Posterior fossa extraaxial cyst: diagnosis with metrizamide CT cisternography

Arachnoid cysts of the cerebellopontine angle: diagnosis and surgery

OBJECTIVE

The optimal surgical management of arachnoid cysts remains controversial. The cerebellopontine angle (CPA) is a rare location for arachnoid cysts, and only 28 cases of arachnoid cysts occurring in the CPA have been reported in the literature. We discuss the diagnosis, radiographic imaging, and surgical management of CPA arachnoid cysts.

METHODS

Five patients (three male and two female patients) with a mean age of 5.6 years have been operated on at our institution since 1980. Magnetic resonance imaging allows for the accurate diagnosis of these arachnoid cysts, which can present with only discrete symptoms, such as headache or ataxia. All five arachnoid cysts compressed the cerebellum or brain stem. One patient had associated hydrocephalus. Three patients presented with refractory headaches associated with nausea and vomiting. The remaining two patients presented with cerebellar signs. No patient had an initial cranial neuropathy.

RESULTS

All patients underwent a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls. One patient underwent two procedures. A cystoperitoneal shunt was inserted at the first operation. After the shunting procedure, the patient's condition deteriorated; however, after the microsurgical resection and fenestration, his symptoms improved. With a mean 5.2-year follow-up, there has been no evidence of clinical or radiographic recurrence.

CONCLUSION

Although CPA arachnoid cysts represent a small number of total arachnoid cysts, the CPA is the second most common location for arachnoid cysts to occur. CPA cysts are congenital lesions found in children who present with subtle signs or symptoms. The definitive treatment for these arachnoid cysts is a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls.

Long-term evaluation of asymptomatic patients operated on for intracranial epidermoid cysts. Comparison of the diagnostic value of magnetic resonance imaging and computer-assisted cisternography for detection of cholesterin fragments

Magnetic resonance imaging (MRI) and/or computer-assisted cisternography (CAc) assessment of latent late recurrences in long-term asymptomatic patients surgically treated for intracranial epidermoid cyst is here presented. MRI was exclusively utilized in one patient; CAc was exclusively employed in three patients with metalic operative clips; both CAc and MRI were employed in another four patients. CAc appears to be more reliable than MRI in detecting cholesterin fragments in asymptomatic patients operated on for intracranial epidermoid cyst.

Transtentorial epidermoid cysts

Epidermoid cysts may occur simultaneously above and below the tentorium. Eleven patients with involvement of both infra- and supra-tentorial cisterns are presented. In two cases the epidermoid, located mainly in the cerebello-pontine angle, spread into the middle cranial fossa; in three the epidermoid extended from the parasellar cisterns to the posterior cranial fossa; in six patients the epidermoid, enlarging the tentorial notch, occupied extensively both cranial fossae. The surgical approach was influenced both by the experience of the surgeon and by the main extension of the epidermoid. Total removal was feasible in two patients only but only one of the eleven patients had a recurrence of the epidermoid. The long term results appear to be unrelated to the size of the epidermoid and to the choice of approach.

Epidermoid cysts of the fourth ventricle

Epidermoid tumors located in the fourth ventricle are exceedingly rare. Seven cases of this pathological condition were observed during a 10-year period. Patients were mostly middle-aged men, with a clinical history of relatively short duration (5 months). Clinical symptoms consisted of vertigo and ataxia, followed by incoordination, dysmetria, and tremor at a later stage. Computed tomography scanning represented the main diagnostic technique for these lesions, and typically showed a highly hypodense, round-shaped area within the fourth ventricle, occasionally accompanied by hydrocephaly. Subtotal surgical removal of the cysts produced excellent results in 86% of the cases. The implications of these findings are discussed.

Trapped fourth ventricle in an adult: radiographic findings and surgical treatment

Trapped fourth ventricle is a rare entity that has most often been reported mainly in children as a late complication of lateral ventricle shunting. We report a case in a previously normal adult who developed symptoms several months after bacterial meningitis. Unique radiographic and surgical findings are discussed, and recommendations are made for the classification and treatment of fourth ventricular enlargement.

Leptomeningeal cysts after spot freezing: transmission and scanning electron microscopic observations

The sequential development of the early phases of leptomeningeal cyst formation was studied in an experimental model. Light, transmission and scanning electron microscopic data were compared with those from human arachnoid cysts. Common features observed were: the participation of leptomeningeal cells in the structure of the cysts with exclusion of dural components; the absence of internal traversing trabeculae; the hyperplasia of leptomeningeal cells, particularly in the dome of the cysts. Other features of the experimental cysts were: the splitting of the pio-arachnoid membrane; the scarcity of collagen at the early stages; the presence of areas of mineralization at more advanced stages; the presence of remodeling parenchymal changes at the underlying nervous tissue.

Transmural passage of subarachnoid metrizamide into a cystic acoustic schwannoma of the cerebellopontine angle: a diagnostic dilemma

CT metrizamide cisternography performed in a patient with a non-enhancing cerebellopontine angle tumour demonstrated an increase in attenuation within the cystic area between the immediate scan and that undertaken 4 h later indicating delayed inward diffusion of the contrast. At operation the tumour was found to be a cystic acoustic schwannoma of the cerebellopontine angle. Diffusion of metrizamide was not previously been reported across the wall of a cystic tumour.

Epidermoid tumor in the fourth ventricle, with particular reference to metrizamide CT cisternography findings

The case of an epidermoid tumor in the fourth ventricle is presented, in which metrizamide computed tomographic (CT) cisternography was carried out. Unique features shown in the study might be specific to this lesion in this particular location. Clinical correlation of this finding was made with those findings seen at the operation.

Arachnoid cysts of the posterior fossa

A series of 6 patients with arachnoid cysts of the posterior fossa who were treated surgically is presented. The diagnosis of the nature of the lesion and of the exact location within the posterior fossa could not be established on a clinical basis. CT scanning is the best method for diagnosing the lesion and for observing the postoperative evolution. Treatment consisted of removing the cyst walls, shunting the cyst to the peritoneum, or both. The differential diagnosis of arachnoid cysts of the posterior fossa from other cerebrospinal fluid collections, such as the megacisterna magna or the Dandy-Walker malformation, are discussed.

Studies of the third circulation. Amipaque CT cisternography and ventriculography

The techniques of Amipaque (metrizamide) computerized tomography (CT) cisternography and Amipaque CT ventriculography are described. Normal, intermediate, delayed, and obstructive cerebrospinal fluid circulation patterns are readily demonstrated by evaluation of ventricular stasis of Amipaque on serial CT scans. Both the morphological and physiological characteristics of intracranial cysts are accurately defined and a diagnostic classification is presented. The functional integrity of ventricular shunts can be appraised using the ventricular persistance of Amipaque as a primary criterion. Other applications of these modalities are described and their place in the neurodiagnostic armamentarium is discussed.

Clinical evaluation of metrizamide for neuroradiology in chilren

Metrizamide is a nonionic water-soluble contrast medium for neuroradiological studies that is less irritating to the nervous system than other water-soluble agents. Studies in adults have shown that metrizamide has advantages over currently available media, but experience with children has been limited. Sixty-two children have had myelography or ventriculography using metrizamide. The children ranged in age from 11 days to 22 years. Technically satisfactory studies were obtained in every patient. No major complications were encountered. Minor side-effects included headache in 11 children (18%), mild nausea or vomiting in 16 children (26%), and fever in 4 children (6%). Seizures did not occur. One infant in the study subsequently died of unrelated problems; there was no evidence of arachnoiditis at postmortem examination. Metrizamide is a safe, effective contrast medium for neuroradiological use in children.

The value of computed tomography in the evaluation of the enlarged head

The contribution of computed tomography (CT) in the assessment of macrocrania has been examined with reference to a consecutive series of 93 cases. In the great majority a definitive diagnosis could be made without resorting to more noxious procedures. Hydrocephalus was present in 46% of this group. The incidence of macrocrania with childhood hydrocephalus and its relationship to the aetiology and other CT features was examined with reference to 109 consecutive cases with hydrocephalus shown on CT. Macrocrania was present in only 11% of cases with an underlying tumour, but in 71% with other obstructing lesions.

Metrizamide CT cisternography combined with Myodil (Pantopaque) cisternography in the investigation of suspected small acoustic neuromata

A combined technique for the investigation of suspected small acoustic neuromata, involving the performance of a metrizamide CT cisternogram, a Myodil (Pantopaque) cisternogram, and also an estimation of the CSF protein level, all at the same examination, is described. An entirely negative result excludes an acoustic neuroma. A few illustrative abnormal cases are described.