Imad Saeed Khan

Inverse Z-spectrum analysis for spillover-, MT-, and T1-corrected steady-state pulsed CEST-MRI – application to pH-weighted MRI of acute stroke

Endogenous chemical exchange saturation transfer (CEST) effects are always diluted by competing effects, such as direct water proton saturation (spillover) and semi‐solid macromolecular magnetization transfer (MT). This leads to unwanted T2 and MT signal contributions that lessen the CEST signal specificity to the underlying biochemical exchange processes. A spillover correction is of special interest for clinical static field strengths and protons resonating near the water peak. This is the case for all endogenous CEST agents, such as amide proton transfer, –OH‐CEST of glycosaminoglycans, glucose or myo‐inositol, and amine exchange of creatine or glutamate. All CEST effects also appear to be scaled by the T1 relaxation time of water, as they are mediated by the water pool. This forms the motivation for simple metrics that correct the CEST signal.

Intracerebral Hemorrhage: A Common and Devastating Disease in Need of Better Treatment

OBJECTIVE To review the poor natural history of intracerebral hemorrhage (ICH), current treatment options for ICH, discuss ongoing trials evaluating minimally invasive techniques for clot evacuation, and offer future directions of investigation for the management of this devastating disease. METHODS A selective review of recent trials regarding treatment of ICH was performed. RESULTS Completed trials of medical and surgical management are reviewed. The supportive research for clot evacuation to limit secondary injury is surveyed. We also provide a comprehensive discussion of current data evaluating minimally invasive techniques to achieve clot removal, including Minimally Invasive Surgery plus tPA for ICH Evacuation (MISTIE), Clot Lysis: Evaluating Accelerated Resolution (CLEAR), and endoscopic evacuation. CONCLUSION We encourage the neurosurgical community to pursue improved therapies for ICH. PRACTICE New minimally invasive treatments for ICH are being developed. IMPLICATIONS Treatment of ICH is an important area of research and should continue to be aggressively pursued because of the significant societal burden and poor outcomes associated with ICH.

Imaging of amide proton transfer and nuclear Overhauser enhancement in ischemic stroke with corrections for competing effects

Chemical exchange saturation transfer (CEST) potentially provides the ability to detect small solute pools through indirect measurements of attenuated water signals. However, CEST effects may be diluted by various competing effects, such as non‐specific magnetization transfer (MT) and asymmetric MT effects, water longitudinal relaxation (T1) and direct water saturation (radiofrequency spillover). In the current study, CEST images were acquired in rats following ischemic stroke and analyzed by comparing the reciprocals of the CEST signals at three different saturation offsets. This combined approach corrects the above competing effects and provides a more robust signal metric sensitive specifically to the proton exchange rate constant. The corrected amide proton transfer (APT) data show greater differences between the ischemic and contralateral (non‐ischemic) hemispheres. By contrast, corrected nuclear Overhauser enhancements (NOEs) around −3.5 ppm from water change over time in both hemispheres, indicating whole‐brain changes that have not been reported previously. This study may help us to better understand the contrast mechanisms of APT and NOE imaging in ischemic stroke, and may also establish a framework for future stroke measurements using CEST imaging with spillover, MT and T1 corrections. Copyright

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

Prototyping of cerebral vasculature physical models

Background: Prototyping of cerebral vasculature models through stereolithographic methods have the ability to accurately depict the 3D structures of complicated aneurysms with high accuracy. We describe the method to manufacture such a model and review some of its uses in the context of treatment planning, research, and surgical training. Methods: We prospectively used the data from the rotational angiography of a 40-year-old female who presented with an unruptured right paraclinoid aneurysm. The 3D virtual model was then converted to a physical life-sized model. Results: The model constructed was shown to be a very accurate depiction of the aneurysm and its associated vasculature. It was found to be useful, among other things, for surgical training and as a patient education tool. Conclusion: With improving and more widespread printing options, these models have the potential to become an important part of research and training modalities.

Resolution of trigeminal neuralgia by coil embolization of a persistent primitive trigeminal artery aneurysm.

The persistent primitive trigeminal artery (PTA) is a rare anastomosis between the carotid artery and basilar artery. While most PTAs are asymptomatic, lateral variants can occasionally compress the trigeminal nerve and precipitate trigeminal neuralgia. Aneurysms of the PTA are exceptionally rare in the literature and have not previously been associated with trigeminal neuralgia. We present the first case of an aneurysm of the PTA causing trigeminal neuralgia. The patient underwent coil embolization of the aneurysm which relieved her symptoms. We propose embolization as a viable therapeutic option for the resolution of trigeminal neuralgia when the condition is secondary to irritation by the high velocity pulsatile flow of an aneurysm.

Is posttraumatic cerebrospinal fluid fistula a predictor of posttraumatic meningitis? A US Nationwide Inpatient Sample database study

OBJECT Various factors have been reported in literature to be associated with the development of posttraumatic meningitis. There is a paucity of data regarding skull fractures and facial fractures leading to CSF leaks and their association with the development of meningitis. The primary objective of this study was to analyze the US Nationwide Inpatient Sample (NIS) database to elucidate the factors associated with the development of posttraumatic meningitis. A secondary goal was to analyze the overall hospitalization cost related to posttraumatic meningitis and factors associated with that cost. METHODS The NIS database was analyzed to identify patients admitted to hospitals with a diagnosis of head injury from 2005 through 2009. This data set was analyzed to assess the relationship of various clinical parameters that may affect the development of posttraumatic meningitis using binary logistic regression models. Additionally, the overall hospitalization cost for the head injury patients who did not undergo any neurosurgical intervention was further categorized into quartile groups, and a regression model was created to analyze various factors responsible for escalating the overall cost of the hospital stay. RESULTS A total of 382,267 inpatient admissions for head injury were analyzed for the 2005-2009 period. Meningitis was reported in 0.2% of these cases (708 cases). Closed skull base fractures, open skull base fractures, cranial vault fractures, and maxillofacial fractures were reported in 20,524 (5.4%), 1089 (0.3%), 5064 (1.3%), and 88,649 (23.2%) patients, respectively. Among these patients with fractures, meningitis was noted in 0.17%, 0.18%, 0.05%, and 0.10% admissions, respectively. Cerebrospinal fluid rhinorrhea was reported in 453 head injury patients (0.1%) and CSF otorrhea in 582 (0.2%). Of the patients reported to have CSF rhinorrhea, 35 (7.7%) developed meningitis, whereas in the cohort with CSF otorrhea, 15 patients (2.6%) developed meningitis. Cerebrospinal fluid rhinorrhea (p < 0.001, OR 22.8, 95% CI 15.6-33.3), CSF otorrhea (p < 0.001, OR 9.2, 95% CI 5.2-16.09), and major neurosurgical procedures (p < 0.001, OR 5.6, 95% CI 4.8-6.5) were independent predictors of meningitis. Further, CSF rhinorrhea (p < 0.001, OR 2.0, 95% CI 1.6-2.7), CSF otorrhea (p < 0.001, OR 2.3, 95% CI 1.9-2.7), and posttraumatic meningitis (p < 0.001, OR 3.1, 95% CI 2.5-3.8) were independent factors responsible for escalating the cost of head injury in cases not requiring any major neurosurgical intervention. CONCLUSIONS Cerebrospinal fluid rhinorrhea and CSF otorrhea are independent predictors of posttraumatic meningitis. Furthermore, meningitis and CSF fistulas may independently lead to significantly increased cost of hospitalization in head injury patients not undergoing any major neurosurgical intervention.

Surgical management of intracranial arachnoid cysts: clinical and radiological outcome.

AIM Intracranial arachnoid cysts account for 1% of all intracranial mass lesions and may require drainage if symptomatic. MATERIAL AND METHODS We retrospectively reviewed the medical records of 45 consecutive patients who underwent surgical drainage for symptomatic intracranial cysts at our institution from January 2000 to January 2010. The average age of our patients was 36.2 years; 26 were female and 19 were males. The most common symptoms included headaches (73.3%) and dizziness (35.6%). RESULTS Cyst wall fenestration was carried out in 29 (64.4%), Cystoperitoneal shunting in 6 (13.3%) and endoscopic fenestration and stealth guided craniotomy in 5 patients each (11.1%). Seven patients had perioperative complications, and on discharge 79.1% of all patients had partial or complete clinical relief and 85.7% showed radiological decompression. A maximum cyst dimension of more than 5.0 cm was significantly associated with worse outcome at discharge (p=0.02). There was no association between post-operative size cyst decompression and resolution of clinical symptoms. The clinical and radiological outcomes were comparable between different surgical methods. CONCLUSION There was no difference in the outcomes between different modalities. The extent of post-operative radiological reduction had no correlation with clinical outcomes, and should be assessed in relation to the patients clinical status.

Do cystic vestibular schwannomas have worse surgical outcomes? Systematic analysis of the literature

OBJECT The goal of this study was to perform a systematic quantitative comparison of the surgical outcomes between cystic vestibular schwannomas (CVSs) and solid vestibular schwannomas (SVSs). METHODS A review of English-language literature published between 1990 and 2011 was performed using various search engines including PubMed, Google Scholar, and the Cochrane database. Only studies that reported surgical results of CVSs in comparison with SVSs were included in the analysis. The primary end point of this study was surgical outcomes, defined by the following: 1) facial nerve outcomes at latest follow-up; 2) mortality rates; or 3) non-facial nerve complication index. Secondary end points included extent of resection and brainstem adherence. RESULTS Nine studies comprising 428 CVSs and 1287 SVSs were included in the study. The mean age of patients undergoing surgery was 48.3 ± 6.75 and 47.1 ± 9 years for CVSs and SVSs, respectively (p = 0.8). The mean tumor diameter for CVSs was 3.9 ± 0.84 cm and that for SVSs was 3.7 ± 1.2 cm (p = 0.7). There was no significant difference in the extent of resection among CVSs and SVSs (81.2% vs 80.7%, p = 0.87) Facial nerve outcomes were significantly better in the cohort of patients with SVSs than in those with CVSs (52.1% vs 39%, p = 0.0001). The perioperative mortality rates for CVSs and SVSs were not significantly different (3% and 3.8%, respectively; p = 0.6). No significant difference was noted between the cumulative non-facial nerve complication rate (including mortality) among patients with CVSs and SVSs (24.5% and 25.6%, respectively; p = 0.75) CONCLUSIONS Facial nerve outcomes are worse in patients undergoing resection for CVSs than in patients undergoing resection for SVSs. There were no significant differences in the extent of resection or postoperative morbidity and mortality rates between the cohorts of patients with vestibular schwannomas.

Intrasellar plasmacytoma: An illustrative case and literature review

Intrasellar plasmacytoma is a rare pituitary pathology. Pre-operative diagnosis remains a challenge as a sellar plasmacytoma mimics a pituitary adenoma in clinical and radiological features. We report a 45-year-old woman, known to have multiple myeloma, presenting to our clinic with a pituitary mass eventually diagnosed as a plasmacytoma. We review 26 similar cases reported in the literature and divide them into three categories, based on their presentation and follow-up data. Pitfalls in diagnosis and reported treatment modalities are also discussed. We conclude that presentation with cranial nerve palsies and an aggressive sellar mass on imaging, and without gross anterior hypophyseal hormonal imbalance, are features of a pituitary plasmacytoma. The presentation and follow-up characteristics may help to determine the prognosis of such patients.