Measuring CSF shunt flow with MRI using flow enhancement of signal intensity (FENSI).

PURPOSE: To develop and validate a noninvasive imaging technique for accurately assessing very slow CSF flow within shunt tubes in pediatric patients with hydrocephalus, aiming to identify obstructions that might impede CSF drainage. THEORY AND METHODS: A simulation of shunt flow enhancement of signal intensity (shunt-FENSI) signal is used to establish the relationship between signal change and flow rate. The quantification of flow enhancement of signal intensity data involves normalization, curve fitting, and calibration to match simulated data. Additionally, a phase sweep method is introduced to accommodate the impact of magnetic field inhomogeneity on the flow measurement. The method is tested in flow phantoms, healthy adults, intensive care unit patients with external ventricular drains (EVD), and shunt patients. EVDs enable shunt-flow measurements to be acquired with a ground truth measure of CSF drainage. RESULTS: The flow-rate-to-signal simulation establishes signal-flow relationships and takes into account the T1 of draining fluid. The phase sweep method accurately accounts for phase accumulation due to frequency offsets at the shunt. Results in phantom and healthy human participants reveal reliable quantification of flow rates using controlled flows and agreement with the flow simulation. EVD patients display reliable measures of flow rates. Shunt patient results demonstrate feasibility of the method and consistent flow rates for functional shunts. CONCLUSION: The results demonstrate the technique's applicability, accuracy, and potential for diagnosing and noninvasively monitoring hydrocephalus. Limitations of the current approach include a high sensitivity to motion and strict requirement of imaging slice prescription.

Management of brain metastasis. Surgical resection versus stereotactic radiotherapy: a meta-analysis.

Background: Treatment of metastatic brain tumors often involves radiotherapy with or without surgical resection as the first step. However, the indications for when to use surgery are not clearly defined for certain tumor sizes and multiplicity. This study seeks to determine whether resection of brain metastases versus exclusive radiotherapy provided improved survival and local control in cases where metastases are limited in number and diameter. Methods: According to PRISMA guidelines, this meta-analysis compares outcomes from treatment of a median number of brain metastases ≤ 4 with a median diameter ≤ 4 cm with exclusive radiotherapy versus surgery followed by radiotherapy. Four randomized control trials and 11 observational studies (1693 patients) met inclusion criteria. For analysis, studies were grouped based on whether radiation involved stereotactic radiosurgery (SRS) or whole-brain radiotherapy (WBRT). Results: In both analyses, there was no difference in survival between surgery ± SRS versus SRS alone two years after treatment (OR 1.89 (95% CI: 0.47-7.55, P = .23) or surgery + WBRT versus radiotherapy alone (either WBRT and/or SRS) (OR 1.18 (95% CI: 0.76-1.84, P = .46). However, surgical patients demonstrated greater risk for local tumor recurrence compared to SRS alone (OR 2.20 (95% CI: 1.49-3.25, P < .0001)) and compared to WBRT/SRS (OR 2.93; 95% CI: 1.68-5.13, P = .0002). Conclusion: The higher incidence of local tumor recurrence for surgical patients suggests that more prospective studies are needed to clarify outcomes for treatment of 1-4 metastasis less than 4 cm diameter.

Brain stiffness following recovery in a patient with an episode of low-pressure hydrocephalus: case report.

The authors describe a follow-up to a case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus during a shunt malfunction. Shortly after management with CSF drainage at negative pressure, a magnetic resonance elastography scan was performed and revealed very low brain stiffness (high compliance). Here we present the case of the same patient seen 2 years later, now 21 years old, who again received a magnetic resonance elastography scan after receiving treatment for another shunt malfunction, this time with high intracranial pressure. This scan revealed recovery of brain stiffness to a near normal value for the patients' age. This observation suggests the low brain stiffness observed during the low-pressure hydrocephalus event is reversible. The authors discuss these findings in relation to biomechanical hypotheses of low-pressure hydrocephalus.

Predictive (subtle or overlooked) initial head CT findings in patients who develop delayed chronic subdural hematoma.

With the aging population, the incidence of chronic subdural hematoma (CSDH) is expected to rise. Once symptomatic the morbidity from CSDH is not insignificant. We studied patients who had a minor head injury and CT brain scan prior to developing CSDH to determine if there were any predictors on these scans for subsequent development of a CSDH. A retrospective review was performed on all patients operated for CSDH over a 3-year period and a review performed on those who had imaging studies at the time of a preceding minor head injury. Seven of 37 patients had CT scans prior to developing CSDH. All had evidence of small increases in CSF intensity on the side or sides of the subsequent CSDH. In conclusion, in those patients with a history of minor head injury prior to developing a CSDH, CT brain demonstrated small increases in cerebral spinal fluid (CSF) intensity on the side or sides of the subsequent CSDH. Recognizing this finding may be helpful in monitoring these patients or initiating medical therapy.

Magnetic Resonance Elastography Demonstrating Low Brain Stiffness in a Patient with Low-Pressure Hydrocephalus: Case Report.

The authors describe the case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus that responded to negative pressure drainage. A magnetic resonance elastography scan performed 3 weeks later demonstrated very low brain tissue stiffness (high brain tissue compliance). An analysis of the importance of this finding in understanding this rare condition is discussed.

Myeloid sarcoma: a rare case of an orbital mass mimicking orbital pseudotumor requiring neurosurgical intervention.

Objective. A rare case of myeloid sarcoma (MS), previously referred to as granulocytic sarcoma or chloroma, is presented. Representing a unique form of acute myeloid leukemia (AML), MS may rarely occur in adults. Even rarer, MS may occur as the initial presentation of AML. Methods. We report a singular and illustrative case of an orbital pseudotumor mimicking mass in a 65-year-old male as the initial presentation of AML. Results. Neurosurgical intervention was required to establish the definitive diagnosis via right modified orbitofrontozygomatic craniotomy as well as to decompress the optic canal, superior orbital fissure, and orbit. Conclusion. Postoperatively, he reported decreased pain and improvement of his vision. Further examination revealed decreased proptosis and improved extraocular mobility. Pathological findings demonstrated MS. We review the literature and discuss the neurosurgical relevance of MS as the initial presentation of AML.

Pelvic pain from a giant presacral Tarlov cyst successfully obliterated using aneurysm clips in a patient with Marfan syndrome.

Patients with Marfan syndrome used to succumb early in life from cardiovascular complications. With the current rapid advance in medical and surgical care, such patients may now have near-normal longevities. Consequently, rare late-life complications are emerging in these patients and represent challenges to clinicians for their diagnoses and treatments. The authors report a rare case of pelvic pain and genital prolapse from a giant presacral Tarlov cyst in a 67-year-old patient with Marfan syndrome. This 67-year-old Caucasian female presented with progressively severe pelvic pain, intermittent explosive diarrhea, and dysuria. Physical and bimanual examination demonstrated genital prolapse and a nontender, cyst-like mass fixed in the midline. She underwent ultrasound, CT, and eventually MRI evaluations that led to the diagnosis of a giant (6.7 × 6.4 × 6.6 cm) Tarlov cyst originating from the right S-2 nerve root sleeve/sacral foramen with intrapelvic extension. She underwent S1-S2 and S2-S3 laminectomy with obliteration of the Tarlov cyst using aneurysm clips. Postoperatively, her pelvic pain and bowel symptoms resolved and the bladder symptoms improved. The 3-month follow-up CT of abdomen/pelvis demonstrated resolution of the cyst. The present case illustrates that clinicians caring for elderly patients with Marfan syndrome need to increasingly recognize such unusual late-life complications. Also, these large Tarlov cysts can be simply and effectively obliterated with aneurysm clips.

Local mechanical properties of white matter structures in the human brain.

The noninvasive measurement of the mechanical properties of brain tissue using magnetic resonance elastography (MRE) has emerged as a promising method for investigating neurological disorders. To date, brain MRE investigations have been limited to reporting global mechanical properties, though quantification of the stiffness of specific structures in the white matter architecture may be valuable in assessing the localized effects of disease. This paper reports the mechanical properties of the corpus callosum and corona radiata measured in healthy volunteers using MRE and atlas-based segmentation. Both structures were found to be significantly stiffer than overall white matter, with the corpus callosum exhibiting greater stiffness and less viscous damping than the corona radiata. Reliability of both local and global measures was assessed through repeated experiments, and the coefficient of variation for each measure was less than 10%. Mechanical properties within the corpus callosum and corona radiata demonstrated correlations with measures from diffusion tensor imaging pertaining to axonal microstructure.

Isolated unilateral temporalis muscle hypertrophy.

Isolated unilateral temporalis muscle hypertrophy is an extremely rare cause of swelling in the temple region, with only 7 cases reported in the literature. The authors report the eighth case of this unique occurrence in a 17-year-old boy and review the current literature.

Cortical blindness as a rare presentation of cerebral venous thrombosis.

Cerebral venous thrombosis (CVT) remains a diagnostic and therapeutic challenge for clinicians. Manifesting in a remarkably wide spectrum of symptoms and signs, CVT often presents in a misleading fashion-if unrecognized or misdiagnosed, it carries potentially fatal consequences. Visual loss is quite rare as the initial presentation of CVT and is typically a finding more frequent in chronic cases with associated papilledema on funduscopy Ferro, Lopes, Rosas and Fontes (Delay in Hospital Admission of Patients with Cerebral Vein and Dural Sinus Thrombosis. Cerebrovasc Dis 2005;19: :152-6). We report a rare case of acute cortical blindness as the initial presentation of CVT in an 18-year-old female patient and review the current literature.

Percutaneous balloon rhizotomy for trigeminal neuralgia using three-dimensional fluoroscopy.

BACKGROUND: Percutaneous balloon rhizotomy is one of the standard techniques for the treatment of trigeminal neuralgia. However, there have been well-reported complications from cannulating the foramen ovale (FO). We describe a novel technique for cannulating the FO using 3-dimensional (3D) rotational fluoroscopy. METHODS: Three-dimensional rotational fluoroscopy is used to reconstruct the skull base. The optimal working projection is thus generated to best visualize the FO. When the optimal working projection is not anatomically feasible, for example, in a patient with severe cervical spondylosis, further rotational fluoroscopic data acquisition can assess the position of the needle to determine its relationship to the foramen. Furthermore, while inflated, the balloon position can also be verified with the same rotational technique. RESULTS: Three-dimensional rotational fluoroscopy allows quick, safe, and easy cannulation of the FO. The equipment is readily available in the biplanar fluoroscopy suite. Its use should decrease the incidence of complications reported with the standard fluoroscopic technique. CONCLUSIONS: Three-dimensional rotational fluoroscopy allows real-time visual guidance to cannulate the FO and determine the optimal position of the inflated balloon. We believe that this is an important adjunct for treating trigeminal neuralgia via percutaneous techniques.

Effect of off-frequency sampling in magnetic resonance elastography.

In magnetic resonance elastography (MRE), shear waves at a certain frequency are encoded through bipolar gradients that switch polarity at a controlled encoding frequency and are offset in time to capture wave propagation using a controlled sampling frequency. In brain MRE, there is a possibility that the mechanical actuation frequency is different from the vibration frequency, leading to a mismatch with encoding and sampling frequencies. This mismatch can occur in brain MRE from causes both extrinsic and intrinsic to the brain, such as scanner bed vibrations or active damping in the head. The purpose of this work was to investigate how frequency mismatch can affect MRE shear stiffness measurements. Experiments were performed on a dual-medium agarose gel phantom, and the results were compared with numerical simulations to quantify these effects. It is known that off-frequency encoding alone results in a scaling of wave amplitude, and it is shown here that off-frequency sampling can result in two main effects: (1) errors in the overall shear stiffness estimate of the material on the global scale and (2) local variations appearing as stiffer and softer structures in the material. For small differences in frequency, it was found that measured global stiffness of the brain could theoretically vary by up to 12.5% relative to actual stiffness with local variations of up to 3.7% of the mean stiffness. It was demonstrated that performing MRE experiments at a frequency other than that of tissue vibration can lead to artifacts in the MRE stiffness images, and this mismatch could explain some of the large-scale scatter of stiffness data or lack of repeatability reported in the brain MRE literature.

Corpus callosum differences associated with persistent stuttering in adults.

Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional segmentation of area and voxel-based morphometry were used to evaluate the corpus callosum. Results revealed that the rostrum and anterior midbody of the CC were larger in AWS than NFA. In addition, the overall callosa area was larger in AWS than NFA. The group comparison of white matter volume showed a cluster of increased white matter volume predominantly encompassing the rostrum across the midline portion in AWS. These results potentially reflect anatomical changes associated with differences in the hemispheric distribution of language processes that have been reported previously in AWS.

fMRI in patients with lumbar disc disease: a paradigm to study patients over time.

Low back pain is a common human ailment. It is estimated that over 70% of the population will experience low back pain that will require medication and/or medical attention. There are many causes for low back pain, one being herniation of the discs of the lumbar spine. Treatment options are very limited. Why patients develop chronic pain especially when there is no known organic cause or when the offending painful stimulus has been removed remains poorly understood. Functional magnetic resonance imaging (fMRI) is a technique that allows researchers to image which regions of the brain that are activated during motor, cognitive, and sensory experiences. Using fMRI to study pain has revealed new information about how the brain responds to painful stimuli and what regions of the brain are activated during pain. However, many of the paradigms used do not replicate the subject's pain or use painful stimuli in volunteers without pain. Also, following patients from their acute phase of pain to the chronic phase with serial fMRI has not been performed. In this study we developed a paradigm that would allow studying patients with low back pain and leg pain including lumbar radiculopathy to better mimic a clinical pain syndrome and to have a method of following patients with this type of pain over time.

High-resolution diffusion tensor imaging of the human pons with a reduced field-of-view, multishot, variable-density, spiral acquisition at 3 T.

Diffusion tensor imaging of localized anatomic regions, such as brainstem, cervical spinal cord, and optic nerve, is challenging because of the existence of significant susceptibility differences, severe physiologic motion in the surrounding tissues, and the need for high spatial resolution to resolve the underlying complex neuroarchitecture. The aim of the methodology presented here is to achieve high-resolution diffusion tensor imaging in localized regions of the central nervous system that is motion insensitive and immune to susceptibility while acquiring a set of two-dimensional images with more than six diffusion encoding directions within a reasonable total scan time. We accomplish this aim by implementing self-navigated, multishot, variable-density, spiral encoding with outer volume suppression. We establish scan protocols for achieving equal signal-to-noise ratio at 1.2 mm and 0.8 mm in-plane resolution for reduced field-of-view diffusion tensor imaging of the brainstem. In vivo application of the technique on the human pons of three subjects shows a clear delineation of the multiple local neural tracts. By comparing scans acquired with varying in-plane resolution but with constant signal-to-noise ratio, we demonstrate that increasing the resolution and reducing the partial volume effect result in higher fractional anisotropy values for the corticospinal tracts.