slowed perfusion and slow MTT
could there be any connection to CCSVI if your Mean Transit Time is faster not slower??? but your jugular is still narrowed?
hmmm...interesting question, Robbie. Usually stenosis is related to slower perfusion and slower MTT- I dunno. Will see if I can find any info. Nice to see your name over here!
Here's a terrific paper explaining MR perfusion technology and how radiologists measure perfusion time and why it's important. Here's the section that deals with arterial stenosis (not the same as venous, but a comparable mechanism)
MR perfusion imaging is useful not only in the assessment of stroke, but also in the assessment of stroke risk. Under normal circumstances, the brain has an autoregulatory mechanism for maintaining adequate cerebral oxygenation in the face of decreasing cerebral perfusion pressure, which allows normal blood flow despite fluctuations in systemic pressure. This mechanism may be impeded in patients with hemodynamically significant carotid artery stenosis who are at high risk for stroke. The ability to maintain an autoregulatory response to hemodynamic stress has been termed "cerebrovascular reserve capacity." Areas of the brain supplied by a markedly stenotic or occluded artery, in which vasodilatation has already occurred to maintain adequate flow, lack cerebrovascular reserve capacity. ....In addition to a poor response to a vasodilatory challenge, perfusion imaging may show other abnormalities in the cerebral hemisphere ipsilateral to a severe carotid stenosis or occlusion, such as delayed bolus arrival time and prolonged mean transit time [42, 43] (Fig. 6A,6B,6C,6D).
Here's the abstract for the latest paper linking CCSVI/MS and hypoperfusion, presented at the AAN meeting in April:
Hypoperfusion of Brain Parenchyma Is Strongly Associated with the Severity of Chronic Cerebrospinal Venous Insufficiency in Patients with Multiple Sclerosis.
OBJECTIVE: To investigate the relationship between chronic cerebrospinal venous insufficiency (CCSVI) and cerebral perfusion in patients with multiple sclerosis (MS). BACKGROUND: CCSVI is a vascular condition described in MS patients, characterized by stenoses of the main extracranial veins with hampered cerebral venous outflow. We hypothesized that the impaired venous outflow contributes to hypoperfusion of brain parenchyma. DESIGN/METHODS: Sixteen consecutive relapsing-remitting MS patients (mean age 36.1yrs, mean disease duration 7.5yrs and median EDSS 2.5) and 8 age- and sex-matched normal controls (NC), were scanned on a GE 3T scanner using dynamic susceptibility contrast enhanced perfusion-weighted imaging (PWI). Cerebral blood flow (CBF), blood volume (CBV) and mean transit time (MTT) were measured in the gray matter (GM), white matter (WM), normal appearing (NA) GM, NAWM, thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala, nucleus accumbens, red nucleus and substantia nigra. Diagnosis of CCSVI was established based on the venous hemodynamic (VH) Doppler criteria (Zamboni, JNNP, 2009) and the severity was based on fulfilled VH criteria (score 0-5) and VH insufficiency severity score (VHISS) (score 0-16). RESULTS: All 16 MS patients fulfilled the diagnosis of CCSVI (median VH=4, median VHISS=9) and none of the NC. There was a significant association between VH criteria and VHISS, and CBF, CBV and MTT in all examined regions of the brain parenchyma in MS patients. The most robust correlations were observed for lower CBF and higher VHISS in the GM, WM, NAGM and NAWM (r= -0.70 to -0.72, p<0.002), and in the thalamus, caudate, putamen, hippocampus, nucleus accumbens (r= -0.6 to -0.72, p<0.008). The correlation coefficients for CBV and MTT were in a range between r= -0.5 to -0.65. No relationship was observed for NC. CONCLUSIONS/RELEVANCE: This study demonstrates that severity of CCSVI is directly associated with hypoperfusion of the brain parenchyma in MS. Supported by: Hillarescere Foundation and Buffalo Neuroimaging Analysis Center.