[Interventional neuroradiologic procedures]

Intracranial aneurysms, cervical carotid stenosis and acute cerebral ischemia constitute the three main and more frequent diseases in which the endovascular approach is considered a valuable alternative to the surgical or pharmacologic treatment. With the introduction of balloon assistance techniques, even intracranial large neck aneurysms can be currently suitable to endovascular treatment. Stent angioplasty is widely used in whole Europe in the treatment of cervical carotid artery stenosis. Mechanical endovascular embolectomy techniques are actually available to be used alone or in combination with pharmacologic thrombolysis in the treatment of acute cerebral ischemia. This article discuss on the new technical possibilities concerning the endovascular approach in these aforementioned diseases.

[Percutaneous vertebroplasty]

Although vertebroplasty was initially a treatment of vertebral haemangioma or metastases, this procedure is now frequent option to the treatment of osteoporotic vertebral fractures. In this review article, we will discuss the indication, the techniques and the follow-up of the vertebroplasty. This is a risky procedure, which should be performed by experimented physicians working with high-resolution fluoroscopic equipments, by biplane fluoroscopy, to reduce the risk and irradiation to the patient. According to the available follow-up studies, there is clear evidence of a strong improvement of quality of life after vertebroplasty by rapid decreasing of back pain at least during the first six months. Other new studies will analyze the long-term follow-up after vertebroplasty.

Endovascular coiling compared with surgical clipping for the treatment of unruptured middle cerebral artery aneurysms: an update

OBJECT

In 1999 we reported that 94% of unruptured middle cerebral artery (MCA) aneurysms managed prospectively between 1993 and 1997, according to a protocol favoring endovascular coiling, were best treated by surgical clipping. The goal of the current study was to delineate the most appropriate treatment option for unruptured MCA aneurysms today, considering the technical advances in imaging and in endovascular treatment.

METHODS

35 consecutive patients harboring 40 unruptured MCA aneurysms were treated between 1997 and December 2000. Patients with unruptured cerebral aneurysms are managed prospectively according to the same protocol as reported previously [1]: the primary treatment recommendation is endovascular packing with Guglielmi detachable coils (GDCs). Surgical clipping is recommended after failed attempt at coil placement or in the presence of angioanatomical features that contraindicate that type of endovascular therapy.

RESULTS

One unruptured MCA aneurysm was treated by endovascular embolization, 37 unruptured MCA aneurysms were clipped, whereas 2 unruptured MCA aneurysms were trapped with simultaneous extracranial-intracranial revascularization. Postoperative angiography revealed complete exclusion of all aneurysms. Preservation of vascular permeability was demonstrated in all clip-reconstructed aneurysms, despite arterial branches frequently originating from the aneurysmal base. Cerebral revascularization of the distal MCA was successful in the 2 patients with giant aneurysms. None of the patients presented permanent disabling complications from the treatment of the unruptured MCA aneurysm.

CONCLUSION

Despite major technical advances in imaging and in endovascular treatment of cerebral aneurysms, surgical clipping still is the most efficient treatment for unruptured MCA aneurysms at the beginning of the new millennium.

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.

[Cerebral venous thrombosis after lumbar puncture and intravenous steroids in two patients with multiple sclerosis]

Two patients affected with a multiple sclerosis developed cerebral venous thrombosis after lumbar puncture and treatment with intravenous methylprednisolone. In one case, the course was favorable. The second patient died in spite of intracerebral thrombolysis. The autopsy confirmed the diagnosis of cerebral venous thrombosis and multiple sclerosis. We discuss the relationship between lumbar puncture, steroid treatment and cerebral venous thrombosis.

Endovascular coil placement compared with surgical clipping for the treatment of unruptured middle cerebral artery aneurysms: a consecutive series

OBJECT

The goal of this study was to delineate the angioanatomical features that determine whether a patient with an unruptured middle cerebral artery (MCA) aneurysm is treated using endovascular coil placement or surgical clipping.

METHODS

Thirty consecutive patients harboring 34 unruptured MCA aneurysms were evaluated. Patients with unruptured aneurysms are managed prospectively according to the following protocol: the primary treatment recommendation is endovascular packing with Guglielmi detachable coils (GDCs). Surgical clipping is recommended after failed attempts at coil placement or in the presence of angioanatomical features that contraindicate that type of endovascular therapy. Of 34 unruptured MCA aneurysms, two (6%) were successfully embolized and 32 (94%) were clipped. Of these 32 surgically treated aneurysms, in 11 (34%) an attempt at GDC embolization had failed, whereas in 21 (66%) primary clipping was performed because of unfavorable angioanatomy. Of the 13 aneurysms treated endovascularly, two (15%) were successfully excluded, whereas GDC treatment failed in 11 (85%). An unfavorable dome/neck ratio (< 2) and an arterial branch originating at the aneurysm base were the reasons for embolization failure.

CONCLUSIONS

Careful evaluation of the angioanatomy of unruptured aneurysms allows selection of the most appropriate treatment. However, for unruptured MCA aneurysms, surgical clipping appears to be the most efficient treatment option. Series of unruptured aneurysms are ideal for comparing treatment results.

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.

Meglumine gadoterate: a new safe radiocontrast medium for endoscopic retrograde cholangiopancreatography?

The radiocontrast substance meglumine gadoterate (MG) is used in magnetic resonance imaging. It is characterized by its low rate of adverse drug reactions. In an open study we tested whether MG is useful in endoscopic retrograde cholangiopancreatography. The patients received in sequence MG and ioxotalamate. MG, in contrast to ioxotalamate, failed to visualize the proximal pancreatic and peripheral intrahepatic ducts. Thus, MG is not useful in routine endoscopic retrograde cholangiopancreatography. However, in patients with a history of severe allergic reactions to conventional contrast media, MG may be recommended when pathological findings of the extrahepatic bile duct or the area of the pancreatic head are suspected.

Parietal kinetic ataxia without proprioceptive deficit

A patient with acute onset "classic" cerebellar ataxia of the right arm without clinically detectable deep sensory loss is reported, in relation to an acute posterior parietal infarct. Wild back and forth swaying of the arm, giving away, or worsening by suppression of vision were not seen. The lesion involved area 5, parts of area 7, the angular gyrus, the middle and posterior parieto-occipital gyri, and posterior parts of the superior and middle temporal gyri. The paracentral lobule, commonly thought to be responsible for parietal ataxia, was spared. Thus posterior parietal lesions can mimick cerebellar ataxia, possibly by severing specific projections to the ventrolateral thalamic nuclei. On the basis of previous studies in primates, the superior parietal gyrus may play a major part in the ataxia presented by this patient.

Meningiomas involving the anterior clinoid process

We report a series of 34 clinoidal meningiomas treated surgically and analyse the results according to cavernous sinus involvement. Fifteen tumours extended into the cavernous sinus. Only four of these could be resected completely, and global outcome was improved or stable in 10 cases. Overall, 20 tumours had a total resection and 14 had a partial resection. Complete removal of the sphenoid wing, including the anterior clinoid and part of the planum sphenoidale, allows early devascularization of the tumour and minimizes brain retraction when associated with resection of the zygomatic arch. The most frequent postoperative complication was transient CSF leak, occurring in three patients. Two patients died postoperatively, and three suffered permanent complications. There was no recurrence after total removal, but five patients showed signs of progressive tumour growth after partial removal, treated by radiotherapy in three and by surgery in two cases. Twenty patients showed preoperative visual impairment. Outcome of vision was improved or stable in 13 (68%) and worse in six cases (32%). We suggest that progressive visual impairment should lead to aggressive surgical treatment, especially when complete resection of cavernous sinus involvement can be performed.

CV 205-502 treatment of macroprolactinomas

CV 205-502, a benzoquinoline, is a new nonergot dopamine agonist compound which has been shown to be effective in lowering PRL levels in normal volunteers and in hyperprolactinemic women. Seven patients (4 men and 3 women) presenting with hyperprolactinemia due to macroprolactinoma were treated with CV 205-502 given as a single daily dose at bedtime for up to 12 months. Six patients presented with impaired gonadal function and 2 with galactorrhea. All patients but one had previously been treated with bromocriptine and 4 had undergone pituitary surgery (3 with complementary radiotherapy). Six patients responded within a few weeks to CV 205-502 treatment, PRL levels being normalized (4 patients, 0.075 to 0.150 mg/day) or significantly reduced to restore normal gonadal function (2 patients, 0.225 mg/day). The seventh patient, who had previously been resistant to bromocriptine, also failed to respond to CV 205-502 treatment even after high doses (0.450 mg/day). Under CV 205-502 treatment, follow-up with magnetic resonance imaging revealed a reduction in tumor size of up to 52% of the initial volume in the "PRL-responders" whereas an increase in tumor size was observed in the "nonresponding" patient. No biological disturbance appeared during CV 205-502 treatment and the drug tolerance was very good, with mild side-effects being reported by only 2 patients. In conclusion, CV 205-502, given once daily, appears to be a safe and effective alternative to other dopamine agonists in the treatment of macroprolactinoma, by reducing hyperprolactinemia and tumor size. It was, however, of no benefit in the one patient whose macroprolactinoma had been resistant to bromocriptine.

Loss of psychic self-activation with bithalamic infarction. Neurobehavioural, CT, MRI and SPECT correlates

Two patients with bilateral thalamo-mesencephalic infarct in the paramedian territory developed vertical gaze dysfunction and marked behavioural changes, in the absence of significant motor inability and formal neuropsychological impairment. While they were physically and emotionally active before stroke, they became apathetic, aspontaneous, indifferent, and seemed to have lost motor and affectic drive, as well as the need itself for any psychic activity. However, this mental and motor inertia was reversible when the patients were repeatedly stimulated by another person. This need for constant external programming, together with a lack of emotional reactivity, made the patients resemble robots. CT and MRI suggested involvement of the dorsomedial and midline nuclei of the thalamus, and SPECT showed remote frontomesial hypoperfusion. A disturbance of the striatal-ventral pallidal-thalamic-frontomesial limbic loop is suggested by previous reports of a similar "loss of psychic self-activation", "pure psychic akinesia", or "athymhormia" with bipallidal, bistriatal, or subcortical bifrontal lesions.

[Supratentorial intracerebral hemorrhage]

The data were reviewed of 76 patients with supratentorial intracerebral hemorrhage, including 38 lobar (LH) and 38 basal ganglion (BGH) hemorrhages. Our aim was to define the clinical and tomodensitometric profiles of the two lesions. Men seem to be at higher risk of BGH and women more frequently of LH. Among the risk factors and causes, only chronic hypertension proved to be clearly associated with BGH. Wide variability of clinical course was observed. However, LH was associated more frequently with headache, initial seizure and show installation over more than 12 hours. CT sections revealed association of intraventricular hemorrhage with BGH. No difference in short term prognosis was found between LH and BGH.

Primitive megalencephaly in children: natural history, medium term prognosis with special reference to external hydrocephalus

We studied 74 children with primitive megalencephaly retrospectively with attention directed to familial megalencephaly, birth history, enlarged pericerebral subarachnoid space (SAS) (idiopathic external hydrocephalus), head and statural growth dynamics, developmental and school prognosis, morphological findings and development of subdural haematoma. In the megalencephalic children, no significant differences were found between those with normal or those with enlarged pericerebral SAS. Out of 62, 31 children (50%) were already megalencephalic at birth. Of 74, 37 children (50%) showed variable degrees of developmental delay which in 18 was transient. Eight out of 74 were mentally retarded. Of 52 children at school age, 42 attend normal schools and 10, of whom 7 are mentally retarded, attend special schools. Three children showed subdural haematoma resulting from apparently minor trauma or occurring spontaneously. We suggest that idiopathic external hydrocephalus represents a variant of primitive megalencephaly with transient increase of intracranial pressure and that it could predispose to the development of idiopathic (spontaneous or non-traumatic) subdural haematoma.

Loose bodies of the temporomandibular joint: arthrographic and CT findings in five patients

We report a series of five patients with symptoms of internal derangements of the temporomandibular joint (TMJ), in whom intraarticular loose bodies were found. Three patients with a single loose body had osteochondrosis dissecans of the temporal part of the joint; one trauma patient had two loose bodies (including a bony and a meniscal fragment). The fifth patient presented with a loose meniscal fragment and a complete meniscal rupture, complicating a long-lasting TMJ dysfunction due to non-reducible anterior meniscus displacement. The diagnosis was made by arthrotomography (3 cases), CT (one case) and by CT and arthrotomography (one case). Surgical confirmation was obtained in all patients. Arthrography and CT are accurate in diagnosing TMJ loose bodies; characteristic findings disclosed in both examinations are described.

[Traumatic dissection of the internal carotid artery]

Two patients with posttraumatic dissection of the internal carotid artery were referred to the neurosurgical department with secondary neurological deterioration following a minor head injury with concussion. Both developed aphasia and right hemiparesis during the first few hours after the accident; one patient also had right focal seizures. On admission, both were only mildly lethargic, which contrasted with the severity of the focal neurological signs. Early CT scan was normal in both cases, whereas cerebral blood flow (CBF) studies by single photon emission computerized tomography (SPECT) with Tc-HMPAO (Ceretec) showed perfusion defects in the region supplied by the left middle cerebral artery (MCA), correlating with the clinical picture. Doppler sonography disclosed pathologic flow patterns, and carotid angiography demonstrated dissection of the internal carotid artery, in one patient on the left only and in the other bilaterally, with embolic occlusion of a branch of the left MCA in the latter case. Clinical features, pathogenesis, diagnostic workup and possible treatment (medical, as in our two cases, versus surgical) of this rare pathology are briefly reviewed.

Pancreatic insuloma causing Cushing's syndrome

The advent of new diagnostic procedures such as petrosal venous sampling and CRF testing has improved the possibilities of precise location of the site of hormonal overproduction in Cushing's syndrome. We report on a case of ectopic ACTH-dependent Cushing's syndrome in which the use of such techniques helped to locate the tumor. A 45-year-old woman with definite ACTH-dependent Cushing's syndrome was referred to our clinic for evaluation. ACTH, cortisol and urinary 17OHCS failed to suppress on high dose dexamethasone oral administration. Computerized tomography showed bilateral adrenal hyperplasia and an empty sella turcica. ACTH and cortisol did not increase after CRF administration. Staged caval system catheterism via both femoral veins up to the inferior petrosal sinuses, including after CRF administration, demonstrated no ACTH gradient between staged samples and simultaneous peripheral venous blood. This suggested a tumor drained by the portal system. An abdominal ultrasonography demonstrated a pancreatic mass, that was surgically excised and appeared as a benign islet cell tumor. Portal vein ACTH promptly decreased after tumor excision and postoperative peripheral cortisol and ACTH were normal. On immunostaining the tumor cells proved to be positive for ACTH.

Thalamic infarcts: clinical syndromes, etiology, and prognosis

We studied forty patients with CT-proven thalamic infarcts without involvement of the superficial territory of the posterior cerebral artery. The delineation into four arterial thalamic territories (inferolateral, tuberothalamic, posterior choroidal, paramedian) corresponded clinically to four different syndromes. The most common etiologies were lacunar infarction, large artery atherosclerosis with presumed artery-to-artery embolism, cardioembolism, and migrainous stroke. We found no risk factor other than age or oral contraceptive use in six patients. One patient died in the acute phase. During follow-up (45.6 months), the stroke or death rate was 7.4% per year. Delayed pain developed in three patients and abnormal movements in three. Late disability was mainly secondary to persisting neuropsychological dysfunction (thalamic dementia).

Migraine stroke

Because the cause of stroke during migraine is not known, we studied 22 (17 females, 5 males; mean age, 32.7 years) classic migraine sufferers who had an ischemic stroke during an attack of migraine, with CT, Doppler ultrasound, cerebral angiography, and two-dimensional echocardiography. We found no cardiac or arterial lesion in 91% of the patients, as compared with 9% of age- and sex-matched migraineurs with stroke remote from a migraine attack and 18% of age- and sex-matched nonmigraineurs with stroke (p less than 0.00001). Mitral valve prolapse, arterial dissection, and vasospasm were not significant causes of stroke during migraine. These patients had longer previous attacks of migraine and their infarct was more frequently in the territory involved during the attacks than the controls, supporting the hypothesis that a prolongation of the migrainous process beyond usual limits may explain most migraine strokes.

Leukoencephalopathy in patients with ischemic stroke

Thirty-one (16 women, 15 men; mean age 68 years) of 1,000 consecutive patients with an ischemic stroke investigated systematically with computed tomography (CT), Doppler, electrocardiography (ECG), and biological tests had a diffuse hypodensity of the cerebral hemispheric white matter on CT, a sign indicative of leukoencephalopathy. In 25 of the 31 patients, the acute infarct was deep. Leukoencephalopathy was more frequent in patients with a deep infarct (8%) than in patients in whom the cortex was involved (0.8%) (p less than 0.01). A history of progressive intellectual impairment (23%) and the finding of a mild or moderate impairment, or severe dementia (84%) were more frequent in study patients (p less than 0.05) than in 31 sex- and age-matched controls with an acute infarct of same size and topography but without leukoencephalopathy. A history of hypertension (81%) and high blood pressure on admission (166 +/- 19/96 +/- 12 mm Hg) were the most common risk factors and were more frequent in study patients (p less than 0.05) than in controls. On the other hand, study patients had a greater than or equal to 50% stenosis or occlusion of the carotid artery (13%) less often than controls (35%) (p less than 0.05). Diabetes (23%), elevated blood cholesterol (13%), hematocrit greater than 45% (23%), smoking (32%), and myocardial ischemia by history or ECG (45%) did not differ. These findings suggest that hypertension may be more strongly associated with leukoencephalopathy than with deep infarcts. In acute stroke patients, leukoencephalopathy on CT should not be considered a fortuitous finding.

Optico-cerebral syndrome: simultaneous hemodynamic infarction of optic nerve and brain

Three (0.5%) of 612 patients with an acute ischemic stroke in the carotid territory also had ipsilateral optic nerve infarction. They had unilateral or bilateral internal carotid artery occlusion and reversed flow in the ophthalmic artery. Hemodynamic infarction was suggested by triggering by a drop in blood pressure, decreased ophthalmic artery flow and perfusion pressure, and cerebral infarction in a watershed area. The "optico-cerebral syndrome" suggests internal carotid artery occlusion with hemodynamic disturbances. In carotid disease, monocular blindness may be due to an optic nerve lesion sparing the retina.

Direct coronal computed tomography of the lumbar spine: a new technical approach in supine position

Computed tomography (CT) was carried out on 46 subjects with L5-S1 disk hernia. All the patients had a L5-S1 angle equal or greater than 40 degrees. Coronal sections of the disk were obtained with a rostral angulation of the gantry, having placed the lumbar spine in a hyperlordotic position. Results are discussed and compared with those obtained from para-axial transverse sections and multidirectional reformated images.

MRI of angiographically occult vascular malformations

Eleven patients with 15 angiographically occult arteriovenous malformations were studied by magnetic resonance (MR) imaging and computed tomography (CT). Five patients had biopsy proof; six were clinically diagnosed from the long-term clinical follow-up (more than 3 years) and imaging features. Of the 15 lesions, 11 were recognized by both CT and MR. Each method was falsely negative for two lesions. The most useful contribution of MR in the characterization of angiographically occult arteriovenous malformations was the depiction of hemorrhagic foci in 12 of 13 lesions seen on MR. High-attenuation foci indicative of hematomas were seen in only five lesions on CT; the rest were iso- or hypoattenuating. CT detected two very small lesions, in one case as punctate foci of enhancement and in the other as punctate calcification, that were not seen with MR. MR complements CT in characterizing angiographically occult arteriovenous malformations and in distinguishing them from similar-appearing lesions, in particular, small neoplasms. However, when such lesions are seen with only focal calcification and subtle enhancement on CT, routine MR may miss them.

Spin-echo MR imaging of intracranial hemorrhage

This retrospective study was performed to describe the appearance of intracranial hemorrhagic lesions on magnetic resonance (MR) imaging at 0.35 tesla using the spin-echo technique, and define the present clinical role of MRI in this particular pathology. Forty-eight examinations of forty-three patients with forty-seven intracranial hemorrhagic lesions (39 true hematomas and 8 hemorrhagic lesions mixed with other tissues) were reviewed for this study. Comparative CT studies were available for all the patients. In our limited experience with acute hematomas (less than 3 days old), low or isointense signal was seen with a short TR (0.5 s), but a relative increase in signal intensity was observed with a long TR (2.0 s). This appearance of acute hematoma was not specific. Chronic hematomas (more than 3 days old) were imaged as foci of bright signal intensity on both short and long TR. This pattern was characteristic of chronic hematoma. With a short TR (0.5 s), two hemorrhagic lesions (5 and 7 days old) were displayed as an isointense signal surrounded by a rim of high intensity signal. This peripheral zone most likely represented liquefaction at the clot's periphery and the initial formation of methemoglobin. T1 and T2 relaxation times were found to be very long for acute hematomas (first two days). T1 values of chronic hematomas (more than 3 days old) were comparatively short and in the same range as T1 of white matter. T2 values of chronic hematomas decreased also but remained very long.

MR imaging of extracranial hematomas: comparison with CT

Thirty MR examinations of twenty-five patients with extracranial hemorrhagic lesions were reviewed. Comparative CT studies were available in 11 patients. The acute hematomas (less than 3 days old) showed intermediate intensity on the short TR (0.5 sec.) and increased in signal intensity on the long TR (2.0 sec.). The MR appearance of acute hematoma was not specific. Clot (more than 3 days old) demonstrated an intermediate intensity on the short TR and increased markedly in signal intensity on the long TR equaling the signal intensity of fat. Serum (more than 3 days old) was imaged as a high intensity lesion on both short and long TR. It is concluded that MR can be very useful for the differential diagnosis of subacute and chronic hemorrhagic lesions from other lesions.

[Cerebellar infarct. Clinical presentation and x-ray computed tomography of the brain]

A series of 12 patients with cerebellar infarcts diagnosed by computerized tomography are reviewed. The clinical features of cerebellar infarctions cover a wide spectrum, mimicking symptoms and signs from an acute labyrinthitis to a rapidly expanding posterior fossa mass lesion with brain stem and cerebral dysfunction. Two patients were asymptomatic and three showed signs of cerebellar dysfunction only. Three patients had evidence of brain stem dysfunction with cranial nerve palsies accompanying the cerebellar deficit. Two presented a pseudovestibular form with sudden onset of nausea, vomiting, rotary dizziness and ataxia. A pseudotumoral form with intracranial hypertension was found in two cases, in which softening tissue acts as a rapidly expanding posterior foss mass lesion. It is difficult to identify the exact artery involved in a cerebellar infarct because of the collateral circulation and connections between the three major arteries. Atherosclerosis and general decrease in blood flow can be regarded as the most likely factors precipitating focal cerebellar infarction. Surveillance is necessary during the first days with anti-edematous therapy. Rapid deterioration of consciousness should be considered a sign of increasing intracranial pressure progressing with the development of hydrocephalus. If necessary, surgical decompression by external drainage or by direct access to the posterior fossa can be carried out.

MR technology: effect of even-echo rephasing on calculated T2 values and T2 images

In multiple spin-echo image sequences of blood flow, the "even-echo" phenomenon produces an absolute increase in signal magnitude from first- to second-echo images of normal vessels harboring slow flow. Distinguishing this from the apparent relatively high signal intensity seen on second-echo images in pathologic foci of stationary tissue is important to the diagnostician. Selected case material containing two tissue types was reviewed retrospectively: tissues known to harbor slow flow, such as normal veins and venous sinuses and vascular malformations, and tissues that have long transverse (T2) relaxation times and appear as intense structures on second-echo images, such as neoplasms, infarcts, and regions of demyelination. Calculations of T2 parameters were made by computer for defined regions of interest. T2 images were also generated. Visual inspection of the acquired images did not reliably distinguish increased intensity due to even-echo rephasing from the relative changes between adjacent tissues seen on second-echo images. More definitive differentiation of the even-echo phenomenon was provided by calculated values of T2 and computer-synthesized T2 images representing acquired intensity data of two-echo sequences. The synthesized images were especially useful when stationary tissue with lengthened T2 values was adjacent to or in proximity to vessels or vascular lesions. A five spin-echo image sequence was valuable for separating slow flow from stationary tissue by a technique of synthesizing T2-difference images using three consecutive echoes.

Intracranial vascular malformations: MR and CT imaging

Twenty-four patients with 29 cerebrovascular malformations were evaluated with a combination of computed tomography (CT), angiography, and magnetic resonance (MR) imaging. Characteristics of the malformations on MR images were reviewed retrospectively, and a comparative evaluation of MR and CT images was made. Of 14 angiographically evident malformations, 13 intra-axial lesions were detected on both CT and MR images, and one dural malformation gave false-negative results on both modalities. The appearance of parenchymal lesions on MR images closely mirrored characteristic CT findings. Calcific foci were difficult to separate from vessels on both images. Clot was more easily identified on MR images. In the detection of 15 angiographically occult malformations, CT proved more sensitive when focal calcification was the only evidence of their presence. MR study failed to detect two small supratentorial lesions evidenced by faint calcifications on CT scans. In two patients, MR images showed small hemorrhages not detectable by CT, and MR provided strong evidence for the diagnosis of hematoma for 12 lesions. Angiographically evident malformations have a highly characteristic appearance on MR images. MR may be more sensitive than CT in the detection of small hemorrhagic foci associated with cryptic arteriovenous malformations and may add specificity in the diagnosis of occult malformations in some cases, but MR is less sensitive than CT for the detection of small calcified malformations.

Carotid artery occlusion. Delayed embolic ischemia from vertebrobasilar atheromatosis

We described a patient with occlusion of an internal carotid artery in whom delayed transient ischemic attacks distal to the occlusion alternated with vertebrobasilar attacks. Microembolization through the vertebrobasilar system was emphasized because the middle cerebral artery was filled by the basilar artery through the posterior communicating artery, and one vertebral artery showed important atheromatous emboligenic changes. Other mechanisms appeared improbable because of the type of collateral circulation and absence of other associated emboligenic changes and hemodynamic phenomena.