Physiological MR signal variations within the brain at 3 T.

The echoplanar technique in magnetic resonance (MR) imaging allows the acquisition of a series of images from a selected slice with a temporal resolution of 10/s. Simultaneous recording of physiological information on pulse and respiration allows correlation of the MR signal intensity with physiological signals, which can be obtained for each pixel examined. Such correlations can be found within the cerebrospinal fluid (CSF) spaces and within vessels if a flow-sensitive MR measurement technique is used. The use of an MR scanner with a field strength of 3 T improves the signal/noise ratio, but there is a stronger signal decay due to local magnetic inhomogeneities. This study shows that 3-T systems can be used for correlation of MR and physiological signals and that clear differentiation between signals from CSF and from vessels can be obtained due to their strongly different signal decays.

B-waves in cerebral and spinal cerebrospinal fluid pulsation measurement by magnetic resonance imaging.

OBJECTIVE: Noninvasive measurement of B-waves is possible by magnetic resonance (MR) imaging using echo planar imaging (EPI) sequences. In this study, the proportion of B-waves in the cerebrospinal fluid (CSF) of the spinal canal and in the aqueductus cerebri was evaluated under normal and pathologic conditions, respectively. The proportion of the influence of pulse and respiration on the CSF pulsations was estimated. METHODS: The spinal CSF was evaluated in 7 volunteers at 5 spinal levels (C1, C2/3, C 6/7, T5, and T12). Examination of the CSF frequencies at the aqueduct was performed in 14 volunteers, 10 patients with normal pressure hydrocephalus, and 5 patients with an aqueductal stenosis. An EPI sequence was applied at 1.5 T. During the 8-minute measurement time, pulse and respiration were coregistered. A MATLAB routine analyzed the spectral portion of the B-waves and the pulse- and respiration-dependent frequencies of the CSF. RESULTS: The amount of B-waves was small in cerebral (2.5%) and spinal measurements (3.4%) but significantly higher in the spinal CSF (P < 0.001). There was no statistically different amount of B-waves in the aqueduct for volunteers and hydrocephalic patients and between the different spinal levels in healthy volunteers. Spinal measurements revealed a rising portion of respiration-related frequencies from C1 to T12, whereas the portion of pulse-related frequencies declined. CONCLUSIONS: The data support that B-waves are a physiologic phenomenon. They can be delineated in the spinal and cerebral CSF. A higher amount of spinal B-waves reflects a stronger venous and respiratory influence.

The influence of pulse and respiration on spinal cerebrospinal fluid pulsation.

RATIONALE AND OBJECTIVES: The aim of the study is to elucidate the location and amount of spinal cerebrospinal fluid pulsations and to differentiate and quantify the cardiac and the respiratory influence. MATERIALS AND METHODS: An echo planar imaging sequence was applied to 5 different levels of the spinal canal of 7 healthy volunteers. The amount of maximal flow and respiratory signal variation were determined by a time and frequency domain analysis, respectively. RESULTS: CSF pulsation was high in the anterior cervical and in the thoracolumbar spine. Respiratory influence rose by 19% at C1 and by 28% at T12. The systolic flow was elevated during late expiration and the diastolic upward movement was pronounced by early expiration. CONCLUSION: The pulsation in the lower spine seems to be related to a second motor of CSF movement because there is a rising respiratory influence and a reappearance of pulsation waves. Physiological spinal CSF pulsation contains a relevant respiratory component.

MRI characteristics of acute and subacute brainstem and thalamic infarctions: value of T2- and diffusion-weighted sequences.

MRI including diffusion-weighted sequences (DW-MRI) has demonstrated its high sensitivity for acute supratentorial ischemic lesions. In this study we examined the sensitivity of different MRI sequences for the detection of acute brainstem and isolated thalamic infarctions. Diffusion- and T2-weighted MRI of 45 consecutive patients with signs and symptoms of infratentorial and thalamic infarction between 6/1997 and 1/2000 were analysed. The time between the onset of symptoms and the first MRI varied between 2 hours to 7 days with a median of 2 days. MRI repeats were performed in 4 patients in whom the clinical brainstem infarction had not been detected initially. Lesion detectability and size were evaluated for different brainstem and thalamic localizations. An acute brainstem or thalamic infarction as defined by the clinical condition could be identified in all patients by comparison of DW-MRI and T2-weighted images. Pons in farctions were the largest, followed by midbrain and thalamic lesions. Medulla oblongata infarctions were small in comparison. Pons, mid-brain and thalamic infarctions were reliably identified beginning 12 hours after the onset of symptoms. In contrast, detectability of medulla oblongata infarctions varied within the first 24 hours and their overall visibility was worse than that of other brainstem infarctions corresponding to their small size. However, regardless of loca tion, none of the 3 infarctions examined within the first 5 hours after the onset of symptoms could be identified. These lesions were demonstrated in follow-up examinations. In conclusion, pontine, midbrain and thalamic infarctions can reliably be visualized by a combination of DW-MRI and T2-weighted images beginning 12 hours after the ischemic attack. However, sensitivity seems to be lower earlier than 12 hours after ischemia and for medulla oblongata lesions.

Recurrent giant cell reparative granuloma of the skull base and the paranasal sinuses presenting with acute one-sided blindness.

The etiology, pathogenesis, histopathologic diagnosis, prognosis, and treatment of giant cell reparative granulomas of the skull are controversial. We report a 14-year-old girl with an advanced recurrent giant cell reparative granuloma of the skull base and paranasal sinuses whose only clinical manifestation was a loss of vision. After undergoing endovascular catheter embolization, the patient underwent repeated surgical resections of the mass via a combined frontobasal and modified infratemporal approach followed by radiation therapy. Histopathologic examination confirmed the diagnosis of giant cell reparative granuloma. A traumatic event in the patient's history-a fossa canina abscess followed by tooth extraction 14 months before admission-supports the theory of a reactive reparative process as a pathogenetic mechanism for this disease. Histopathologic criteria and clinical aggressiveness must be considered to achieve adequate treatment of giant cell lesions of the skull.