Arteries and Veins of the Sylvian Fissure and Insula: Microsurgical Anatomy

We present a vascular anatomical study of the arteries and veins of the sylvian fissure and insula.A good knowledge of the sylvian fissure, the insula, and their vascular relationship would seem mandatory before performing surgery in this area, whatever the type of surgery (aneurysms, arteriovenous malformations, insular tumors).We start with the sylvian fissure and insula morphology, followed by the MCA description and its perforators, with special attention paid to the insular perforators. We demonstrate that the long insular perforators penetrating in the superior part of the posterior short gyrus and long gyri vascularize, respectively, the corticonuclear and corticospinal fasciculi. We particularly insist too on three anatomical constants regarding the vascularization of the insula, already described in the literature: The superior periinsular sulcus is the only sulcus on the lateral surface of the brain without an artery along its axis; the superior branch of the MCA supplies the anterior insular pole and both the anterior and middle short gyri in 100 % of cases; in at least 90 % of cases, the artery that supplied the central insular sulcus continued on to become the central artery.We end with the anatomical study of the veins and cisterns.

Sylvian Fissure Arteriovenous Malformations

OBJECTIVE

The Sugita classification for sylvian fissure arteriovenous malformations (AVMs) categorizes them into four types based on nidus location in the fissure: pure, lateral, medial, and deep. This classification scheme is simple and appealing, but is rarely applied. We applied the Sugita classification to a consecutive, single-surgeon experience with 28 patients to better characterize the Sugita subtypes.

METHODS

Twenty-eight patients with sylvian fissure AVMs were identified from a series of 314 AVM patients treated microsurgically over a 9-year period. According to the Sugita classification, six (21%) AVMs were pure, four (14%) were lateral, nine (32%) were medial, and nine (32%) were deep. Fifteen (54%) patients presented with hemorrhage.

RESULTS

There was no surgical mortality in this experience. Four (14%) patients had transient deterioration and one (3.6%) patient with a pure sylvian AVM was permanently worse. At late follow-up (mean duration, 20 mo), good outcomes (Modified Rankin Scale scores 0–2) were observed in 25 (89%) patients.

CONCLUSION

The Sugita classification does not modify the surgical approach or predict patient outcomes with sylvian fissure AVMs, but it does clarify anatomic differences between subtypes. These AVMs are a diverse group, with each subtype having unique relationships between arteries, veins, nidus, and adjacent brain that influence microsurgical technique. Despite their eloquent location and technical challenges, results with microsurgical resection are excellent, making this the preferred treatment option for low-grade AVMs.

Abnormalities of CSF flow patterns in the cerebral aqueduct in treatment-resistant late-life depression: a potential biomarker of microvascular angiopathy

There is growing evidence that microvascular angiopathy (MVA) plays an important role in the development of dementia and affective disorders in older people. At currently available image resolutions it is not possible to image directly the vascular changes associated with MVA, but the effects on blood and cerebrospinal fluid (CSF) flow may be detectable. The aim of this study was to investigate a potential biomarker for MVA based on MRI of abnormalities in CSF flow. Since there is considerable indirect evidence that treatment resistance in late-onset depressive disorder is related to MVA, we assessed the method in a group of 22 normal volunteers and 29 patients with responsive (N=21) or treatment-resistant (N=8) late-onset depressive disorder. Single-slice quantified phase-contrast (PC) images of cerebral blood and CSF flow were collected at 15 points over a cardiac cycle, and the resulting flow curves were parameterized. Significant differences in the CSF flow (width of systolic flow peak and diastolic flow volume, both P<0.01) through the cerebral aqueduct were observed for the group of treatment-resistant patients when compared to age matched controls. No significant difference was observed for a group of 21 patients with treatment-responsive depression. The findings support the hypothesis that MR measurement of CSF flow abnormalities provides a biomarker of MVA, and thus could have application in a wide range of age-related diseases.

Endoscopic aqueductal stent placement for the treatment of a trapped fourth ventricle

OBJECT

Endoscopic aqueductal stent therapy has evolved into an important technique in the treatment of a trapped fourth ventricle (TFV). The authors analyzed five cases of symptomatic TFV treated by endoscopic aqueductal stent therapy and, on the basis of intraoperative findings, discuss aspects of TFV formation.

METHODS

Patients' ages ranged from 2 to 17 years (mean 9.2 years). Two patients underwent endoscopy via a coronal bur hole approach and three via a small suboccipital craniectomy. The mean follow-up period was 30 months (range 24-38 months). In four cases, a membrane occluding the orifice of the aqueduct and covering part of the walls of the ventricle was observed. Despite slit ventricles in four cases, there was no intraoperative evidence of aqueduct wall collapse. All procedures were successful, and all patients experienced positive outcomes. In one patient, Parinaud syndrome, rotatory nystagmus, and abducent nerve palsy developed postoperatively; these deficits resolved after a preexisting supratentorial shunt was upgraded. There were no cases of aqueduct reocclusion during the follow-up period.

CONCLUSIONS

Aqueductal stent therapy is an effective method of TFV treatment. Because it prevents aqueduct reocclusion by chronic inflammatory processes in postinflammatory hydrocephalus, it has been shown to be more efficient than aqueductoplasty alone and to be an important alternative to the placement of a fourth ventricle shunt. Intraventricular processes leading to membrane formation play an important role in occlusion of the cerebral aqueduct orifices and final isolation of the fourth ventricle in postinflammatory hydrocephalus.

An unusual cause of hydrocephalus: aqueductal developmental venous anomaly

Vascular malformations are infrequent causes of aqueductal stenoses, developmental venous anomaly (DVA) being the rarest among them. DVAs, also known as venous angiomas, are congenital in origin and characterized by dilatation of vessels in the superficial and deep venous system. Although they are usually clinically silent, they can be complicated by hemorrhage, seizures and neurologic deficits. Herein, we report MR imaging findings of a 7-year-old girl whose hydrocephalus was due to an abnormal vein coursing through the aqueduct.

Pure sylvian fissure arteriovenous malformations

OBJECT

Pure sylvian fissure arteriovenous malformations (AVMs) are vascular malformations confined to the sylvian fissure without parenchymal involvement. Because the branches of the middle cerebral artery are arteries of passage and the margins between the AVM and the insula cortex may be ill defined, many surgeons regard pure sylvian fissure AVMs as inoperable. The authors reviewed their surgical experience with eight patients harboring pure sylvian fissure AVMs to determine the incidence of operative morbidity.

METHODS

All eight patients experienced seizures, five (63%) had headaches, and three (38%) experienced hemorrhages. Preoperatively, six patients (75%) were normal neurologically and two (25%) had neurological deficits. Five (63%) of eight sylvian fissure AVMs were located in the dominant hemisphere. The size of the nidus ranged from 6 to 27 cm3 (mean 14 cm3). Complete removal of the AVM was documented by postoperative angiography in every case. Seizures were reduced or eliminated and headaches were relieved in all affected patients. Transient neurological deficits, which included aphasia, short-term memory loss, and hemiparesis, occurred in four patients (50%). Within 3 months, all patients were functioning independently with no new neurological deficits. The status of two patients who had had preoperative neurological deficits improved postoperatively. Neuropsychological testing showed no new cognitive deficits.

CONCLUSIONS

With appreciation for transient instances of postoperative morbidity, the outcome was excellent in all patients. The authors thus advocate microsurgery as the primary treatment for pure sylvian fissure AVMs.

Making sense out of jargon: a neurolinguistic and computational account of jargon aphasia

OBJECTIVE

To identify the cognitive and neuroanatomic bases of neologistic jargon aphasia with spared comprehension and production of written words.

METHODS

Detailed analysis of performance across experiments of naming, reading, writing, repetition, and word/picture matching by a 68-year-old woman (J.B.N.) served to identify which cognitive mechanisms underlying naming and word comprehension were impaired. J.B.N.'s impairments were then simulated by selectively "lesioning" a computer model of word production that has semantic, word form, and subword phonologic levels of representation (described by Dell in 1986).

RESULTS

In comprehension experiments, J.B.N. made far more errors with spoken word input than with written word or picture input (chi-square = 40-59; df = 1; p < 0.0001) despite intact auditory discrimination. In naming experiments (with picture, definition, or tactile input), J.B.N. made far more errors in spoken output relative to written output (chi-square = 14-56; df = 1; p < 0.0001). These selective impairments of spoken word processing were simulated by reducing connection strength between word-level and subword-level phonologic units but maintaining full connection strength between word-level and semantic units in Dell's model. The simulation yielded a distribution of error types that was nearly identical to that of J.B.N., and her CT and MRI scans showed a small subarachnoid hemorrhage in the left sylvian fissure without infarct. Cerebral angiogram showed focal vasospasm in sylvian branches of the left middle cerebral artery.

CONCLUSION

Focal left perisylvian dysfunction can result in a highly selective "disconnection" between word-level and subword-level phonologic representations manifest as neologistic jargon aphasia with intact understanding and production of written words.

Obstructive hydrocephalus caused by an abnormal vein in the aqueduct. Case report

A case is reported of aqueductal stenosis caused by an abnormal draining vein and demonstrated by computerized tomography and magnetic resonance imaging. Placement of a ventriculoperitoneal shunt relieved the patient's progressive headaches.

Hypofrontal vs. hypo-Sylvian blood flow in schizophrenia

Hypofrontality in schizophrenia has been a frequent but not consistent finding in regional cerebral blood flow studies. However, the contributions of subject and state variables such as age, education, task activation, and anxiety, some of which are known to influence blood flow profiles, have not been thoroughly examined in this population. Here, in a sample including 24 normal, 18 schizophrenic, 22 bipolar, and 13 unipolar depressive subjects, narrative prose memory deficit was found to distinguish both schizophrenic and bipolar subjects from normal controls. Further, when these subjects were engaged in repeated trials of a verbal recognition memory task, left hemisphere hypofrontal blood flow in the early stage of learning was related to narrative memory, independent of diagnostic group. In the late stage of learning, state anxiety was significantly associated with left hypofrontality, while right hypofrontality was significantly related to narrative memory--both findings again independent of diagnostic group. A focal suppression of left hemispheric peri-Sylvian activation (in Broca's and Wernicke's areas) uniquely characterized schizophrenia after taking into account variance due to age, education, gender, state anxiety, and verbal memory. It is concluded that a failure of left peri-Sylvian activation during memory task performance reflects a unique language-related focal deficit in schizophrenia.

Sylvian fissure arteriovenous malformations

We have operated on 16 cases of arteriovenous malformation (AVM) in and around the sylvian fissure. We call these lesions "sylvian fissure AVMs" and classify them into four subdivisions, namely, pure, lateral, medial, and deep AVMs. By others, they have been variously called AVMs of the basal ganglia, insula, anterior choroidal artery, frontal lobe, or temporal lobe. These sylvian fissure AVMs showed similar angiographic findings: the feeders in all cases were branches of the middle cerebral artery; in some cases, additional feeders from the anterior and posterior choroidal and posterior communicating arteries were present also. We describe the characteristic features of these AVMs from the anatomical and surgical points of view. The surgical results were satisfactory in 15 cases (no additional neurological deficits), and 1 patient died.

Venous malformation of the aqueduct of Sylvius treated by interventriculostomy: 15 years follow-up

A single venous shunt obstructing the aqueductus of Sylvius was treated by interventriculostomy. A passage for CSF was obtained between the third and fourth ventricles. The catheter which was left in the aqueduct collapsed the malformation, possibly preventing a future haemorrhage. A Simple rubber catheter in the aqueduct of Sylvius has been well tolerated by the patient for 15 years.

Computed tomography of Moyamoya disease: demonstration of occluded arteries and collateral vessels as important diagnostic signs

Diagnosis of moyamoya disease primarily depends on the angiographic demonstration of stenosis and occlusion of the carotid bifurcation, and extensive parenchymal and leptomeningeal collaterals. According to previous reports, computed tomography (CT) reveals multiple low density areas in the brain, with atrophic changes. Based on this review of six cases, CT with contrast enhancement often reveals tortuous, curvilinear vessels in the basal ganglia, corresponding to extensive parenchymal and leptomeningeal collaterals on angiography. The most proximal portions of the anterior and middle cerebral arteries are often poorly visualized. When multiple low density areas or subarachnoid hemorrhages are encountered on CT, these findings in the basal ganglia should be sought for differential diagnosis.