to delineate the microsurgical anatomy of the cisternal segment of the anterior choroidal artery (AChA). The authors also propose a new classification of this segment on the basis of its complicated course within the carotid and crural cisterns in relation to important neurovascular structures, and the site of origin, course, and areas of supply of perforating arteries.

Methods

Thirty cadaveric cerebral hemispheres injected with colored latex were dissected under surgical magnification to view the cisternal segment of the AChA and its perforators. Fiber dissections using the Klingler technique were performed in two additional latex injected hemispheres to follow the penetration points, courses, and terminal areas of supply of perforating branches that arise from the cisternal segment of the AChA.

Results

The cisternal segment of the AChA was divided into pre- and postoptic parts that meet at the artery's genu, the most medial extension point of the cisternal segment where the artery makes an abrupt turn after passing under the optic tract. The preoptic part of the AChA extended from its origin at the inferomedial side of the internal carotid artery to the artery's genu, which is commonly located just inferomedial to the initial part of the optic tract. The postoptic part coursed within the crural cistern and extended from the genu to the inferior choroidal point. The genu of the AChA was 8 mm medial to the artery's origin and was located medial to the optic tract in 13% of the hemispheres. The postoptic part was longer than the preoptic part in all hemispheres and had more perforating arteries supplying critical deep structures (preoptic 3.4 per hemisphere vs postoptic 4.6 per hemisphere), and these results were statistically significant (p = 0.01). At the preoptic part, perforating arteries arose from the superolateral portion of the artery and coursed laterally; at the postoptic part, perforators arose from the inferomedial portion of the artery and coursed medially. Perforating arteries from both segments passed most commonly to the optic tract, followed by the anterior segment and apex of uncus in the preoptic part and the cerebral peduncle in the postoptic part.

Conclusions

Both parts of the cisternal segment of the AChA come into surgical view during surgeries for different pathologies in and around the perimesencephalic cisterns. However, attending to the artery's genu and defining pre- and postoptic parts during surgery may help the surgeon locate the origin and eventual course of these perforators, and even estimate the terminal areas of supply of most of the perforating arteries. The proposed classification system can prove helpful in planning any operative procedure along the crural cistern and may reduce the probability of inadvertent injury to perforating branches of the cisternal segment.

Endovascular treatment of aneurysms arising from the proximal segment of the anterior cerebral artery

Objective

Aneurysms arising from the proximal segment of the anterior cerebral artery (A1) are rare and challenging to treat. The aim of this study was to report our experience with endovascular treatment of A1 Aneurysms.

Methods

From August 2007 through May 2012, eleven A1 aneurysms in eleven patients were treated endovascularly. Six aneurysms were unruptured and 5 were ruptured. One patient with an unruptured A1 aneurysm presented with subarachnoid hemorrhage due to rupture of an anterior communicating artery aneurysm. Procedural data, clinical and angiographic results were reviewed retrospectively.

Results

All of the aneurysms were successfully treated with coil embolization. Six were treated with a simple technique while the remaining 5 required adjunctive technique : double catheters (n=2), balloon-assisted (n=2), and stent-assisted (n=1). The immediate angiographic control showed a complete occlusion in all cases. Procedure-related complication occurred in only one patient : parent artery occlusion, which was not clinically significant. All patients had excellent clinical outcomes but one patient was discharged with a slight disability. No neurologic deterioration or bleeding was seen during the follow-up period in this cohort of patients. Follow-up angiography (mean, 20 months) was available in ten patients and revealed stable occlusion in all cases.

Conclusion

Endovascular treatment is a feasible and effective therapeutic modality for A1 aneurysms. Tailored microcatheter shaping and/or adjunctive techniques are necessary for successful aneurysm embolization because of the projection and location of A1 aneurysms.

Management of aneurysms of the proximal (A1) segment of the anterior cerebral artery

OBJECTIVE

Aneurysms originating from the proximal segment (A1) of the anterior cerebral artery are rare; however, because of their small size, the risk of injury of perforating arteries, and the location of the aneurysm in the surgical field, they are challenging to treat. We report on 15 patients with A1 aneurysms and review surgical views according to the direction of aneurysms.

METHODS

Fifteen patients were diagnosed with A1 aneurysms and underwent surgical clipping or endovascular coiling at our institution between January 2006 and March 2012. We conducted a retrospective review of clinical and radiological features of all patients with A1 aneurysms.

RESULTS

Nine patients underwent surgical clipping, and six patients received endovascular coiling. Six patients (40%) had multiple aneurysms. A1 aneurysms ranged in size from 1.5 to 8.2 mm, with an average size of 3.26 mm. Most A1 aneurysms (73%) had a posterior direction. In the surgical view, A1 aneurysms projecting posteriorly were located behind the A1 trunk. The A1 aneurysm projecting posteroinferiorly was completely eclipsed by the parent artery. In A1 aneurysms with a posterosuperior or superior direction, finding and clipping the aneurysm neck was relatively easy. Thirteen patients (87%) had an excellent outcome, one had moderate disability, and one died.

CONCLUSION

A1 aneurysms have certain characteristics; small size, multiple aneurysms, and, usually, a posterior direction. A1 aneurysms with a posterosuperior or superior direction are relatively easy to assess, however, clipping of A1 aneurysms with a posterior or posteroinferior direction is more difficult. Endovascular coiling is an alternative therapeutic option when surgical clipping is expected to be difficult.

Endovascular coiling of middle cerebral artery aneurysms as an alternative to surgical clipping

Surgical clipping is preferred to endovascular coil embolization for the treatment of middle cerebral artery (MCA) aneurysms. The aim of this study was to describe our experience of coiling for MCA aneurysms, to analyze the reasons for choosing coiling instead of clipping, and to evaluate the appropriateness of the choice. We retrospectively reviewed data of 30 patients who had coiling for MCA aneurysms in our Institute from January 2008 to February 2011. We analyzed the morphologies, techniques, angiographic results and complications of 30 aneurysms treated with coiling, and compared the outcomes with those of 78 clipped aneurysms during the same period. The most common reason for choosing coiling instead of clipping was the short length of the M1 artery (17/30, 56.7%). Complete obliteration of the aneurysm was achieved in 28 of 30 coiling patients (93%) and in 72 of 78 clipping patients (92%). In the coiling group, two of 30 patients (6.7%) had post-procedural infarctions on radiologic evaluation, with only one infarction in clinically relevant territory. There was one intra-procedural rupture and one aneurysm recanalization requiring retreatment in the coiling group. In the clipping group, two infarctions, one subdural hygroma and two intracerebral hematomas were found as postoperative complications, with two clinical deteriorations. Endovascular coil embolization should be considered for treatment of MCA aneurysms as it has angiographic results equivalent to surgical clipping and acceptable post-procedural complications. It is particularly appropriate for patients with serious medical problems or where there is the risk of damaging perforating lenticulostriate arteries on the MCA during surgery.

Bypass or not? Adjustment of surgical strategies according to motor evoked potential changes in large middle cerebral artery aneurysm surgery

OBJECTIVE

To report the use of neuroelectrophysiologic monitoring to alter the course in aneurysm surgery to minimize postoperative infarction and bypass-related adverse events.

METHODS

Two patients with large middle cerebral artery (MCA) aneurysms were admitted to the authors' hospital. Direct clipping seemed to be difficult, and postoperative paralysis was not rare in the authors' experience owing to prolonged temporal occlusion of the parent artery. Balloon test occlusion (BTO) was positive in one patient, who developed paralysis and aphasia 3 minutes after balloon occlusion of the feeding M1 artery. A bypass procedure seemed to be inevitable in both patients. Motor evoked potentials (MEPs) and sensory evoked potentials (SEPs) were used for monitoring during the operation.

RESULTS

For the patient with a positive BTO result, MEP waves did not change until 17 minutes after temporary clip placement. The aneurysm was clipped, and the occlusion time was 24 minutes. MEP waves recovered quickly after reperfusion. In the other patient, there were early changes in MEP waves after temporary clipping. After bypass construction from the temporal artery to the inferior M2 trunk, the time window of safe occlusion was prolonged to 7-8 minutes. Both the aneurysm and the bypassed branch were obliterated, and the clip reconstruction was done to preserve the flow from M1 to the superior M2 trunk. Permanent postoperative disability did not occur in either patient.

CONCLUSIONS

Intraoperative physiologic monitoring is a complementary method to preoperative BTO to evaluate the window of safe occlusion with high reliability.

Z-shaped microcatheter tip shaping for embolization of aneurysms at the proximal A1 segment of the anterior cerebral artery: a technical note

Embolization of an aneurysm at the proximal A1 segment of the anterior cerebral artery (ACA) is technically challenging. We treated four consecutive patients with unruptured aneurysms at the proximal portion of the A1 segment of the ACA. We tested various microcatheter tip shapes before we successfully embolized a lesion with a zigzag-shaped microcatheter tip, which was made by steam shaping. The shape of this microcatheter tip resembled the letter "Z", had a relatively long distal straight segment and was helpful in prompt catheterization of the aneurysm sac and stable placement of the catheter and delivery of coils.

Segmental anatomy of cerebellar arteries: a proposed nomenclature

Object

The conceptual division of intracranial arteries into segments provides a better understanding of their courses and a useful working vocabulary. Segmental anatomy of cerebral arteries is commonly cited by a numerical nomenclature, but an analogous nomenclature for cerebellar arteries has not been described. In this report, the microsurgical anatomy of the cerebellar arteries is reviewed, and a numbering system for cerebellar arteries is proposed.

Methods

Cerebellar arteries were designated by the first letter of the artery's name in lowercase letters, distinguishing them from cerebral arteries with the same first letter of the artery's name. Segmental anatomy was numbered in ascending order from proximal to distal segments.

Results

The superior cerebellar artery was divided into 4 segments: s1, anterior pontomesencephalic segment; s2, lateral pontomesencephalic segment; s3, cerebellomesencephalic segment; and s4, cortical segment. The anterior inferior cerebellar artery was divided into 4 segments: a1, anterior pontine segment; a2, lateral pontine segment; a3, flocculopeduncular segment; and a4, cortical segment. The posterior inferior cerebellar artery was divided into 5 segments: p1, anterior medullary segment; p2, lateral medullary segment; p3, tonsillomedullary segment; p4, telovelotonsillar segment; and p5, cortical segment.

Conclusions

The proposed nomenclature for segmental anatomy of cerebellar artery complements established nomenclature for segmental anatomy of cerebral arteries. This nomenclature is simple, easy to learn, and practical. The nomenclature localizes distal cerebellar artery aneurysms and also localizes an anastomosis or describes a graft's connections to donor and recipient arteries. These applications of the proposed nomenclature with cerebellar arteries mimic the applications of the established nomenclature with cerebral arteries.

Trigeminal ganglion neuron density and regulation of anterior choroid artery vasospasm: In a rabbit model of subarachnoid hemorrhage

Background:

Subarachnoid hemorrhage (SAH) is associated with severe vasospasm caused by a variety of neurochemical mechanisms. The anterior choroid arteries (AChAs) are innervated by vasodilated fibers of the trigeminal ganglion (TGG). The goal of this study was to determine whether there is a relationship between the neuron density of the TGG and the severity of AChAs vasospasm with SAH.

Methods:

Thirty-two rabbits were used for the study; eight served as the baseline control group, seven as a SHAM group, with injections of 1 cc of isotonic saline solution, and 17 rabbits were included in the experimental SAH group, with injection of homologous blood into the cisterna magna. After 10 days, the histopathology of the AChAs and TGGs were examined. The AChAs vasospasm index (VSI) of the external/internal diameter and the neuron density of the ophthalmic root of the TGGs were evaluated stereologically. The AChAs VSI was preferred -- a measure of the degree of vasospasm. As the VSI increased, the degree of arterial vasospasm increased. The results were statistically analyzed.

Results:

The mean AChAs VSI was significantly higher and the mean neuronal density of the ophthalmic root of the TGG was significantly lower in the group with severe vasospasm associated with SAH compared to the controls, SHAM, and the group with mild vasospasm associated with SAH (P< 0.05). The ophthalmic root of the TGG neuron density in the 7 rabbits that developed severe vasospasm was statistically less than that observed in the 10 rabbits with mild vasospasm. There was a linear relationship between the low neuronal density in the ophthalmic root of the TGG and the severity of the AChA vasospasm.

Conclusions:

The trigeminal ganglion neuron density may be an important factor in the regulation of AChAs diameter and cerebral blood flow. Low neuron density of the ophthalmic root of the TGG may play a role in the pathogenesis of AChAs vasospasm associated with SAH.

Angiographic characteristics of unruptured middle cerebral artery aneurysms predicting perforator injuries

PURPOSE

The aim of the present study was to delineate preoperative factors that may predict perforator injuries following open surgery for an unruptured middle cerebral artery (MCA) aneurysm.

METHODS

The authors conducted a retrospective review of 85 consecutive patients who underwent surgical clipping of 91 unruptured MCA aneurysms. In addition to demographic profiles, angiographic characteristics of aneurysms, which included the side, size, projection, height from the origin of the ophthalmic artery, and distance between the internal carotid artery (ICA) bifurcation and the aneurysm origin, were analysed and correlated with perforator injuries. Compared with the preoperative CT and/or MRI, any newly-developed infarctions in the striatocapsular area were regarded as perforator injuries even if they were very small and asymptomatic.

RESULTS

A perforator injury was found in 14 out of 91 cases (15%). Although the majority of them remained asymptomatic, neurological deterioration occurred in four patients. Of the analysed variables, both the height (from the origin of the ophthalmic artery) and the distance (between the ICA bifurcation and the aneurysm origin) were significantly associated with perforator injuries. A stepwise increment of the risk was observed as the position of aneurysms became higher or as the distance to the ICA bifurcation became shorter.

CONCLUSIONS

These results would be helpful in estimating surgical risks for an unruptured MCA aneurysm, one of the most commonly encountered aneurysms in the neurosurgical field.

Surgical management of anterior cerebral artery aneurysms of the proximal (A1) segment

OBJECTIVE

To report a series of 20 consecutive patients with aneurysms of the proximal segment (A1) of the anterior cerebral artery (ACA.

METHODS

The medical records of patients who had undergone surgery for intracranial aneurysms at two institutions between January 1, 1989, and February 1, 2009, were reviewed. Mean patient age was 52.15 years (range 39-69 years). All 20 patients underwent direct surgery, with clipping or trapping, via standard pterional craniotomy.

RESULTS

The incidence of A1 segment aneurysm was 0.59%. There were 16 women and 4 men, showing a strong predominance of this lesion in women. Mean aneurysm size was 6.95 mm (range 3-10 mm). Four patients (20%) had multiple aneurysms, and three patients (15%) had associated vascular anomalies. Among patients whose aneurysms originated from perforating arteries, dissection sacrificed the perforating arteries in two patients, and the perforating arteries occluded postoperatively in three patients. In the patients whose aneurysms did not originate from perforating arteries, no perforating arteries were sacrificed during dissection, and perforating arteries became occluded in two patients postoperatively. There was no statistically significant difference between the two groups of patients regarding the incidence of injury or occlusion. Clinical outcomes were as follows: good recovery in 15 (75%) patients, moderate disability in 2 (10%) patients, severe disability in 2 (10%) patients, and death in 1 (5%) patient.

CONCLUSIONS

The important consideration in surgery for intracranial aneurysms is preservation of the perforating arteries, through cautious dissection around the neck or dome and avoidance of direct clip compression, even after releasing the retracted frontal lobe.

Through the choroidal fissure: a quantitative anatomic comparison of 2 incisions and trajectories (transsylvian transchoroidal and lateral transtemporal)

BACKGROUND

We compared the transsylvian transchoroidal (TSTC) approach with the lateral transtemporal (LTT) approach. Both approaches proceed through the choroidal fissure but through different incisions and along different trajectories.

METHODS

Four fixed, silicon-injected heads (8 sides) were used. Nine strategic anatomic points within the dissections were compared between the TSTC and LTT approaches in 7 other silicon-injected heads (14 sides). Neuronavigation was used to gather coordinates from selected points of both approaches to calculate surgical angles and distances to common targets.

RESULTS

The surgical angle of the TSTC approach for the inferior choroidal point was wider compared with the LTT approach (P < .05). The surgical angles for the P2a-P2p point were similar for both approaches. In the TSTC approach, the P2-P3 point angle was smaller than in the LTT approach (P < .05). The TSTC approach provided (except for the P2-P3 point) significantly shorter distances to all defined anatomic targets compared with the LTT approach. When the posterior cerebral artery was the target in the TSTC approach, the hippocampus was retracted 3 to 8 mm compared with 8 to 13 mm in the LTT approach.

CONCLUSION

We quantitatively described anatomic features of the TSTC approach and compared them with the LTT approach. For approaching the mesial temporal region, the TSTC approach offers an adequate surgical angle and shorter or similar distances proximal to P2-P3 and requires less temporal lobe and hippocampal retraction than the LTT approach. Such information can help surgeons select the optimal approach to the mesial temporal lobe and its surrounding structures. The TSTC approach should be considered for lesions located in the medial temporal region.

Ruptured internal carotid artery aneurysm at the origin of a perforating artery associated with a hyperplastic anomalous anterior choroidal artery--case report

A 65-year-old man presented with a hyperplastic anomalous anterior choroidal artery (AChA) associated with a ruptured internal carotid artery aneurysm at the origin of a perforating artery manifesting as sudden onset of headache and vomiting. The aneurysm was too small for endovascular embolization, so we performed open surgery via the left pterional approach. Aneurysm clipping with preservation of the perforator was impossible, so we clipped the aneurysm neck and sacrificed the perforator. We also performed dome clipping because dome puncture resulted in continuous bleeding. Head computed tomography obtained 3 days after the operation showed cerebral infarction at the territory of the sacrificed perforator, but the patient suffered no neurological deficits. This case of internal carotid artery aneurysm with a perforating artery arising from the aneurysm dome shows that sacrifice of the perforator may be necessary to prevent rebleeding.

Microsurgical anatomy of the temporal lobe: part 2--sylvian fissure region and its clinical application

OBJECTIVE

We present observations of the anatomy of the sylvian fissure region and their clinical application in neuroimaging, microsurgery for middle cerebral artery aneurysms and insular lesions, frontobasal resections, and epilepsy surgery.

METHODS

Sixty adult cadaveric hemispheres and 12 adult cadaveric heads were studied after perfusion of the arteries and veins with colored latex. The anatomic information was applied in more than 200 microsurgeries in and around the sylvian fissure region in the past 15 years.

RESULTS

The sylvian fissure extends from the basal to the lateral surface of the brain and presents 2 compartments on each surface, 1 superficial (temporal stem and its ramii) and 1 deep (anterior and lateral operculoinsular compartments). The temporal operculum is in opposition to the frontal and parietal opercula (planum polare versus inferior frontal and precentral gyri, Heschl's versus postcentral gyri, planum temporale versus supramarginal gyrus). The inferior frontal, precentral, and postcentral gyri cover the anterior, middle, and posterior thirds of the lateral surface of the insula, respectively. The pars triangularis covers the apex of the insula, located immediately distal to the genu of the middle cerebral artery. The clinical application of the anatomic information presented in this article is in angiography, middle cerebral artery aneurysm surgery, insular resection, frontobasal resection, and amygdalohippocampectomy, and hemispherotomy.

CONCLUSION

The anatomic relationships of the sylvian fissure region can be helpful in preoperative planning and can serve as reliable intraoperative navigation landmarks in microsurgery involving that region.

MICROSURGICAL AND ENDOSCOPIC ANATOMY OF THE SUPRATENTORIAL ARACHNOIDAL MEMBRANES AND CISTERNS

OBJECTIVE

A limitation of previous studies of the arachnoid cisterns and membranes is that the act of opening the sylvian and interhemispheric fissures and basal arachnoid often led to destruction of the cisternal compartments and their membranous walls. The goal of this study was to overcome this limitation by combining the surgical microscope and endoscope for the examination of the cisternal compartments and their membranous walls.

METHODS

The supratentorial cisterns were examined in 22 cadaveric brains using both the operating microscope and the endoscope.

RESULTS

There are 2 types of arachnoid membranes: outer and inner. The outer arachnoidal membrane surrounds the whole brain, and the inner membranes divide the subarachnoid space into cisterns. Twelve inner arachnoid membranes were identified in the supratentorial area: diencephalic, mesencephalic, medial carotid, intracarotid, intracrural, olfactory, medial and lateral lamina terminalis, and proximal, medial, intermediate, and lateral sylvian membranes. These membranes partially or completely separate the subarachnoid space into 9 supratentorial cisterns: sylvian, carotid, chiasmatic, lamina terminalis, pericallosal, crural, ambient, oculomotor, and interpeduncular. There is a confluent area between the carotid, interpeduncular, and crural cisterns, which frequently has no membrane separating these cisterns.

CONCLUSION

Twelve inner arachnoid membranes and 9 cisterns were identified in this study.

Human fetal medial striate artery or artery of Heubner

OBJECT

The authors describe some of the features of the medial striate branch or recurrent artery of Heubner (RAH). This structure has indisputable functional, neurological, and neurosurgical significance, and originates from the A(1) and/or A(2) segments of the anterior cerebral artery.

METHODS

Microdissection of 94 human fetal specimens was performed. The RAH was observed in 97.3% (single in 71.6%, double in 25.1%, and triple in 3.3%) of the cases. Its origin was from A(2) in 42.3% of specimens, from the A(1)-A(2) junction in 25.7%, and from A(1) in 20%.

RESULTS

Five types and 14 subtypes of the RAH were identified, determined based on vessel origin and number. In its course, the RAH gave 1-12 branches, and the terminal part most frequently penetrated into the brain through the anterior perforated substance at the level of the sphenoid segment of the middle cerebral artery. The specimens with a single RAH fenestration, abnormal double RAH anastomosis, and unusual RAH origin and relationship to the surrounding vessels represented new data.

CONCLUSIONS

The authors' observations of common anatomical variations in the number and origin of the RAH, as well as its abnormalities, may assist neuroradiologists in the interpretation of diagnostic test results and neurosurgeons in performing procedures in the anterior cerebral circulation.

Neuropathology of central nervous system arterial syndromes. Part I: the supratentorial circulation

The objective of this review is to illustrate the principal cerebrovascular arterial pathoanatomical syndromes using the unique collection of whole brain sections in the Raymond Escourolle Neuropathology Laboratory at Salpêtrière in Paris. The arterial supratentorial syndromes are presented in Part I; the infratentorial and spinal cord syndromes will be presented subsequently in Part II. No attempt is made to be all-inclusive in the review of the literature; rather, we cite only those bibliographic references that are historically noteworthy and with some exceptions that particularly emphasize the neuropathologic rather than radiographic/imaging aspects of the vascular syndromes. From these studies and our own archival material, we have synthesized the salient clinicopathologic aspects of the individual syndromes.

The cerebrum. Anatomy

The cerebrum is the crown jewel of creation and evolution. It is a remarkably delicate, intricate, and beautiful structure. The goal of this chapter is to provide the information needed to permit the neurosurgeon to navigate accurately, gently, and safely around and through the cerebrum and intracranial space. The location of deep structures is frequently described in relation to cranial and superficial cerebral landmarks in order to develop the concept of see-through, x-ray type knowledge of the cerebrum. In numerous illustrations, stepwise dissections are used to clarify the relationship between structures in different layers. Important clinical and surgical concepts are intermixed with the description of the cerebrum and its arteries, veins, and ventricles.

Microneurosurgical management of aneurysms at the A2 segment of anterior cerebral artery (proximal pericallosal artery) and its frontobasal branches

BACKGROUND

Aneurysms originating from the A2 segment of ACA and its frontobasal branches are rare, forming less than 1% of all IAs. There are only few reports on management of A2As. In this article, we review the practical anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and clipping of A2As.

METHODS

This review, and the whole series on IAs, is mainly based on the personal microneurosurgical experience of the senior author (JH) in two Finnish centers (Helsinki and Kuopio), which serve, without patient selection, the catchment area in Southern and Eastern Finland.

RESULTS

These two centers have treated more than 10000 patients with IAs since 1951. In the Kuopio Cerebral Aneurysm Database of 3005 patients and 4253 IAs, there were 35 patients carrying 35 A2As, forming 1% of all patients with IAs, 0.8% of all IAs, and 3% of all ACA aneurysms. Twenty-one (60%) patients presented with ruptured A2As with ICH in 11 (52%) and IVH in 7 (33%). Nineteen patients (54%) had multiple aneurysms.

CONCLUSIONS

A2As are often small, even when ruptured, with relatively wide base, and they are frequently associated with ICHs of IVHs. Our data suggest that A2As rupture at smaller size than IAs in general. The challenge is to select appropriate approach, locate the aneurysm deep inside the interhemispheric fissure, and to clip the neck adequately without obstructing branching arteries at the base. Unruptured A2As also need microneurosurgical clipping even when they are small.

Main anatomical features of the M1 segment of the middle cerebral artery: a 3D time-of-flight magnetic resonance angiography at 3 T study

The purpose of our study was to determine the main anatomical features of the M1 segment of middle cerebral artery (MRA) using a 3D TOF-MRA at 3 T. Reconstructed and post-processed MRA images were independently analysed by two anatomists in order to determine the course patterns, the division patterns and the early cortical branches patterns of the M1 segments. The division patterns were defined as bipode, tripode or other. The ECB were studied according to their number and their distance from the origin of the M1 segment. The interobserver agreement, to determine the division patterns of the M1 segment, was calculated. The division of the M1 segment was bipode in 73% of the MCAs, monopode in 17%, tripode in 9%, and fan-shaped in 1. In 46% of the cases no ECB was found. In the other cases, only 1 ECB was found and it arose from the medium part of the M1 segment. Our results confirm post-mortem microdissection studies and show that strict anatomical criteria may be applied to 3D TOF MRA at 3 T.

Intracranial intrasellar kissing carotid arteries: case report

Intracranial "kissing" carotid arteries are a rare variant of the carotid arteries, where both internal carotid arteries deviate medially and touch each other near the midline within the sphenoid sinus or the sphenoid bone, including the sella. This anomaly is particularly important since it may cause or mimic pituitary disease and also may complicate transsphenoidal surgery. We report a rare case of intracranial intrasellar kissing carotid arteries in a 57-years-old woman that was submitted to a computed tomography angiography during investigation of a sudden headache, and to discuss the clinical relevance of this radiological finding.

[Endoscopic anatomy of the terminal portion of the basilar artery and its distal perforating branches]

The aim of this study was to describe and highlight the endoscopic anatomy of the tip of the basilar artery and its perforating branches. Knowledges of the anatomy are crucial for neurosurgeons to avoid pitfalls during endoscopic third ventriculostomy.

Distal lenticulostriate artery aneurysm in deep intracerebral haemorrhage

Aneurysms of the distal lenticulostriate artery (LSA) are rare. Only 16 cases have been reported in the literature. Early detection and treatment of these aneurysms is also difficult because of their deep location, small size and angioarchitecture. We report two additional patients with aneurysms, arising from the distal LSA, who presented with deep intracerebral haemorrhage. The conclusions drawn from our experience and a comprehensive review of the literature include the following. (1) A distal LSA aneurysm should be considered in young (mean 38.5 years) and non-hypertensive (80%) patients with deep intracerebral haemorrhage. (2) These aneurysms are frequently very small (<5 mm). Therefore, they cannot be detected on initial angiograms in some cases. (3) These aneurysms have higher rates of associated vascular lesions. Deep intracerebral haemorrhage, even in those over the age of 50 years, can still be due to underlying, treatable structural abnormalities, and should not be dismissed as being a result of hypertension. In addition, a more comprehensive diagnostic approach seems to be warranted in younger patients and those without known hypertension.

Microneurosurgical management of proximal anterior cerebral artery aneurysms

BACKGROUND

Aneurysms originating from the proximal segment of anterior cerebral artery (A1As) are rare, forming less than 1% of all IAs. There are only few reports on microneurosurgical management of A1As. In this article, the authors review the practical anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and clipping of A1As.

METHODS

This review, and the whole series on IAs, is mainly based on the personal microneurosurgical experience of the senior author (JH) in 2 Finnish centers (Helsinki and Kuopio), which serve without patient selection the catchment area in Southern and Eastern Finland.

RESULTS

These 2 centers have treated more than 10,000 patients with aneurysm since 1951. In the Kuopio Cerebral Aneurysm Database of 3005 patients with 4253 aneurysms, there were 23 patients carrying 23 A1As, forming 0.8% of all patients with aneurysm, 0.5% of all aneurysms, and 2% of all ACA aneurysms. Twelve (52%) patients presented with ruptured A1As with ICH in 3 (25%) and IVH in 2 (17%). Seventy percent of patients had at least 1 associated aneurysm.

CONCLUSIONS

Aneurysms arising from A1 are usually small, with a fragile wall. Our data suggest that A1As rupture at smaller size than IAs in general. Because of their small size and involvement of perforating arteries at their base, microneurosurgical clipping is the method of choice in treatment of ruptured A1As. Unruptured A1As also need microneurosurgical clipping even when they are small.

Microneurosurgical management of middle cerebral artery bifurcation aneurysms

BACKGROUND

Of the MCA aneurysms, those located at the main bifurcation of the MCA (MbifA) are by far the most frequent. The purpose of this article is to review the practical anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and clipping of MbifAs.

METHODS

This review, and the whole series on intracranial aneurysms, is mainly based on the personal microneurosurgical experience of the senior author (JH) in 2 Finnish centers (Helsinki and Kuopio), which serve without patient selection the catchment area in southern and eastern Finland.

RESULTS

These 2 centers have treated more than 10,000 patients with intracranial aneurysm's since 1951. In the Kuopio Cerebral Aneurysm Data Base of 3005 patients with 4253 aneurysms, MbifAs formed 30% of all ruptured aneurysms, 36% of all unruptured aneurysms, 35% of all giant aneurysms, and 89% of all MCA aneurysms. Importantly, in 45%, rupture of MbifA caused an ICH.

CONCLUSIONS

Middle cerebral artery bifurcation aneurysms are often broad necked and may involve one or both branches of the bifurcation (M2s). The anatomical and hemodynamic features of MbifAs make them usually more favorable for microneurosurgical treatment. In population-based services, MbifAs are frequent targets of elective surgery (unruptured), acute surgery (ruptured), and emergency surgery (large ICH), even advanced approaches (giant). The challenge is to clip the neck adequately, without neck remnants, while preserving the bifurcational flow.

Microneurosurgical management of distal middle cerebral artery aneurysms

BACKGROUND

Distal middle cerebral artery aneurysms originate from branches of MCA distal to its main bifurcation or the peripheral branches. Distal middle cerebral artery aneurysms are the least frequently seen among the middle cerebral artery aneurysms. The purpose of this article is to review the practical anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and clipping of MdistAs.

METHODS

This review, and the whole series on intracranial aneurysms, are mainly based on the personal microneurosurgical experience of the senior author (JH) in 2 Finnish centers (Helsinki and Kuopio), which serve without patient selection the catchment area in Southern and Eastern Finland.

RESULTS

These 2 centers have treated more than 10000 aneurysm patients since 1951. In the Kuopio Cerebral Aneurysm Database of 3005 patients with 4253 aneurysms, 69 patients carrying altogether 78 MdistAs formed 5% of all MCA aneurysms. Among the 18 patients with ruptured MdistAs (23%), an ICH occurred in 9 (50%).

CONCLUSIONS

Distal middle cerebral artery aneurysms are rare. The microneurosurgical treatment of MdistAs is challenging. They are often difficult to localize during the operation, and lack of collateral circulation makes their occlusion more demanding. High rate of ICH and high tendency of rebleeding urge acute or emergency surgery in most of ruptured cases. Microneurosurgical clipping is the most effective treatment of MdistAs.

Use of intraoperative monitoring of somatosensory evoked potentials to prevent ischaemic stroke after surgical exclusion of middle cerebral artery aneurysms

OBJECTIVE

The aim of this study was to assess the value of monitoring somatosensory evoked potentials (SEP) in the prevention of ischaemic stroke occurring during surgical exclusion of middle cerebral artery aneurysms.

METHODS

SEP monitoring was performed during the surgical exclusion of 131 aneurysms in 122 patients. All SEP variations over 30% were notified to the surgeon and those over 50% were considered as highly significant. If this happened, and in concert with the conduct of the operation, a return to the basal level was systematically sought.

RESULTS

Post-operative ischemic stroke was observed after 15 (11.4%) operations, leading to a permanent neurological deficit in 12 (9.2%). During nine (6.9%) operations there was a highly significant SEP change that persisted, or was only partially reversed, after corrective procedure. Nine of these patients had a post-operative ischaemic stroke. In 25 (19%), operations there was a highly significant SEP change followed by complete recovery. Of these 25 patients, 2 suffered a post-operative ischemic stroke. Following 49 operations (37.4%) with less significant SEP modifications, 4 patients suffered a post-operative stroke (8%). A stroke did not occur in the 48 (36.6%) operations during which there was not a variation in SEP. The strokes were related to temporary clipping in 9 patients to definitive clipping in 3 to sylvian fissure opening in 1 to brain retraction in and to dissection of the aneurysm in 1 (1 case).

CONCLUSION

Changes in the SEP correlated well with the occurrence of post-operative stroke. This early detection of ischemia directs attention to the need for measures such as withdrawal of temporary clipping or identification of another factor (e.g. release of brain retraction or repositioning of an occlusive clip) so that the risk of post-operative is reduced.

Microneurosurgical management of proximal middle cerebral artery aneurysms

BACKGROUND

The M1As are located in the main trunk (M1) of the MCA, between the bifurcation of the ICA and the main bifurcation of M1. Proximal MCA aneurysms are often small and thin-walled, which makes their proper clipping tedious. There are few reports on their microsurgery.

METHODS

This review, and the whole series on intracranial aneurysms, is mainly based on the personal microneurosurgical experience of the senior author (JH) in 2 Finnish centers (Helsinki and Kuopio), which serve, without selection, the catchment area in the southern and eastern Finland.

RESULTS

These 2 centers have treated more than 10000 patients with aneurysm since 1953. We review the practical anatomy, preoperative planning, and avoidance of complications in the microsurgical dissection and clipping of M1As which form 7.4% of all intracranial and 14% of all MCA aneurysms in our patients.

CONCLUSIONS

Proximal MCA aneurysms are often wide-necked and intimately connected to an M1 branch at its origin on M1, features that favor exosurgery rather than endosurgery. The direction and course of the parent and branching arteries and the orientation of the fundus are the most important factors affecting the efficacy and safety of clipping.

Vascular determinants of cholinergic deficits in Alzheimer disease and vascular dementia

Alzheimer's disease (AD) and vascular dementia (VaD) are widely accepted as the most common forms of dementia. Cerebrovascular lesions frequently coexist with AD, creating an overlap in the clinical and pathological features of VaD and AD. This review assembles evidence for a role for cholinergic mechanisms in the pathogenesis of VaD, as has been established for AD. We first consider the anatomy and vascularization of the basal forebrain cholinergic neuronal system, emphasizing its susceptibility to the effects of arterial hypertension, sustained hypoperfusion, and ischemic cerebrovascular disease. The impact of aging and consequences of disruption of the cholinergic system in cognition and in control of cerebral blood flow are further discussed. We also summarize preclinical and clinical evidence supporting cholinergic deficits and the use of cholinesterase inhibitors in patients with VaD. We postulate that vascular pathology likely plays a common role in initiating cholinergic neuronal abnormalities in VaD and AD.

[Microsurgical anatomy of the human basal anterior perforated substance]

The anterior perforated substance (APS) is a landmark in the basal forebrain. It has a basal face located above the carotid bifurcation in the subarachnoid space, and an interhemispheric one. It is the site of passage of the arteries to the caudate nucleus, putamen, internal capsule, adjacent areas of the globus pallidus and thalamus. Fifty hemispheres from twenty-five adult cadavers were obtained. The arteries were perfused with colored latex, Batsons resin and gelatin colored with carmine. Using a surgical microscope we have determined the origin, local and number of origin from the parent vessel. The sites of penetration in the mediolateral and anteroposterior direction were also recorded. The anterior communicating artery contribution to the basal APS was reviewed. Significant vascular variations and anastomoses were encountered mainly involving middle cerebral and anterior choroidal arteries. The precise understanding of these vessels has surgical and clinical implications in the management of vascular and tumoral maladies related to the anterior perforated substance.