Denis Melançon

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 patients clinical evolution since it clearly shows rebleed, edema follwoing vasospasm, and hydrocephalus.

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)

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. Ninetyfour 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.

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.

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

SummaryWe 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.

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

SummarySevere 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 sternoclcidomastoid 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.

Supratentorial neurenteric cysts—A fascinating entity of uncertain embryopathogenesis

The histopathological, immunologic, and ultrastructural findings of neurenteric cysts support an endodermal derivation. These developmental cystic lesions are generally located in the posterior mediastinum, abdomen, and pelvis and may also contain some mesodermal and neuroectodermal elements. In contrast, neurenteric cysts of the central nervous system are very infrequent and occur most commonly in the spinal canal. Intraspinal neurenteric cysts are usually encountered in the cervicothoracic region with an intradural, extramedullary location and are commonly associated with congenital defects of the overlying skin and/or vertebral bodies. Intracranial neurenteric cysts are very uncommon and typically located in the posterior fossa. Several hypotheses have been postulated to explain the origin of intracranial neurenteric cysts. However, the embryologic basis of these fascinating lesions remains incompletely understood. Supratentorial neurenteric cysts are distinctly rare often represent a diagnostic challenge on preoperative neuroimaging. In fact, only 22 cases of supratentorial neurenteric cysts have been reported in the literature including our own patient with a laterally based convexity extraaxial cyst presenting with seizures. In this report, we review the clinical, radiographic, and histological findings of supratentorial neurenteric cysts. We discuss the differential diagnoses and surgical considerations in the management of these intriguing lesions. We also provide an extensive review of normal human embryogenesis and discuss putative mechanisms of embryopathogenesis of supratentorial neurenteric cysts.

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.

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.

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.