Increase in apparent diffusion coefficient in normal appearing white matter following human traumatic brain injury correlates with injury severity

Following diffuse traumatic brain injury, there may be persistent functional or psychological deficits despite the presence of normal conventional MR images. Previous experimental animal and human studies have shown diffusion abnormalities following focal brain injury. Our aim was to quantify changes in apparent diffusion coefficient (ADC) and absolute relaxation times of normal appearing white matter (NAWM) in humans following traumatic brain injury. Twenty-three patients admitted with a diagnosis of head injury (nine mild, eight moderate, and six severe) were scanned an average of 7.6 days after injury using a quantitative echo planar imaging acquisition to obtain co-registered T1, T2, and ADC parametric maps. Mean NAWM values were compared with a control group (n = 13). The patient group showed a small but significant increase in ADC in NAWM, with no significant change in T1 or T2 relaxation times. There was a correlation between injury severity and increasing ADC (p = 0.03) but no correlation with either T1 or T2, suggesting that ADC is a sensitive and independent marker of diffuse white matter tissue damage following traumatic insult. None of the patients had a reduced ADC, making ischaemia unlikely in this cohort. Pathophysiological mechanisms that may explain diffusely raised ADC include vasogenic edema, chronic ischemic phenomena, or changes in tissue cytoarchitecture or neurofilament alignment.     

Grisel's syndrome: a case of potentially lethal spinal cord injury in the adult

A 22-year-old woman presented with respiratory difficulty and quadriparesis two weeks after an upper respiratory tract infection. CT showed mild (Type I) rotatory atiantoaxial subluxation, but MRI demonstrated a severely contused and oedematous spinal cord at C2-3. The case was managed conservatively with collar, steroid and antibiotics. The outcome was excellent.     

Measurement of changes in brain water in man by magnetic resonance imaging

John Hunter was undoubtedly aware of the water content of normal brain tissue, and described cerebral oedema. The advent of nuclear magnetic resonance (NMR) shed new light on brain water, and the derivation of spatial information and hence images from NMR signals, has permitted studies of regional brain water in man in vivo. The initial study described here tested whether NMR longitudinal relaxation time (T1) correlates with brain water content in the cerebral cortex and white matter in man, and significant relationships have been demonstrated in cortex (r = 0.65, P less than 0.002) and white matter (r = 0.94, P less than 0.0001), the latter having narrow 95% confidence limits. The residual variance allows the prediction of water content from the T1 of white matter, measured from the image of a single patient, with an accuracy of +/- 4% of total tissue water with 95% confidence. In the further study described, the effects of dexamethasone and an infusion of 20% mannitol on brain water content has been assessed in patients with intrinsic cerebral tumours. Dexamethasone had no significant effect on the T1 of normal brain, oedematous peritumoural white matter, or tumour tissue. It must be concluded that the water content of these tissues is not changed by dexamethasone and that the clinical improvement seen in patients with cerebral tumours immediately after dexamethasone has to be explained by some mechanism other than a reduction in cerebral oedema. Mannitol did reduce the T1 of oedematous peritumoural white matter, and the T1 of tumour tissue, but did not change the T1 of normal brain significantly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gd-DTPA对脑肿瘤扩散张量成像观测指标的影响

目的评价钆喷替酸葡甲胺(Gd-DTPA)对脑肿瘤扩散张量成像(DTI)观测指标表观扩散系数(ADC)值和部分各向异性分数(FA)值的影响。方法对27例经手术病理或临床证实的脑肿瘤患者术前行常规MRI及DTI检查,DTI分别于Gd-DTPA注入前、注入后即刻和7min进行。分别测量肿瘤强化区、瘤周水肿区、对侧正常脑组织及正常胼胝体的ADC值和FA值,并进行统计学分析。结果肿瘤强化区ADC值、FA值在增强前与增强后即刻及增强前与增强后7min间比较,差异均有统计学意义(P均0.01),但增强后即刻与增后7min比较,差异无统计学意义(P0.05);瘤周水肿区、对侧正常脑组织和胼胝体压部ADC值、FA值在增强前、增强后即刻及增强后7min间两两比较,差异均无统计学意义(P均0.05)。结论静脉注入Gd-DTPA后可致肿瘤强化部分ADC值明显降低和FA值明显升高。如需进行DTI,应尽量在增强扫描前完成。     

Analysis of the diffusion tensor imaging parameters of a normal cervical spinal cord in a healthy population

Background: Diffusion tensor imaging (DTI) shows great advantage in the diagnosis of brain diseases, including cervical spinal cord (CSC) disease. This study aims to obtain the normal values of the DTI parameters for a healthy population and to establish a baseline for CSC disease diagnosis using DTI.

Methods: A total of 36 healthy adults were subjected to magnetic resonance imaging (MRI) for the entire CSC using the Siemens 3.0?T MR System. Sagittal DTI acquisition was carried out with a single-shot spin-echo echo-planar imaging (EPI) sequence along 12 non-collinear directions. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were determined at different cervical levels using a region of interest (ROI) method, following which they were correlated with parameters, like age and sex. Further, diffusion tensor tracking (DTT) was carried out to reconstruct the white matter fiber bundles of the CSC.

Results: The full and complete fiber bundle structure of a normal CSC was confirmed in both the T2-weighted and DTI images. The FA and ADC values were significantly negatively correlated with each other and showed strongly negative and positive correlations with age, respectively, but not with sex. Additionally, there was no significant difference between the FA and the ADC values at different cervical levels.

Conclusion: The DTI technique can act as an important supplement to the conventional MRI technique for CSC observation. Moreover, the FA and ADC values can be used as sensitive parameters in the DTI study on the CSC by taking the effects of age into consideration.     

Quantitative Ultrashort Echo Time Magnetic Resonance Imaging Evaluation of Postoperative Menisci: a Pilot Study

BackgroundMagnetic resonance imaging (MRI) visualization of meniscal signal is particularly challenging as the highly organized ultrastructure of meniscal fibrocartilage yields very short T2 values (∼6 ms) and a paucity of signal intensity during conventional image acquisition.Question/PurposeThe purpose of this study was to evaluate the feasibility of imaging postoperative menisci using an experimental, quantitative ultrashort echo time (UTE) MRI pulse sequence. This sequence acquires short echo images (echo time (TE) ∼0.3 ms) to produce multi-echo images for quantitative T2* calculations that provide an objective measure of collagen organization.ResultsA wide range of mean T2* values for both postsurgical groups was measured, and these values changed for each patient between the 6- and 12-month intervals. In many instances, the UTE sequence demonstrated quantitative differences between the two time intervals that were not detected with conventional sequences.ConclusionsThis pilot study presents preliminary, observational data to be used as a baseline for future studies. Although the T2* values did not reveal a trend in either group or correlate with expected signal changes on conventional MRI, we speculate that the UTE sequence may detect ultrastructural alterations in meniscal composition that are otherwise not perceived with routine fast spin echo (FSE) sequences.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-014-9420-x) contains supplementary material, which is available to authorized users.     

Paraplegia after interlaminar epidural steroid injection: a case report

We report the first case of paraplegia observed after epidural steroid injection in the upper spine. The patient was a 42-year-old male who underwent surgery two years earlier for stenosis of the lumbar spine from L2 to the sacrum leading to early manifestations of an equina cauda syndrome. This first operation provided satisfactory function with complete resolution of the objective neurological symptoms. The patient later developed bilateral radiculalgia involving the L3 and L4 territories and was treated by radio-guided epidural steroid injection (125 mg hydrocortancyl) delivered in the L1-L2 interlaminar space. The injection was achieved with no technical difficulty and there was no injury to the dural sac. Immediately after the injection, the patient developed complete motor and sensorial paraplegia from T12. CT and MRI performed 30 min and 4h, respectively, after the accident revealed a medium-sized discal herniation behind the L2 body. No other lesion was observed. Emergency surgery was performed for radicular release but to no avail. The patient's neurological status remained unchanged and four days later the T2 MRI sequence revealed a high-intensity intramedullar signal in the cone. The diagnosis of ischemia of the medullary cone was retained, hypothetically by injury to the dominant radiculomedullary artery via an undetermined mechanism. This complication has been previously described after upper foraminal steroid injections but not after intralaminar epidural steroid injection.     

Diffusion-weighted imaging of edema following traumatic brain injury in rats: effects of secondary hypoxia

Hypoxia and edema are frequent and serious complications of traumatic brain injury (TBI). Therefore, we examined the effects of hypoxia on edema formation after moderate lateral fluid percussion (LFP) injury using NMR diffusion-weighted imaging (DWI). Adult Sprague-Dawley rats were separated into four groups: sham uninjured (S), hypoxia alone (H), trauma alone (T), and trauma and hypoxia (TH). Animals in Groups T and TH received LFP brain injury, with Groups H and TH undergoing 30 min of moderately severe hypoxia (FiO2 = 0.11) immediately after surgery or TBI (respectively). DWIs were obtained at 2, 4, and 24 h and at 1 week post injury, and apparent diffusion coefficient (ADC) maps were constructed. Animals in Groups T and TH showed an early decrease (p < 0.001) in ADC values in the cortex ipsilateral to TBI 4 hr post injury, followed by elevated ADCs 1 week later (p < 0.05). No significant differences in ADC values were seen between T and TH groups in the ipsilateral cortex. In contrast, the ipsilateral hippocampus for Group TH showed only increasing ADC values. This hyperintensity in the ADC map began at 2 h after TBI, was significant by 24 h (p < 0.05), and reached a maximum at 1 week. This hyperintensity was not observed in Group T. Histopathology seen in TBI animals corresponded well with the pathology observed with MRI. Midline shifts reflecting edema were only observed in TBI animals with little difference between normoxic (T) and hypoxic animals (TH). In sum, this study demonstrates that the development and extent of brain edema following TBI can be examined in vivo in rats using DWI technology. TBI resulted in an early decrease in ADC values indicating cytotoxic edema in the cortex that was followed at 1 week by an increase in the ADC that was associated with decreased tissue cellularity. Histopathology corresponded well to the regions of brain injury and edema visualized by T2 and DWI procedures. Overall, the addition of hypoxia to brain injury resulted in a small increase in the magnitude of edema in hippocampus and cortex over that seen with trauma alone.     

Diffusion weighted magnetic resonance imaging of rat testes: a method for early detection of ischemia.

PURPOSE: We investigated the feasibility of diffusion weighted magnetic resonance imaging (MRI) for the early detection of ischemia in the testis. MATERIALS AND METHODS: Circulation to the right testis in Wistar rats was occluded by surgical ligation of the right funicle. The left side was sham operated and served as a control. The diffusion and T2-weighted MRI images of the 2 testes was performed postoperatively by a 1.5 Tesla MRI unit using a knee coil. On apparent diffusion coefficient images and T2-weighted images the region of interest values in the 2 testes were measured and statistically compared. RESULTS: At 1 hour after testicular funicle ligation the apparent diffusion coefficient was 18% lower in the ischemic than in the sham operated testis (p <0.0098). At 2 hours the difference was 20% (p <0.0017). In the signal-to-noise ratio on T2-weighted images there was no difference in the left and right testes. CONCLUSIONS: Altered diffusion occurs in an ischemic testis, which can be measured on MRI at 1.5 Tesla. Thus, diffusion-weighted MRI may be a helpful method for the differential diagnosis of acute testicular torsion.     

MRI诊断一氧化碳中毒性脑病

目的探讨一氧化碳(CO)中毒性脑病的MRI特征。方法回顾性分析38例CO中毒性脑病患者的影像学资料,17例为急性CO中毒性脑病,21例为急性CO中毒后迟发性脑病,观察其MRI特征。结果共26例苍白球受累,其中急性CO中毒性脑病占53.85%(14/26),CO中毒后迟发性脑病占46.15%(12/26);25例脑白质受累,其中急性CO中毒性脑病占20.00%(5/25),CO中毒后迟发性脑病占80.00%(20/25);苍白球和(或)脑白质受累伴小脑和大脑皮质受累各1例,伴胼胝体受累9例。4例苍白球受累者T1WI呈稍高及高信号,其他病变区域T2WI呈稍高及高信号,T1WI呈等低信号。10例CO中毒后迟发性脑病患者接受DWI,其中6例脑白质受累,病变区ADC值减低;4例脑白质和苍白球同时受累,病变区ADC值升高;3例伴胼胝体受累,病变区ADC值减低。2例CO中毒后迟发性脑病患者接受SWI,均显示苍白球受累,双侧苍白球呈对称性不均匀低信号。结论 CO中毒性脑病MRI具有典型特征,对评估病情及预后具有重要价值。     

Differences in Blood-Tumour-Barrier Leakage of Human Intracranial Tumours: Quantitative Monitoring of Vasogenic Oedema and its Response to Glucocorticoid Treatment

Summary Purpose. To study differences in tumour capillary permeability as expressed by the unidirectional transport rate constant K_i, extracellular distribution volume V_d and relaxation time T1 in human intracranial tumours using a recently described MRI method, and apply the model to study differences in these parameters after glucocorticoid (GC) treatment. Patients and Methods. Seventeen brain tumour patients were studied. There were seven glioblastoma (GLI), four metastasis (MET), and six meningioma (MM) patients. Nine patients were studied before and after an average of 6 days of GC treatment. A 1.5 Tesla MR imaging scanner was used, and a two compartment diffusion model for Gd-DTPA was applied. Results. There was a significant difference between pre-treatment K_i in GLI's and MM's, MM's having the highest permeability. There were no significant differences between pre-treatment V_d or T1 among the different tumour types. After GC treatment K_i decreased 15% on average (52% in GLI's and MET's, but only 4% in MM's). V_d decreased 14% on average in all tumours, but 47% in GLI's and MET's (p<0.04), but increased 2% during treatment of MM's. T1 decreased 9% in all tumours (p<0.04), but 11% in GLI's and MET's (p<0.003), and only 6% in MM's. Conclusions. It is possible to estimate K_i, V_d and T1 simultaneously in brain tumour patients in a clinical MRI system. K_i was significantly higher in MM's compared to GLI's and MET's, suggesting that MM's differ in some physiological parameter at the blood-tumour interface. MM's did not respond to GC treatment, neither in K_i, V_d nor in T1, whereas GLI's and MET's primarily decreased their extracellular distribution volume, suggesting that this may be an important effect in GC's mode of action in these tumour types.     

Magnetic resonance imaging detects and predicts early brain injury after subarachnoid hemorrhage in a canine experimental model

Abstract The canine double hemorrhage model is an established model to study cerebral vasospasm, the late sequelae of subarachnoid hemorrhage (SAH). The present study uses magnetic resonance imaging (MRI) to examine the recently reported early brain injury after SAH. Double hemorrhage SAH modeling was obtained by injecting 0.5 mL/kg of autologous arterial blood into the cisterna magna of five adult mongrel dogs on day 0 and day 2, followed by imaging at day 2 and day 7 using a 4.7-Tesla (T) scanner. White matter (WM) showed a remarkable increase in T2 values at day 2 which resolved by day 7, whereas gray matter (GM) T2 values did not resolve. The apparent diffusion coefficient (ADC) values progressively increased in both WM and GM after SAH, suggestive of a transition from vasogenic to cytotoxic edema. Ventricular volume also increased dramatically. Prominent neuronal injury with Nissl's staining was seen in the cortical GM and in the periventricular tissue. Multimodal MRI reveals acute changes in the brain after SAH and can be used to non-invasively study early brain injury and normal pressure hydrocephalus post-SAH. MR can also predict tissue histopathology and may be useful for assessing pharmacological treatments designed to ameliorate SAH.     

1H magnetic resonance imaging of normal brain tissue response to photodynamic therapy.

1H Magnetic resonance imaging (MRI) was used to study the effects of photodynamic therapy (PDT) on normal rat brain (n = 5) using T1-, T2-, diffusion-, and proton density (rho)-weighted images. Rats received intraperitoneal injections of 12.5 mg/kg of Photofrin II, and 48 hours later the dural area over the frontal cortex was treated with 35 J/cm2 of light (632 +/- 1 nm). The T1-, T2-, and diffusion-weighted images revealed an evolving high contrast region of brain that corresponded to the PDT-treated area. Lesioned brain exhibited significant increases in T1 and T2 relaxation times at 1 day (P less than 0.01) and 3 days (T1, P = 0.018; T2, P less than 0.01) after treatment, compared with the contralateral equivalent volume of nonlesioned brain. Water proton diffusion coefficient (DW) in the lesioned area decreased at 1 day (P = 0.026) and increased at 3 days (P = 0.012) compared with nonlesioned brain. An increase in the proton density ratio (rho D/rho O) from PDT (rho D) versus nonlesioned side (rho O) was found 3 days after PDT treatment (P = 0.03). The data indicate that the biophysical parameters obtained from magnetic resonance imaging scans, T1, T2, DW, and proton density, can be used to monitor changes in an evolving photochemically induced lesion.     

Multi-modal magnetic resonance imaging alterations in two rat models of mild neurotrauma

Magnetic resonance imaging (MRI) is increasingly used in the assessment of the severity and progression of neurotrauma. We evaluated temporal and regional changes after mild fluid percussion (FPI) and controlled cortical impact (CCI) injury using T2-weighted-imaging (T2WI) and diffusion-weighted imaging (DWI) MRI over 7 days. Region of interest analysis of brain areas distant to the injury site (such as the hippocampus, retrosplenial and piriform cortices, and the thalamus) was undertaken. In the hippocampus of CCI animals, we found a slow increase (51%) in apparent diffusion coefficients (ADC) over 72 h, which returned to control values. The hippocampal T2 values in the CCI animals were elevated by 18% over the 7-day time course compared to control, indicative of edema formation. Histological analysis supported the lack of overt cellular loss in most brain regions after mild CCI injury. FPI animals showed a generalized decrease in hippocampal ADC values over the first 72 h, which then returned to sham levels, with decreased T2 values over the same period, which remained depressed at 7 days. Histological assessment of FPI animals revealed numerous shrunken cells in the hippocampus and thalamus, but other regions showed little damage. Increased immunohistochemical staining for microglia and astroglia at 7 days post-injury was greater in FPI animals within the affected brain regions. In summary, traumatic brain injury is less severe in mild CCI than FPI, based on the temporal events assessed with MRI.     

Magnetic resonance imaging measurement of relaxation and water diffusion in the human lumbar intervertebral disc under compression in vitro.

STUDY DESIGN: Twelve lumbar intervertebral disc specimens were imaged with magnetic resonance imaging to estimate relaxation constants, T1 and T2, and tissue water diffusion, before and after applying compression. OBJECTIVES: The objectives of the study were to measure T1, T2, and water diffusion for differences with loading state, region of the disc (anulus fibrosus or nucleus pulposus), and grade of degeneration. SUMMARY OF BACKGROUND DATA: Magnetic resonance imaging can be used qualitatively to estimate water content and degeneration of the intervertebral disc. Beyond structural information of images, the relaxation times T1 and T2 may contain information on the changes occurring with degeneration. A modified spin-echo sequence can be used to estimate tissue water diffusion in cartilage and disc specimens with the ability to measure anisotropy. METHODS: Specimens were imaged in a 1.5-Tesla clinical scanner. T1, T2, and water diffusion were estimated from midsagittal images. Magnetic resonance imaging parameters were calculated before and after axial loading. The measured T1, T2, and D (diffusion coefficient) were compared before and after compression, and for the diffusion data, also by direction to consider anisotropy. RESULTS: For the T1 data, a significant difference was found by region, nucleus > anulus, and loading state, loaded > unloaded. For the T2 values, there was a significant difference by region, nucleus > anulus, and Thompson grade. For diffusion, significant differences were found by region, nucleus > anulus, Thompson grade, direction of diffusion, and state of compression, loaded > unloaded. CONCLUSIONS: This study demonstrated that magnetic resonance imaging can be used to measure significant changes in T1, T2, or diffusion in intervertebral disc specimens by region, loading condition, or Thompson grade.     

Acute spinal subdural hematoma with hemiplegia after acupuncture: a case report and review of the literature

Background context

Subdural spinal hematoma (SDH) is a very rare entity; however, it can lead to serious complications resulting from injuries to the spinal cord and roots. Although acupuncture has been a popular method for the management of pain control, we encountered the first case of SDH after acupuncture.

Purpose

The purpose of this case report was to present the first case of subdural hematoma after acupuncture and the reasons for the risks of blind cervical acupuncture.

Study design

A case report and review of the previous literature are presented.

Methods

A 69-year-old man complained of progressive weakness in the right upper and lower extremities 2 hours after acupuncture on the cervical spine and back. The diagnosis was delayed because of unilateral weakness, and the symptom was initially misinterpreted as a transient ischemic attack because of no sensory change and pain and normal findings of two brain magnetic resonance imaging (MRI).

Results

Cervical MRI 36 hours after onset revealed acute hematoma from the C3–C5 level; hematoma showed an isointensity on T1-weighted image (WI) with the preservation of epidural fat and a hypointensity on T2WI. A decompressive surgery was scheduled to perform within 2 days after the cervical MRI scan because of a previous anticoagulation therapy, but the patient refused it. Finally, 9 days after the onset, surgical decompression and removal of hematoma were performed. Three months postoperatively, the patient had fully recovered demonstrating fine hand movement and good ability to walk up and down the stairs.

Conclusions

Our study indicates that it is essential to perform cervical MRI when a patient does not show an improvement in the neurologic deficit and has a negative brain MRI after acupuncture. In addition, blind acupuncture if not correctly practiced may be harmful to the cervical structures.     

Head circumference in infants undergoing Foker process for long-gap esophageal atresia repair: Call for attention

IntroductionWe extended our pilot study in infants following long-gap esophageal atresia (LGEA) repair to report head circumference, an easily obtainable indirect measure of brain size. Data are presented in the context of previously reported body weight and T2-weighted MRI measures of intracranial and brain volumes.MethodsClinical information and head circumference were obtained for term-born (n = 13) and premature (n = 13) infants following LGEA repair with Foker process, as well as healthy term-born controls (n = 20) <1-year corrected age who underwent non-sedated research MRI. General Linear Model univariate analysis with corrected age at scan as a covariate and Bonferroni adjusted p values assessed group differences.ResultsWe report no difference in head circumference between the three groups. Such findings paralleled trends in body weight and total intracranial volume but not in brain volume as previously reported for the same pilot cohort.DiscussionResults suggest uncompromised somatic and head growth after repair of LGEA. In contrast, a novel finding of discrepancy between head circumference (novel data) and brain size (previously published data) in the same cohort suggests that head circumference might not be the best indirect measure of brain size in selected group of patients.     

Postoperative hyperperfusion in a patient with a dural arteriovenous fistula with retrograde leptomeningeal venous drainage: case report

OBJECTIVE AND IMPORTANCE: Hyperperfusion has been reported after carotid endarterectomy or stenting for stenosis of the internal carotid artery. Because few reports have examined postoperative hyperperfusion after treatment for dural arteriovenous fistulae (DAVFs), we present a case describing a patient who manifested this clinical entity. CLINICAL PRESENTATION: The patient was a 63-year-old man with a DAVF in the left transverse sigmoid sinus with retrograde leptomeningeal venous drainage. He experienced slowly progressive disorientation lasting for several months. Preoperative single-photon emission computed tomography with (123)I-labeled N-isopropyl-p-iodoamphetamine revealed an area of hyperintensity on T2-weighted magnetic resonance imaging (MRI) scans that coincided with the hypoperfusion area; it was not increased after acetazolamide challenge. Complete DAVF obliteration was achieved by embolization, then sinus isolation. After treatment, he experienced frequent generalized convulsions that were terminated by 2-day barbiturate therapy. INTERVENTION: On T2-weighted MRI scans obtained 3 days after surgery, the hyperintense area not only persisted but had expanded to the left parietal lobe. Moreover, a subcortical hyperintense lesion was recognized on T1-weighted MRI scans; this was considered to reflect cortical laminar necrosis. Single-photon emission computed tomography revealed hyperperfusion in the left parietal lobe; it changed to hypoperfusion a month after treatment. CONCLUSION: In patients with DAVFs with preoperative findings of marked low perfusion and a poor perfusion reserve, postoperative study may reveal hyperperfusion on single-photon emission computed tomography or cortical laminar necrosis on MRI. This may be evidence of severe perfusion disturbance as a result of venous infarction. In these patients, careful blood pressure control and early treatment of seizures are important after DAVF treatment.     

Correlation of quantitative MR imaging findings with symptoms in patients with incidentally detected inflammatory sinonasal disease

Purpose

To assess the relationships between mucosal thickness, T1-weighted, T2-weighted signals and restricted diffusion on magnetic resonance imaging (MRI) with the degree of symptoms in patients with incidentally detected inflammatory sinonasal disease.

Altered diffusion and perfusion in hydrocephalic rat brain: a magnetic resonance imaging analysis

OBJECT: It can be inferred from data published in the literature that brain compression occurs in the early stages of acute hydrocephalus and that drainage of extracellular waste products is impaired. The authors hypothesized that compression of the cortex would alter water distribution and retard the diffusion of fluid in the hydrocephalic brain. METHODS: Proton diffusion, blood perfusion, and T1 and T2 relaxation times were determined in adult rat brain by using magnetic resonance imaging prior to, and 1 and 8 days after induction of hydrocephalus by kaolin injection. Five anatomical regions of interest were studied. The striatum, dorsal cortex, and lateral cortex exhibited decreased T2 and apparent diffusion coefficient (ADC) values but no change in perfusion. Examination of white matter revealed an initial decrease in ADC followed by a significant increase. The T2 relaxation times increased and perfusion decreased progressively between 1 and 8 days after induction of hydrocephalus. CONCLUSIONS: Acute experimental hydrocephalus causes compression of gray matter, perhaps associated with reduction in total water, which impairs diffusion of water in the tissue. White matter compression and hypoperfusion precede the development of edema. These findings have importance for understanding the neurochemical changes that occur in hydrocephalic brains.