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[Observation of CSF pulsatile flow in MRI--the signal void phenomenon]
S Ohara1, T Matsumoto, H Nagai
1Department of Neurosurgery, Nagoya City University Medical School, Japan.
Abstract:
In a comparative study of MR images of 289 neurosurgical patients, loss of the signal intensity (signal void phenomenon) of CSF in the aqueduct was observed in 77 patients. This signal void phenomenon was seen most frequently in infants with chronic subdural hematoma (12 of 18) and patients of all age groups suffering from communicating hydrocephalus (10 of 14). It is known that CSF in the cranial cavity flows toward the spinal CSF space in to and fro manner responding to brain parenchyma pulsations. The velocity of this flow is to be faster in the narrower parts through the ventricular systems such as the aqueduct, Monro's foramen and the 4th ventricles. We think that in T2 weighted images signal void phenomenon reflects "high velocity signal loss" due to CSF flow. When the subarachnoid adhesions secondary to subarachnoid hemorrhage stagnate CSF flow in the subarachnoid space, the intraventricular CSF flow forms the main buffer for changes of the brain volume. This causes an increase in the amplitude of the pulsatile flow in the ventricular systems. Therefore the signal void phenomenon in the aqueductal CSF becomes more pronounced. It may be possible to differentiate normal circulation of CSF from abnormal with the bigger amplitude of CSF pulsatile flow, to understand the mechanisms of the normal pressure hydrocephalus or to diagnose a shunt malfunction. Therefore more insight in the CSF flow as imaged by MRI is needed, quantification of CSF flow will be the subjects of our further research.
Insights
High-velocity cerebrospinal fluid (CSF) flow in the aqueduct, visualized as signal loss on MRI, is linked to conditions like hydrocephalus and subdural hematoma. This phenomenon may help differentiate normal from abnormal CSF circulation.
Area of Science:
- Neurosurgery
- Neuroradiology
- Fluid Dynamics
Background:
- Cerebrospinal fluid (CSF) circulates within the cranial cavity and spinal space.
- Pulsatile CSF flow dynamics are crucial for maintaining intracranial pressure and volume homeostasis.
- Narrower ventricular pathways, such as the aqueduct, are expected to exhibit higher CSF flow velocities.
Observation:
- A comparative study analyzed MR images of 289 neurosurgical patients.
- Signal void phenomenon (loss of signal intensity) in the aqueductal CSF was observed in 77 patients.
- This phenomenon was most frequent in infants with chronic subdural hematoma and patients with communicating hydrocephalus.
Findings:
- The signal void phenomenon in T2-weighted MRI sequences is hypothesized to represent "high velocity signal loss" due to rapid CSF flow.
- Subarachnoid adhesions secondary to subarachnoid hemorrhage can impede CSF flow, increasing intraventricular CSF pulsatile flow amplitude.
- Increased pulsatile flow amplitude in the ventricular system correlates with a more pronounced aqueductal signal void phenomenon.
Implications:
- The signal void phenomenon may serve as an MRI marker to differentiate normal CSF circulation from abnormal patterns.
- Quantifying CSF pulsatile flow amplitude could aid in understanding normal pressure hydrocephalus mechanisms.
- This imaging finding may assist in diagnosing shunt malfunction in neurosurgical patients.