Axial Sections of Brainstem Safe Entry Zones and Clinical Importance of Intrinsic Structures: A Review.

Brainstem surgery is more difficult and riskier than surgeries in other parts of the brain due to the high density of critical tracts and cranial nerves nuclei in this region. For this reason, some safe entry zones into the brainstem have been described. The main purpose of this article is to bring on the agenda the significance of the intrinsic structures of the safe entry zones to the brainstem. Having detailed information about anatomic localization of these sensitive structures is important to predict and avoid possible surgical complications. In order to better understand this complex anatomy, we schematically drew the axial sections of the brainstem showing the intrinsic structures at the level of 9 safe entry zones that we used, taking into account basic neuroanatomy books and atlases. Some illustrations are also supported with intraoperative pictures to provide better surgical orientation. The second purpose is to remind surgeons of clinical syndromes that may occur in case of surgical injury to these delicate structures. Advanced techniques such as tractography, neuronavigation, and neuromonitorization should be used in brainstem surgery, but detailed neuroanatomic knowledge about safe entry zones and a meticulous surgery are more important. The axial brainstem sections we have drawn can help young neurosurgeons better understand this complex anatomy.

The Nightmare of Aneurysm Surgery: Intraoperative Rupture.

Intraoperative rupture is the most important complication of aneurysm surgery1-5 and occurs in 3 different stages: premature (before dissection), dissection, and clipping.5 We present a video of premature rupture and its management (Video 1). A 45-year-old patient presented with subarachnoid hemorrhage originating from a dorsal internal carotid artery (ICA) aneurysm of the communicating segment. Due to our sufficient experience, we preferred direct clipping in this case. The Sylvian fissure could only be partially opened due to excessive adhesions. During retraction of the frontal lobe, severe bleeding occurred. This was a premature rupture since neither the aneurysm nor the ICA had yet been seen. While aspirating the bleeding just over the rupture site with the left hand, the ICA was explored with the right hand and a temporary clip was placed. The bleeding continued, though it decreased. The aneurysm dome was rapidly explored with 1 hand, and a pilot clip was placed on the dome to stop the bleeding. Immediately afterwards, the aneurysm neck was dissected and clipped parallel to the ICA with a sideward clip. The temporary clip and pilot clip were removed. The temporary occlusion time was 7 minutes and 40 seconds. Postoperative angiogram confirmed complete aneurysm occlusion. The patient discharged with normal neurologic examination. In the literature review including 10,540 cases,1 the mean incidence of IOR is 16.6%. Therefore every neurosurgeon should be prepared for this important complication and know its management well. This case reminds us once again the golden rule of aneurysm surgery: proximal control first.

Microsurgical Treatment of Previously Coiled Giant Aneurysms: Experience with 6 Cases and Literature Review.

OBJECTIVE: Surgical treatment of insufficiently embolized (coiled) or recurrent giant aneurysms has not been well established in the literature. The aim of this study is to bring up the surgical difficulties of these rare aneurysms and to offer solutions. METHODS: A database was queried for giant aneurysms that had been previously embolized and subsequently required surgical treatment. We only found 29 aneurysms in the literature and here, we report 6 more surgical cases with patient characteristics, radiological studies, applied surgical techniques, and outcomes which were reviewed retrospectively. RESULTS: Four females and 2 males, with a mean age of 45.6 years took part in the study. The most common aneurysm location was the middle cerebral artery. While 5 aneurysms were successfully clipped, 1 was excised and the neck was closed with micro sutures. The coils were compulsorily removed in 3 patients. Postoperative digital subtraction angiography confirmed total occlusion of the aneurysms in all cases. Overall morbidity was 16.6%. There was no mortality. No recurrence was observed in the angiographic follow-up (mean 22.6 months, range 7-47 months). The literature review also determined that 97.1% of 35 previously coiled giant aneurysms (including ours) were occluded using various surgical techniques, with 82.8% good outcome. CONCLUSIONS: Surgical clipping is a safe and effective procedure for the treatment of insufficiently embolized or recurrent giant aneurysms after coiling. If possible, the coils should not be removed. However, if safe clipping is not possible due to the coils, the removal of the coils should not be avoided.

Bilateral middle cerebral artery aneurysms: a comparative study of unilateral and bilateral approaches.

The best surgical method for the treatment of patients with bilateral middle cerebral artery (bMCA) aneurysms has not been fully determined yet. The main purpose of this study is to compare the surgical results of unilateral and bilateral approaches to bMCA aneurysms including mean operation time, mean hospital stay, and mean cost, in the experience of the same neurosurgical team. Between January 2001 and June 2010, 22 patients with bMCA aneurysms were surgically treated in our institution. In 12 cases (54.5 %), ipsilateral and contralateral MCA aneurysms were successfully clipped via unilateral approach. In the remaining 10 cases, bilateral approach was necessary because of some technical difficulties. Although the surgical results were almost the same, mean operation time and mean hospital stay were, respectively, 46 and 37 % shorter and mean cost per person was 23 % lower for the patients in the unilateral group. In addition, the severity of brain edema, total length of the contralateral (A1+M1) segment, and the configuration of contralateral aneurysm were found to be the determinant parameters affecting the feasibility of the unilateral approach. To our knowledge, this is the first study in the literature that compares the clinical outcomes of unilateral and bilateral approaches to bMCA aneurysms. The results of surgery for both approaches are almost the same. However, the unilateral approach has certain advantages compared to the bilateral approach. Therefore, the unilateral approach may be a good alternative in surgical management of patients with bMCA aneurysms in selected cases and the abovementioned parameters can help the neurosurgeon in patient selection.

Kissing Aneurysms: Radiological and Surgical Difficulties in 30 Operated Cases and a Proposed Classification.

OBJECTIVE: The first aim of this study is to bring up the radiological and surgical difficulties of kissing aneurysms and to present solutions. The second aim is to develop a classification that can help to predict the difficulties encountered during surgery. METHODS: The records of 817 patients who were operated on for aneurysm were reviewed retrospectively to identify kissing aneurysms. The radiological and clinical databases of these patients were evaluated in detail. RESULTS: Kissing aneurysms were detected in 30 patients (3.6%). Radiologically correct diagnosis rate of kissing aneurysms was 80% throughout the series. The most common locations were the anterior communicating artery (12 cases, 40%) and the middle cerebral artery (12 cases, 40.0%). The ruptured aneurysm could not be detected preoperatively in 24% of the patients. Intraoperative rupture occurred in 4 patients (13.3%). Accompanying vascular anomaly/variation was seen in 16 patients (53.3%). As detailed in the text, kissing aneurysms were divided into 3 types according to their position with each other on the parent artery from the surgeon's point of view during surgery: type I (proximal/distal), type II (superior/inferior), and type III (right/left). CONCLUSIONS: Despite advanced angiographic techniques, even today, kissing aneurysms can be misinterpreted as a single bilobular aneurysm. The ruptured aneurysm may not be detectable preoperatively. These complex aneurysms have a high intraoperative rupture risk. Accompanying vascular anomalies are more common than expected. Clip selection and sequencing are important. Proposed classification helps the surgeon to be aware of intraoperative difficulties that he/she may encounter in advance.

Intraoperative Aneurysm Rupture: Surgical Experience and the Rate of Intraoperative Rupture in a Series of 1000 Aneurysms Operated on by a Single Neurosurgeon.

OBJECTIVE: This study aims to examine the risk factors that can cause intraoperative rupture (IOR), and especially, the role of surgical experience. To our knowledge, this is the first study to analyze the effect of the surgeon's experience on the IOR rate in 2 different perspectives. METHODS: A total of 1000 aneurysms in 775 patients were operated on by a single neurosurgeon. The clinical and radiologic data and intraoperative video recordings of all patients were retrospectively analyzed. To evaluate the role of the surgeon's experience on the IOR rate, the aneurysms were divided chronologically into both 5-year periods and each 100 aneurysms. Number, stage, severity, location, management of IORs, and patients' outcomes were determined. RESULTS: IOR occurred in 55 aneurysms (5.5% per aneurysm). The incidence of IOR decreased gradually in the first 2 groups of 5-year periods (11.4% and 5.9%, respectively). However, in the last 3 groups, the decline remained stable (4%-5%). Considering all groups, this decrease was statistically significant (P = 0.037). When this evaluation was made for each group of 100 aneurysms, similar results were obtained. Mortality also gradually decreased over the years (P = 0.035). Of 8 possible risk factors, rupture status was found to be the only independent predictor for IOR (OR, 8.68; 95% confidence interval, 3.69-20.47; P <0.001). CONCLUSIONS: Increased surgical experience reduces the IOR rate from 10%-11% to 4%-5% after an average of 250 aneurysm operations. However, this rate does not decrease further with more experience. To our knowledge, a learning curve regarding IOR is presented for the first time in the literature.

The Longest Angiographic and Clinical Follow-Up of Microsurgically Treated Giant Intracranial Aneurysms: Experience with 70 Cases.

BACKGROUND: Giant intracranial aneurysms (GIAs), if left untreated, have an extremely poor natural history. Despite many reports about the surgical treatment of GIAs, their long-term clinical and angiographic results are unclear. To our knowledge, this study reports the longest clinical and angiographic follow-up of microsurgically treated GIAs in the English literature. METHODS: Between January 1997 and December 2017, 70 patients with giant anterior circulation aneurysms treated using microsurgery were retrospectively reviewed. The applied microsurgical techniques and especially long-term clinical and angiographic follow-up data were evaluated. RESULTS: The mean aneurysm size was 29.2 mm (range, 25-58 mm). The aneurysm neck was occluded in 61 patients (87.2%). Nine aneurysms were clipped using an aneurysm clip compression technique. In 8 patients (11.4%), the aneurysm neck was found smaller at surgery than expected according to angiographic findings. Postoperative angiograms showed complete occlusion in 52 of 61 patients (85.2%). The treatment results at discharge were excellent-good (modified Rankin Scale score ≤2) in 75.3% of the patients. The overall mortality was 7.6%. At long-term clinical follow-up (mean, 105.2 months), 48 patients (78.6%) showed excellent-good outcome. At late angiographic follow-up (mean, 98.0 months), no recurrence was seen in patients with complete aneurysm closure. CONCLUSIONS: Most giant anterior circulation aneurysms can be successfully clipped, with acceptable morbidity and mortality. Some giant aneurysms have a smaller neck than expected. The aneurysm clip compression technique is useful in clipping of GIAs. This longest clinical and angiographic follow-up in the literature shows that clip ligation has excellent durability in GIAs, also.

Distal anterior choroidal artery aneurysms.

BACKGROUND: Distal AChoA aneurysms are quite rare. Only 12 operated cases have been reported in the English medical literature. Treatment of these aneurysms is also difficult because of their deep location, small size, and angioarchitecture. METHODS: The authors report 2 additional patients with aneurysms, arising from the distal AChoA and located within the temporal horn of the lateral ventricle. In the first patient, the aneurysm could also be visualized with CTA, which is the first demonstration in the literature. RESULTS: The aneurysms were explored and resected via a transtemporal/ventricular approach in both patients. One patient was discharged as neurologically intact and the other died because of severe vasospasm. CONCLUSIONS: The conclusions drawn from our experience and a comprehensive review of the literature include the following: (1) A distal AChoA aneurysm should be considered in patients with isolated medial temporal intracerebral hematoma with intraventricular extension. (2) These aneurysms are frequently very small (<5 mm). Therefore, they cannot be detected on initial angiograms in some cases. (3) These small aneurysms cannot be usually clipped without sacrificing the parent artery. (4) Sacrificing distal AChoA (beyond the plexal point) does not usually cause any neurological deficit, but, whenever possible, this artery should be preserved.

Thalamomesencephalic ossified cavernoma presenting with Holmes' tremor.

BACKGROUND: Midbrain cavernoma associated with Holmes' tremor is a rare entity. Although there have been 4 other cases of Holmes' tremor caused by a cavernoma, this is the first case that was cured by surgical removal of the cavernoma. In addition, heavy ossification and Holmes tremor as a clinical presentation are 2 unusual features of the cavernoma. Possible mechanisms of these very rare entities are discussed in relation to the present report and relevant literature is reviewed. CASE DESCRIPTION: We present a case of 60-year-old woman with heavily ossified cavernoma of the thalamomesencephalic junction with neuroimaging and histologic features. The only manifestation was Holmes' tremor. The patient was operated on via posterior interhemispheric approach while in the sitting position. After the arachnoid folds of the quadrigeminal cistern were opened, the thin neural tissue on the surface of the dorsal midbrain was incised and the lesion was visualized and totally removed as a single piece. The tremor was almost completely suppressed. CONCLUSION: Ossified cavernoma is a rare entity but has a characteristic MRI appearance. It should be considered in the differential diagnosis of intracerebral hypointense lesions on both T1- and T2-weighted MR images because they are potentially curable by surgical removal.

Effect of raloxifene on cerebral vasospasm following experimental subarachnoid hemorrhage in rats.

The effect of raloxifene on cerebral vasospasm following experimental subarachnoid hemorrhage (SAH) was investigated in a rat model. Seven groups of seven rats underwent no SAH, no treatment; SAH only; SAH plus vehicle; SAH plus 3 days intraperitoneal raloxifene treatment; SAH plus 4 days intraperitoneal raloxifene treatment; SAH plus 3 days intrathecal raloxifene treatment; and SAH plus 4 days intrathecal raloxifene treatment. The basilar artery cross-sectional areas were measured at 72 or 96 hours following SAH. The results showed raloxifene decreased SAH-induced cerebral vasospasm in all treatment groups, and suggested no difference between intraperitoneal and intrathecal application, or between 3 days and 4 days of raloxifene treatment. The present study demonstrates that raloxifene is a potential therapeutic agent against cerebral vasospasm after SAH.

Comparative dural closure techniques: a safety study in rats.

BACKGROUND: Some neurosurgical procedures have high morbidity and mortality rates due to cerebrospinal fluid (CSF) fistula development, particularly when dural defects are in relatively inaccessible areas or surrounded by friable dura. We used a rat model to test 4 different dural closure techniques to determine which one was significantly superior for achieving a watertight dural closure with minimal harm to brain tissue. METHODS: The rats were randomly divided into 2 groups. The first group (group A, n = 40) was used to test the strength of the adhesivity for CSF leakage. Histopathologic studies were used to evaluate the granulation tissue between the dura and dural graft. Effects on the brain tissue were studied in the second group (group B, n = 40) where lipid peroxidation was determined. These 2 groups consisted of 5 subgroups: control, methyl metacrylate, n-butyl cyanoacrylate, fibrin glue, and CO(2) laser. RESULTS: Methyl metacrylate and CO(2) laser techniques were inadequate for stopping dural leakage and had harmful effects on brain tissue. Cerebrospinal fluid leak was observed only in 1 rat in the n-butyl cyanoacrylate subgroup and this result was statistically significant (P = .0005), but lipid peroxidation levels for this material showed that it was not safe for dural closure in case it leaked through the dural defect. The lipid peroxidation levels of the fibrin glue subgroup were not statistically significantly different from the control group (P = .440). CONCLUSIONS: Fibrin glue was the safest material with a CSF leakage risk that was higher than n-butyl cyanoacrylate (25% vs 12.5%) but acceptable. This study showed no relationship between the CSF leak and histopathologic findings for sealant properties of the tissue adhesives.

Multiple aneurysms of the anterior communicating artery: radiological and surgical difficulties.

OBJECT: Multiple aneurysms of the anterior communicating artery (ACoA) occur rarely and have not been well investigated previously. The authors report on a consecutive series of six patients who each harbored multiple ACoA aneurysms. The radiological and surgical difficulties encountered in treating these complex and uncommon aneurysms are described and the pertinent literature is reviewed. METHODS: Between October 1996 and August 2003, the authors surgically treated 146 patients with ACoA aneurysms. Six (4.1%) of these patients harbored multiple aneurysms of the ACoA. Four of these patients were men and two were women; their ages ranged from 36 to 72 years. Five patients had two aneurysms and one patient had three. All underwent surgery performed using the pterional approach. The clinical presentations, angiograms, intraoperative difficulties, and surgical results were retrospectively analyzed. All patients had premorbid hypertension. In two cases, the aneurysms were initially misdiagnosed as a single complex aneurysm based on routine cerebral angiograms, but special angiographic views demonstrated double aneurysms. In one case, multiple ACoA aneurysms could be identified using three-dimensional (3D) computerized tomography (CT) angiography. The size of the ACoA aneurysms ranged from 3 to 12 mm (mean 5.3 mm). A total of 13 ACoA aneurysms were successfully occluded in the six patients. Four patients were discharged in good condition, and two patients died. CONCLUSIONS: Although multiple ACoA aneurysms are quite rare, the following points should be kept in mind. (1) In bilobular ACoA aneurysms, special angiographic projections and 3D CT angiography or 3D digital subtraction angiography should also be performed to obtain a correct diagnosis. The differentiation of two aneurysms from a bilobular aneurysm during the preoperative period is important for surgical planning. (2) Angiographically, detection of the ruptured aneurysm is often difficult. (3) Resection of the gyrus rectus is necessary to obtain a good operative exposure. 4) Clip selection and sequencing are important. Straight clips with short blades should be preferred to avoid narrowing of the surgeon's view and a collision between the clips.

Rare cause of subarachnoid hemorrhage: spinal meningeal carcinomatosis. Case report.

Subarachnoid hemorrhage (SAH) of spinal origin is a rare entity accounting for approximately 1% of all cases of SAH. Its most frequent causes are trauma and vascular malformations. Although primary spinal tumors, especially ependymomas, are also relatively common causes, SAH secondary to a metastatic spinal tumor arising from outside the central nervous system is an extremely rare condition; only one case has been reported in the literature. The authors present a case of spinal meningeal carcinomatosis secondary to cutaneous malignant melanoma in which the patient presented with only symptoms of SAH. Although very rare, this case underscores several factors. 1) Spinal SAH due to spinal metastases should be considered in the differential diagnosis of patients with previously known malignancy. 2) Spinal SAH may manifest without paraparesis or sensory deficit. 3) Magnetic resonance imaging of the spinal cord may be important to determine the source of SAH in patients in whom four-vessel cerebral angiography demonstrates no abnormal findings.

Aneurysm Clip Compression Technique in the Surgery of Aneurysms with Hard/Calcified Neck.

OBJECTIVE: One of the most important technical problems in surgery to repair aneurysms is the presence of a hard/calcified neck. In this situation, various techniques can be used for proper clipping. In addition to well-known techniques, we have used a different technique for more than 10 years. This technique probably also has been used by other neurosurgeons, but we could not find any publications about it in the English literature. Therefore, we would like to report the details of this technique and our own experience. METHODS: More than 600 anterior circulation aneurysms were clipped between January 2003 and December 2014. It was necessary to apply this technique in 25 aneurysms because of a hard/calcified neck. This series was reviewed retrospectively. If the hard-calcified plaque at the neck does not allow for full closure of the clip and the known techniques are not sufficient for clipping, we carefully and slowly compress the aneurysm clip itself at the neck with a hemostatic clamp. The hard plaque usually is crushed with this technique, and full closure of the clip is immediately obtained. RESULTS: Complete occlusion of the neck was achieved in 16 aneurysms (64%) with this technique. Technique-related complication developed as intraoperative rupture of the aneurysm in two patients (8%). However, this complication was managed with other techniques in both cases. No distal thromboembolism developed in any patient. CONCLUSIONS: Our aneurysm clip compression technique may be a viable option in surgery of aneurysms with hard-calcified neck.

Lipid peroxidation in cerebral tumors.

BACKGROUND: Serum and tissue concentrations of tumor markers or some metabolites are considered to be helpful in diagnosis and follow-up of the central nervous system (CNS) disease. However, markers currently available are not sufficiently sensitive and specific to be used as actual diagnostic tools. Differentiation between the malignant and benign lesions of the CNS is very important, both for determining the optimum therapeutic approach and to predict morbidity and mortality of the disease. Accurate diagnosis of a malignant disease is mostly performed through a surgical resection and histopathologic evaluation. Free oxygen radicals (FOR) are thought to take part in oncogenesis and cellular differentiation. We explored whether FORs can be used as diagnostic tumor markers. METHODS: We investigated the concentration of malondialdehyde (MDA) in the serum and tumor tissue of patients with glial tumor. We have studied 30 patients with malign glial tumor (grades III and IV astrocytoma), 30 patients with low grade glial tumor, 28 healthy individuals, and 10 patients with nontumorous lesions (lobectomy for epilepsy). RESULTS: Patients with CNS tumors showed higher serum MDA concentration compared to control groups (epilepsy patients and healthy subjects). These patients had a higher tumor tissue MDA concentration compared to lobectomy tissue from epilepsy patients. Serum and tissue MDA concentrations were also higher in the malignant glial tumor group compared to the low grade glial tumor group. CONCLUSIONS: Although not specific, tissue and serum concentrations of FORs can be used as a marker to detect the presence and grade of CNS tumors. Further studies are needed to determine the optimum cutoff value for use of serum and tissue MDA concentrations in brain tumors.

Spinal dural arteriovenous fistula and venous aneurysm: an unusual association.

OBJECTIVE: Although spinal intradural arteriovenous malformations have frequently been associated with venous aneurysms, spinal dural arteriovenous fistulas typically are not. We describe a case of conus medullaris compression by a large saccular venous aneurysm of a spinal dural arteriovenous fistula. As these lesions are slow-flow arteriovenous shunts, development of a venous aneurysm is an unexpected condition. Pathogenesis of these aneurysms is briefly discussed. METHODS: A 61-year-old man presented with progressive spastic paraparesis of 1-year duration. Spinal magnetic resonance (MR) suggested abnormal serpiginous vessels and a partially thrombosed aneurysm at the level of conus medullaris. Spinal angiography was performed but some lower thoracal and upper lumbar segments could not be catheterized because of severe atherosclerosis. As a result, vascular anomaly could not be demonstrated angiographically, but surgical exploration was found to be necessary because of positive clinical and MR findings. RESULTS: An arteriovenous fistula that entered the spinal canal beneath the L1 pedicle on the left was identified. It was easily coagulated and cut. The partially thrombosed aneurysm within the conus medullaris was also resected. CONCLUSIONS: Our case illustrates two important points related to patients harboring spinal dural arteriovenous fistulas (AVF): First, clinical suspicion and MR findings are important in diagnosis of these lesions and surgical exploration is indicated despite negative or nondiagnostic angiographic results in such cases. Second, venous aneurysms may be associated with spinal dural AVFs, and although spinal dural AVFs are low-flow lesions, the development of the venous aneurysm is probably a result of high venous pressure.

Angiographically occult epidural arteriovenous fistula of the craniocervical junction.

BACKGROUND: Spinal dural and intradural arteriovenous fistulas (AVFs) have been the subject of numerous reports but purely epidural AVFs causing venous congestion within the spinal cord are rare. CASE DESCRIPTION: We describe a patient with an exclusively epidural arteriovenous fistula and congestive myelopathy. There are three interesting features of this case as described below: 1) The presence of a purely epidural AVF of the cranio-cervical junction. According to our knowledge this is the first case of an AVF in this location. 2) The lesion was angiographically occult. This was probably because of the extremely slow flow of the fistula. 3) Despite the negative angiograms, exploratory surgery was conducted because of positive clinical and MR findings. CONCLUSIONS: Epidural AVF/AVM of the foramen magnum should be considered in the differential diagnosis in patients with chronic myelopathy, even if cranial and spinal angiograms are negative. In these cases, we recommend that if clinical and radiological investigations strongly suggest the presence of an arteriovenous fistula, surgical exploration should be performed.