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Biomedical subjects

S M Wolpert

Publications and source records attributed to S M Wolpert.

At least 19 recordsLinked to original sources
PubMed1995

Cerebrospinal fluid flow waveforms: analysis in patients with Chiari I malformation by means of gated phase-contrast MR imaging velocity measurements.

PURPOSE: To determine the features of the cardiac cycle-related cerebrospinal fluid (CSF) flow pulsations in with Chiari I malformation before and after decompressive surgery. MATERIALS AND METHODS: Fifteen patients and 23 healthy subjects underwent cine phase-contrast magnetic resonance imaging. Ten patients were also examined after decompressive surgery. Four regions of interest were selected in the upper cervical subarachnoid space and premedullary cistern. Velocity and fraction of the cardiac cycle waveforms were plotted, and amplitude, temporal, and CSF displacement parameters were assessed. RESULTS: In the Chiari I patients, impaired systolic and unaltered diastolic CSF flow pulsations immediately below the foramen magnum were identified. After surgery, the systolic flow pulsations immediately below the foramen magnum improved. Good correlation with post-surgical improvement was observed. CONCLUSION: CSF flow waveform analysis helps demonstrate abnormalities in CSF flow at the foramen magnum and the benefits of decompressive surgery in patients with the Chiari I malformation.

Adolescent↗
PubMed1995

Analysis of cerebrospinal fluid flow waveforms with gated phase-contrast MR velocity measurements.

PURPOSE: To analyze the characteristics of normal cerebrospinal fluid (CSF) flow waveforms and to relate them to the arterial input and venous output flow waveforms in healthy volunteers. METHODS: Cine phase-contrast MR was obtained in 17 volunteers. The temporal velocity information from the cervical pericord CSF spaces, basal cisterns, and aqueduct, as well as the internal carotid and vertebral arteries and internal jugular veins, were plotted as waveforms. The waveforms were analyzed for configurations, amplitudes, and temporal patterns. In four volunteers the reproducibility of the precord CSF flow waveforms was examined on different days. In three volunteers the effect of jugular venous compression on the precord and aqueductal CSF flow waveforms was also evaluated. RESULTS: (a) Distinct and reproducible configurational features were observed in the CSF flow waveforms. Jugular venous compression produced elevation of the disatolic slope of the precord waveforms. (b) The amplitudes were variable. Jugular venous compression reduced the precord CSF velocities. (c) The systolic temporal parameters were less variable and more reproducible than the diastolic temporal parameters. Jugular venous compression resulted in delay in the systolic parameters of the precord waveforms. (d) Craniocaudal and caudocranial postcord CSF flow occurred either simultaneous with or earlier than the precord CSF flow. Pericord CSF flow in either direction preceded that in the cisterns and in the aqueduct. (e) A significant temporal relationship was noted in the precord space between the time of the R wave to the maximum velocities and the arterial flow. CONCLUSION: CSF flow waveform analysis seems to be a reliable, reproducible, and sensitive method for assessing the CSF dynamics.

Adult↗
PubMed1994

Chiari I malformations: assessment with phase-contrast velocity MR.

PURPOSE: To assess movement of the medulla, tonsils, and upper cervical cord as well as that of the posterior fossa cerebrospinal fluid pathways in both normal subjects and those with Chiari I malformations. METHODS: Nine healthy volunteers and eight patients with Chiari I malformations were examined with phase-contrast cine MR. With a region-of-interest cursor, the directions and intensities of the brain and cerebrospinal fluid were assessed and intensity-versus-time graphs generated. RESULTS: Cerebrospinal fluid flow patterns of the patients with Chiari I malformations were normal except for absence of valleculla flow. In addition, increased velocities (10 times normal) of the tonsils of all patients with Chiari I malformations together with posterior movement of the medulla (rather than the expected anterior movement seen in volunteers) occurred. CONCLUSIONS: Increased velocities of the tonsils may be the result of the carotid systolic pulse being delivered to a structure (the tonsil) without the normal surrounding cerebrospinal fluid, resulting in impact of the tonsils in the confined foramen magnum and a consequent caudocranial recoil. An alternative explanation would include the Bernoulli effect caused by the confined location of the tonsils. There may be a decrease in the peak tonsillar velocities after surgery.

Adolescent↗
PubMed1994

Hemimegalencephaly: a longitudinal MR study.

An infant with hemimegalencephaly was studied with MR at 5 days and again at 10 months of age. The initial scan showed an abnormally large left cerebral hemisphere. At the age of 10 months, the left cerebral hemisphere was smaller than the right--an apparent left-sided micrencephaly caused by normal growth of the right hemisphere and arrested growth of the left. The age of imaging of a patient with hemimegalencephaly can be important if the correct diagnosis is to be made.

Brain↗
PubMed1992

Recombinant tissue plasminogen activator in acute thrombotic and embolic stroke.

An open angiography-based, dose rate escalation study on the effect of intravenous infusion of recombinant tissue plasminogen activator (rt-PA) on cerebral arterial recanalization in patients with acute focal cerebral ischemia was performed at 16 centers. Arterial occlusions consistent with acute ischemia in the carotid or vertebrobasilar territory in the absence of detectable intracerebral hemorrhage were prerequisites for treatment. After the 60-minute rt-PA infusion, arterial perfusion was assessed by repeat angiography and computed tomography scans were performed at 24 hours to assess hemorrhagic transformation. Of 139 patients with symptoms of focal ischemia, 80.6% (112) had complete occlusion of the primary vessel at a mean of 5.4 +/- 1.7 hours after symptom onset. No dose rate response of cerebral arterial recanalization was observed in 93 patients who completed the rt-PA infusion. Middle cerebral artery division (M2) and branch (M3) occlusions were more likely to undergo recanalization by 60 minutes than were internal carotid artery occlusions. Hemorrhagic infarction occurred in 20.2% and parenchymatous hematoma in 10.6% of patients over all dose rates, while neurological worsening accompanied hemorrhagic transformation (hemorrhagic infarction and parenchymatous hematoma) in 9.6% of patients. All findings were within prospective safety guidelines. No dose rate correlation with hemorrhagic infarction, parenchymatous hematoma, or both was seen. Hemorrhagic transformation occurred significantly more frequently in patients receiving treatment at least 6 hours after symptom onset. No relationship between hemorrhagic transformation and recanalization was observed. This study indicates that site of occlusion, time to recanalization, and time to treatment are important variables in acute stroke intervention with this agent.

Acute Disease↗
PubMed1992

Current role of cerebral angiography in the diagnosis of cerebrovascular diseases.

The role of cerebral angiography in the diagnosis of cerebrovascular disease is currently being questioned because of the increasing availability of MR angiography. The purpose of this essay is to place the use of cerebral angiography in perspective in light of these new developments. In patients with atherosclerotic cerebrovascular disease, MR angiography can almost entirely supplant cerebral angiography as a screening procedure in the evaluation of the carotid bifurcation. However, detection of "pseudoocclusion" still requires cerebral angiography for accurate diagnosis. Atherosclerotic stenosis or occlusion of the major intracranial vessels at the base of the brain can be detected with MR angiography, but not as accurately as with cerebral angiography. Furthermore, for detection of more distal occlusions, cerebral angiography is still needed. A number of erroneous concepts about the risks and value of cerebral angiography have prevented its optimal use for patients with cerebrovascular disease. These myths can be countered by applying several rules to optimize the use of cerebral angiography. Subarachnoid hemorrhage is best evaluated with CT followed by detailed cerebral angiography, although MR angiography can be used as a screening test for aneurysms 3 mm or larger. Cerebral angiography is still necessary to confirm the diagnosis of cerebrovascular malformations, although MR angiography is a useful screening test. Cerebral angiography is required for the definitive diagnosis of arteritis, arterial dissection, or fibromuscular dysplasia.

Cerebral Angiography↗