Intrinsic atrophy of the calf musculature is a common finding in Charcot-Marie-Tooth disease. Peroneal nerve atrophy leading to weakness in the anterior and lateral compartments is the most common clinical pattern, but considerable variability exists in the pattern of atrophy. Magnetic resonance imaging offers a valuable method for identifying the distribution and symmetry of muscle degeneration. Twenty-three patients with Charcot-Marie-Tooth disease had axial T-1 magnetic resonance images obtained at proximal, middle and distal calf muscle locations. Areas of fatty infiltration and muscle atrophy were measured in the four calf muscle compartments. The worst areas of involvement, on a scale of one to four, with four being worst, were in the lateral compartment in the mid calf (mean, 2.5) and in the anterior, posterior and lateral compartments of the distal calf (2.6, 2.8 and 2.5). Comparing right and left legs showed that there was visible asymmetry, which was not statistically significant. There was considerable variation in the pattern of involvement from patient to patient. The fact that all four calf muscle compartments may be involved asymmetrically and in varying degrees is important for treatment planning, including surgery. Not all patients have the classic symmetrical peroneal pattern of denervation.

Adolescent↗

PubMedDate not supplied

The retrorenal colon on computed tomography: a normal variant.

In a review of 200 patients, the position of the colon in relation to the posterior aspect of the kidneys on CT was studied. A small part of the colon was found in the left retrorenal position in 1.0% of the patients. An illustrative case report of an unusual colonic variation in which the colon coursed directly behind the kidneys is described. The anatomy of the retroperitoneal fascia and the significance of the retrorenal colon are discussed.

Colon↗

PubMedDate not supplied

MR imaging of syringobulbia.

The magnetic resonance (MR) examinations of 65 patients with syringomyelia were evaluated to determine the incidence and MR characteristics of syringobulbia. Syringobulbia was identified in 11 patients (17%), 10 of whom had communicating syringomyelia (associated with the Chiari I malformation) and one idiopathic syringomyelia. The cavities extended from 5 to 20 mm above the plane of the foramen magnum. Two types of syringobulbia were identified. The 10 patients with Chiari I malformation had thin clefts or slits extending into the medulla. These cavities were much smaller than the cervical cavities. The other patient had saccular syringobulbia in which the medullary cavity was similar to the cervical syrinx cavity. The T1-weighted images were most useful in detection of syringobulbic cavities. The theory of syringobulbia development and a brief review of the literature are included.

Adolescent↗

PubMedDate not supplied

Cerebral venous angiomas: MR findings.

Seven patients with suspected cerebral venous angioma studied by either CT or angiography were imaged with magnetic resonance. Six of seven cases demonstrated a stellate appearance on contrast enhanced CT. In two patients this finding was verified by angiography. Flow void was identified on both T1- and T2-weighted pulse sequences. In one patient a field echo sequence demonstrated high intensity signal within the venous angioma. Magnetic resonance proved superior to CT in the identification of these lesions. A stellate configuration with an emanating transcortical vein and centrifugal drainage (transcortical venous flow) from the angioma into a sinus was present in all cases. Centripetal drainage via thalamostriate and internal cerebral veins was not seen. There was no evidence of mass effect, scar, or hemorrhage. Four of the angiomas were located in a frontal lobe and three in a cerebellar hemisphere. This distribution of the lesions is similar to that reported in the literature in which the frontal lobe is the most common location followed by the cerebellar hemisphere. An embryological explanation is cited and supported by a review of the literature.

Adolescent↗

PubMedDate not supplied

Measurements of the normal cervical spinal cord on MR imaging.

The purpose of this study was to determine normal measurements of the C1-T3 spinal cord in anteroposterior and transverse planes from MR images and to compare these with previously published data. Seven hundred and fifty-six measurements were made from 66 randomly selected MR studies of the cervical spine. We measured the anteroposterior and transverse diameters of the cord at each vertebral level and computed the simple product of these diameters to provide a single useful numerical value, termed the approximate cord area (ACA). The cord varies in average anteroposterior and transverse diameters from 8.8 mm x 12.4 mm at C2 to 8.7 mm x 14 mm at C4 to 7.4 mm x 11.4 mm at C7. The cervical enlargement was found from C4 to C6 and was most evident by comparing the ACA values. At C2 the average ACA was 110 mm2, at C4 it was 121.9 mm2, and at C7 the average ACA was 84.6 mm2. Comparison of our data with the literature reveals disparate measurements that vary up to 6 mm from our mean values. However, our results correlated well with the postmortem studies of Nordquist (1964). A single number cannot be used as the basis for evaluating spinal cord size. Each level should be compared with the normal range specific for that level.

Adult↗

PubMedDate not supplied

Sarcoidosis of the CNS: comparison of unenhanced and enhanced MR images.

Sarcoidosis involving the CNS has a predilection for the leptomeninges, although parenchymal involvement occurs. We retrospectively evaluated the appearance of CNS sarcoidosis on unenhanced and enhanced MR images. MR studies were abnormal in 17 of 20 patients with CNS sarcoidosis. In all 17 patients, meningeal disease was detected on the gadopentetate-dimeglumine-enhanced T1-weighted images; the disease was detected on unenhanced images in three patients. Well-defined leptomeningeal patterns of enhancement were present in 15 patients. Other areas of involvement were the dura; brain parenchyma including hypothalamus, periventricular white matter, and ventricular ependyma; optic chiasm; and pituitary gland. Gadopentetate dimeglumine optimally evaluates meningeal disease and highlights the importance of the leptomeninges and Virchow-Robin spaces in the pathogenesis of CNS sarcoidosis. Enhanced MR is the preferred imaging technique for the evaluation of CNS sarcoidosis.

Adult↗

PubMedDate not supplied

MR imaging of CSF-like choroidal fissure and parenchymal cysts of the brain.

The purposes of this study were to delineate the MR characteristics of CSF-like parenchymal or fissural cysts of the brain and to correlate them with the clinical findings. Clinical data and MR images of 34 patients with these abnormalities were reviewed. Pathologic correlation was not available. Two types of cystic lesions were identified and separated by location: medial temporal lobe cysts arising in or near the choroidal fissure (26 patients) and parenchymal or pseudoparenchymal cysts not related to the choroidal fissure (eight patients). The choroidal fissure cysts simulated intraparenchymal cysts on axial images but their extraaxial location was well portrayed on the coronal images. Choroidal fissure cysts had a characteristic spindle shape on sagittal images. The other cysts were found in the temporal lobe (seven patients) or thalamus (one patient) and appeared parenchymal but situated close to the subarachnoid space. These lesions were round or ovoid. There was no abnormal enhancement in 10 patients studied with gadopentetate dimeglumine. Coronal images were most useful, revealing the cysts as focal CSF-intensity lesions expanding the choroidal fissure of the temporal lobe. All the cysts appeared to represent incidental findings that did not correlate with the clinical signs and/or symptoms that prompted the imaging evaluations. The MR characteristics of CSF-like cysts are important to recognize so that they are not confused with other, more serious entities, such as intraaxial cystic tumors, infarctions, or parasitic lesions.

Adolescent↗

PubMedDate not supplied

Magnetic resonance demonstration of normal CSF flow.

The magnetic resonance (MR) imaging appearance and incidence of flowing cerebrospinal fluid (CSF) in the brain were investigated. The MR scans of 46 randomly selected patients with normal examinations were retrospectively reviewed. All patients were studied using both T2-weighted and T1-weighted spin-echo pulse sequences. Thirty-one patients (67%) had decreased intensity in the aqueduct of Sylvius on the T2-weighted images when compared with the intensity of CSF in the lateral ventricles. This was termed the CSF flow-void sign. The feature was present in the caudal fourth ventricle in 15 patients (32%) and in the third ventricle in two patients (4%) on T2-weighted scans. It was seen in only 13% of patients on T1-weighted scans. It is believed the CSF flow-void sign represents pulsatile CSF flow. Its recognition is important because it explains the inhomogeneity in the appearance of the CSF, which could be confused with pathologic processes. It may be valuable in the routine evaluation of MR examinations if it does reflect CSF circulatory dynamics.

Adult↗

PubMedDate not supplied

MR demonstration of altered cerebrospinal fluid flow by obstructive lesions.

We investigated the MR imaging appearance of flowing cerebrospinal fluid (CSF) in the brain in the presence of obstructive lesions of the ventricular pathways. The pulsatile movement of CSF through the ventricular system is seen as an area of low signal intensity that has been termed the CSF flow-void sign (CFVS). This is best appreciated in areas of narrowing within the ventricular system; that is, the aqueduct of Sylvius, foramen of Magendie, and interventricular foramina. MR studies of 27 patients with lesions affecting the ventricular pathways were reviewed for the presence of the CFVS. Single-echo T1-weighted and T2-weighted multisection techniques were used in all cases. The CFVS was always seen more prominently on the T2-weighted images. The presence of the CFVS indicated patency of the ventricular pathway in which it was identified. The absence of the CFVS in the presence of hydrocephalus indicated that a possible obstructive lesion was present, but it did not directly indicate the level of the obstruction. The CFVS was absent in the aqueduct of Sylvius in 13 patients with obstruction or stenosis of the aqueduct, but it was also absent in one patient with a colloid cyst of the interventricular foramina. In three patients with preoperative and postoperative MR, the CFVS was seen in the area of interest only after resection of the obstructing lesion. We concluded that the presence of the CFVS is a useful indicator of the patency of the ventricular pathway in which it is seen. The absence of the CFVS at a location in which it is normally seen may indicate the presence of an obstruction, but it must be correlated with other signs to be interpreted correctly.

Adolescent↗

PubMedDate not supplied

Significance of cerebellar tonsillar position on MR.

It has been noted that a low degree of ectopia of the cerebellar tonsils on MR is of questionable significance. We measured the position of the cerebellar tonsils with respect to the inferior aspect of the foramen magnum in 200 normal patients and in 25 patients with a firm diagnosis of Chiari I malformation. In the normal group, the mean position of the tonsils was 1 mm above the foramen magnum with a range from 8 mm above the foramen magnum to 5 mm below. In the patients with Chiari I malformations, the mean position was 13 mm below the foramen magnum with a range from 3 mm below the foramen magnum to 29 mm below. Fourteen percent of normal patients had tonsils extending slightly below the foramen magnum. If 2 mm below the foramen magnum is taken as the lowest extent for tonsils in a normal patient, our sensitivity in predicting symptomatic patients is 100% and our specificity is 98.5% (three false positives). If 3 mm below the foramen magnum is taken as the lowest normal tonsillar position, our sensitivity is 96% and our specificity is 99.5%. MR demonstration of less than 2 mm of tonsillar ectopia is probably of no clinical significance in the absence of syringomyelia.

Arnold-Chiari Malformation↗

PubMedDate not supplied

The MR appearance of CSF pulsations in the spinal canal.

We investigated the MR appearance and incidence of low-signal areas within the CSF of the spinal canal. Nonuniform areas of decreased signal intensity in intracranial CSF have been named the CSF flow-void sign (CFVS) and appear to be due to spin dephasing secondary to pulsatile CSF motion. Similar areas are seen in the spinal canal. The MR scans of 50 randomly selected patients, constituting a total of 63 spinal studies, were reviewed. There were 27 cervical, 16 thoracic, and 20 lumbar spine examinations. All patients were studied using T2-weighted and T1-weighted spin-echo pulse sequences. T2-weighted images were done with sufficiently long TE and TR to cause the CSF to appear hyperintense compared with brain and spinal cord tissue. Two patients with enlarged spinal canals and two patients with syringohydromyelia were also included to illustrate the appearance of prominent CSF pulsations. The CFVS was identified on T2-weighted scans in the cervical spinal canal in nine patients (33%), in the thoracic spinal canal in one patient (6%), and possibly in the lumbar spinal canal in two patients (10%). The CFVS was prominent in two patients with enlarged CSF spaces and was also seen in the intramedullary cavity of the patients with syringohydromyelia. The CFVS could obscure small dural lesions and, in some instances, simulate enlarged vessels. Recognition of the spinal CFVS is important to avoid the incorrect diagnosis of intraspinal lesions.

Adolescent↗

PubMedDate not supplied

MR imaging of the mesencephalic tectum: normal and pathologic variations.

Variations of the quadrigeminal plate (mesencephalic tectum) were determined on midline sagittal MR images of the brain in 93 patients without known mesencephalic abnormalities and in 10 patients with known aqueductal stenosis or obstruction. Measurements of the thicknesses of the superior and inferior colliculi and the length of the tectum were made on the midline sagittal section. Images were obtained with a 0.5 T system with spin-echo pulse sequences using a TE of 30 or 40 msec with a TR of 500-1500 msec. The average thickness of the superior and inferior colliculi was about 5 mm, but the range was from 2-7 mm on the midline sagittal section. Abnormally thin colliculi appeared to have no clinical significance while abnormal thickness was observed in patients with neoplastic disease, sarcoidosis, and mesencephalic "beaking." While most neoplasms have abnormal signal intensity on T2-weighted images, small lesions may be difficult to perceive on transaxial images due to volume averaging or noncontiguous sections. Measurements of the tectum, on the commonly obtained midline sagittal section, may be useful for patients with small infiltrative lesions.

Adolescent↗

PubMedDate not supplied

MR of postoperative syringomyelia.

Twenty-seven MR scans of 20 patients surgically treated for syringomyelia were reviewed. Thirteen patients had syringomyelia associated with the Chiari I malformation, four cases were posttraumatic, and three were idiopathic. The operations performed included syringosubarachnoid and syringoperitoneal shunts, myelotomies, and foramen magnum decompressions. Three of the foramen magnum decompressions had associated posterior fossa duroplasties, two had fourth-ventricle-to-subarachnoid shunts, and two had plugging at the obex. On 20 scans of patients in whom the syrinx cavity had been shunted, the shunt catheter was seen in 15 (75%). When adequately treated by shunting, syringes are completely collapsed and show no flow void. Nine patients were treated by foramen magnum decompression; all were well seen by MR. Three of these patients had a poor clinical result; these were the only patients in whom CSF was not seen between the foramen magnum and the neural structures of the posterior fossa on any images. The proposed mechanisms of syrinx formation and extension are discussed and related to the surgical procedures used to treat syringomyelia.

Adult↗

PubMedDate not supplied

Erdheim-Chester disease: computed tomography in two cases.

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Aged↗