Neuromyelitis optica with hypothalamic involvement

We describe two cases of neuromyelitis optica (NMO) with clinical and radiographically confirmed features of hypothalamic involvement, in the absence of other parenchymal brain lesions. Their course is otherwise typical of Devic’s form of NMO. A review of the literature identifies additional cases of NMO in which clinical features attributable to under-recognized dysfunction of the hypothalamic-pituitary axis were present. We propose that the currently accepted criteria for the diagnosis of NMO could be revisited to recognize the possibility of lesions developing within hypothalamic structures.

Amyloid-related imaging abnormalities-haemosiderin (ARIA-H) in patients with Alzheimer's disease treated with bapineuzumab: a historical, prospective secondary analysis

BACKGROUND

Amyloid-related imaging abnormalities due to haemosiderin deposition (ARIA-H) occur in patients with mild to moderate dementia due to Alzheimer's disease (AD) and have been reported with increased incidence in clinical trials of amyloid-lowering therapies under development for AD.

OBJECTIVE

Our objective was to explore the relationship between the incidences of ARIA-H during treatment with placebo and different doses of bapineuzumab, a humanised monoclonal antibody directed against amyloid β.

METHODS

Two neuroradiologists independently reviewed 2572 GRE/T2* MRI sequences from 262 participants in two phase two clinical trials of bapineuzumab and an open-label extension study. Readers were blinded to the participant's therapy, APOE ε4 genotype and medical history.

RESULTS

Several risk factors for small ARIA-H <10 mm (microhaemorrhages) were identified: APOE ε4, bapineuzumab treatment, pre-existing small ARIA-H and use of antithrombotics. The HR (95%CI) for incident ARIA-H <10 mm associated with the number of APOE ε4 alleles was 11.9 (3.3 to 42.5) for 2 versus no alleles and 3.5 (1.0 to 12.0) for 1 versus no allele. The HR for bapineuzumab therapy was 3.5 (1.0 to 12.0); for the presence of baseline ARIA-H <10 mm, it was 3.5 (1.6 to 7.8), and for the use of antithrombotic agents it was 2.2 (1.0 to 4.8). The incidence rate for ARIA-H <10 mm was elevated only in the initial 6 months of active treatment and declined after this interval to a rate similar to that observed in the group treated with placebo.

CONCLUSIONS

ARIA-H represents a spectrum of MRI findings due to haemosiderin deposition that appears to be related to impaired vascular integrity. The increased risk for ARIA-H associated with APOE ε4 allele frequency, pre-existing ARIA-H, treatment with bapineuzumab and use of antithrombotic agents provides additional support for this hypothesis of loss of integrity of cerebral vessels due to amyloid burden.

TRIAL REGISTRATION

NCT00112073 and NCT00606476.

Multi-level Split Cord Malformation: Do We Need a New Classification?

Split cord malformations (SCMs) are thought to be rare abnormalities representing 3.8-5% of all spinal cord anomalies. The prevalence is estimated to be 1 in 5499 live births (0.02%), with a slight female predominance (1.3:1). Although the estimates of prevalence vary, Type I SCM occurs more frequently than Type II SCM. In this paper, we are reporting the clinical presentation and imaging findings of multi-level SCM in a 27-year-old male. A literature review of the embryological background of SCM and pathological hypothesis for this entity is provided. A systematic review has been conducted to identify multi-level SCM cases reported in the literature, followed by proposing a new classification system to further our understanding and management of SCMs.

Re-growth of a posterior inferior cerebellar artery aneurysm after resection of the associated posterior fossa arteriovenous malformation

Arteriovenous malformation (AVM)-related aneurysms have been described in the literature. Their behavior varies based on their location in relation to and the activity of the shunting through the index AVM. The intuitive expectation supported by numerous reports is that these aneurysms should regress if the AVM is excluded from the circulation. We describe a case of 46-year-old man who presented with a posterior fossa AVM with an aneurysm on the posterior inferior cerebellar artery feeding the AVM. The nidus of the AVM was successfully excluded by glue embolization, with initial regression of the PICA aneurysm on serial imaging. Five years after the endovascular treatment, the aneurysm showed significant re-growth necessitating endovascular coiling. This case presents the re-growth of an AVM-related aneurysm and emphasizes the importance of long-term follow-up of such aneurysms even if the AVM is completely excluded.

MR imaging features of amyloid-related imaging abnormalities

BACKGROUND AND PURPOSE

AD is one of the few leading causes of death without a disease-modifying drug; however, hopeful agents are in various phases of development. MR imaging abnormalities, collectively referred to as amyloid-related imaging abnormalities, have been reported for several agents that target cerebral Aβ burden. ARIA includes ARIA-E, parenchymal or sulcal hyperintensities on FLAIR indicative of parenchymal edema or sulcal effusions, and ARIA-H, hypointense regions on gradient recalled-echo/T2* indicative of hemosiderin deposition. This report describes imaging characteristics of ARIA-E and ARIA-H identified during studies of bapineuzumab, a humanized monoclonal antibody against Aβ.

MATERIALS AND METHODS

Two neuroradiologists with knowledge of imaging changes reflective of ARIA reviewed MR imaging scans from 210 bapineuzumab-treated patients derived from 3 phase 2 studies. Each central reader interpreted the studies independently, and discrepancies were resolved by consensus. The inter-reader κ was 0.76, with 94% agreement between neuroradiologists regarding the presence or absence of ARIA-E in individual patients.

RESULTS

Thirty-six patients were identified with incident ARIA-E (17.1%, 36/210) and 26 with incident ARIA-H (12.4%, 26/210); of those with incident ARIA-H, 24 had incident microhemorrhages and 2 had incident large superficial hemosiderin deposits.

CONCLUSIONS

In 49% of cases of ARIA-E, there was the associated appearance of ARIA-H. In treated patients without ARIA-E, the risk for incident blood products was 4%. This association between ARIA-E and ARIA-H may suggest a common pathophysiologic mechanism. Familiarity with ARIA should permit radiologists and clinicians to recognize and communicate ARIA findings more reliably for optimal patient management.

Volumetric measurement of vestibular schwannoma tumour growth following partial resection: predictors for recurrence

Vestibular schwannomas (VS) have a higher risk of recurrence following subtotal resection than following near-total resection. We measured tumor remnant growth volumetrically in an attempt to determine potential predictors for postoperative recurrence following subtotal resection. We reviewed the charts of patients who had undergone VS surgery between 1998 and 2007. Thirty patients had an incomplete resection. The principal outcome measure was change in tumor volume (TV) on serial imaging. At a median follow-up of 6.8 years, volumetric measurements showed that 12 patients (40%) developed further tumor growth, while 18 patients remained with stable residual disease. The median rate of growth was 0.53 cm(3)/year. Two-dimensional measurements confirmed growth in only eight of these patients. The postoperative residual TV correlated significantly with subsequent tumor growth (p = 0.038). All patients with residual volumes in excess of 2.5 cm(3) exhibited recurrence. On univariate analysis, only postoperative TV was significantly associated with growth. Median time to failure was 21.5 months. This is the first report of volumetric measurements of VS tumor growth postoperatively. Volumetric measurements appear to be superior to two-dimensional measurements in documenting VS growth and patients with residual tumors >2.5 cm(3) have a significantly higher rate of recurrence.

Imaging pattern of calvarial lesions in adults

Calvarial lesions often present themselves as clinically silent findings on skull radiographs or as palpable masses that may cause localized pain or soreness. This review aims to explore the radiographic, computed tomography (CT), and magnetic resonance imaging (MRI) characteristics of calvarial neoplastic, inflammatory, and congenital lesions that are common in adults in order to facilitate a structured approach to their diagnosis and limit the differential diagnosis. In addition to reviewing the literature, we reviewed the records of 141 patients of the Montreal Neurological Institute and Hospital with radiologically documented calvarial lesions between 2001 and June 2009. CT is ideal for detecting bony lesions and is helpful in precisely localizing a lesion pre-surgically. MRI is best at identifying intradiploic lesions before they affect the cortical tables and is able to establish extraosseous involvement, especially when paramagnetic contrast is employed.

Imaging in primary central nervous system lymphoma

Primary central nervous system (CNS) lymphoma (PCNSL) accounts for approximately 3% of all primary CNS tumors. Congenital or acquired immunodeficiency is the only established risk factor for PCNSL. Rates decreased slightly in the mid-1990s, concordantly with the decreasing rates of AIDS. However, the incidence has been increasing in the elderly immunocompetent population, and this trend seems to be independent of improvements in diagnostic techniques, and of overall trends in the incidence of brain tumors and systemic lymphomas. This study presents our experience with the imaging features of PCNSL. Computed tomography (CT) and magnetic resonance imaging (MRI) findings were reviewed in a series of 38 cases of pathologically proven PCNSL. The incidence rate of PCNSL was higher in men than in women (58% versus 42%). Mean age at presentation was 63 years; 120 lesions were demonstrated in the 38 patients, with a 53% frequency of tumor multiplicity. Both CT and MR mainly showed solitary or multiple well-defined round or oval-shaped mass lesions, typically hyperdense on unenhanced CT scans, iso to hypointense on T2 MR weighted images. These lesions also showed an increased signal intensity on diffusion-weighted images. Virtually all lesions enhanced after intravenous administration of contrastmedium. On (1)H-magnetic resonance spectroscopy ((1)H-MRS) most lesions presented increased Cho/Cr, Cho/NAA and lactate/Cr ratios when compared to normal gray matter. No changes in the imaging presentation have occurred over the past two decades, apart from lesions now being smaller at diagnosis. Our imaging findings are in agreement with the existing literature data and with the reported increasing trend of multifocal tumors. Our epidemiologic results add value to the existing evidence of increasing incidence rates among the immunocompetent elderly population.

Low-grade oligodendroglioma: an indolent but incurable disease? Clinical article

OBJECT

The authors reviewed their institutional experience with pure low-grade oligodendroglioma (LGO), correlating outcomes with several variables of possible prognostic values.

METHODS

Sixty-nine patients with WHO-classified LGOs were treated between 1992 and 2006 at the McGill University Health Center. Clinical, pathological, and radiological records were carefully reviewed. Demographic characteristics; the nature and duration of presenting symptoms; baseline neurological function; extent of resection; Karnofsky Performance Scale score; preoperative radiological findings including tumor size, location, and absence/presence of enhancement; and pathological data including chromosome arms 1p/19q codeletion and O-methylguanine-DNA methyltransferase promoter gene methylation status were all compiled. The timing and dose of radio- and/or chemotherapy, date of tumor progression, pathological finding at disease progression, treatment at time of disease progression, and status at the last follow-up were also recorded.

RESULTS

The median follow-up period was 6.1 years (range 1.3-16.3 years). The majority (78%) of patients presented with seizures; contrast enhancement was initially seen in 16 patients (25%). All patients had undergone an initial surgical procedure: gross-total resection in 27%, partial resection in 59%, and biopsy only in the remaining 13%. Fifteen patients received adjuvant radiotherapy. Data on O-methylguanine-DNA methyltransferase promoter gene methylation status was available in 47 patients (68%) and in all but 1 patient for 1p/19q status. Survival at 5, 10, and 15 years was 83, 63, and 29%, respectively. Multivariate analysis showed that seizures at presentation and the absence of contrast enhancement were the only independent favorable prognostic factors for survival. The 5-, 10-, and 15-year progression-free survival rates were 46, 7.7, and 0%, respectively.

CONCLUSIONS

This retrospective review confirms the indolent but progressively fatal nature of LGOs. Contrast enhancement was the most evident single prognostic factor. New treatment strategies are clearly needed in the management of this disease.

Myoinositol Trends in Different Types of Brain Lesions

Myoinositol (Myo) is a not yet well known metabolite detected using short echo time proton magnetic resonance spectroscopy (HMRS). We examined the role of Myo in 26 patients with new diagnosis of brain lesions including tumors, inflammatory and infectious processes. Histological confirmation of the diagnosis was obtained during gross total surgical resection or stereotactic biopsy of the lesions. The highest ratios of Myo/Cr were found in the hemangiopericytoma and meningioma followed by cortical dysplasia, low grade gliomas, gliobastomas, lymphomas, demyelinating lesions and toxoplasmosis. There was no Myo detected in the cases of metastasis and abscess. Increased Myo levels correlated with low grade gliomas suggesting its potential use in the differentiation of glial tumor. Myo demonstrated a unique pattern in hemangiopericytoma.

Is Bone Enhancement a Helpful Finding in the Diagnosis of Convexity Meningiomas?

We have assessed the enhancement of the overlying bone as a new finding in patients with convexity meningioma. This finding was present in 68.6% of cases in our series. This finding was found very helpful in the differential diagnosis of atypical and cystic meningiomas.

Late-onset temporal lobe epilepsy and dilatation of the hippocampal sulcus by an enlarged Virchow-Robin space

MRI signal changes within the hippocampal sulcus have been attributed to a dilated Virchow-Robin space within that sulcus, but no clinical correlates have previously been described. We present a 64-year-old man who developed right temporal seizures. MRI revealed an unusually enlarged Virchow-Robin space within the hippocampus, suggesting space-occupying effect. Such an abnormality should be considered a possible etiology in patients with late-onset temporal lobe epilepsy.

The role of computed tomographic angiography in the assessment of intracranial vascular disease

Both technical and clinical implications of three-dimensional computed tomographic angiography in the evaluation of intracranial circulation, and in particular cerebral aneurysms, are presented. Three-dimensional computed tomographic angiography allows excellent visualization of the aneurysm, its neck, and its relationship with the parent artery and important adjacent bony structures. This technique has a major role in the evaluation of difficult aneurysms. In addition, advantages and disadvantages are discussed in comparison with more conventional techniques such as magnetic resonance imaging, magnetic resonance angiography, and digital subtraction angiography. Three-dimensional computed tomographic angiography will continue to develop with the advent of more rapid computed tomography scanners, playing a key role in the investigation and screening of patients with a family history of cerebral aneurysms.

Gliomatosis cerebri

PURPOSE

To characterize gliomatosis cerebri on computed tomographic (CT) and magnetic resonance (MR) images.

MATERIALS AND METHODS

MR and CT studies of 22 patients with cerebral gliomatosis were reviewed retrospectively. Tumor was confirmed with autopsy (n=5) or biopsy. Distribution and extent of disease were assessed, and disease progression was followed.

RESULTS

Tumor involved at least two lobes of the brain in all patients, with extension to the corpus callosum in 12, basal ganglia and thalamus in 17, brain stem in three, and cerebellum in two patients. Widespread invasion with hyperintensity was noted on proton-density- and T2-weighted MR images. At CT, areas of hypo- or isoattenuation were noted, and no contrast enhancement occurred. Extent of tumor was greater on MR images than on concurrent CT scans in all patients. The MR findings closely correlated with the autopsy findings.

CONCLUSION

Gliomatosis cerebri is best detected with MR imaging. The pattern is infiltrative with enlargement of cerebral structures.

The negative angiogram in subarachnoid haemorrhage

Our purpose was to review the incidence of negative cerebral panangiography in acute nontraumatic subarachnoid haemorrhage (SAH); to document the amount and distribution of subarachnoid blood on CT and determine its relationship to findings on repeat angiography; and to study the outcome of these patients from the time of presentation to hospital discharge. From 1983 to 1992, 295 patients underwent cerebral angiography for acute SAH at our institution. The CT, angiographic and MRI findings and clinical course of patients with initially negative angiograms were reviewed retrospectively. The overall incidence of negative cerebral panangiography was 31% (92/295). An aneurysm was disclosed on a second angiogram in 4 cases, and on a third angiogram in 1, giving a total false negative rate of 5%. In 55% of cases, only a small amount of SAH was present on CT. The distribution of the subarachnoid blood was nonspecific and resembled the pattern seen in aneurysmal SAH. Ninety-four percent of the patients presented in Hunt-Hess grades I and II. The complications of conservative treatment were few: a rebleed rate of 4%, delayed cerebral ischemia in 4%, cerebral infarcts in 8% and hydrocephalus requiring shunting in 3%. On discharge, 93% of patients had recovered completely and the others were left with moderate disability. There were two deaths related to massive rebleeding. Patients with perimesencephalic SAH (35%) fared particularly well; none developed complications during their hospital stay and repeat angiograms never revealed an underlying aneurysm. In such cases, further angiographic investigations do not seem warranted.

Intramedullary schwannoma

OBJECTIVE

To present the imaging findings for two cases of intramedullary schwannoma involving the thoracic cord and the conus medullaris.

PATIENTS AND METHODS

a 34-year-old man and a 53-year-old woman presented with symptoms of weakness and pain in the lower limbs. Myelography and magnetic resonance imaging as well as other examinations, were performed.

RESULTS

The imaging failed to indicate the correct diagnosis in either patient. However, intramedullary schwannoma was confirmed pathologically in both patients. Subtotal excision resulted in local tumour recurrence at 5 and 3 years, respectively.

CONCLUSIONS

Intramedullary schwannoma should be considered in the differential diagnosis of spinal cord tumours. The importance of accurate diagnosis from frozen sections at surgical biopsy is emphasized .

Three-dimensional computed tomographic angiography of cerebral aneurysms

We describe our technique and results of dynamic, reconstructed, three-dimensional (3-D) computed tomographic (CT) angiography in our first 18 patients with either complex aneurysms, producing subarachnoid hemorrhage or the compression of neighboring structures, or small asymptomatic aneurysms, and assess the role of this technique in treatment planning. A dynamic, infused CT scan producing 1.5-mm cuts of the area of interest was performed, and the two-dimensional images were reconstructed in three dimensions with the ISG Allegro system (ISG Technologies, Toronto, Ontario, Canada). Results were compared with intra-arterial digital subtraction angiography and magnetic resonance angiography. All aneurysms over 3 mm and half of the aneurysms less than or equal to 3 mm were demonstrated by 3-D CT angiography. The neck of the aneurysm, its relationship to the parent artery and associated branches, and its relationship to surrounding bony structures, such as the anterior clinoid, were also demonstrated. This was especially useful for ophthalmic aneurysms. The 3-D image could be rotated on the screen to mimic the operative approach. The active, filling portion and the thrombosed part of partially thrombosed, giant aneurysms could be seen on the same image, and the active, filling portion could be better appreciated with 3-D CT angiography than with magnetic resonance angiography. A partially treated, acrylic-coated aneurysm that could not be completely assessed otherwise has been demonstrated by this technique. 3-D CT angiography is useful in the evaluation of aneurysms, especially when the local anatomy is obscured or distorted by its mass or by the anterior clinoid.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcranial Doppler ultrasonographic changes after embolization of cerebral arteriovenous malformations

The authors assessed the potential role of transcranial Doppler ultrasonography (US) in monitoring hemodynamic changes induced by embolization of cerebral arteriovenous malformations. Transcranial Doppler US was performed in eight patients with such lesions before and after embolization with n-butyl cyanoacrylate [corrected]. Changes in mean flow velocity and pulsatility index were analysed in all feeding and nonfeeding arteries. Anatomic and hemodynamic observations were also correlated with the results of digital subtraction angiography. A consistent trend was observed in all treated feeding arteries after embolization: the flow velocity decreased by a mean of 26% or 33 cm/s (p = 0.01, paired t-test), and the pulsatility index increased by a mean of 27% or 0.15 (p = 0.005). Although these changes did not correlate with the degree of angiographic reduction of the nidus (r = -0.31), they were most marked in malformations with a lower Spetzler grade or a higher degree of shunt obliteration. After embolization, recruitment of untreated feeding arteries was documented in two cases and a decrease in the "steal effect" from contralateral nonfeeding arteries in three. Changes in the nonfeeding arteries ipsilateral and contralateral to the malformation were variable. The authors conclude that transcranial Doppler US is a convenient and reliable method to evaluate quantitatively the hemodynamic effects of embolization of cerebral arteriovenous malformations.

Extension of a cerebellar cystic astrocytoma into the cervical canal, demonstrated by magnetic resonance imaging

One characteristic feature of ependymomas of the fourth ventricle is a tendency to extend through the foramina, specifically the foramina of Luschka and Magendie, the foramen magnum and the aqueduct of Sylvius. The authors report a case of pilocytic astrocytoma of the cerebellum that mimicked such extension into the upper cervical canal. This finding was revealed by magnetic resonance imaging and confirmed at surgery.

CT and MR imaging findings in adults with cerebellar medulloblastoma: comparison with findings in children

The goal of this study was to determine if certain imaging features suggest the diagnosis of cerebellar medulloblastoma in adults and to determine how often the classic CT appearance seen in children is present in adults. The study included 28 adult patients with proved cerebellar medulloblastoma. The tumor was located in the cerebellar vermis in 14 patients and in a cerebellar hemisphere in 14 patients. Thirteen patients had unenhanced CT of the brain, all patients had contrast-enhanced CT, and eight patients had unenhanced MR imaging. The imaging features in adults were compared with those in children, as described in the literature. In our adult patients, all tumors were hyperdense compared with gray matter on unenhanced CT and showed a slight to moderate increase in density after injection of contrast medium. Thirteen lesions had well-defined margins, and 15 had poorly defined margins. Low-density areas consistent with cystic and necrotic degeneration were detected in 23 (82%) of the 28 tumors. By comparison, in children, medulloblastoma usually originates in the vermis. As in adults, the mass is hyperdense on unenhanced CT, but enhances markedly and homogeneously after injection of contrast medium. Usually no evidence of cyst formation or necrosis is seen, and the tumor margins are well defined. This classic CT appearance of medulloblastoma in children was identified in only three (11%) of the 28 adult patients. Medulloblastoma has a variable MR appearance in both children and adults. On T2-weighted images, lesions are hypo-, iso-, or hyperintense compared with normal gray matter. The CT findings of medulloblastoma in adults usually differ from those of medulloblastoma in children. The tumor has a variable and nonspecific appearance in adults and should always be considered in the differential diagnosis of a mass in the posterior fossa.

Low-grade myxoid chondrosarcoma of the base of the skull: CT, MR, and histopathology

A retrospective CT, MR, and histopathologic study was performed in five patients with histologically verified low-grade myxoid chondrosarcoma of the base of the skull. In four patients, the tumor originated off the midline and was associated with bone destruction at the petrous apex near the petrooccipital fissure. Tumor extent included the cerebellopontine angle in three patients and the parasellar area in two patients. The fifth tumor originated on the midline and was associated with destruction at the dorsum sellae. Three tumors contained calcifications, whereas two lesions were mostly isodense with brain on CT scan. All tumors were hypointense on T1-weighted MR images and very intense on T2-weighted images except for areas of signal void consistent with calcifications. Light microscopy revealed islands of mature hyaline cartilage in an abundant myxoid ground substance. Histology and immunocytochemical analysis were consistent with a low-grade myxoid chondrosarcoma. The CT and MR features of low-grade myxoid chondrosarcoma are comparable with those of chordoma. Chordoma usually arises from the midline, but cases with origin from the lateral portion of the clivus or the petrous apex have been described. Low-grade myxoid chondrosarcoma has distinct histologic and immunocytochemical features and includes lesions formerly called "chondroid chordomas."

Hydrocephalus and prominence of the choroid plexus: an unusual computed tomographic presentation of cerebral toxoplasmosis in AIDS

Toxoplasmosis is a frequent cause of infection of the central nervous system (CNS) in patients with acquired immunodeficiency syndrome. Computed tomography (CT) usually shows solitary or multiple parenchymal lesions, which are most often located in the cortex, the juxtacortical white matter and the basal ganglia. The authors describe a 30-year-old immunocompromised Haitian woman with pathologically proven CNS toxoplasmosis who presented with hydrocephalus and prominence of the choroid plexus; there was no evidence of focal parenchymal lesions in contrast-enhanced CT scans. An autopsy revealed diffuse destruction of the ependyma of the lateral, the third and the fourth ventricles. Necrosis was evident, and the periventricular tissues and the choroid plexus were infiltrated with neutrophils and macrophages. Pseudocysts of Toxoplasma were identified near the ventricular surface.

Multiple occult vascular malformations of the brain and spinal cord: MRI diagnosis

We report a patient with multiple angiographically occult vascular malformations in the brain and spine. Magnetic resonance imaging showed multiple lesions in brain and spine with hypointense areas on both T1 and T2-weighted images. These hypointense areas are usually secondary to hemosiderin deposits consistent with remote bleeding in the lesions. We conclude that when magnetic resonance reveals an intraspinal lesion with signal intensity characteristics consistent with a vascular malformation, an examination of the brain should be performed to rule out associated intracranial lesions. The finding of multiple lesions in the brain with identical signal intensity characteristics reinforces the diagnosis of vascular malformation.

Electroencephalography, magnetic resonance imaging and pathology in patients treated surgically for temporal lobe epilepsy

In a consecutive series of 40 patients selected by EEG studies for surgical treatment of temporal lobe seizures, magnetic resonance imaging showed structural lesions in 25% and signal abnormalities, usually in the mesial temporal region, in another 35%. Pathological changes included structural lesions in over 30% of patients and sclerosis of the amygdala in almost half of the series. These findings further substantiate the implication of the amygdala in the pathogenesis of temporal lobe seizures with automatism and amnesia.

Magnetic resonance imaging of hypothalamic hamartomas causing gelastic epilepsy

Hypothalamic hamartomas may cause a peculiar epileptic syndrome characterized by seizures of laughter and precocious puberty. Four mentally handicapped patients suffering from gelastic epilepsy were referred to our institution for investigation; three of them also presented with precocious puberty. In all four cases magnetic resonance imaging (MRI) revealed a space-occupying lesion of the hypothalamus that was considered to be a hamartoma. Biopsies were not performed. Hamartomas appear isodense in plain computed tomography scans, and they do not enhance. Such lesions display an isointense signal in T1-weighted magnetic resonance images and a hyperintense signal in proton density and T2-weighted images. MRI is the procedure of choice for detecting such lesions at the base of the brain.

A simplified terminology for abnormalities of the lumbar disk

The terminology for abnormalities of the lumbar disk has always been a source of confusion. Recent advances in pathological studies have inspired the authors to propose a simple classification of common disk anomalies suitable not only for diagnostic radiologists but also for referring clinicians. Although the diagnosis of a few pathological entities will only be possible with specific imaging techniques, the proposed classification is appropriate for reporting observations from plain films, conventional tomograms, myelograms, diskograms, computed tomography scans and magnetic resonance images. All lumbar disks can thus be classified into one or more of the following categories: normal, aging, scarred, ruptured and herniated. A disk herniation is defined as a localized exit of disk material beyond the limits of the original intervertebral space.

[Sub-callus epidermoid cyst. A case report]

The cranio-encephalic epidermoid cysts are rare tumors. These lesions are extra-axial and can occur at the infratentorial or supratentorial level. The epidermoid cysts are classically in contact with the base of the skull, and less often intraventricular; the other locations are exceptional. Because of their CT aspect (hypodense lesion, rarely isodense, well defined, without contrast enhancement, and without surrounding edema) and MR aspect (in more than 70% of the cases: more or less homogeneous lesion, hypointense in T1 and hyperintense in T2), the authors believe that it is possible to suggest such a diagnosis even with an atypically located case. We report the case of an epidermoid cyst located between the corpus callosum and the falx cerebri.

"Pre" subclavian steal syndromes and their treatment by angioplasty. Hemodynamic classification of subclavian artery stenoses

Early modifications of the flow in the vertebral artery due to subclavian artery stenosis are presented. They have been successfully treated by angioplasty of the subclavian artery. A hemodynamic classification into four types of subclavian artery stenosis is also presented.

Traumatic intracranial aneurysm due to arterial injury at surgery. Case report

A case is presented of false intracranial aneurysm of traumatic origin which developed following direct surgical attack on a congenital anterior communicating artery aneurysm. The secondary aneurysm was discovered on the 25th postoperative day and was clipped at a subsequent procedure. The possible pathophysiology is discussed with respect to other direct vessel injuries.

The computerized tomographic assessment of brain infarcts

The computed tomographic (CT) examinations of one hundred and sixty patients with a clinical diagnosis of cerebral infarction were reviewed. A characteristic CT pattern was noted. Infused scans and follow-up studies allowed for considerable accuracy in diagnosis.

High resolution computed tomography in cervical syringomyelia

Thirty-two cases of documented cervical syringomyelia, 13 of which were already surgically proven, were explored by high resolution computed tomography (CT). A central cavitation was demonstrated in all cases. High resolution CT appears to be more reliable than myelography and should be the examination of choice in cervical syringomyelia.

Development of high resolution computed tomography of the spinal cord

Computed tomography of the spinal cord was a natural development of total body scanning. Much time and effort was spent in order to visualize the spinal cord and the various conditions affecting it. This was achieved by using an EMI CT5005 scanner and a series of step by step modifications and improvements to obtain a very high degree of resolution. The large variety of intraspinal lesions seen at the Montreal Neurological Hospital allowed us, by selecting appropriate cases, to determine the value of CT of the spinal cord.

Hypoglossal paralysis due to compression by a tortuous internal carotid artery in the neck

Severe hemiatrophy of the right half of the tongue in a 22 year old patient was demonstrated to be due to compression of the hypoglossal nerve by a tortuous internal carotid artery in the neck. The nerve was trapped between an abnormal loop of the internal carotid artery and the sternocleidomastoid branch of the occipital artery. Although impairment of cranial nerve function with cases of tortuous and dilated vessels has been reported frequently, twelfth nerve palsy has never been demonstrated before.

Evaluation of the age of subdural hematomas by computerized tomography

The computerized tomography (CT) scans of 50 patients with surgically proven subdural hematomas were subdivided into three groups on the basis of the attenuation coefficients of the subdural fluid collections: 28% were more dense, 24% isodense, and 48% less dense than the surrounding brain. The 42 patients with the available data were then subdivided into three groups; acute, subacute, and chronic, according to the time interval between trauma or duration of symptoms and date of CT scanning. Subdural hematomas were found to be hyperdense in 100% of acute patients, isodense in 70% of the subacute group, and hypodense in 76% of the chronic group.

Computed tomography in the evaluation of intracranial aneurysms and subarachnoid hemorrhage

Computed tomography (CT) is a reliable technique for examining patients with subarachnoid hemorrhage and intracranial aneurysms. Extravasated blood is easily recognized and the location of the ruptured aneurysm may frequently be predicted by its distribution into the subarachnoid spaces and brain parenchyma. CT alleviates the need for repeat angiography while following the patient's clinical evolution since it clearly shows rebleed, edema follwoing vasospasm, and hydrocephalus.

Computed tomography in intracranial arteriovenous malformations

22 patients with proved intracranial arteriovenous malformations (AVM) were studied by computed tomography (CT). Of these, 18 were also studied by CT after intravenous injection of contrast material. The plain scan was normal in 23% of cases. A combination of plain and contrast-enhancement CT proved to be superior to other screening techniques in patients with a possible intracranial AVM.