True posterior communicating artery aneurysms: are they more prone to rupture? A biomorphometric analysis.

OBJECT: Posterior communicating artery (PCoA) aneurysms can occur at the junction with the internal carotid artery, posterior cerebral artery (PCA), or the proximal PCoA itself. Hemodynamic stressors contribute to aneurysm formation and may be associated with parent vessel size and aneurysm location. This study evaluates the correlation of various biomorphometric characteristics in 2 of the aforementioned types of PCoA aneurysms. METHODS: Patients with PCoA aneurysms were analyzed using CT angiography. Source images and reconstructions were used to determine which aneurysms originated purely from the PCoA and those that originated from the internal carotid artery/PCoA junction. Morphometric analysis was performed on the aneurysm, the precommunicating segment of the PCA (P(1)), the ambient segment of the PCA (P(2)), and both PCoA arteries and were correlated to clinical presentation. Parametric and nonparametric analyses were performed to test for significance. RESULTS: A total of 77 PCoA aneurysms were analyzed, and 10 were found to be true PCoA aneurysms (13.0%). The ipsilateral PCoA/P(1) ratio (1.77 +/- 0.44 vs 0.82 +/- 0.46, p = 0.0001) and ipsilateral P(2)/P(1) ratio (1.73 +/- 0.40 vs 1.22 +/- 0.41, p = 0.0003) were significantly larger in true PCoA aneurysms. Interestingly, aneurysm size was statistically larger in the junctional aneurysms (0.14 +/- 0.1 vs 0.072 +/- 0.04 cm(3), p = 0.03). The prevalence of ruptured aneurysms was similar in both groups (approximately 80%, p value not significant). CONCLUSIONS: These data suggest that true PCoA aneurysms have a larger PCoA relative to the ipsilateral P(1) segment. To the authors' knowledge, this represents the first such biomorphometric comparison of these different types of PCoA aneurysms. Although statistically smaller in size, true PCoA aneurysms also have a similar prevalence of presenting as a ruptured aneurysm, suggesting that they might be more prone to rupture than a junctional aneurysms of similar size. Further analysis will be required to determine the biophysical factors affecting rupture rates.

Predicting aneurysm rupture probabilities through the application of a computed tomography angiography-derived binary logistic regression model.

OBJECT: The goal of this study was to establish a biomathematical model to accurately predict the probability of aneurysm rupture. Biomathematical models incorporate various physical and dynamic phenomena that provide insight into why certain aneurysms grow or rupture. Prior studies have demonstrated that regression models may determine which parameters of an aneurysm contribute to rupture. In this study, the authors derived a modified binary logistic regression model and then validated it in a distinct cohort of patients to assess the model's stability. METHODS: Patients were examined with CT angiography. Three-dimensional reconstructions were generated and aneurysm height, width, and neck size were obtained in 2 orthogonal planes. Forward stepwise binary logistic regression was performed and then applied to a prospective cohort of 49 aneurysms in 37 patients (not included in the original derivation of the equation) to determine the log-odds of rupture for this aneurysm. RESULTS: A total of 279 aneurysms (156 ruptured and 123 unruptured) were observed in 217 patients. Four of 6 linear dimensions and the aspect ratio were significantly larger (each with p < 0.01) in ruptured aneurysms than unruptured aneurysms. Calculated volume and aneurysm location were correlated with rupture risk. Binary logistic regression applied to an independent prospective cohort demonstrated the model's stability, showing 83% sensitivity and 80% accuracy. CONCLUSIONS: This binary logistic regression model of aneurysm rupture identified the status of an aneurysm with good accuracy. The use of this technique and its validation suggests that biomorphometric data and their relationships may be valuable in determining the status of an aneurysm.

Repair of lumbosacral meningomyeloceles with acelluar cadaveric dermal matrix: an added layer of protection.

OBJECTIVE: Providing adequate soft tissue cover while preventing wound breakdown and infection can present a challenge when repairing large meningomyeloceles. Adding an extra barrier to protect the underlying dural elements in the event of complications should lower the morbidity and mortality associated with large repairs, which are at risk of dehiscence and subsequent exposure of the neural elements. METHODS: Acellular cadaveric dermal matrix (ACDM) (AlloDerm, Life Cell Corporation, Branchburg, New Jersey) in freeze-dried sheets (thin, 0.2 mm and 0.4 mm), fixed with chromic sutures and placed over the dural repair and underneath associated soft tissue coverage/skin, which in our cases included lumbar fascial flaps, latissimus dorsi flaps, and skin flaps. The neural tube defects were repaired by neurosurgery, and plastic surgery performed the surface closure. A layer of ACDM was placed over the dural repair, fixed in place with chromic suture, and then covered with skin and soft tissue flaps. RESULTS: In the series of 12 patients, there were 2 cases of wound dehiscence, one of which required secondary repair and closure. There were no long-term sequelae in our series. CONCLUSION: ACDM can be used as an added layer of protection in neurosurgical repair of large meningomyeloceles that are at risk for dehiscence.

Monitoring papilledema with Heidelberg Retina Tomograph in a patient with ruptured aneurysm: a case report.

BACKGROUND: Heidelberg Retina Tomograph is a scanning laser ophthalmoscope that is routinely used for the assessment and serial measurement of optic nerve morphology and nerve fiber layer anatomy in the setting of elevated intraocular pressure typically encountered in glaucoma. Recent studies have explored the use of this device in the objective assessment of optic nerve head swelling occurring in the setting of elevated intracranial pressure, also known as papilledema. We explore the utility of HRT as a complementary evaluation to serial fundoscopic examination of the optic nerve head in a patient with a high-grade SAH, raised intracranial pressure, and papilledema secondary to rupture of a giant intracranial aneurysm. To our knowledge, this represents the first report of the use of this technology as an objective assessment of papilledema in the setting of SAH. CASE DESCRIPTION: A 23-year-old man presented with spontaneous SAH secondary to a ruptured giant internal carotid artery aneurysm. The patient underwent endovascular embolization to prevent further hemorrhage and was monitored with HRT on a monthly basis. Severe papilledema, present at the outset and confirmed by the neuro-ophthalmologic consultant, was followed by serial examination with the device. CONCLUSION: Heidelberg Retina Tomograph is a promising device for the analysis of optic nerve head topography in the setting of papilledema in SAH. Worsening or resolution of papilledema can be qualitatively demonstrated with serial studies using this device.

The use of Hypertonic Saline in the Treatment of Post-Traumatic Cerebral Edema: A Review.

Effective methods for treating cerebral edema have recently become a matter of both extensive research and significant debate within the neurosurgery and trauma surgery communities. The pathophysiologic progression and outcome of different forms of cerebral edema associated with traumatic brain injury have yet to be fully elucidated. There are heterogeneous factors influencing the onset and progress of post-traumatic cerebral edema, including the magnitude and type of head injury, age, co-morbid conditions of the patient, the critical window for therapeutic intervention and the presence of secondary insults including hypoxia, hypotension, hypo/hyperthermia, degree of raised intracranial pressure (ICP), and disruption of blood brain barrier (BBB) integrity. Although numerous studies have been designed to improve our understanding of the etiology of post-traumatic cerebral edema, therapeutic interventions have traditionally been focused on minimizing secondary insults especially raised ICP and improving cerebral perfusion pressure. More recently, fluid resuscitation strategies using hyperosmolar agents such as pentastarch and hypertonic saline (HS) have achieved some success. HS treatment is of particular interest due to its apparent advantageous action over other types of hyper-osmotic solutions in both clinical and laboratory studies. In this review, we provide a summary of recent literature concerning the pathogenesis and mechanisms involved in the various types of cerebral edema, and the possible mechanisms of action of HS for the treatment cerebral edema.

Monitoring papilledema in a patient with pineal pilocytic astrocytoma by using Heidelberg Retina Tomograph II. Case report.

The Heidelberg Retina Tomograph (HRT) II is a confocal scanning laser device used to acquire images of the optic nerve head. In this paper the authors report a novel use of this device in the assessment of papilledema in a patient with pilocytic astrocytoma of the pineal region. They also present a new technique to objectively produce 3D data of the optic nerve head. An 11-year-old girl presented with headache and bilateral papilledema; magnetic resonance imaging revealed a lesion in the pineal region. A suboccipital craniectomy was performed, and HRT images were obtained both before (baseline) and after (follow-up) the operation. The authors analyzed the height variation of the retinal surface along the vertical and horizontal cross-lines passing the center of the optic nerve head. The postoperative images, studied on the 2nd day after operation, demonstrated visible reduction of the papilledema. The height variation of the retinal surface along the contour line created by the software demonstrated that elevation of the optic nerve head became depressed due to resolved swelling. The height variation of the retinal surface along vertical and horizontal cross-lines demonstrated significant differences between the elevated preoperative curve and the postoperative curve (p < 0.001), consistent with improvement of her symptoms. Initial data suggest that changes in the optic nerve head topography after surgical decompression can be quantitatively documented by 3D data from the HRT II.

Cranial surgery with an expanded compact intraoperative magnetic resonance imager. Technical note.

In this article the authors report the implementation of an expanded compact intraoperative magnetic resonance (iMR) imager that is designed to overcome significant limitations of an earlier unit. The PoleStar N20 iMR imager has a stronger magnetic field than its predecessor (0.15 tesla compared with 0.12 tesla), a wider gap between magnet poles, and an ergonomically improved gantry design. The additional time needed in the operating room (OR) for use of iMR imaging and the number of sessions per patient were recorded. Stereotactic accuracy of the integrated navigational tool was assessed using a water-covered phantom. Of the 55 patients who have undergone surgery in the PoleStar N20 device, diagnoses included glioma in 13, meningioma in 12, pituitary adenoma in nine, other skull base lesions in seven, and miscellaneous other diagnoses. The extra time required for use of the system averaged 1.1 hours (range 0.5-2 hours). Imaging sessions averaged 2.3 per surgery (range one-six sessions). Measurement of stereotactic accuracy revealed that T1-weighted images were the most accurate. Thinner slices yielded measurably greater accuracy, although this was of questionable clinical significance (all sequences < or =4 mm had a mean error of < or = 1.8 mm). The position of the phantom in the center compared with the periphery of the magnetic field did not affect accuracy (mean error 0.9 mm for each). The PoleStar N20 appears to make intraoperative neuroimaging with a low-field-strength magnet much more practical than it was with the first-generation device. Greater ease of positioning resulted in a decrease in added time in the OR and encouraged a larger number of imaging sessions.

Use of a compact intraoperative low-field magnetic imager in pediatric neurosurgery.

OBJECT: The majority of investigations on the utility of and indications for intraoperative magnetic resonance imaging (iMRI) have been in adult patients. We report our initial experience utilizing low-field iMRI in pediatric patients. METHODS: We performed 21 procedures on 20 patients aged 2 months to 18 years (mean 8.9 years) utilizing the PoleStar -10 iMRI system. The procedures included 15 craniotomies, 2 shunts, and 1 each of the following surgeries: transsphenoidal, craniotomy/transsphenoidal, cranioplasty, and endoscopic biopsy and fenestration. Treated lesions included low-grade astrocytoma (5), craniopharyngioma (3), cortical dysplasia (3), hydrocephalus (2), and others (8). The number of scans ranged from 2 to 5 with a mean of 3.2. Intraoperative imaging and navigation provided valuable information on the extent of resection and catheter placement. In eight procedures it influenced the surgical strategy. No untoward events attributable to the system occurred. CONCLUSIONS: The low-field PoleStar -10 iMRI system can safely assist pediatric neurosurgeons treating a variety of diseases. In addition to neuronavigation it provides information on extent of resection, real-time guided catheter placement, and avoidance of complications.

Intraoperative magnetic resonance imaging at 0.12 T: is it enough?

Low magnetic field strength MRI provides the anatomic information needed for intracranial procedures in which intraoperative imaging is needed. Stereotactic accuracy is proven. The distinct advantage of this technologic approach is that it allows the neurosurgical team to operate an iMRI system with minimal disruption to the OR routine. Technical improvements are likely to increase the power and versatility of low field strength iMRI. Logic dictates that ergonomics and economics will make this the iMRI technique desired by most neurosurgeons.

Neurosurgical reconstruction with acellular cadaveric dermal matrix.

Acellular cadaveric dermal matrix (ACDM) is processed from human cadaver skin (AlloDerm; Life Cell Corp., Branchburg, NJ). It does not require an immediate blood supply but can transmit essential interstitial fluids for nourishment of overlying tissues. A number of neurosurgical reconstructions have required the use of tissue that fills these specifications. The material has been used most recently for reconstruction of dura during craniotomies when primary closure is not possible or harvesting from an autologous site is not available. Because ACDM is harvested from nonneurologic cadaveric tissues and because the cellular and antigenic elements have been removed from the matrix, prion diseases are not a transmission risk. We present 6 examples of previously unreported uses of ACDM for successful repair of meningomyelocele, cauda equina, encephalocele, cerebrospinal fluid fistula, and neuroma. We propose the use of ACDM as a valuable tool in neurosurgical reconstruction.