Spiral 2D T2-Weighted TSE Brain MR Imaging: Initial Clinical Experience.

BACKGROUND AND PURPOSE: Spiral MR imaging may enable improved image quality and higher scan speeds than Cartesian trajectories. We sought to compare a novel spiral 2D T2-weighted TSE sequence with a conventional Cartesian and an artifact-robust, non-Cartesian sequence named MultiVane for routine clinical brain MR imaging. MATERIALS AND METHODS: Thirty-one patients were scanned with all 3 sequences (Cartesian, 4 minutes 14 seconds; MultiVane, 2 minutes 49 seconds; spiral, 2 minutes 12 seconds) on a standard clinical 1.5T MR scanner. Three readers described the presence and location of abnormalities and lesions and graded images qualitatively in terms of overall image quality, the presence of motion and pulsation artifacts, gray-white matter differentiation, lesion conspicuity, and subjective preference. Image quality was objectivized by measuring the SNR and the coefficients of variation for CSF, GM, and WM. RESULTS: Spiral achieved a scan time reduction of 51.9% and 21.9% compared with Cartesian and MultiVane, respectively. The number and location of lesions were identical among all sequences. As for the qualitative analysis, interreader agreement was high (Krippendorff α > .75). Spiral and MultiVane both outperformed the Cartesian sequence in terms of overall image quality, the presence of motion artifacts, and subjective preference (P < .001). In terms of the presence of pulsation artifacts, gray-white matter differentiation, and lesion conspicuity, all 3 sequences performed similarly well (P > .15). Spiral and MultiVane outperformed the Cartesian sequence in coefficient of variation WM and SNR (P < .01). CONCLUSIONS: Spiral 2D T2WI TSE is feasible for routine structural brain MR imaging and offers high-quality, artifact-robust brain imaging in short scan times.

Diffusion-Weighted Zonal Oblique Multislice-EPI Enhances the Detection of Small Lesions with Diffusion Restriction in the Brain Stem and Hippocampus: A Clinical Report of Selected Cases.

Diffusion restriction is the morphologic hallmark of acute ischemic infarcts and excitotoxic brain injury in various cerebral pathologies. Diffusion restriction is visible as hyperintensity on DWI and as hypointensity on ADC maps. Due to the vicinity of multiple anatomic structures in the brain stem and hippocampus, very small lesions with diffusion restriction may result in severe clinical symptomatology, but these small lesions easily go undetected on standard cerebral DWI due to insufficient spatial resolution, T2* blurring, and image artifacts caused by susceptibility-related image distortions. Diffusion-weighted zonal oblique multislice-EPI with reduced FOV acquisition permits a considerable increase in spatial resolution and enhances the visualization of very small pathologic lesions in the brain stem and hippocampus. Improved performance in the depiction of different pathologic lesions with diffusion restriction in the brain stem and hippocampus using this sequence compared with standard DWI in selected cases is presented.

How Common Is Signal-Intensity Increase in Optic Nerve Segments on 3D Double Inversion Recovery Sequences in Visually Asymptomatic Patients with Multiple Sclerosis?

BACKGROUND AND PURPOSE: In postmortem studies, subclinical optic nerve demyelination is very common in patients with MS but radiologic demonstration is difficult and mainly based on STIR T2WI. Our aim was to evaluate 3D double inversion recovery MR imaging for the detection of subclinical demyelinating lesions within optic nerve segments. MATERIALS AND METHODS: The signal intensities in 4 different optic nerve segments (ie, retrobulbar, canalicular, prechiasmatic, and chiasm) were evaluated on 3D double inversion recovery MR imaging in 95 patients with MS without visual symptoms within the past 3 years and in 50 patients without optic nerve pathology. We compared the signal intensities with those of the adjacent lateral rectus muscle. The evaluation was performed by a student group and an expert neuroradiologist. Statistical evaluation (the Cohen κ test) was performed. RESULTS: On the 3D double inversion recovery sequence, optic nerve segments in the comparison group were all hypointense, and an isointense nerve sheath surrounded the retrobulbar nerve segment. At least 1 optic nerve segment was isointense or hyperintense in 68 patients (72%) in the group with MS on the basis of the results of the expert neuroradiologist. Student raters were able to correctly identify optic nerve hypersignal in 97%. CONCLUSIONS: A hypersignal in at least 1 optic nerve segment on the 3D double inversion recovery sequence compared with hyposignal in optic nerve segments in the comparison group was very common in visually asymptomatic patients with MS. The signal-intensity rating of optic nerve segments could also be performed by inexperienced student readers.

Femtosecond all-optical synchronization of an X-ray free-electron laser.

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30 fs r.m.s. for 90 fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses.

Transient oedema of the cervical spinal cord.

Transient but very intense oedema of the cervical spinal cord was observed in two patients with obstruction of the cerebrospinal fluid (CSF) pathways. Both presented with hydrocephalus, one due to an infratentorial obstructing mass and the other due to postmeningitic adhesive obstruction of the outlet foramina of the fourth ventricle. In animal experiments with obstruction of CSF pathways (due to outlet foramina obstruction or to downward tentorial herniation) flattening and stretching of the ependymal cells along the central canal is observed, followed by disruption and splitting of the ependymal lining and then by extracellular oedema of the subependymal tissue. Without treatment, frank cavity formation develops in a fourth stage. In our two patients, however, most probably because of appropriate decompressive therapy, the oedema disappeared completely without a residual spinal cord lesion.

Spatial relationship between vestibular schwannoma and facial nerve on three-dimensional T2-weighted fast spin-echo MR images.

BACKGROUND AND PURPOSE: During surgical removal of a vestibular schwannoma, correct identification of the facial nerve is necessary for its preservation and continuing function. We prospectively analyzed the spatial relationship between vestibular schwannomas and the facial nerve using 3D T2-weighted and postcontrast T1-weighted spin-echo (SE) MR imaging. METHODS: Twenty-two patients with a unilateral vestibular schwannoma were examined with MR imaging. The position and spatial relationship of the facial nerve to adjacent tumor within the internal auditory canal (IAC) and cerebellopontine angle cistern (CPA) were assessed on multiplanar reformatted 3D T2-weighted fast spin-echo (FSE) images and on postcontrast transverse and coronal T1-weighted SE images. The entrance of the nerve into the bony canal at the meatal foramen and the nerve root exit zone along the brain stem were used as landmarks to follow the nerve course proximally and distally on all images. RESULTS: The spatial relationship between vestibular schwannoma and facial nerve could not be detected on postcontrast T1-weighted SE images. In 86% of the patients, the position of the nerve in relation to the tumor was discernible on multiplanar reformatted 3D T2-weighted FSE images. In tumors with a maximal diameter up to 10 mm, the entire nerve course was visible; in tumors with a diameter of 11 to 24 mm, only segments of the facial nerve were visible; and in tumors larger than 25 mm, the facial nerve could not be seen, owing to focal nerve thinning and obliteration of landmarks within the IAC and CPA. CONCLUSION: Identification of the facial nerve and its position relative to an adjacent vestibular schwannoma is possible on multiplanar reformatted 3D T2-weighted FSE images but not on postcontrast T1-weighted SE images. Detection of this spatial relationship depends on the tumor's size and location.

Ramsay Hunt syndrome associated with brain stem enhancement.

Postcontrast T1-weighted MR images in a patient with Ramsay Hunt syndrome showed an enhancing lesion in the region of the nucleus of the pontine facial nerve and abnormal enhancement of the intrameatal, labyrinthine, and tympanic facial nerve segments and of the geniculate ganglion, as well as enhancement of the vestibulocochlear nerve and parts of the membranous labyrinth. This enhancement most probably resulted from a primary neuritis of the intrameatal nerve trunks of the seventh and eighth cranial nerves.

3D T2-weighted fast spin-echo MRI sialography of the parotid gland.

The diagnostic value of 3D T2-weighted MRI sialography and 2D T2-weighted fast spin-echo (FSE) images for delineation of the normal duct system and characterisation of parotid gland duct pathology was compared in a prospective study. We studied eight healthy volunteers and 18 patients with pathology of the parotid gland (tumours in 3, sialolithiasis in 6, Sjögren's disease in 4, recurrent or chronic parotitis in 4, post-traumatic stricture of the main parotid duct in 1). A heavily T2-weighted 3D FSE sequence was compared with a conventional 2D T2-weighted FSE sequence. The normal main parotid duct was always visible on 3D sialography and seen in 68% of the 2D T2-weighted FSE studies. The diagnostic reliability of both sequences for diagnosis of luminal concretions in sialolithiasis and dilatation of the duct in duct stricture or chronic parotitis was equal, although slight intraglandular dilatation was appreciated only on 3D sialography. Extraductal pathology resulting in obstruction or displacement of ducts was better characterised on 2D T2-weighted images. However, 3D MRI sialography offered the advantage of postprocessing with overview images and multiple maximum-intensity projection images in any plane.

T2-weighted three-dimensional fast spin-echo MR in inflammatory peripheral facial nerve palsy.

PURPOSE: Our objective was to identify histologically and intraoperatively verified focal nerve thickening of the distal intrameatal segment on three-dimensional fast spin-echo (FSE) T2-weighted MR images as a new diagnostic criterion in patients with inflammatory peripheral facial nerve palsy. METHODS: Twenty-two patients with clinically diagnosed unilateral (n = 20) or bilateral (n = 2) inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR imager using noncontrast and contrast-enhanced T1-weighted SE sequences and 3-D T2-weighted FSE sequences with secondary reformations. Abnormal contrast enhancement and possible focal nerve thickening of the distal intrameatal segment, labyrinthine nerve segment, and geniculate ganglion region were analyzed prospectively. RESULTS: In all patients, the T1-weighted postcontrast SE images showed characteristic smooth, linear, abnormally intense contrast enhancement of the distal intrameatal segment, indicating peripheral inflammatory nerve palsy. In 23 nerves (96%) a focal bulbous nerve thickening of the distal intrameatal segment was observed on 3-D T2-weighted FSE images. In 100% of patients with peripheral inflammatory facial nerve palsy, postcontrast T1-weighted SE images showed a smooth, linear, and abnormally intense contrast enhancement of the distal intrameatal segment; reformatted very thin 3-D T2-weighted FSE images showed a focal bulbous nerve thickening of the distal intrameatal segment in 96% of patients. These findings corresponded to intraoperative and histologic findings. CONCLUSION: Three-dimensional T2-weighted FSE sequences are fast and cheap compared with T1-weighted postcontrast images, but secondary reformations are time-consuming and require exact anatomic knowledge for careful analysis of the different nerve segments.

Comorbid conditions in old patients with femur fractures.

BACKGROUND AND METHODS: The incidence of preexisting medical diseases (comorbid conditions) and their influence on the high rate of falls, associated severe injuries, operative treatment, and outcome including mortality rate, duration of hospitalization, and rehabilitation success was retrospectively evaluated in a group of 102 patients (mean age, 81 years; 81% women) with femoral fractures. A comparison of polymorbidity rates in a control group of 102 patients (mean age, 79 years; 86% women) with proximal humeral fractures was added. RESULTS: The associated polymorbidity rate among patients with femoral fractures (FF) usually was statistically significantly higher than among patients with proximal humeral fractures (PHF) despite a comparable age and sex distribution: 80% of the patients with FF presented with cardiovascular (p < or = 0.001), 41% with pulmonary (p < 0.001), 67% with gastrointestinal (p < or = 0.001), 71% with neurologic (p < or = 0.001), 55% with urologic (p < or = 0.001), 75% with musculoskeletal (p < or = 0.1), and 61% with psychiatric (p < or = 0.001) disorders and complaints. Ninety percent of the patients used different medications (diuretics, cardiac agents, anticoagulants, antidiabetic agents, steroids, hypnotics, analgesics, psychotropic agents). The postoperative mortality rate was 11%, and the mean hospitalization period was 30 days. Forty-nine percent of the patients were discharged to their homes. Only 56% of the patients with PHF, however, presented with cardiovascular, 8% with pulmonary, 11% with gastrointestinal, 8% with neurologic, 9% with urologic, 64% with musculoskeletal, and 10% with psychiatric disorders. CONCLUSION: The polymorbidity in the old patient probably is a major intrinsic cause of the high incidence of falls and associated severe femoral fractures. It influences the perioperative and postoperative medical and anesthesiologic treatment, the postoperative mortality rate, and the duration and success of the postoperative rehabilitation phase.

Contrast-enhanced MR of the facial nerve in patients with posttraumatic peripheral facial nerve palsy.

PURPOSE: To estimate the value of noncontrast and contrast-enhanced T1-weighted MR imaging in detecting the underlying mechanisms of injury and regeneration in immediate- or delayed-onset posttraumatic peripheral facial nerve palsy. METHODS: Twenty-four patients with posttraumatic peripheral facial nerve palsy were examined on a 1.5-T MR imaging unit with precontrast and postcontrast T1-weighted spin-echo and gradient-echo sequences. RESULTS: Abnormal enhancement of the distal intrameatal nerve segment was visible in 92% of the patients up to 2 years after their initial trauma. A hematoma within the geniculate ganglion was seen in 33% of the patients with a longitudinal fracture. The greater superficial petrosal nerve (in 32% of patients) and the geniculate ganglion (in 48% of patients) were thick and intensely enhancing. Hematoma within the cochlea/vestibule or enhancement of the cochlea/vestibule and the vestibulocochlear (eighth) nerve was observed in transverse fractures. CONCLUSION: MR images can show long-lasting abnormal nerve enhancement, especially in the distal intrameatal nerve segment, related to the long-lasting breakdown of the blood/peripheral nerve barrier associated with nerve degeneration and regeneration after traumatic stretching of the greater superficial petrosal nerve. Additionally, intraoperatively observed perineural and intraneural scar formation leads to thickening and intense enhancement of the affected nerve segments on MR images. A hematoma in the region of the geniculate ganglion can be seen in some but not all patients. Associated damage of the inner ear structures in patients with transverse fractures is also visible on MR images.

MR differentiation of adamantinous and squamous-papillary craniopharyngiomas.

PURPOSE: To determine MR criteria for differentiating adamantinous from squamous-papillary craniopharyngiomas. METHODS: The MR imaging features of 42 histologically proved craniopharyngiomas (25 adamantinous, 15 squamous-papillary, and two mixed subtypes) were examined with multiplanar T2-weighted and noncontrast and contrast-enhanced T1-weighted imaging. Differences in the mR features of both subtypes were evaluated retrospectively. RESULTS: The adamantinous craniopharyngioma is a mixed solid-cystic or mainly cystic lobulated suprasellar or intrasellar/suprasellar tumor occurring in children and adults, typically with large nonenhancing hyperintense cysts on T1-weighted images. The squamous-papillary craniopharyngioma is a predominantly solid or mixed solid-cystic suprasellar tumor occurring in adults, appearing as a hypointense cyst on noncontrast T1-weighted images. Calcifications and recurrent tumors are more often observed in adamantinous tumors but can be seen in squamous-papillary tumors as well. Statistically significant parameters useful for differentiating the two tumor subtypes are the encasement of vessels, the lobulated shape, and the presence of hyperintense cysts in adamantinous tumors, and the round shape, the presence of hypointense cysts, and the predominantly solid appearance in squamous-papillary tumors. CONCLUSION: Craniopharyngiomas can be divided into two clinically, histologically different subtypes, which suggests a different pathogenesis of these two types of tumor.

Spinal MRI in vacuolar myelopathy, and correlation with histopathological findings.

We correlated MRI features with histopathological findings in an HIV-positive patient with vacuolar myelopathy. On MRI symmetrical nonenhancing high-signal areas in the posterior columns on T2-weighted images result from extensive vacuolation visible on histological sections.

[Inflammatory facial paralysis in MRI. An overview]. / Die entzündliche Fazialisparese in der MRT. Eine Ubersichtsarbeit.

In inflammatory peripheral facial nerve palsy pathologically intense, linear and smooth enhancement of the distal intrameatal nerve segment can always be observed on T1-w- SE- MR sequences. The other nerve segments often present with a pathological enhancement as well. On T2-w- SE sequences, a thickening of the distal intrameatal nerve segment can be observed. The pathological enhancement persists over weeks and months; even in patients with complete clinical recovery, a persistent enhancement of the distal intrameatal nerve segment can be demonstrated. No correlation can be established between the intensity of the enhancement, the clinical condition and the electrophysiological data on electroneurography. The persistent enhancement of the different nerve segments is due to a long-lasting breakdown of the blood-peripheral nerve-barrier related to the process of degeneration and regeneration of the facial nerve in inflammatory palsy.

[Inflammatory diseases of the spinal cord and spinal nerve roots in the MRI]. / Entzündliche Erkrankungen des Rückenmarks und der Nervenwurzeln in der MRT.

PURPOSE: To evaluate characteristic and reliable MRI patterns of different inflammatory lesions of the spinal cord and the nerve roots in immunologically compromised and immunologically competent patients in order to be able to establish a correct diagnosis based on MRI findings. MATERIAL AND METHODS: The MRI examinations of 52 patients (27 men, 25 women, mean age 38.5 years, range 14-75 years) with proven inflammatory lesions (39 patients) or tumorous/postactinic lesions of the spinal cord (6 patients) and vascular malformations of the spinal cord (7 patients) were retrospectively analyzed. All examinations were performed on a 1.5 T MR unit, using bi- or triplanar T1-w pre- and postcontrast as well as T2-w SE sequences. Additionally, a review of the common medical literature concerning inflammatory lesions of the spinal cord was included. RESULTS: Clinical and radiological examinations allow a subdivision of inflammations of the spinal cord and the nerve roots into (meningoradiculo) myelitis and meningoradiculo (myelitis) in immunologically suppressed or competent patients. The MRI patterns of these two inflammatory subtypes vary: meningoradiculitis presents with an enhancement of the nerve roots and the leptomeninges; myelitis itself is characterized by single or multiple, diffuse or multifocal, with or without nodular, patchy or diffusely enhancing intramedullary lesions, with or without thickening of the cord and leptomeningeal inflammation. This differentiation helps to determine the underlying etiology in some of the patients. The immunologically suppressed patient suffers from viral infections (especially herpes simplex, varicella-zoster virus, cytomegalovirus), bacterinal infections (tuberculosis), but rarely from parasitic infections. The immunologically competent patient suffers from bacterial (borreliosis), but rarely viral infections, sarcoidosis and demyelinating diseases. Idiopathic myelitis is also common. CONCLUSIONS: Secondary ischemic and demyelinating processes result in a complex morphology of inflammatory lesions on MRI, and therefore the whole spectrum of demyelinating, ischemic and inflammatory lesions has to be included in the differential diagnosis. Even tumors may imitate inflammatory myelitis and radiculitis. Most commonly, meningoradiculitis can be separated from myelitis. A reliable diagnosis of a specific inflammatory lesion is difficult and is mostly achieved in patients with multiple sclerosis and in patients with HIV-associated cytomegalovirus infection.

Intensity of MR contrast enhancement does not correspond to clinical and electroneurographic findings in acute inflammatory facial nerve palsy.

PURPOSE: To determine the value of MR contrast enhancement in predicting the course of acute inflammatory facial nerve palsy and in selecting patients for surgical decompression. METHODS: Six patients with an acute inflammatory incomplete or complete peripheral facial nerve palsy (five idiopathic and one herpetic in origin) had repeated MR imaging studies with and without contrast enhancement, electroneurography, and clinical examinations to establish a connection between the intensity of contrast enhancement on MR images, the clinical condition, and the electrophysiological data. The examinations were performed every second day starting on the first day of admission until clinical recovery was proved by clinical deblockage (spontaneous clinical improvement). The last examination was performed 3 months after the onset of the facial nerve palsy. RESULTS: An abnormal, very intense contrast enhancement of the facial nerve was always present in the distal intrameatal and proximal tympanic segments and in the geniculate ganglion. The labyrinthine segment exhibited a mild to moderate enhancement, and the distal tympanic and mastoid segments showed a moderate to intense enhancement. The intensity of contrast enhancement did not correspond to the severity, duration, or course of the facial nerve palsy, and the electroneurographic data had no predictive value in indicating the severity of the inflammatory process. Three months after clinical recovery, a persistent and more or less unchanged or even slightly more intense contrast enhancement was observed. CONCLUSION: The long-lasting intense contrast enhancement seen in the facial nerve segments of patients who have acute peripheral inflammatory facial nerve palsy is explained by a two-phase breakdown of the blood-nerve barrier.

Angioplasty balloon catheters used for distraction of the ankle joint.

Arthroscopy of the ankle joint is now routinely performed in diagnostic and therapeutic interventions but is still a demanding and difficult operative procedure in this very small and tight joint. Arthroscopy can be facilitated by a sufficient distraction that gives a better overview of the joint space. However, it is still a matter of debate how to obtain the adequate distraction. Distention by manual strength as well as by the help of a technical device have been proposed. We report our experience with distraction of the ankle joint by the help of one or two intraarticularily located and secondarily insufflated angioplasty balloon catheters that are routinely used in interventional radiology. These special catheters allow a careful and controlled distention of the joint with a fixed space of distraction and, according to our limited experience, without any morbidity.

Correlation of MRI, clinical, and electroneuronographic findings in acute facial nerve palsy.

Intratemporal enhancement of (Gd-DTPA) was investigated by an interleaved-overlapping magnetic resonance imaging (MRI) technique in 35 cases of acute facial palsy. In a reference group (normal facial function), enhancement was localized from the ganglion geniculi to the stylomastoid foramen. In cases of acute palsy, the facial nerve enhanced in the meatal fundus independent of etiology (idiopathic, herpetic, or traumatic). In 70% of those with Ramsay-Hunt syndrome, the vestibular and cochlear nerves, the labyrinth, and the sheets of the internal and external auditory canal additionally enhanced. No correlation was found between intensity, extension, and duration of the enhancement and the clinical, intraoperative, or electroneuronographic degree of the facial palsy. The pathogenesis of the Gd-DTPA enhancement of the facial nerve appears to be closely connected with the vascular supply of the fallopian canal and the permeability of the neural sheets.

[Anatomy and pathology of the parotid gland. COrrelation with magnetic resonance tomography]. / Anatomie und Pathologie der Glandula parotis. Korrelation mit der Magnetresonanztomographie (MRT).

Due to a very complex embryological development a variety of different tissues are mixed together within the parotid gland. Secondary degenerative metaplastic and regenerative alterations result in additional tissue variety. Epithelial cells of distinct differentiation, lymphatic tissue, partly within lymph nodes, partly in clusters, sebaceous tissue, fat and peripheral nervous tissue may be the origin of a pathological neoplastic or inflammatory intraparotid lesion. MRI is an optimal tool for the delineation of the anatomy of the parotid gland and of various intraparotid lesions and often permits differentiation among malignant and benign neoplastic and inflammatory lesions. The morphology of the different pathological lesions on MRI reflects the underlying histopathology. Due to great interindividual variations in the tissue characterization of a specific intraparotid lesion, great differences in MR morphology have to be expected.