Surgical anatomy of the juxta-dural ring area

OBJECT

The authors report on the surgical anatomy of the juxta-dural ring area of the internal carotid artery to add to the information available about this important structure.

METHODS

Twenty sides of cadaver specimens were used in this study. The plane of the dural ring was found to incline in the posteromedial direction. Medial inclination was measured at 21.8 degrees on average against the horizontal line in the anteroposterior view on radiographic studies. Posterior inclination was measured at 20.3 degrees against the planum sphenoidale in the lateral projection, and the medial edge of the dural ring was located 0.4 mm above the tuberculum sellae in the same projection. The lateral edge of the dural ring was located 1.4 mm below the superior border of the anterior clinoid process. The carotid cave was situated at the medial or posteromedial aspect of the dural ring; however, two of the 20 specimens showed no cave formation. The carotid cave contained the subarachnoid space in 13 sides, the arachnoid membrane only in three sides, and the extraarachnoid space in two sides. The authors propose that the marker of the medial side of the dural ring, which is more proximal than the lateral, is the tuberculum sellae in the lateral view on radiographic studies. In the medial aspect of the dural ring the intradural space can be situated below the level of the tuberculum sellae because of the existence of the carotid cave.

CONCLUSIONS

An aneurysm arising from the medial side of the juxta-dural ring area even below the tuberculum sellae is a potential cause of subarachnoid hemorrhage.

Nontraumatic convexity intradiploic arachnoid cyst

A 63-year-old male presented with an unusual case of nontraumatic intradiploic arachnoid cyst in the frontotemporal convexity area. Skull radiography showed a circular osteolytic lesion of the right parietal bone. Computed tomography revealed a defect of the inner table, widened diploic space, and thinned outer table. Magnetic resonance imaging showed a cyst containing cerebrospinal fluid. Bone scintigraphy showed no abnormal uptakes. Intraoperative observation confirmed the neuroimaging findings. Histological examination found no abnormal findings in specimens of skull bone or arachnoid membrane. Intradiploic arachnoid cyst is characterized by parasagittal, multiple, well-demarcated osteolytic lesions on radiographs in the elderly. However, the clinical features of this disease remain unclear and diagnosis without an exploratory surgical procedure may not be possible.

Idiopathic syringomyelia and the importance of occult arachnoid webs, pouches and cysts

Syringomyelia is the condition in which longitudinal cavities are found within the spinal cord. The use of drainage procedures has been widely practised with good short term results. However, the long-term results in some large series have been less favourable. There are many associated conditions and in most forms a blockage to the normal flow of CSF, either at the foramen magnum or in the spinal canal, can be identified. Most surgeons would now direct their efforts to the establishment of normal CSF flow rather than a shunting procedure. In a certain group of patients, even with the advent of sophisticated MRI, no associated abnormality or CSF block is easily identified. This type of syringomyelia is often termed idiopathic. We report 10 patients with symptomatic syringomyelia without readily recognized predisposing factors. In eight patients preoperative myelography revealed a block to the flow of contrast compatible with subarachnoid obstruction. Eight patients underwent laminectomy and division of the obstructing arachnoid webs. Five experienced good improvement and three only moderate improvement. Two of the patients underwent syrinx shunting procedures only, which resulted in a worsening of their symptoms. At operation one patient was found to have an arachnoid cyst. We believe that patients with idiopathic symptomatic syringomyelia may need myelography to identify such arachnoid abnormalities. Subsequent surgery should be directed at the establishment of normal CSF flow by laminectomy and excision of the offending lesion.

Do spinal meningiomas penetrate the pial layer? Correlation between magnetic resonance imaging and microsurgical findings and intracranial tumor interfaces

OBJECTIVE

To study the relationships between spinal dura-arachnoid and tumor-cord interfaces in spinal meningiomas and to investigate whether a disruption of the pial layer and penetration of the tumor in the spinal cord occurs.

METHODS

Fifteen patients with histologically proven meningiomas underwent magnetic resonance imaging (MRI) preoperatively. All patients underwent microsurgery. The histological characteristics of the tumors were compared with MRI and microsurgical findings.

RESULTS

At surgery, the peritumoral hypointense rim revealed by MRI in 10 of 15 patients corresponded to a well-defined cerebrospinal fluid-containing space confined between the outer arachnoidal layer and the inner leptomeningeal layer. In those patients in whom the hypointense peritumoral rim was absent, the inner layer was either difficult to identify or clearly absent, and the blood vessels were extremely adherent to the tumor, requiring a more cautious dissection. Penetration of the tumors through disruption of the pial surface was not documented.

CONCLUSION

Previous anatomic and electron microscopy studies demonstrated, in human spinal meninges, the presence of an intermediate layer attached to the inner aspect of the arachnoid, extending laterally over the dorsal surface of the spinal cord and arborizing over the nerve roots and blood vessels. The intermediate layer is not present in human cerebral leptomeninges. The presence/absence of this layer might explain the hypointense rim detected by MRI and might also explain why no penetration and no peritumoral edema is observed in spinal meningiomas as compared with intracranial meningiomas.

A continuous microneurosurgical irrigation and suction system: technical note

OBJECTIVE

We describe a continuous microneurosurgical irrigation and suction technique. This technique automatically clears the operative field, frees the surgeon to perform microdissection with both hands, and actually aids in dissection of the arachnoid layer.

TECHNIQUE

The suction catheter (MicroVac; P.M.T., Inc., Hopkins, MN) described by Spetzler and Iverson and an additional continuous microirrigation technique are discussed. The catheter design has a sump effect and is secured in a dependent position in the operative field to continuously remove blood, irrigate the area, and reduce cerebrospinal fluid accumulation. The irrigation system consists of standard intravenous tubing with an angiocatheter used to direct a precise stream into the operative field.

RESULTS AND CONCLUSION

The irrigation and suction system, when properly adjusted, continuously clears the operative site of minute amounts of blood that may obscure the surgeon's view and assists in dissection of the arachnoid layer. It has been used since 1991 with excellent success and satisfaction.

Herniation of the spinal cord 38 years after childhood trauma

We report an unusual post-traumatic spinal cord herniation, which became symptomatic 38 years after the trauma. A 44-year-old man presented with a 2-year history of increasing impotence, neuropathic bladder dysfunction and dissociated sensory loss below the level of T6. At the age of 6 years he had a severe blunt spinal injury with transient paraparesis. MRI revealed right lateral and ventral displacement of the spinal cord at the T5/6 level. The spinal cord was surgically exposed and found to herniate through a ventral defect of the arachnoid membrane and the dura mater. As there were no other events that could have precipitated spinal cord herniation the reported blunt trauma in childhood is the most likely cause for the spinal cord herniation in this patient.

Blood supply of the olfactory nerve. Meningeal relationships and surgical relevance

The authors report the results of a series of dissections and anatomic sections of the fronto-basal region of the brain and of the anterior cranial fossa in human cadavers. The constant presence of an arachnoidal cistern above the olfactory nerve was verified. The arachnoid separates from the pial membrane and forms a bridge with the ventral part of the olfactory bulb and tract, from the lateral edge of the olfactory sulcus to the medial edge of the gyrus rectus. The cistern is wide in its anterior portion, between the gyrus rectus and the olfactory bulb, and is reduced to a virtual slit in its posterior portion where the tract is lodged in the olfactory sulcus. The olfactory nerve can be separated without damaging fronto-basal arachnoidial adhesions over several centimeters. Dissection of this region after intravascular injection of colored media shows the constant presence of an artery destined to the olfactory bulb and tract. It originates either from the lateral surface of the anterior cerebral a. (segment A2), or from the medial fronto-basal a., and consistently provides terminal branches in front of the olfactory trigone in the medial olfactory sulcus. At their ventral extremity, the olfactory structures are therefore vascularised independently for several centimeters, from the lower face of the frontal lobe. The independent vascularisation of the olfactory nerve, the tenuous and easily detachable adhesions, and the actual presence of a true arachnoidal cistern all contribute to enabling surgical techniques which conserve olfactory function during anterior approaches.

Hemifacial spasm in childhood and adolescence

Hemifacial spasm (HFS), a hyperactive dysfunction of the facial nerve, is rarely seen in young people. Between 1984 and 1994, we treated 924 patients with HFS by microvascular decompression at our institution. Of these, 8 (0.9%) were younger than 30 years. In most of the older patients with HFS, the offending artery which compresses the root exit zone was elongated, redundant, and focally arteriosclerotic as a result of hemodynamic effects due to aging or hypertension. On the other hand, the offending artery did not exhibit such characteristic changes of the vasculature in children and adolescents with HFS. In all of the young patients who underwent initial microvascular decompression at our clinic, the arachnoid membrane around the facial nerve was thickened and encased the artery, resulting in compression of the root exit zone of the facial nerve. Such thickening of the arachnoid surrounding the offending vessel may play an important role in the pathogenesis of HFS by trapping and encasing the artery to compress the root exit zone, particularly in the young patients.

Symptomatic intraventricular arachnoid cyst in an elderly man

A case of intraventricular arachnoid cyst in an elderly man is reported. A 63-year-old man developed a progressive gait disturbance over a five-year period. CT scan showed a large cyst in the left lateral ventricle which was negative to contrast enhancement. CT cisternography revealed gradual accumulation and more than 48 hours retention of contrast medium in the cyst. The patient underwent left frontal craniotomy, and the cyst wall was partially resected for histopathological examination. Although limit microscopic examination could not establish a diagnosis, arachnoid cyst was diagnosed by electron microscopic findings. Biochemical analysis did not detect any difference between cyst fluid and CSF obtained during surgery. It is suggested that a ball-valve mechanism caused progressive enlargement of the cyst and gradual development of symptoms in this elderly patient.

Treatment of cranial dural arteriovenous fistulae by interruption of leptomeningeal venous drainage

Cranial dural arteriovenous fistulae (AVF's) of the tentorial incisura or the dura of the middle fossa have a much higher incidence of draining via leptomeningeal veins than do AVF's of the transverse-sigmoid sinuses or the cavernous sinus. Such a drainage pattern is associated with an increased incidence of intracranial hemorrhage and progressive focal neurological deficits. Patients with cranial dural AVF's often undergo surgical excision and/or endovascular embolization for elimination of the AVF. Since these lesions are frequently large and involve the skull base or adjacent dural sinuses, extensive surgery is often required. In contrast, spinal dural AVF's with only intradural venous drainage to the medullary venous system are treated successfully by simply interrupting the vein that drains the dural AVF as it enters the subarachnoid space. The authors identified a subgroup of patients with cranial dural AVF's in whom the AVF was drained only by leptomeningeal veins, and sought to establish whether simple interruption of the vein draining the blood from the AVF into the subarachnoid space is effective and lasting treatment in this subgroup of patients, as it is in patients with spinal dural AVF's. Four adult patients with symptomatic cranial dural AVF's (two petrotentorial, one middle fossa floor, and one posterior fossa base) were identified on arteriography as having fistulae that were supplied by the internal and/or external carotid arteries and drained only via leptomeningeal veins (two entered the petrosal vein, one a cerebellar hemispheric vein, and one a mesencephalic vein). All patients underwent interruption of the vein draining the dural AVF as it penetrated the dura to enter the subarachnoid space, and experienced neurological improvement after surgery. Repeat arteriography at 1 to 2 weeks (three patients), 3 months (3 patients), 12 to 15 months (three patients), and 4 years (two patients) revealed no residual AVF and no evidence of abnormal blood flow. Many cranial dural AVF's with leptomeningeal venous drainage (the type with the most aggressive behavior) are drained only by leptomeningeal veins. This subgroup of patients can be identified by selective arteriography and requires only interruption of the draining vein as it enters the subarachnoid space for successful, lasting elimination.

Surgery of giant gliomas of chiasma and IIIrd ventricle

During a period of 17 years (from 1976 till now) 45 patients with giant gliomas of the chiasma and the IIIrd ventricle out of a total amount of 120 patients with hypothalamic gliomas were operated. The following classification of tumours was used: I) tumours with predominant anterior growth; II) tumours which infiltrate chiasma and penetrate into the IIIrd ventricle; III) gliomas of the floor of the IIIrd ventricle and the chiasma, growing into the ventricle cavity; IV) tumours of the chiasma, optic tract and thalamus. The authors come to the conclusion, that surgical removal of giant tumours of the chiasma and the IIIrd ventricle, though risk, may result in an improvement or stabilisation of visual functions (77%) and a long period free from recurrencies (9.5%). The postoperative period is relatively favourable and the mortality is low (6%). The main contraindication in our opinion is a wide infiltration of adjacent brain structures by the tumour and spreading along both optical tracts. We consider the giant size of a tumour in itself a sufficient indication for surgery.

Thecal repair in post-surgical pseudomeningocoele

A postsurgical pseudomeningocoele (PSPM) forms when cerebrospinal fluid extravasates through a dura-arachnoidal tear and becomes encysted within the wound. Patients may become symptomatic with wound swelling, headache and radiculopathy. A uniform method of repairing PSPMs is described which includes separation of the dura from the arachnoid, dural repair under operating microscope control, and the use of overlapped local flaps to reinforce the dura and obliterate the PSPM sac. Four recent cases are presented which were successfully treated using this method.

A pilot investigation of poloxamer 407 for the prevention of leptomeningeal adhesions in the rabbit

Leptomeningeal adhesion formation frequently complicates operations and diseases of the central nervous system. Chronic adhesive arachnoiditis may follow intraspinal surgery for disc, tumor, and closure of myelomeningocele, eventually producing pain and declining neurological status of the patient. Reoperation for scar removal is seldom successful as the arachnoidal adhesions reform. Poloxamer 407 (P407) has been shown to reduce postoperative peritoneal adhesion formation in rats and golden hamsters. In a rabbit model, we investigated the potential of P407 to prevent the production of arachnoidal adhesions and nerve root scarring following laminectomy and surgical meningeal injury. The lumbar spinal roots of 8 New Zealand white rabbits were surgically isolated under magnification. One root sleeve axilla was opened and immediately closed with 10-0 suture (control site) and a second root sleeve axilla was opened, P407 injected, and closed with 10-0 suture (treatment site). Five of 7 rabbits treated with P407 and followed for 7-42 days showed no arachnoidal adhesions at the level of the nerve root. Four New Zealand white rabbits had the lamina removed, and the dura over the spinal cord was opened at two sites separated by one to two lumbar segments. At one site P407 was inserted beneath the dura following durotomy, and the other site was opened in a similar fashion and immediately closed without the insertion of P407. There was a 50% reduction in leptomeningeal adhesion formation with the use of P407. P407 may be useful in neurosurgery for the prevention of arachnoidal adhesions.

Cerebral oedema associated with WHO-I, WHO-II, and WHO-III-meningiomas: correlation of clinical, computed tomographic, operative and histological findings

Meningiomas were studied in 60 patients retrospectively. Clinical, operative and histological findings were correlated with the occurrence and extension of peritumoural oedema as measured by computerized tomography. A relationship was found between both oedema and seizures and between oedema and tumour location. No relationship between tumour size, arachnoid breaching, WHO-grade or tumour vascularity and oedema was detected. In four patients with severe pre-operative oedema, cerebral signs and symptoms persisted despite uncomplicated tumour removal. The present study shows that peritumoural oedema is not only epileptogenic but that it can also cause irreversible cerebral damage as well. Since this study purports to demonstrate that meningiomas with intact leptomeninges can show severe peritumoural oedema, the blood barrier breakdown theory cannot be considered as the only aetiological factor.

Presentation and management of suprasellar arachnoid cysts. Review of 20 cases

The clinical presentation and treatment of suprasellar arachnoid cysts remain controversial. The authors review 20 cases treated at their institution and 86 cases from the literature reported in sufficient detail for analysis. The high frequency of endocrinological disorders, which not only persist following treatment but may also develop years later despite the satisfactory decrease in volume of the cyst, are emphasized and documented. The difficulties of management are discussed, including; subfrontal approaches to these cysts; removal and/or marsupialization of the cysts, procedures that are frequently dangerous and ineffective; and ventricular shunting which often leads to a paradoxical increase in the size of the cysts. The authors emphasize the advantages of percutaneous ventriculocystostomy, which is a simple, benign, and efficacious procedure.

Symptomatic arachnoid cyst at the clivus drained stereotactically through the vertex

A 40-year-old man had an acute ischemic event affecting the pons. He had no cardiac illness or vasculities and was not diabetic or hypertensive. The contrast-enhanced computed tomographic scan disclosed nothing abnormal, and a vertebral angiogram showed an avascular mass markedly displacing the basilar artery and pons posteriorly and toward the right. A magnetic resonance image clearly delineated a homogeneous arachnoid cyst containing cerebrospinal fluid. To avoid manipulating posterior fossa arteries, after the recent pontine stroke, this arachnoid cyst with unusually favorable anatomical landmarks was approached stereotactically through the vertex. Fenestration and drainage of the cyst was accomplished under local anesthesia and benzodiazepine sedation with low morbidity. The procedure was well tolerated, and the patient returned to gainful employment shortly afterward. He remains asymptomatic at 3 years' follow-up. The successful outcome of this case suggests that in carefully selected symptomatic arachnoid cysts, stereotactic interventions could become a useful surgical alternative. Stereotaxis may also be helpful in other cumbersome surgical cases in which a second port for contrast injection or simple manipulation would be advantageous.

magnetic resonance diagnosis of spinal arachnoid cyst. A report of two cases

Magnetic resonance (MR) findings in one case each of extradural and intradural arachnoid cyst are described. Thoracic segments were involved in both cases. The cysts were slightly more intense than cerebrospinal fluid in both cases on T1 weighted images. The nature and extent of the lesions were better demonstrated on MR images as compared with combined myelography and computed tomography.

Surgical treatment of patients with midline arachnoid cysts

Usually, arachnoid cysts are found in the Sylvian fissure (about 85%); midline arachnoid cysts are rare. Typical clinical symptoms are increased intracranial pressure, caused by a concomitant hydrocephalus, as well as visual and/or endocrinological disturbances. Six patients were examined, treated with one of two different surgical methods (cyst shunting or open treatment, either craniotomy/cyst membrane resection or laser endoscopy). Better results were observed following open treatment methods.

Middle fossa arachnoid cyst eroding into the middle ear: case report

We describe an unusual presentation of a large middle fossa cyst which eroded through the anterior petrous ridge into the middle ear. The significance of this and considerations related to its treatment are discussed.

[Surgical treatment of intracranial arachnoid cysts]

The results of surgical treatment in 21 cases of intracranial arachnoid cysts, mostly in adults, are reviewed. There were 19 supratentorial and 2 infratentorial cysts. In all but one supratentorial cyst cases epileptic seizures were the major clinical presentation. CT scan was helpful in the diagnosis in most cases. In 7 patients CT-cisternography was performed and in 3 cases a connection of cyst cavity to intracranial cerebrospinal fluid space was demonstrated. The cysts were treated surgically in different ways including craniotomy for fenestration of cyst wall, resection of cyst wall and neighbouring cerebral structures or cyst-peritoneal shunting. In some cases successive surgical treatment was necessary since the initial surgery proved to be unsuccessful. The authors believe that the best results were achieved by cyst removal with resection of cerebral structures being the source of epileptic discharges under intraoperative electrocorticographic control. The regression or diminished intensity of seizures can be achieved in this way. The fenestration of cyst alone leads to cyst recurrence. Cyst-peritoneal shunting usually did not lead to significant reduction of cyst size and delayed complications caused this kind of treatment to be uneffective. The significant number of infectious complications in all surgical treated cases of arachnoid cysts suggest the need for avoiding operation in asymptomatic or oligosymptomatic cases.

Vicryl (polyglactin 910) mesh as a dural substitute in the presence of pia arachnoid injury

Previously presented data showed that Vicryl mesh was a potentially effective dural grafting material. It is easily handled, relatively inexpensive, absorbed over time, and elicits a minimal inflammatory response. The present experimental project was conducted to investigate the effectiveness of a tightly woven version of the material as a watertight seal and to evaluate its performance in the presence of pia arachnoid injury. The mesh formed a seal promptly and adhesion formation was slight. Tightly woven Vicryl mesh appears to have a significant potential as an absorbable dural substitute.

An arachnoid cyst extending above and below the foramen magnum

A case of progressive bulbar and long tract symptoms with hydrocephalus of eleven years duration in a 23-year-old man, in whom an arachnoid cyst of the cisterna magna cerebellomedullaris was disclosed at operation.

Intradiploic arachnoid cysts. Report of two cases

Two patients are presented in whom cranial arachnoid cysts developed as diverticuli of the arachnoid membrane through small defects in the dura mater, eroded through the inner table, expanded within the diploe, and eroded the outer table of the skull. Based on observations at the time of surgery and the histological examination of these lesions, it is proposed that they are congenital in origin. Previously reported cases of "traumatic arachnoid cyst without fracture," "intradiploic cerebrospinal fluid fistula," and "middle fossa pitholes" appear to represent the same pathological process as the lesions reported in this paper. It is proposed that "intradiploic arachnoid cyst" is the most appropriate term by which these lesions should be described.

Abnormal origin of the ophthalmic artery from the anterior cerebral artery: neuroradiological and intraoperative findings

A 7-year old male child with an abnormal ophthalmic artery arising from the A1 segment of the anterior cerebral artery is described. The patient suffered growth inhibition which was thought to be caused by a craniobasal cystic lesion affecting the hypothalamus. Preoperative angiograms revealed no vascular abnormalities. The right ophthalmic artery, however, could not be identified. During resection of a large arachnoid cyst the ophthalmic artery was found to arise from the A1 segment of the anterior cerebral artery. To the best of our knowledge, this exact anomaly has not previously been reported. The clinical, neuroradiological and intraoperative findings are presented.