Brain involvement in haemolytic-uraemic syndrome: MRI features of coagulative necrosis

We describe radiological demonstration of brain involvement in haemolytic-uraemic syndrome (HUS) in two siblings with a very different clinical course. While the brother presented with a mild, reversible encephalopathy, his sister developed high-signal lesions in the cortex, putamen and caudate nucleus on T1-weighted images, seen as dense areas on CT. Biopsy revealed coagulative necrosis due to microthrombosis without haemorrhage, calcification or infection. These findings suggest a possible prognostic role for MRI in cases of encephalopathy due to HUS.

Simultaneous measurement of regional cerebral blood flow by perfusion CT and stable xenon CT: a validation study

BACKGROUND AND PURPOSE

Knowledge of cerebral blood flow (CBF) alterations in cases of acute stroke could be valuable in the early management of these cases. Among imaging techniques affording evaluation of cerebral perfusion, perfusion CT studies involve sequential acquisition of cerebral CT sections obtained in an axial mode during the IV administration of iodinated contrast material. They are thus very easy to perform in emergency settings. Perfusion CT values of CBF have proved to be accurate in animals, and perfusion CT affords plausible values in humans. The purpose of this study was to validate perfusion CT studies of CBF by comparison with the results provided by stable xenon CT, which have been reported to be accurate, and to evaluate acquisition and processing modalities of CT data, notably the possible deconvolution methods and the selection of the reference artery.

METHODS

Twelve stable xenon CT and perfusion CT cerebral examinations were performed within an interval of a few minutes in patients with various cerebrovascular diseases. CBF maps were obtained from perfusion CT data by deconvolution using singular value decomposition and least mean square methods. The CBF were compared with the stable xenon CT results in multiple regions of interest through linear regression analysis and bilateral t tests for matched variables.

RESULTS

Linear regression analysis showed good correlation between perfusion CT and stable xenon CT CBF values (singular value decomposition method: R(2) = 0.79, slope = 0.87; least mean square method: R(2) = 0.67, slope = 0.83). Bilateral t tests for matched variables did not identify a significant difference between the two imaging methods (P >.1). Both deconvolution methods were equivalent (P >.1). The choice of the reference artery is a major concern and has a strong influence on the final perfusion CT CBF map.

CONCLUSION

Perfusion CT studies of CBF achieved with adequate acquisition parameters and processing lead to accurate and reliable results.

Developmental venous anomaly with an arteriovenous shunt and a thrombotic complication. Case report

Developmental venous anomalies (DVAs) are common congenital variations of normal venous drainage that are known for their benign natural history. Isolated cases of symptomatic DVAs with associated arteriovenous (AV) shunts have recently been reported. The present case, in which thrombosis occurred in a DVA involving an AV shunt, raises intriguing questions regarding the clinical characteristics of these lesions and can be used to argue in favor of considering such lesions to be arteriovenous malformations (AVMs). A 39-year-old man presented with acute thrombosis in a complex system of anomalous hemispheric venous drainage, which included two distinct DVAs, one of which involved an AV shunt. The hemodynamic turbulences induced by a communication between shunted and normal venous outflows were the possible predisposing factor of the thrombosis. Follow-up angiographic and magnetic resonance images revealed complete recanalization of the thrombosed vessel and provided a thorough visualization of the particular angioarchitecture of the DVA. Acute thrombosis within a DVA with an AV shunt has not been reported previously and, thus, this case can be added to other reports of complications that arise in this particular type of DVA. The authors hypothesize that the presence of an AV shunt in a DVA is a risk factor for aggressive clinical behavior of the anomaly, rendering those lesions prone to complications similar to AVMs. Although no treatment can be offered, the presence of an AV shunt in a DVA warrants close follow-up observation because such lesions may represent a particular subtype of AVM and, therefore, may exhibit an aggressive clinical behavior.

Atrial fibrillation with small subcortical infarcts

OBJECTIVES

To evaluate the characteristics of cardioembolic small (maximum lesion diameter<1.5 cm) subcortical infarcts (SSI) in patients with atrial fibrillation (AF).

METHODS

Twenty seven patients with chronic AF and an isolated SSI established by CT/MRI in the anterior circulation (SSI-AF group) were evaluated and their characteristics compared with those of 45 age matched (+/-1 year) patients with SSI, but no arterial or cardiac embolic source (SSI-control group). Using the criterion of the presence or absence of established risk factors (hypertension or diabetes mellitus) for small artery disease (SAD), the SSI-AF group we also subdivided into two groups, SSI-AF-SAD+ (n=22) and SSI-AF-SAD- (n=5) and their characteristics compared.

RESULTS

Although the lack of any significant difference in the distribution of hypertension and diabetes mellitus between the SSI-AF and SSI-control groups emphasises SAD as a common cause of infarct in SSI-AF, the presence of AF-together with the higher frequency of neuropsychological disturbances in the SSI-AF group versus the SSI-control group (15% v 2%; p=0.066)-favours cardioembolism as a potential cause of infarct in several patients. The characteristic factors seen more often in the SSI-AF-SAD- group compared with the SSI-AF-SAD+ group were secondary haemorrhagic transformation, faciobrachial pure motor weakness, subinsular involvement, and better recovery of neurological deficits.

CONCLUSIONS

The study suggests that either SAD or cardioembolism can be the cause of SSI in patients with AF. Atrial fibrillation is not always coincidental in patients with SSI and a clinical lacunar stroke. Certain clinical and radiological findings may be useful in differentiating cardioembolism from SAD in patients with SSI.

Using 80 kVp versus 120 kVp in perfusion CT measurement of regional cerebral blood flow

Perfusion CT studies of regional cerebral blood flow (rCBF), involving sequential acquisition of cerebral CT sections during IV contrast material administration, have classically been reported to be achieved at 120 kVp. We hypothesized that using 80 kVp should result in the same image quality while significantly lowering the patient's radiation dose, and we evaluated this assumption. In five patients undergoing cerebral CT survey, one section level was imaged at 120 kVp and 80 kVp, before and after IV administration of iodinated contrast material. These four cerebral CT sections obtained in each patient were analyzed with special interest to contrast, noise, and radiation dose. Contrast enhancement at 80 kVp is significantly increased (P < .001), as well as contrast between gray matter and white matter after contrast enhancement (P < .001). Mean noise at 80 kVp is not statistically different (P = .042). Finally, performance of perfusion CT studies at 80 kVp, keeping mAs constant, lowers the radiation dose by a factor of 2.8. We, thus, conclude that 80 kVp acquisition of perfusion CT studies of rCBF will result in increased contrast enhancement and should improve rCBF analysis, with a reduced patient's irradiation.

Acquired hippocampal damage after temporal lobe seizures in 2 infants

Two infants developed unilateral hippocampal swelling on magnetic resonance imaging after prolonged seizures of temporal origin. Subsequent images suggested hippocampal sclerosis. The first child had febrile status epilepticus with exanthem subitum and developed refractory complex partial seizures. Histological findings after temporal lobectomy confirmed hippocampal sclerosis but also revealed sequelae of a focal encephalitis and microdysgenesis of the hippocampus. The second child had signs of brain dysgenesis, but acquired hippocampal damage affecting each side successively was documented by serial magnetic resonance imaging. These cases illustrate that different clinical conditions combining preexisting and acquired pathological characteristics can lead to hippocampal sclerosis.

Interhemispheric transfer of visual motion information after a posterior callosal lesion: a neuropsychological and fMRI study

Interhemispheric transfer of visual information was investigated behaviourally and with functional magnetic resonance imaging (fMRI) 6 months after a lesion of the posterior two-thirds of the corpus callosum. On tachistoscopical left hemifield presentation, the patient was severely impaired in reading letters, words and geographical names and moderately impaired in naming pictures and colours. In contrast, interhemispheric transfer of visual motion information, tested by verbal report of the direction of short sequences of coherent dot motion presented within the left hemifield, was preserved. The pattern of cerebral activation elicited by apparent motion stimuli was studied with fMRI and compared to that of normal subjects. In normal subjects, apparent motion stimuli, as compared to darkness, activated strongly striate and extrastriate cortex. When presented to one hemifield only, the contralateral calcarine region was activated while regions on the occipital convexity, including putative area V5, were activated bilaterally. A similar activation pattern was found in the patient with a posterior callosal lesion; unilateral left or right hemifield stimulation was accompanied by activation in the contralateral and ipsilateral occipital convexity. Ipsilateral hemifield representation in the extrastriate visual cortex is believed to depend on callosal input. Our observation suggests that this is not the case for visual motion representation and that other, probably parallel, pathways may mediate visual motion transfer after posterior callosotomy.

Brain biopsy in patients with acquired immunodeficiency syndrome: diagnostic value, clinical performance, and survival time

BACKGROUND

Despite extensive discussion in recent years, brain biopsy in patients positive for human immunodeficiency virus who manifest cerebral mass lesions remains an ill-defined step in management.

METHODS

Prebiopsy data of 26 human immunodeficiency virus-positive patients with cerebral mass lesions who underwent computed tomography-guided stereotactic brain biopsy (SBB) were reviewed by a specialist in infectious diseases and by a neuroradiologist to establish a clinical diagnosis and a treatment plan for each patient. The postbiopsy diagnosis was compared with the prebiopsy diagnosis. Long-term patient outcome after SBB was recorded by means of a clinical performance scale to estimate its impact on life expectancy and clinical performance.

RESULTS

The SBB was diagnostic in 25 patients (96%). Potentially treatable disease was diagnosed in 21 patients (81%), and specific therapy was initiated in 17 patients (65%); 10 patients (39%) were able to complete therapy. The SBB corroborated the clinical diagnosis in 13 (52%) of 25 patients. The group with identical clinical and biopsy-proved diagnoses showed significantly better response to therapy (P = .02), clinical performance (P = .04), and survival after biopsy (P = .01), as compared with the group with different clinical and biopsy-proved diagnosis, although no significant difference was found for the degree of immunosuppression. Only completion of the treatment plan increased life expectancy significantly (P = .008).

CONCLUSIONS

These data show that in human immunodeficiency virus-positive patients with brain mass lesions, SBB has a high diagnostic yield. A subgroup of patients will benefit from specific therapy guided by the SBB result. The procedure should, however, be strictly limited to patients able to tolerate specific therapy.

Multiple brain infarcts: clinical and neuroimaging patterns using diffusion-weighted magnetic resonance

The capability of diffusion-weighted (DW) magnetic resonance imaging (MRI) to identify very early ischemic brain injury better than conventional MRI is well known. This technique, which successfully discriminates acute from old infarcts, is particularly useful in patients with multiple brain infarcts (MBI). Among 142 patients with acute stroke consecutively admitted to our primary care center, we selected 43 patients with two or more brain infarcts on conventional MRI. All patients presented with clinical deficits consistent with acute cerebral ischemia and underwent conventional spin echo for T(1) (T1-WI) and T(2)-weighted images (T2-WI), T(1)-W gadolinium-enhanced images, and echo-planar technique for DW MRI sequences. Patients underwent DW MRI examinations within 15 days of stroke onset (mean +/- SD: 3 +/- 3 days). In all but 1 case, the infarcts detected on DW MRI were also visible on T2-WI. The different signal pattern on DW MRI, compared with T2-WI, facilitated the detection of acute infarcts in all patients. T1-WI with gadolinium enhancement was only helpful in 5 (11.6%) patients. DW MRI enabled precise clinicotopographic correlations in 79% of our patients and provided additional clinically relevant findings in 72% of the patients. Based on the neuroradiological findings, patients were divided into three clinicotopographic types of MBI as follows: 13 patients (30.2%) presented with multiple acute infarcts, 24 patients (55.8%) with a single acute infarct and multiple old infarcts, and 6 patients (13.9%) with multiple acute and old infarcts. In conclusion, DW MRI can easily be added to conventional MRI in order to be able to distinguish acute from old infarcts, and to identify acute multiple lesions. Therefore, a better correlation between clinical symptoms and the site of lesions can be obtained, considerably improving patient care.

Diagnosis of cerebral venous thrombosis with routine magnetic resonance: an update

Magnetic resonance imaging and angiography is the technique of choice in the diagnosis and follow-up of cerebral venous thrombosis: Thrombosis appears as an absence of flow void on spin echo images and lack of signal in angiographic techniques. The thrombus signal intensity is different on T1 and T2 spin echo weighted images and evolves according to hemoglobin degradation. Recognition of pitfalls and artefacts related to the different magnetic resonance imaging techniques employed is essential to interpret dural venous sinus thrombosis. In this paper the imaging of 27 patients with cerebral venous thromboses is reviewed. We describe the type of signal abnormalities, the different types of clot- and flow-related artefacts, and the indirect signs of cerebral venous thrombosis.

[Skew deviation]

BACKGROUND

Skew deviation is a vertical ocular misalignment of prenuclear origin. Although well described in the literature, it is still probably underdiagnosed. Natural history of skew deviation is not well described in the literature.

PURPOSE

To describe the clinical presentations, etiologies and follow-up of skew deviation.

METHODS

Retrospective study of 29 patients diagnosed with skew deviation between 1993 and 1996.

RESULTS

The commonest cause was cerebrovascular accident (12/29) and the commonest localisation was mesencephalic (9/29). Other causes included surgery (7/29), tumor (4/29), trauma (3/29), degeneration (3/29), inflammatory (2/29), increased intracranial pressure (1/29). Other localisations included cerebellum (5/29), ponto-mesencephalic (3/29), and medulla (2/29). Vertical diplopia was always accompanied by other neuro-ophthalmologic abnormalities. 69.2% (18/26) patients were totally asymptomatic after 7.5 months. 30.8% (8/26) were still symptomatic (diplopia). One patient required surgery, three patients were relieved with prisms, one patient needed monocular occlusion. One patient died during follow-up and precise data were lacking in two symptomatic patients.

CONCLUSION

Skew deviation is not so rare, 10% of the cases referred to us for diplopia in 3 years. The diagnosis of skew deviation should be entertained when vertical diplopia cannot be explained by pathology of extraocular muscles, peripheral or central cranial nerve III or IV palsies, myasthenia, or orbital pathology. Prognosis for recovery in patients with skew deviation is good. 70% will recover, after a median time of 7.5 months. Surgery should be postponed at least for 12 months.

Dynamic MRI of cerebrospinal fluid flow in endoscopic percutaneous ventriculostomy

Endoscopic percutaneous ventriculostomy (EPV) is a new technique to restore the flow of the cerebrospinal fluid (CSF) to the basal cistern in patients with non-communicating hydrocephalus (NCH). Cardiac gated MRI techniques have been applied to demonstrate normal and abnormal CSF flow in humans. The aim of this study was to evaluate the ability of a new multislice spin echo dynamic MRI technique and amplitude and phase reconstruction to demonstrate the impairment of CSF flow through the aqueduct preoperatively and to assess the patency of the ventriculostomy after surgery. Thirteen patients with NCH were studied with dynamic MRI before and after EPV using multiple sagittal multislice gated SE acquisitions to demonstrate the CSF flow. Nine patients were clinically improved by EPS, two remained unchanged and two deteriorated. The permeability of the ventriculostomy was confirmed in all patients. We think that MRI flow studies are useful to demonstrate the site of impairment of CSF flow and its aetiology preoperatively, and to assess the permeability of the ventriculostomy after surgery in a non invasive way.

Bihippocampal damage with emotional dysfunction: impaired auditory recognition of fear

A right-handed man developed a sudden transient, amnestic syndrome associated with bilateral hemorrhage of the hippocampi, probably due to Urbach-Wiethe disease. In the 3rd month, despite significant hippocampal structural damage on imaging, only a milder degree of retrograde and anterograde amnesia persisted on detailed neuropsychological examination. On systematic testing of recognition of facial and vocal expression of emotion, we found an impairment of the vocal perception of fear, but not that of other emotions, such as joy, sadness and anger. Such selective impairment of fear perception was not present in the recognition of facial expression of emotion. Thus emotional perception varies according to the different aspects of emotions and the different modality of presentation (faces versus voices). This is consistent with the idea that there may be multiple emotion systems. The study of emotional perception in this unique case of bilateral involvement of hippocampus suggests that this structure may play a critical role in the recognition of fear in vocal expression, possibly dissociated from that of other emotions and from that of fear in facial expression. In regard of recent data suggesting that the amygdala is playing a role in the recognition of fear in the auditory as well as in the visual modality this could suggest that the hippocampus may be part of the auditory pathway of fear recognition.

Development of a cavernous malformation of the brain

We report the appearance of a cavernous malformation associated with a developmental venous anomaly in a young boy 3 years after radiation therapy for a posterior fossa medulloblastoma. The presence of a stenosis of the venous drainage of the anomaly led us to postulate that venous restrictive disease, induced by radiation therapy, resulted in increased venous pressure and caused the formation of the cavernous malformation.

Post-traumatic mutism in children: clinical characteristics, pattern of recovery and clinicopathological correlations

Among the numerous clinical syndromes observed after severe traumatic head injury, post-traumatic mutism is a disorder rarely reported in adults and not studied in any detail in children. We report seven children between the ages of 3 1/2 and 14 years who sustained severe head injury and developed post-traumatic mutism. We aim to give a precise clinical characterization of this disorder, discuss differential diagnosis and correlations with brain imaging and suggest its probable neurological substrate. After a coma lasting from 5 to 25 days, the seven patients who suffered from post-traumatic mutism went through a period of total absence of verbal production lasting from 5 to 94 days, associated with the recovery of non-verbal communication skills and emotional vocalization. During the first days after the recovery of speech, all patients were able to produce correct small sentences with a hypophonic and monotonous voice, moderate dysarthria, word finding difficulties but no signs of aphasia, and preserved oral comprehension. The neurological signs in the acute phase (III nerve paresis in three of seven patients, signs of autonomic dysfunctions in five of seven patients), the results of the brain imaging and the experimental animal data all suggest the involvement of mesencephalic structures as playing a key role in the aetiology of post-traumatic mutism.

Face recognition and postero-inferior hemispheric lesions

Two patients with severe and lasting prosopagnosia were studied for visuo-cognitive functions and anatomo-clinical correlations. Both patients were deficient in recognizing familiar faces and items of previously well known categories (plants and fish for patient 1, mountains for patient 2). Patient 2, but not patient 1, was also deficient for matching of unknown faces. Patient 1, but not patient 2, was achromatopsic. Both patients had bilateral symmetrical lesions. Patient 1 had a lesion of the inferior occipito-temporal cortex, including inferior parts of early stage visual areas. Patient 2 had a lesion of the inferior temporal and fusiform gyri anterior to the early stage visual areas. When compared in Talairach space, the lesions of both patients had minimal overlap. Thus, severe and lasting prosopagnosia was associated with two almost exclusive lesion sites in the postero-inferior part of the hemispheres. Comparison between activation studies of face processing (by others) and our lesion study uncovered several paradoxes. Lesions of regions involved in a given task in normal subjects do not produce a deficit in this task, as shown here for gender discrimination and partially for face matching. Conversely, lesions of a region not specifically involved in a given task in normal subjects can produce a deficit in the task, as shown here for face identification.

Magnetic resonance detection of myelodysplasia in children with Currarino triad

PURPOSE

To evaluate the role of MRI in the detection of myelodysplasia in children with Currarino triad.

MATERIALS AND METHODS

Six patients (two girls, four boys, aged 7 months-14 years, mean age 6 years) were studied with MRI, voiding cystourethrogram and barium enema or fistulography. CT and ultrasonography were also performed in two patients.

RESULTS

All patients presented with partial agenesis of the sacrum. Three patients suffered from an intermediate form of anorectal malformation (ARM) and three had a high form of ARM. The presacral masses consistent with Currarino triad included anterior meningocoele in three patients, lipoma in two patients and anterior lipomeningocoele in one patient. MRI diagnosed tethering of the spinal cord in four of six patients. The tethering of the spinal cord was due to a lipomeningocoele in one patient, an intradural lipoma in one patient and a lipoma of the filum in two patients.

CONCLUSION

The association of Currarino triad with tethered spinal cord seems more common than generally reported in the literature. Preoperative MRI of the lumbosacral spine is essential to detect significant myelodysplasia in all patients with Currarino triad.

Lemierre's syndrome in children: high-resolution CT and color Doppler sonography patterns

Lemierre's syndrome is an anaerobic sepsis occurring after oropharyngeal infection in healthy teenagers and young adults. We report two cases of adolescent girls suffering from Lemierre's syndrome studied with cervical color Doppler ultrasonography (CDUS), cervicothoracic helical CT, and high-resolution CT (HRCT) scanning. In both patients, HRCT allowed a good depiction of multiple cavitated pulmonary nodules of various sizes suggestive of this entity and was able to detect small or peripheral nodules. CDUS helped to pinpoint the extent of thromboses of the internal jugular vein demonstrated by CT. CDUS and HRCT should be performed as early as possible to confirm and treat this life-threatening condition.

[Spontaneous intracranial hypotension syndrome]

Spontaneous intracranial hypotension is a rare but well known entity first described by the German neurosurgeon Schaltenbrand. We report the clinical and radiological findings of four patients (2 males, 2 females, mean age 55 years) presenting with this clinical entity and peculiar constant MRI findings. Intense postural headache was present in all patients together with a very low CSF pressure at lumbar tap although none of the patients had any history of recent lumbar puncture, spinal or cerebral surgery or cranio-cervical trauma. MRI revealed in all patients an intense meningeal enhancement and thickening which was most prominent on the dural side of the subdural space. The ventricular system was thin, presenting almost like slit ventricules. A downward shift of the cerebellar tonsils and hemorrhagic subdural collections were also observed in two patients. Biopsy of meninges performed in two patients showed fibrosis of the leptomeninges together with signs of old hemorrhage in one case. We postulate that histologic and radiologic changes are due to chronic subdural bleeding in relation with abnormal displacement of the nervous structures due to intracranial hypotension. The underlying cause of spontaneous intracranial hypotension is rarely established and the course of the disease is benign. Some authors have advocated to perform isotopic cysternography in search for a CSF leak, particularly in the spine, that could be surgically corrected. No such investigation has been conducted yet in our patients because the spontaneous evolution has been mostly favorable.

[Magnetic resonance angiography in vertebro-basilar ischemic accidents]

This study evaluates the use of MR angiography in the diagnosis of vertebrobasilar stroke. The MRI/MR angiography and clinical presentation of 50 unselected adult patients who presented with ischemic symptoms in the vertebrobasilar territory (10 TIAs, 40 strokes) were prospectively evaluated. Conventional T1 and T2-spin echo sequences were obtained for evaluation of the brain parenchyma, with gadolinium injection in 41 cases and 3D time-of-flight MR angiography in all patients. Data were reconstructed with a maximal intensity projection algorithm and displayed in 3D. Arterial and parenchymal lesions and clinical data were correlated. MR angiography showed intracranial vertebrobasilar lesions in 30 patients (5 stenosis or occlusion of a vertebral artery, 17 stenosis or occlusion of the basilar artery, 6 stenosis of arterial branches of the basilar artery, 10 dolichoectasia of the basilar artery). 7 patients had multiple lesions. Recognized etiologies of the strokes were: 23 vertebrobasilar lesions, 16 nonvertebrobasilar causes, 6 mixed (vertebrobasilar and associated alternative causes) cases, while 5 cases had no recognized cause of stroke. Our study demonstrates a high incidence of intracranial arterial lesions in patients suffering from vertebrobasilar stroke and suggests that MRA can help in a noninvasive way to determine the origin of vertebrobasilar strokes.