CSF Flow Studies of Intracranial Cysts and Cyst-like Lesions Achieved Using Reversed Fast Imaging with Steady-State Precession MR Sequences
Karl T. Hoffmann
,a,
Norbert Hostena,
Bernd U. Meyera,
Simone Rörichta,
Christian Sprunga,
Johann Oellingera,
Matthius Gutberleta and
Roland Felixa
a From the Departments of Radiology (K.T.H., N.H., J.O., M.G., R.F.), Neurology (B.U.M., S.R.), and Neurosurgery (C.S.) Charité, Campus Virchow-Klinikum, Humboldt-University, Berlin, Germany.
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FIG 1. A, Diagram of the PSIF pulse sequence. pn (the PSIF echo) is a spin echo that results from refocusing the echo fn-1 by the RF pulse, n. fn-1 (the FISP echo) is a gradient echo of the RF pulse, n-1, refocused by the readout gradient, Gr. Only the PSIF echoes are sampled with this sequence. This results in TEeff > TR, with TE(p) = 2TR - TE(f) in the symmetric arrangement of RF pulses and gradients shown. The phase-encoding gradients are applied before and after the echo (including a compensating pulse) for a zero net phase-encoding gradient between RF pulses to avoid affecting the established steady state. Data are sampled during the interpulse interval to avoid interference with RF transmission (6).
B, Alternating RF pulses and oscillating transverse magnetization in relation to the free induction decay (FID) and spin echo (SE) in SSFP imaging with the PSIF sequence.
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FIG 2. 19-year-old woman with incidentally found arachnoid cysts in the cerebellopontine angle.
A, Transverse T2-weighted SE image (2000/80/1) shows high signal intensity within the enlarged cerebellopontine angles (arrows) and in the prepontine cistern. The shape of the enlarged CSF space suggests arachnoid cysts.
B, On the corresponding SSFP image (20/25/1), signal attenuation due to CSF flow is found in the prepontine cistern and fourth ventricle (curved arrows). Persistently high signal intensity is found in the cerebellopontine cysts (straight arrows) due to stationary CSF, confirming the diagnosis of arachnoid cysts.
C, Sagittal T1-weighted SE image (500/12/2) with suspected thin membrane (long arrow) between the isointense subpeduncular space (curved arrow) and the left cerebellopontine mass (short straight arrow).
D, Corresponding sagittal SSFP image (500/12/2) shows functional separation of the hypointense pulsating CSF between the temporal bone and the cerebellar peduncles (curved arrow) and the hyperintense stationary CSF within the cyst (straight arrow).
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FIG 3. 44-year-old man with left-sided tinnitus and hearing loss, paraesthesia, and respiratory distress.
A, T1-weighted transverse image (500/12/2) of the posterior fossa shows a paramedullary, space-occupying lesion with signal intensity similar to CSF, compressing the left ventrolateral portion of the medulla oblongata (arrow).
B, T2-weighted SE image (2000/80/1) of the same section as in A. Different compartments are not visible; the lesion has the same signal intensity as the surrounding CSF spaces, and margins of the cyst are not reliably detectable, making the diagnosis of an arachnoidal cyst highly probable.
C, Corresponding preoperative SSFP image (20/25/1) shows a circumscribed, hyperintense, premedullary lesion (large arrow), indicating stationary CSF of a noncommunicating arachnoid cyst in contrast to the significantly reduced signal of moving CSF in neighboring compartments (small arrows) and in the fourth ventricle (arrowhead). This finding strongly supports the decision for neurosurgical intervention.
D, SSFP image (20/25/1) after membranectomy shows signal attenuation in most parts of the formerly hyperintense cyst (arrow), indicating communication with neighboring CSF spaces. The patient experienced relief of his symptoms.
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FIG 4. 31-year-old woman after membranectomy of left temporal and right temporofrontal arachnoid cysts.
A, Transverse T2-weighted SE image (2000/80/1) shows slightly inhomogeneous, hyperintense temporal cysts (straight arrows). The frontal part of the large right-sided cyst is depicted (curved arrow).
B, Corresponding SSFP image (20/25/1) of the same section clearly shows a jet phenomenon with distinct signal reduction arising from the right prepontine and left chiasmatic cisterns, indicating communication between the cysts and cisterns (black arrows). Marked signal reduction results from moving CSF in the prepontine cistern (white arrow). The contents of the arachnoid cysts appear, with local flow attenuation, more inhomogeneous in the SSFP image (20/25/1) owing to higher sensitivity to turbulent flow.
C and D, Transverse (C) and coronal (D) CT cisternograms show homogeneous contrast enhancement within the basal cisterns and both the left temporal and right temporofrontal cysts. The regions of bilateral membranectomy are indicated by arrows. The coronal image also shows a frontal part of the right cyst (small arrow).
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FIG 5. 23-year-old man with a left-sided temporal arachnoid cyst, suffering from occasional headaches.
A, Transverse T2-weighted SE image (2000/80/1) shows a hyperintense left temporal arachnoid cyst.
B, Coronal PSIF image (20/25/1) depicts distinct signal reduction (arrow) arising from the basal cisterns, indicating probable communication.
C, CT cisternogram (3-hour delay) shows slight contrast enhancement within the cyst, confirming slow communication. The contrast enhancement was confirmed by measuring a clear increase of intracystic HU. The site of communication was not detectable on the CT cisternogram owing to proposed valve mechanism with slow communication.
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FIG 6. 6-year-old girl with a system of temporal, supra- and parasellar, and paracerebellar arachnoid cysts.
A, Transverse T2-weighted SE image (2000/80/1) shows a right and small left temporal, suprasellar, and paracerebellar cysts. Note hamartoma of the tuber cinereum (arrow) anterior to the rotated brain stem.
B, Parasagittal PSIF image (20/25/1) shows some evidence of communication between the parasellar and paracerebellar cysts in the form of a continuous flow void (arrow).
C, CT cisternogram shows contrast enhancement with layering in the parasellar and paracerebellar cysts (arrows), providing further evidence of communication. Layering was caused by the patient's prolonged supine position.
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FIG 7. 28-year-old man with a prepontine arachnoid cyst, corpus callosum anomaly, hydrocephalus, ventriculoperitoneal shunt, and headaches.
A, T2-weighted axial image (2000/80/1) shows a hyperintense cyst (arrow) within the prepontine cistern, pushing the crura cerebri and the optic chiasm apart.
B, Midsagittal T2-weighted section (2000/80/1) shows defined margins of the cyst (straight black arrows), except for the narrowing between the basilar artery and skull base (white arrow). Note callosal dysplasia (curved arrow). The bottom of the third ventricle is elevated.
C, Midsagittal SSFP image (20/25/1) reveals broad-based signal void within the cyst (black arrow) probably due to transmission of pulsations from the basilar artery. A continuous jet phenomenon between the prepontine cistern with pronounced signal void (straight white arrow) on the one hand and the cyst on the other hand is not demonstrable, making communication unlikely. Flow void within the fourth ventricle was absent (curved arrow) owing to occlusion of the aqueduct. Membranectomy was not performed, because the patient had no evidence of visual impairment.
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