Magnetic resonance imaging and clinical correlates of intellectual impairment in myotonic dystrophy

Although intellectual impairment is common in patients with myotonic dystrophy, this aspect of the disease has received relatively little research attention. We examined 41 patients with myotonic dystrophy using objective neuropsychological procedures and magnetic resonance imaging. Ten patients (24%) had severe and generalized intellectual dysfunction, while lesser or no cognitive impairment characterized the remaining patients. Degree of intellectual impairment was not related to neuromuscular status or sex. Patients with severe intellectual disturbance had significantly earlier onset of both myotonia and weakness and were more likely to inherit the disease from their mother. Magnetic resonance imaging findings indicated that while degree of cerebral atrophy was not related to severity of intellectual impairment, skull thickness, focal white matter lesions, and anterior temporal lobe abnormalities were significantly more common in patients with severely disturbed intellect. This study reports a number of previously unreported cerebral magnetic resonance imaging findings associated with intellectual impairment in myotonic dystrophy, but the etiology of these changes awaits neuropathologic examination.     

High-resolution MR of the intraparotid facial nerve and parotid duct.

PURPOSETo describe a high-resolution MR imaging technique that depicts the complex anatomy of the region of the parotid gland, focusing on the intraparotid components of the facial nerve and parotid duct.METHODSHigh-resolution T1-weighted images of the parotid gland were acquired with a prototype three-dimensional Fourier transform gradient-echo sequence that permits a very short echo time (4.2 milliseconds) by using a modified phase-encoded time-reduced acquisition scheme. The sequences were obtained at 1.5 T with a head and neck coil. Postprocessed multiplanar, curved and volumetric images were obtained. The most clinically useful images were acquired at parameters of 40/4.2 (TR/TEeff) a flip of 30 degrees, a field of view of 18 to 20 cm, a matrix of 512 x 288 or 512 x 256, an axial plane, 60 images, no gaps, and a section thickness of 1.5 mm. Eighteen healthy subjects were examined. The position of the facial nerve within the parotid gland was determined by identifying the facial nerve in the stylomastoid foramen and then following it on sequential sections through the parotid gland. Curved reformations were used to confirm the visibility of the nerve. A similar technique was used for the parotid duct.RESULTSThe image contrast obtained was similar to that of standard spin-echo T1-weighted images. The parotid gland showed intermediate signal intensity while the fat spaces showed high signal intensity. The vessels had variable signal intensity depending on saturation. The cerebrospinal fluid, nerves, muscles, and ducts had lower signal intensity. In all 18 subjects, the facial nerve from the brain stem to the parotid gland, and the parotid duct from the mouth to the hilus of the gland were seen bilaterally. The proximal intraparotid facial nerve to the level of the retromandibular vein was seen in 72% of the subjects and the main intraparotid ducts were seen in 66% of the subjects.CONCLUSIONHigh-resolution MR imaging offers simultaneous display of most of the important structures in the region of the parotid gland, including the intraparotid duct and facial nerve.     

Epoxy-resin injection of the cerebral arterial microvasculature: An evaluation of the limits of spatial resolution in 8 Tesla MRI

The purpose of this study was to quantify the spatial resolution of microscopic arteries on magnetic resonance images acquired at 8 Tesla (T). Techniques similar to those used for standard MRI of the human brain in vivo at 8 T were utilized to generate high-resolution gradient echo (GE) images of a whole postmortem human brain whose common carotid arterial system had been injected with an epoxy-resin. Single slice images, along with summed images of up to 5 contiguous slices, were then compared to color digital photographs detailing the distribution of the arterial system on the surface of the same injected brain. There was excellent MR visualization of the microscopic cerebral arteries down to a spatial resolution of 200 microm. Through the use of an 8 T whole-body MRI scanner and standard GE imaging sequences, microscopic arterial structures can be clearly resolved down to a dimension of 200 microm.     

Human leptomeningeal and cortical vascular anatomy of the cerebral cortex at 8 Tesla

PURPOSE: The purpose of this work was to describe the human leptomeningeal and cortical vascular anatomy as seen at high resolution on an 8 T UHFMRI system. METHOD: With a 1024 x 1024 matrix, axial gradient echo images of the cerebral cortex were acquired on a human volunteer at 8 T with TR 500 ms, TE 16 ms, flip angle 22.5 degrees, bandwidth 53 kHz, and slice thickness 2.84 mm. The same subject was evaluated at 1.5 T using similar parameters. The images were then reviewed in detail and compared with known cortical and leptomeningeal vascular anatomy. RESULTS: Two hundred forty micron in-plane resolution images of the human brain were acquired at 8 T without evident artifact from susceptibility distortions, RF penetration, or dielectric resonances. The CSF, gray matter, and white matter structures were well discerned. The microscopic leptomeningeal vascular anatomy was well visualized, and the course of small perforating cortical vessels could be followed from the cortical surface to the white matter junction. CONCLUSION: Initial 8 T images of the brain demonstrate detailed leptomeningeal and cortical vascular anatomy.     

Computed tomography of the ethmoid sinuses

CT scanning of the ethmoid sinuses is a significant advancement in the diagnostic evaluation of patients with pathology in this region. It allows for simultaneous and accurate evaluation of fine bony detail as well as subtle soft tissue abnormalities.     

In vivo high-resolution MR imaging of the carpal tunnel at 8.0 tesla

OBJECTIVE: To determine the feasibility of acquiring in vivo images of the human carpal tunnel at 8 tesla (T). DESIGN: The wrist of an asymptomatic volunteer was imaged with an 8 T /80 cm magnet. The subject was imaged prone with the arm over the head and the wrist placed in neutral position in a custom-built dedicated shielded wrist coil. Axial two-dimensional gradient-echo (GRE) images of the wrist were acquired. RESULTS: Image contrast and resolution at 8 T are excellent. The infrastructure of the median nerve, particularly the interfascicular epineurium and individual fascicles, is better visualized at 8 T than at 1.5 T. The flexor tendons are well delineated from each other and the surrounding soft tissues, and tertiary tendon fiber bundles are resolved. The boundaries of the carpal tunnel are better defined at 8 T. CONCLUSION: We have obtained the first high-quality in vivo images of the human carpal tunnel at 8 T. The 8 T images demonstrated better contrast and resolution than those obtained at 1.5 T.     

Flexed sitting maneuver for complete lumbar myelography in patients with severe spinal stenosis and apparent block

A new technique has been designed to improve myelography examinations of the entire lumbar spinal canal in patients with severe spinal stenosis using a single needle puncture. When a high-grade obstruction to the caudal flow of contrast material is encountered, the patient is placed in a flexed sitting position for 1 minute. This technique was performed in eight patients with severe lumbar spinal stenosis. It successfully helped depict the lower lumbosacral canal below an apparently complete block in four patients and resulted in improved visualization of the lower sac in four patients with partial block.     

Computed tomography and magnetic resonance imaging of the normal anatomy of the temporal bone

The high image quality provided by current high resolution CT bone algorithms in conjunction with the multiplanar and soft tissue imaging capabilities of MRI, provide exquisite anatomic detail of the temporal bone structures. This allows the radiologist to visually dissect this complex, three-dimensional structure, if a firm understanding of normal anatomy exists. In this way, the pathological processes involving the temporal bone can be better understood and correlated with the clinical setting.     

High-resolution 3DFT MR imaging of the endolymphatic duct and soft tissues of the otic capsule

This study compares the visualization of otic capsule anatomy by thin-section three-dimensional Fourier transformation (3DFT) MR imaging with that by high-resolution CT. The osseous margins of the otic capsule are delineated by high-resolution CT, while MR displays the soft-tissue structures. Routine two-dimensional Fourier transformation (2DFT) spin-echo MR techniques have been limited by slice thickness and signal to noise. Previous longer TE 3DFT gradient-echo MR images of the otic structures have been degraded by magnetic susceptibility effects, which limit spatial resolution and decrease signal to noise. These effects are especially prevalent in the otic capsule, where small soft-tissue structures interface with surrounding air and bone. We developed a high-resolution 3DFT MR technique to image five normal subjects. MR images were compared with high-resolution CT images of the same subjects. Axial, sagittal, and coronal 3DFT gradient-echo MR images with a short TR/TE and 15 degrees flip angle were acquired on a General Electric 1.5-T Signa unit using a 3-in. circular, receive-only surface coil. Axial, sagittal, and coronal 1.5-mm-thick contiguous high-resolution CT bone-algorithm images were obtained also. There was a high correlation between the MR and CT findings. The 3DFT MR images demonstrated significantly higher spatial resolution and soft-tissue detail than the high-resolution CT images did. For example, the endolymphatic duct was seen on twice the number of consecutive sagittal and axial MR slices. Other soft-tissue otic capsule structures routinely seen on the 3DFT MR images included the entire facial nerve, membranous labyrinth including cochlea, and tensor tympani muscle. This study demonstrates a new high-resolution 3DFT MR technique for visualizing the soft-tissue microstructures of the otic capsule and achieves a level of spatial resolution beyond that possible with high-resolution CT.