Biomedical subjects
Publications and source records attributed to D Melanson.
Choroid plexus papillomas are rare intracranial neoplasms that are generally benign in nature. They are seen in both children and adults and have a male preponderance. Magnetic resonance imaging, a noninvasive diagnostic tool, demonstrated the intraventricular location and the surrounding anatomy with striking clarity, more effectively than angiography and computed tomography scanning.
We reviewed the CT findings of 387 patients with new-onset seizures after the age of 50. Seizures were generalized in 212 patients, focal in 160, and indeterminant in 15. CT scanning revealed cerebral atrophy in 113 cases, ischemic lesions in 75, cerebral neoplasms in 20, and no abnormality in 177 cases. Tumours were found in only three patients with generalized seizures, and all three had focal neurological deficits at the time of CT diagnosis, while 17 neoplasms were discovered in patients with a focal seizure disorder. The majority of patients with late-onset epilepsy have a normal CT scan with cerebral atrophy being the most common abnormality detected. Cerebral vascular disease appears to be the most frequently identified cause of late-onset epilepsy, while cerebral neoplasms are uncommon.
The authors report their experience with the combined use of digital subtraction angiography (DSA) and magnetic resonance imaging (MRI) for the stereotactic placement of intracerebral electrodes in epilepsy and for the radiosurgical treatment of otherwise inoperable arteriovenous malformations of the brain. Both imaging techniques, when used in conjunction, have been found most useful and complementary. For deep electrode placement, they permit optimal visualization of the cerebral structures to be reached by the electrode array while allowing the avoidance of vessels in the vicinity. For radiosurgery of arteriovenous malformations, DSA provides optimal visualization of the feeders and of the malformation itself, while the MRI reveals the cerebral structures to be spared by the photon beam of the linear accelerator. A discussion of their respective roles is presented, with the specific question as to whether MRI alone could be used for both procedures.
Meningioma is a histologically benign tumor that is second in frequency only to gliomas among primary intracranial tumors. Its extracerebral development and generally clear demarcation from the brain does not make it easier to detect on magnetic resonance (MR) scanning. Only 2 to 3% of meningiomas occur in the foramen magnum, and these tumors are often clinically misdiagnosed. We discuss four cases of foramen magnum meningioma, with emphasis on MR scanning.
We report a patient with acute epidural hematoma diagnosed using computed tomography shortly after decompressive surgery of a contralateral subdural hematoma not resulting in clinical evidence of improvement. The patient underwent successful second emergency decompressive surgery. Prompt recognition is essential for a successful outcome, and poor recovery, when not otherwise anticipated, should alert immediately to a possible contralateral hematoma.
An unusual patient with pyogenic spondylodiscitis and preservation of the disc space anteriorly is reported. The diagnosis of pyogenic spondylodiscitis may be difficult when there is underlying spinal disease. We emphasize the need for early systematic imaging studies and intervention in such patients, including careful evaluation of vertebral endplates on plain films, early use of radionuclide studies, and prompt needle aspiration.
Seventeen venous angiomas in 16 patients were evaluated radiologically at the Montreal Neurological Hospital. Radiologic investigations included contrast-enhanced computed tomograms (CECT) in 15 patients, cerebral angiograms with a long venous phase study in 15, and magnetic resonance (MR) imaging with a spin-echo pulse sequence technique in six. CECT revealed abnormalities including six nodular nonspecific enhancing lesions and nine enhanced draining veins, whereas plain CT revealed intracerebral hemorrhages in four patients and calcification in one. All the angiograms showed the characteristic pattern of venous angiomas consisting of medullary veins converging to a large draining vein during the late venous phase. All six patients examined by MR showed abnormal vascular structures; parenchymal hemorrhages were present in two patients. In five patients with venous angiomas, medullary veins converging to a large draining vein were demonstrated as echo-void curvilinear structures. In two patients, the increased signal from medullary veins in long echo delay sequences was suggestive of a slow venous flow rate. Demonstration of the venous nature of the malformation may, in the future, obviate the need for angiography.
Functional vascular anastomoses at the base of the brain allow for temporary occlusion of the carotid or vertebral arteries. Six embolizations with temporary balloon occlusion of the internal carotid or vertebral artery are reported. Polyvinyl alcohol was the embolic material in all cases and all procedures were performed using digital angiography. The size of the embolic particles and the positioning of the balloon related to the branches of the occluded vessel is discussed.
Five patients with spinal arteriovenous malformations (AVMs) supplied at least in part by the anterior spinal artery were treated by embolization. Complete occlusion of the malformations was obtained without complication in all patients. Improved endovascular treatment of spinal AVMs is now possible with the use of calibrated particles of polyvinyl alcohol, serial digital subtraction angiography, and temporary balloon occlusion of the vertebral artery in cervical AVMs supplied by a pedicle arising from the vertebral artery.
Eight cases of neurocysticercosis were encountered at the two major neurological centers affiliated with McGill University in Montreal in 4 years. All patients were immigrants who had been in Canada for a period of 1 to 18 years and came from South America (three cases), Haiti (three cases), and Greece (two cases). Five patients had parenchymal cysts and presented with epilepsy; three had the racemose form and presented with hydrocephalus. Four patients with parenchymal cysts were treated by removal of the cysticercus and did well. One patient with numerous cysts was treated with praziquantel with good clinical and radiological results. Two patients with the racemose form were treated by cyst aspiration, cerebrospinal fluid (CSF) diversion, and praziquantel and did well. Another patient with the racemose form, seen before the advent of praziquantel, died of cysticercosis infection. Neurocysticercosis is not uncommon in the immigrant population of large North American cities. Single symptomatic cysts can be evacuated surgically with good results; multiple parenchymatous cysts can be treated with praziquantel. Patients with the racemose form who are treated with CSF diversion and praziquantel do well, although those who are only treated surgically die of their disease.
A case of extraaxial ependymoma of the posterior fossa, arising along the inferolateral aspect of the left cerebellar hemisphere, is reported. The clinical, radiologic, and histologic features of this lesion are presented. The unusual location of the tumor and its possible origin are discussed in the light of previous experience with other extraaxial ependymomas of the neuraxis.
We studied six cases of intracranial meningioma with cyst formation. Manifestations included focal neurologic signs (four cases), seizures (three cases), headache (three cases), and personality changes (two cases). CT revealed a cystic enhancing supratentorial lesion in five cases. Angiographic changes of meningioma were observed in only three cases, and correct preoperative diagnosis was made in only half the cases so studied. Histologically, all lesions were syncytial meningiomas. Cyst fluid was always xanthochromic, acellular, and highly proteinaceous. The variety of anatomic configurations suggests several pathophysiologic mechanisms in formation of the cysts that are commonly misdiagnosed preoperatively. Tissue analysis is needed for all cystic, enhancing lesions of the brain.
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A case is presented of agenesis of the right internal carotid artery in a fifteen-year-old female with an unrelated seizure disorder. Conventional angiography revealed an absent right internal carotid artery, supply to the right anterior cerebral artery from the left internal carotid artery, and supply to the right middle cerebral artery by anastomosis through the vertebral basilar system. The congenital nature of the anomaly was confirmed by intravenous digital subtraction angiography, which revealed no portion or remnant of the right internal carotid artery to be present, and by computerized tomography of the base of the skull, which demonstrated no bony carotid canal on the right side. This is the first reported case of internal carotid artery agenesis to be elucidated by intravenous digital subtraction angiography. A brief discussion concerning the congenital nature of this anomaly is presented, including the role of angiography and computed tomography in establishing the diagnosis of this condition.
Three patients with medically refractory partial complex seizures were shown to have small and initially unsuspected encephaloceles of the middle fossa. All had bitemporal, independent, interictal epileptogenic abnormalities, and the side of origin of the seizures could not be determined by surface EEG alone. The encephaloceles were missed on the initial radiologic studies and were found retrospectively in two patients; the third was found at operation and was not demonstrable radiologically, even in retrospect. One was the sequel of remote mastoid surgery, another was neoplasm-related, and the third, developmental. In all, bony defects of the middle cranial fossa were associated with temporal lobe herniation. The patients were treated surgically and have had no further partial complex seizures since operation.
The following plain film findings of retrocrural disease were demonstrated by two patients: a) silhouetting, by a soft-tissue density, of a previously seen inner margin of the crus, b) lateral displacement of the crus, c) lateral deviation of the inferior portion of the paraspinal line, and d) abrupt obliteration of the upper portion of a well defined crus.
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