Migration: a notable feature of cerebral sparganosis on follow-up MR imaging.

BACKGROUND AND PURPOSE: Cerebral sparganosis is a rare parasitic infection caused by sparganum, which can migrate in the brain. The purpose of this study was to demonstrate the migration of cerebral sparganosis and describe its patterns on MR imaging. MATERIALS AND METHODS: MR images of 14 patients with cerebral sparganosis treated from 2005 to 2011 were retrospectively reviewed. Diagnosis was made on the basis of a constellation of clinical history, laboratory tests, imaging findings, and histopathology. At least 3 MR imaging studies were performed for each patient during the follow-up period ranging from 12 to 38 months. Time interval, sites, enhanced pattern, and presumed routes of migration were evaluated. RESULTS: Both the initial lesions and migrated ones exhibited the "tunnel" sign and multiloculated rim enhancement. Migration was detected between 4 and 18 months after the baseline MR imaging in 14 lesions (in 14 patients), while 3 of 14 lesions showed a second migration between 22 and 38 months. Nearly all migrations were limited to the same hemisphere except for 2 contralateral migrations through the thalamus. Most of the migrations were in close proximity (within the same lobe, to the adjacent lobe, from the basal ganglia to the cortex, from the cerebellum to the pons and interthalamus) except 1 from the basal ganglia to the cerebellum. A signal change along the presumed route of migration was seen in 3 patients. CONCLUSIONS: Migration is a notable feature of cerebral sparganosis. Demonstration of migration on MR imaging could be a key diagnostic clue and beneficial for the treatment policy.

Perfusion and permeability MR imaging of gliomas.

Conventional contrast-enhanced MR imaging is the current standard technique for the diagnosis and treatment evaluation of gliomas and other brain neoplasms. However, this method is quite limited in its ability to characterize the complex biology of gliomas and so there is a need to develop more quantitative imaging methods. Perfusion and permeability MR imaging are two such techniques that have shown promise in this regard. This review will highlight the underlying principles, applications, and pitfalls of these evolving advanced MRI methods.

A unique magnetic resonance imaging feature of glioblastoma multiforme: the 'pseudopalisade' sign.

This study was designed to investigate the unique magnetic resonance imaging (MRI) appearance of histopathologically-proven glioblastoma multiforme (GBM) with pseudopalisade necrosis and to assess its value for grading gliomas and providing a differential diagnosis. The study included 169 patients with intracranial masses who underwent surgery and had a proven histopathological diagnosis: 50 with GBM, 77 with gliomas (46 grade II and 31 grade III) and 42 with other intracranial masses (20 metastases, 14 lymphomas and eight abscesses). All patients underwent preoperative brain MRI including post-contrast T(1)-weighted imaging. The presence of the 'pseudopalisade' sign on post-contrast T(1)-weighted images was compared among the different types of brain mass. The frequency of the 'pseudopalisade' sign in GBMs (94.00%) was significantly higher than that seen in grade II and III gliomas (11.69%) and other intracranial masses (7.14%). The 'pseudopalisade' sign on post-contrast T(1)-weighted images was useful for grading gliomas and for differentiating GBM from other brain masses.

A phantom study of the geometric accuracy of computed tomographic and magnetic resonance imaging stereotactic localization with the Leksell stereotactic system.

OBJECTIVE: To assess the spatial accuracy of magnetic resonance imaging (MRI) and computed tomographic stereotactic localization with the Leksell stereotactic system. METHODS: The phantom was constructed in the shape of a box, 164 mm in each dimension, with three perpendicular arrays of solid acrylic rod, 5 mm in diameter and spaced 30 mm apart within the phantom. In this study, images from two different MRI scanners and a computed tomographic scanner were obtained using the same Leksell (Elekta Instruments, Stockholm, Sweden) head frame placement. The coordinates of the rod images in the three principal planes were measured by using a tool provided with Leksell GammaPlan software (Elekta Instruments, Norcross, GA) and were compared with the physical phantom measurements. RESULTS: The greatest distortion was found around the periphery, and the least distortion (<1.5 mm) was present in the middle and most other areas of the phantom. In the phantom study using computed tomography, the mean values of the maximum errors for the x, y, and z axes were 1.0 mm (range, 0.2-1.3 mm), 0.4 mm (range, 0.1-0.8 mm), and 3.8 mm (range, 1.9-5.1 mm), respectively. The mean values of the maximum errors when using the Philips MRI scanner (Philips Medical Systems, Shelton, CT) were 0.9 mm (range, 0.4-1.7 mm), 0.2 mm (range, 0.0-0.7 mm), and 1.9 mm (range, 1.3-2.3 mm), respectively. Using the Siemens MRI scanner (Siemens Medical Systems, New York, NY), these values were 0.4 mm (range, 0.0-0.7 mm), 0.6 mm (range, 0.0-1.0 mm), and 1.6 mm (range, 0.8-2.0 mm), respectively. The geometric accuracy of the MRI scans when using the Siemens scanner was greatly improved after the implementation of a new software patch provided by the manufacturer. The accuracy also varied with the direction of phase encoding. CONCLUSION: The accuracy of target localization for most intracranial lesions during stereotactic radiosurgery can be achieved within the size of a voxel, especially by using the Siemens MRI scanner at current specifications and with a new software patch. However, caution is warranted when imaging peripheral lesions, where the distortion is greatest.

The trigeminal nerve.

The trigeminal nerve is the largest of the cranial nerves, serving as a major conduit for sensory information from the head and neck and primarily providing motor innervation to the muscles of mastication. An understanding of the pathologic processes that may involve this nerve requires a detailed knowledge of its origin within the brain stem as well as its course intracranially. This article describes the neuroanatomy of the nerve and divides it into its various segments to provide a differential diagnosis of common and some uncommon pathologic processes.

Computed tomographic characteristics of chronic subdural hematomas.

Although medical history and physical examination should lead to diagnosis of chronic subdural hematomas, 40% of these patients are likely to be misdiagnosed because many of these symptoms occur in other disease processes, such as transient ischemic attacks, stroke, dementia, and tumors. Computed tomography remains one of the most useful tools in the evaluation of these patients because of its rapidity, cost, availability, and pathologic sensitivity.

Imaging of neurocysticercosis.

Neurocysticercosis produces a variety of neurologic syndromes resulting from the cysticerci infestation of the central nervous system by the larvae of Taenia solium. Because of increased immigration to the United States from endemic areas, the incidence of neurocysticercosis has increased, especially in California, Texas, Arizona, and other southwestern states. Neuroimaging studies play a significant role in the diagnosis and management of patients with neurocysticercosis.

Fungal infections of the central nervous system.

The diagnosis and treatment of central nervous system fungal infections typically pose problems for the clinician. With an increased incidence of fungal infections in immunocompromised patients, neuroradiologic imaging has become essential in determining complications and outcomes. This article provides a summary of the more common organisms encountered in fungal infections of the central nervous system and the imaging features primarily seen with CT and MR imaging.

Intracerebral Whipple's disease diagnosed by stereotactic biopsy: a case report and review of the literature.

OBJECTIVE AND IMPORTANCE: This case demonstrates the rare occurrence of intracerebral Whipple's disease in a patient lacking classic systemic manifestations of the disease. Because of the nonspecific presentation and the typically deep-seated location of cerebral lesions in these patients, definitive diagnosis is frequently problematic. We present the first reported use of stereotaxy-guided brain biopsy to confirm the diagnosis of isolated intracranial Whipple's disease. CLINICAL PRESENTATION: The patient was a 36-year-old man who presented with a 4-month history of progressive lethargy, hypersomnia, behavioral changes, and weight gain. The results of the physical examination were remarkable only for findings of hypogonadism. Subsequent laboratory evaluation confirmed the diagnosis of hypogonadotrophic hypogonadism, with low levels of testosterone, luteinizing hormone, cortisol, and prolactin. INTERVENTION: A magnetic resonance image of the brain demonstrated hyperintense lesions on T2-weighted images in the regions of the right fornix, hypothalamus, and putamen that subsequently enhanced with intravenously administered contrast medium. A biopsy was then obtained from the right putaminal lesion under stereotactic guidance. Histopathological analysis of the tissue revealed findings consistent with intracerebral Whipple's disease that were subsequently confirmed using electron microscopy. CONCLUSION: Intracerebral Whipple's disease should be included in the differential diagnosis of patients presenting with progressive dementia and cognitive decline. In these patients, lesions have typically been observed in the hypothalamus, cingulate gyrus, basal ganglia, insular cortex, and cerebellum. As evidenced by our case, stereotaxy affords clinicians the attractive option of a minimally invasive technique by which to obtain tissue from such deep-seated areas. A review of this rare neurosurgical entity is presented.

Cerebral vasculopathy in sickle cell anemia: diagnostic contribution of positron emission tomography.

Children with sickle cell anemia (SS) have an increased risk for cerebral vasculopathy with stroke (CVA) and cognitive impairment. The present study examines the extent to which adding positron emission tomography (PET) to magnetic resonance imaging (MRI) can improve the detection of cerebral vasculopathy. Whereas MRI has been the prime modality for showing anatomical lesions, PET excels at assessing the functional metabolic state through glucose utilization 2-deoxy-2 [18F] fluoro-D-glucose (FDG) and microvascular blood flow ([15O]H2O). Forty-nine SS children were studied. Among them, 19 had clinically overt CVA, 20 had life-threatening hypoxic episodes or soft neurologic signs, and 10 were normal based on neurological history and examination. For the entire sample of 49 subjects, 30 (61%) had abnormal MRI findings, 36 (73%) had abnormal PET findings, and 44 (90%) showed abnormalities on either the MRI or the PET or both. Of the 19 subjects with overt CVA, 17 had abnormal MRI (89%), 17 had abnormal PET (89%), and 19 (100%) had either abnormal MRI or PET or both. Among the 20 subjects with soft neurologic signs, 10 (50%) had abnormal MRI, 13 (65%) had abnormal PET, and 17 (85%) had abnormal MRI and/or PET. Six (60%) of the 10 neurologically normal subjects had abnormal PET. Among the 30 subjects with no overt CVA, 25 (83%) demonstrated imaging abnormalities based on either MRI or PET or both, thus, silent ischemia. Lower than average full-scale intelligence quotient (FSIQ) was associated with either overt CVA or silent ischemic lesions. Four subjects who received chronic red blood cell transfusion showed improved metabolic and perfusion status on repeat PET scans. In conclusion, (1) the addition of PET to MRI identified a much greater proportion of SS children with neuroimaging abnormalities, particularly in those who had no history of overt neurologic events. (2) PET lesions are more extensive, often bihemispheric, as compared with MRI abnormalities. (3) PET may be useful in management as a tool to evaluate metabolic improvement after therapeutic interventions, and (4) the correlation of PET abnormalities to subsequent stroke or progressive neurologic dysfunction requires further study.

CT of head trauma.

The advent of CT in the early 1970s revolutionized the diagnosis and management of head trauma patients. CT remains to be the imaging modality of choice in the evaluation of patients with acute head trauma. High resolution CT is excellent for evaluating facial and skull fractures. Neurosurgically significant lesions such as epidural hematomas, subdural hematomas, or depressed skull fractures are already detected by CT. The early detection of extra-axial hematomas made possible by the increased availability of CT, results in early surgical interventions with marked improvement in morbidity and mortality in head trauma patients.

Unique CT imaging advantages. Hemorrhage and calcification.

Computed tomography remains the imaging modality of choice in the detection of two processes: acute intracranial hemorrhage and calcification; however, in the subacute and chronic stages of hemorrhage, MR imaging is more sensitive in aging and staging hemorrhage. FLAIR imaging increases the sensitivity of MR imaging in the detection of subarachnoid hemorrhage. The signal characteristics of calcification on MR imaging is variable, especially on T1-weighted images decreasing its detectability. CT is superior to MR imaging in the detection of calcification. A number of factors including slice thickness, as well as window width and level may affect the detectability of calcification on CT.

Role of stereotactic biopsy in the diagnosis and management of brain tumors.

Stereotactic biopsy has evolved as a powerful and safe tool to provide tissue diagnoses with minimal disruption of normal functioning brain. It plays a significant role in the management of malignant brain tumors, where the benefit of open surgery might not justify the concomitant risks. Stereotactic procedures are closed procedures, and thus direct feedback is not provided to the surgeon during manipulation of brain tissue. This difference from most other neurosurgical procedures necessitates rigor in the preoperative workup, the planning of the procedure, and the conduct of the procedure. The success of the procedure is measured by the ability of the team to make an accurate histopathological diagnosis of the lesion; in experienced hands, the rate of success should exceed 95%. Complications and mortality can be minimized with appropriate attention to detail.

High resolution magnetic resonance imaging of the rat spinal cord.

A two turn saddle shaped surface coil receiver was developed that allowed high resolution magnetic resonance imaging of the rat spinal cord. This is particularly important in laboratory animals where central nervous system regions of interest are relatively small. A continuous copper wire 1.5 mm in diameter was wound into two turns 28 mm in diameter. The saddle shape of the second turn improved the homogeneity of the signal within the region of interest and maintained sufficient field of view and depth of penetration. The quality factor (Q) for the surface coil was Q = 199 unloaded, and Q = 60 loaded. Using this surface coil with a GE CSI II 2.0 Tesla small bore magnet, spin echo T1 (TR = 500 msec, TE = 25 msec) and T2 (TR = 2000 msec, TE = 100 msec) weighted images were obtained in cross section, using 2 mm slice thickness with 2 excitations per phase encoding step. A sagittal gradient echo (rapid scan, TR = 85 msec, TE = 10 msec) was used to document reestablishment of vascular flow following ischemia. Spinal cord ischemia was induced by 14 minute temporary occlusion of spinal cord blood supply. MRI was performed at 18 hours following ischemia. There was a 1.4 fold increase in T2 image intensity in ischemic rat spinal cord (n = 4), consistent with edema formation, compared to normal rat spinal cord (n = 4). Preliminary studies show that similar high resolution images can be performed on the rat brain. This technique uses standard MRI equipment and the surface coil is made from inexpensive readily available materials. There are various animal models of cerebral and spinal cord injury that would benefit from improved high resolution MRI. This coil design may have application in larger animal models and the clinical setting.

Magnetic resonance angiography in neck masses.

Carotid MR angiography has primarily been used to evaluate for stenotic lesions. We performed 2D time of flight MR angiography in 25 patients with palpable neck masses. There were 23 masses confirmed histologically. Two of the masses represented abnormal carotid arteries. Carotid deviation was seen in 23 of 25 (92%) of patients. Widening of the carotid bifurcation was identified in seven patients, including four carotid body tumors, one inflammatory mass, one benign salivary gland tumor, and one schwannoma. Increased vascularity was identified in one carotid body tumor and in one metastatic papillary carcinoma of the thyroid. MR angiography may be useful to demonstrate flow within vessels and represents a familiar imaging display for surgical planning. Splaying of the carotid bifurcation is useful in demonstrating carotid space lesions.

The application of magnetic resonance techniques to the evaluation of the patient with sickle-cell disease.

Sickle-cell anemia presents unique challenges to the clinician who wishes to obtain important data regarding anatomic lesions and metabolic states without subjecting the patient to additional risks involving the imaging techniques. Two applications-magnetic resonance angiography and magnetic resonance spectroscopy-are described in this review.

Mechanical malfunction of the Leksell Gamma knife during patient treatment.

During the course of a patient treatment with a North American U-type gamma unit, the remote hydraulic valve controlling the direction of couch motion failed to change state. The couch, helmet and patient remained in treatment position after the expiration of treatment time for one of the target shots. No unusual equipment warning indications had been observed prior to the malfunction. The gamma unit was new, having been used to treat approximately 20 patients since it had begun to be used clinically 11 weeks previously. This specific situation was not addressed in our posted Emergency Procedures, which dealt explicitly with loss of electrical power, and loss of hydraulic pressure. In the present case, the hydraulic gauges indicated full pressure. After attempts to disengage the patient remotely proved unsuccessful, personnel entered the room. The table clutch at the foot of the couch was operated to disengage the couch/helmet assembly from its docked position. While this was not mentioned in our emergency procedures, the act had the effect of causing the cobalt-60 sources to be misaligned with the collimator apertures, thereby immediately terminating the patient treatment. This also had the unanticipated effect of substantially reducing radiation leakage exposure rate next to the couch near the tunnel opening. The patient was released from the helmet trunnions using a manufacturer-supplied long-handled special Allen key. The key was used conventionally, to release the trunnion locking mechanism, and also unconventionally to force a separation of a trunnion from the docking slot on the patient head frame. The patient was then removed from the tunnel by sliding out the pad on which she was lying. Anesthesiology personnel accompanied the patient out of the room. The unit functioned properly upon the replacement of the valve by manufacturer service personnel the next day. The patient returned for completion of treatment 1 week later. There were only minor changes to the overall patient dosimetry as a result of the malfunction. Personnel exposures were very low. The malfunction was reported to State authorities, who conducted an investigation, that was in turn followed up by an investigation by the Nuclear Regulatory Commission.

Third ventricular cysticercal cyst mimicking a colloid cyst: case report.

We describe a case of a 28-year-old Latino man who presented with signs and symptoms of raised intracranial pressure and radiographic evidence of a third ventricular cystic lesion. The cyst was removed via a transcallosal approach; the histology was noted to be a cysticercal lesion. The radiographic and histological features of this interesting case are discussed.