MR myelography: imaging findings.

MR myelography, heavily T2-weighted fast spin-echo imaging with fat suppression, enhances the signal intensity of CSF with subtraction of the surrounding background signal. Krudy [1], who first described the technique, used multiple projections per examination. We illustrate the findings in 80 patients who were examined with a modified MR imaging technique that provides increased spatial resolution and uses a single coronal sequence after the conventional MR study. This report illustrates the usefulness of MR myelography in cases of spinal stenosis or spinal block, in both the lumbar and thoracic regions.

MR cisternography: initial experience in 41 cases.

PURPOSE: To present our initial experience with MR cisternography, an application of fast spin-echo MR with fat suppression, and compare it with routine MR cranial studies in the evaluation of the subarachnoid cisterns and their contents. METHODS: MR cisternography is a heavily T2-weighted fast spin-echo technique with high spatial resolution; it uses fat suppression and video reversal of the images. A small number of individual sections (two to four) are compressed into a composite image by a maximum-intensity projection algorithm, providing better depiction of anatomy in three dimensions. MR cisternography enhances the signal intensity of the cerebrospinal fluid (CSF) with suppression and subtraction of the background. A total of 41 patients were examined during a period of 6 months. MR cisternography was performed as an additional one (n = 31) or two (n = 10) sequences after conventional MR study. RESULTS: Twenty-one cases of disease were examined by MR cisternography, including 8 neoplasms, 4 CSF fistulas, and 3 large intracranial aneurysms. MR cisternography provided information unavailable by conventional MR studies in 17 cases. These included visualization of fistulous tracks in patients with CSF rhinorrhea, origin of a large suprasellar aneurysm, an additional loculus of a posterior fossa aneurysm and its relation to surrounding structures, and proper location of three tumors (intraaxial versus extraaxial). Clear depiction of the pituitary gland separate from the cavernous sinus was noted in 60% of the cases, and a new observation of a CSF sleeve around the third nerve in the posterior cavernous sinus was made in 85% of the cases. CONCLUSION: MR cisternography is superior to conventional MR studies in depicting anatomic structures within the subarachnoid spaces. This technique is recommended in the evaluation of cranial CSF fistulas and suprasellar and posterior fossa masses and in diagnosis of intraaxial versus extraaxial location of intracranial tumors.

Neuroimaging features of neurenteric cysts: analysis of nine cases and review of the literature.

PURPOSE: To gain a better understanding of neurenteric (NE) cysts via correlation of imaging findings and surgical and pathologic data. METHODS: The medical records, imaging studies, surgical information, and pathologic material were retrospectively reviewed in nine patients with NE cysts, including seven proved and two very probable cases. RESULTS: NE cysts occurred in the cerebellopontine angle in one case and extended from the cerebellopontine angle to the C2 level in a second. In the latter patient and the remaining seven with intraspinal lesions, the NE cyst was always located anterior to the spinal cord. The most common myelographic and CT myelographic appearance was that of a lobulated intradural extramedullary (IDEM) mass. Two patients had an intramedullary NE cyst with a somewhat unusual appearing exophytic IDEM-appearing expansion that can be a characteristic feature of these lesions. MR imaging demonstrated the NE cyst to be isointense to hyperintense relative to cerebrospinal fluid on long TR sequences and isointense or slightly hyperintense to cerebrospinal fluid on T1-weighted images. These signal characteristics correlate with the high-protein-content fluid within the cysts, usually described at surgery as milky or mucinous in character. CONCLUSION: The diagnosis of NE cyst should be considered when imaging studies reveal the presence of a lobulated IDEM or an exophytic intramedullary cystic mass, especially in association with anterior spina bifida or other vertebral anomalies. MR can uniquely confirm the cystic nature of these masses and is the method of choice for their imaging investigation. Because cyst recurrence can occur, MR should also be used for long-term patient follow-up.

Michelin tire baby syndrome: familial constriction bands during infancy and early childhood in four generations.

We report on an infant with an unusual pattern of transitory familial constriction bands distributed symmetrically and circumferentially over the neck, forearms, and lower legs. Family history showed the occurrence of similar bands among individuals in 4 generations transmitted as an autosomal dominant trait. Neck and limb distribution in the other affected family members was also symmetrical and circumferential, with spontaneous resolution taking place during childhood. This case represents another example of the Michelin tire baby syndrome, also known as multiple benign circumferential skin creases of the limbs, and further demonstrates its autosomal dominant mode of inheritance.

Conventional MR neuroangiography.

MR angiography of the brain plays an important role in the diagnosis of vessel thrombosis and dissection, giant aneurysms, and occult vascular malformations. This essay highlights some of the features of the intra- and extracranial circulation that make conventional MR neuroangiography valuable in the demonstration of vascular anatomy and vascular disease.

MR imaging in patients with intractable complex partial epileptic seizures.

Detailed neurologic studies, high-field-strength MR imaging, and CT scanning were performed preoperatively in 53 patients with intractable complex partial seizures who underwent surgical treatment for epilepsy. Macroscopic structural (tumoral or vascular) lesions were found in 28% of patients. The remainder had pathologic findings consistent with mesial temporal gliosis. Tumors were found in 22% of the patients and were benign or of low-grade malignancy in every case. MR was accurate in the preoperative diagnosis of structural lesions, including very small occult tumors and cryptic vascular malformations. In patients with mesial temporal gliosis, there was correlation between the MR observation of a unilaterally dilated anterior temporal horn and the EEG-identified seizure focus and side of temporal lobectomy. However, MR demonstrated T2-weighted signal abnormalities correlating with the epileptogenic focus in only 8% of cases of mesial temporal gliosis. MR provided useful information in 28% of patients who underwent surgery for refractory complex partial epilepsy. MR obviated invasive EEG monitoring in 93% of the patients with structural lesions. MR was useful in only 8% of the patients with pathologic changes of mesial temporal gliosis.

MR imaging in patients with intractable complex partial epileptic seizures.

Detailed neurologic studies, high-field-strength MR imaging, and CT scanning were performed preoperatively in 53 patients with intractable complex partial seizures who underwent surgical treatment for epilepsy. Macroscopic structural (tumoral or vascular) lesions were found in 28% of patients. The remainder had pathologic findings consistent with mesial temporal gliosis. Tumors were found in 22% of the patients and were benign or of low-grade malignancy in every case. MR was accurate in the preoperative diagnosis of structural lesions, including very small occult tumors and cryptic vascular malformations. In patients with mesial temporal gliosis, there was correlation between the MR observation of a unilaterally dilated anterior temporal horn and the EEG-identified seizure focus and side of temporal lobectomy. However, MR demonstrated T2-weighted signal abnormalities correlating with the epileptogenic focus in only 8% of cases of mesial temporal gliosis. MR provided useful information in 28% of patients who underwent surgery for refractory complex partial epilepsy. MR obviated invasive EEG monitoring in 93% of the patients with structural lesions. MR was useful in only 8% of the patients with pathologic changes of mesial temporal gliosis.

Frequency and variation of the posterior pituitary bright signal on MR images.

Sagittal T1-weighted series with 3-mm sections have routinely been used for all cranial MR studies at our institution. It was apparent from examining these studies that the rate of occurrence of a normal posterior pituitary bright signal was lower than has been previously reported, particularly in older patients. This prompted both a retrospective and a prospective review and analysis of the posterior lobe bright signal in three patient categories. The overall frequency of posterior pituitary bright signal and the influence of sex and age were evaluated in one category. An age-related statistically significant decline in the frequency of posterior pituitary bright signal was found, with a decline rate of approximately 1% per year. An evaluation of the occurrence of anatomic variation in the location of posterior lobe bright signal was made in a second group of 1500 patients. Abberrant location of the posterior lobe was found to be uncommon and was seen most frequently in patients with a sellar fossula. Temporal variation in the presence or absence and size of the posterior lobe bright signal was evaluated in a third group of 36 patients who had at least two MR examinations available for review. Follow-up MR study showed an obvious posterior lobe bright signal in 8% of these patients for whom no bright signal was apparent at the time of initial examination. Loss of the posterior lobe bright signal was apparent in another 25% of patients. A significant change in size of the bright signal was apparent in 19% of patients within this category. Our results indicate that variation in the bright signal of the posterior pituitary lobe should be expected as a normal physiological occurrence.

Frequency and variation of the posterior pituitary bright signal on MR images.

Sagittal T1-weighted series with 3-mm sections have routinely been used for all cranial MR studies at our institution. It was apparent from examining these studies that the rate of occurrence of a normal posterior pituitary bright signal was lower than has been previously reported, particularly in older patients. This prompted both a retrospective and a prospective review and analysis of the posterior lobe bright signal in three patient categories. The overall frequency of posterior pituitary bright signal and the influence of sex and age were evaluated in one category. An age-related statistically significant decline in the frequency of posterior pituitary bright signal was found, with a decline rate of approximately 1% per year. An evaluation of the occurrence of anatomic variation in the location of posterior lobe bright signal was made in a second group of 1500 patients. Aberrant location of the posterior lobe was found to be uncommon and was seen most frequently in patients with a sellar fossula. Temporal variation in the presence or absence and size of the posterior lobe bright signal was evaluated in a third group of 36 patients who had at least two MR examinations available for review. Follow-up MR study showed an obvious posterior lobe bright signal in 8% of these patients for whom no bright signal was apparent at the time of initial examination. Loss of the posterior lobe bright signal was apparent in another 25% of patients. A significant change in size of the bright signal was apparent in 19% of patients within this category. Our results indicate that variation in the bright signal of the posterior pituitary lobe should be expected as a normal physiological occurrence.

MR findings on primitive neuroectodermal tumors.

Primitive neuroectodermal tumors (PNETs) are highly cellular primitive CNS neoplasms that resemble microscopically the undifferentiated cells of the germinal matrix of the primitive neural tube. These tumors exhibit a highly malignant behavior with a tendency to disseminate along the CSF pathways. Previous descriptions of the neuroradiological findings in patients with PNET were published prior to the clinical application of magnetic resonance (MR) imaging. We describe our experience with the MR evaluation of four patients with pathologically proven PNET.

Attentional mechanisms during the intracarotid amobarbital test.

We investigated the integrity of attentional mechanisms following unilateral intracarotid amobarbital injection in 23 patients undergoing preoperative evaluation for epilepsy surgery. Performance for ipsilateral hand-button response to a quasi-random strobe flash was markedly altered following unilateral amobarbital injection as evidenced by decreased correct responses and increased perseverative errors. The increase in perseverations was inversely correlated with subsequent memory performance. The results indicate that unilateral amobarbital injection commonly produces a marked reduction in attention as well as disturbances in strategic control mechanisms.

MR imaging of the ectopic bright signal of posterior pituitary regeneration.

High-field-strength MR studies of 13 patients with sellar and/or parasellar tumors revealed an aberrant location of the posterior pituitary bright signal in the hypothalamus in seven cases and in relation to the pituitary infundibulum in six cases. Five of the MR studies were obtained in patients who had not had surgery and had pituitary adenomas producing compression and/or destruction of the posterior lobe. In the other eight cases, the aberrant bright signal occurred after hypophysectomy in seven patients and after removal of a craniopharyngioma in the eighth. Accumulation of neurosecretory material and regeneration of pituitary tissue in these ectopic locations have been documented previously in animal experiments and in a few reports in humans after hypophysectomy. MR imaging now provides further corroborative evidence in vivo of this process in which a "miniature posterior lobe" is formed.

Hemisphere asymmetry for eye gaze mechanisms.

To investigate left/right asymmetries in cerebral gaze mechanisms, eye deviation was evaluated in 90 patients following intracarotid sodium amylobarbitone injections. For right-handed subjects with left cerebral language dominance, the occurrence and severity of eye deviation were greater for right versus left hemisphere injections. In contrast, subjects with mixed cerebral dominance for language/handedness exhibited no left/right difference in the incidence of eye deviation. The results are consistent with right cerebral dominance for attentional/intentional mechanisms directed at external space. Further analysis suggests that the cerebral asymmetry for gaze may be due to an evolutionary loss of attentional/intentional mechanisms by the left cerebral hemisphere as language function developed.

Right cerebral specialization for tactile attention as evidenced by intracarotid sodium amytal.

Although several components of neglect syndrome have been reported to occur more frequently following right cerebral lesions, a right cerebral predominance for directed tactile attention has not been demonstrated. The intracarotid sodium amytal procedure (ISA, or Wada test) offers the opportunity to investigate differential effects for symmetric acute dysfunction of each cerebral hemisphere in each subject. In the present study, 18 patients undergoing preoperative evaluation for epilepsy surgery were trained in a nonverbal task of tactile attention. Left/right mean ISA dosages and left/right tactile test times postinjection were matched. Results revealed more correct responses following left ISA, and greater tactile inattention with more extinction-type responses following right ISA. No effect of seizure focus, sex, order of injection, or dosage was present. The finding that tactile inattention occurs more frequently with right cerebral dysfunction is consistent with right cerebral dominance for scanning attentional mechanisms directed at the external milieu.

Severe behavioral complications following intracarotid sodium amobarbital injection: implications for hemispheric asymmetry of emotion.

The intracarotid sodium amobarbital (ISA) procedure is effective in determining cerebral language dominance. However, severe emotional and behavioral reactions during ISA evaluation may invalidate the results or necessitate aborting the procedure. In an effort to identify patients at risk for behavioral complications, we reviewed 92 patients undergoing ISA evaluation and found five with severe changes in affect and behavior following amobarbital injection, ranging from prolonged coma to an extended confusional state. Severe behavioral disturbances were more likely to occur in patients with left frontal structural lesions upon injecting amobarbital into the right hemisphere. Analysis of patients with structural lesions of the anterior regions of the right hemisphere showed no evidence of similar behavioral complications. These findings suggest a special role for the left frontal region in the inhibition of affective expression and provide further evidence of the importance of right hemisphere mechanisms in emotion.

MR imaging of Chiari II malformation.

High-field-strength MR imaging was performed in one patient with Chiari III and 19 patients with Chiari II malformations. The MR features were compared with descriptions in the literature and correlated with previously described surgical and postmortem findings and with the results of previous radiologic investigations in this group of patients. Several new observations were apparent from the MR examinations. In 75% of the 20 cases, the underdeveloped tentorium with a wide incisura allowed inferior displacement of the medial posterior cerebrum, which appeared closely applied to a flattened aspect of the superior cerebellum. Previously reported CT descriptions of "pseudotumor of the tentorium" and "towering cerebellum" may be more related to the technique of the radiologic examination than to true upward herniation of the cerebellum. Elongation of the mesencephalon with increase in the mamillopontine distance was present in the majority of our cases and has not been previously emphasized. Some patients had atypical changes or appeared to be borderline cases between the Chiari I and Chiari II categories of malformation, and MR provided considerable diagnostic assistance in these cases. The noninvasive, in vivo evaluation of MR contributed a great deal to our further understanding of this congenital Chiari malformation.

MR evaluation of hydrocephalus.

An analysis of sagittal T1-weighted MR studies was performed in 23 patients with hydrocephalus, 58 patients with atrophy, and 100 normal patients. The average mamillopontine distance was 1.15 cm for the normal group, 1.2 cm for patients with atrophy, and 7.5 mm for patients with hydrocephalus. A reduction of the mamillopontine distance below 1.0 cm was found in 22 patients with hydrocephalus, 5 patients with atrophy, and 15 normal patients. Dilatation of the anterior third ventricle was noted in 21 patients in the hydrocephalus group and in none of the patients in the atrophy and normal groups. The average thickness of the corpus callosum at the level of the foramen of Monro was 6 mm in normal subjects and was reduced below 6 mm in 16 of the hydrocephalus patients. Smooth elevation of the corpus callosum was noted in 20 hydrocephalus patients, in 2 patients with atrophy, and in none of the normal patients. MR improves the accuracy of diagnosis in patients with hydrocephalus both because of its ability to show small obstructing lesions that are not depicted by CT and because the mass effect of the distended supratentorial ventricles produces anatomic changes that are delineated with precision by MR.

Hematogenous spinal leptomeningeal metastasis: a unique CT enhancement pattern.

A distinct CT enhancement pattern of leptomeningeal metastasis from a systemic malignancy is described, corresponding to the pathologic and myelographic patterns of this entity. The uniform total subarachnoid enhancement, simulating intrathecal contrast, heralded sheetlike tumor proliferation along the surface of the spinal cord in an asymptomatic patient. Since the majority of hypervascular intraspinal abnormalities show focal enhancement with intravenous contrast, recognition of this pattern may provide unique clinical information.