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A desmoplastic infantile astrocytoma (DIA) is an extremely rare tumor that comprises a solid astrocytic tumor accompanied by a large cyst and involves the superficial cerebral cortex and leptomeninges in infants. The solid part of this type of tumor has been well described in various reports and books, but characteristics of the cystic portion have remained unclear. Because adequate resection is required to ensure a favorable prognosis, information about the cyst is very important for diagnostic purposes and surgical planning. The authors report on the clinical and histological features of the cyst in a case of a DIA. A 12-month-old boy presented with vomiting. Contrast-enhanced magnetic resonance imaging revealed a strongly enhancing single-lobed large cyst located in the deep white matter, under the solid part of the tumor attached to the dura mater of the left frontal lobe. Both the solid and cystic portions of the tumor were surgically removed. The border between the cyst wall and surrounding white matter was unclear. Histologically, the cyst wall was composed of gliosis representing a rough accumulation of reactive astrocytes, lymphocytes, and small capillary vessels in edematous parenchyma, but no tumor cells. The present case and previous reports suggest that the cyst does not contain tumor cells, even if strongly depicted on contrast-enhanced neuroimaging, and that a thickly enhancing cyst wall indicates gliosis with accumulation of numerous small vessels.

Intraventricular congenital lesions and colloid cysts comprise a rather large spectrum of different pathologic conditions. In most cases, treatment in not warranted unless there is progressive ventricular obstruction with hydrocephalus or growth of the lesion itself, making tissue biopsy and histopathologic diagnosis necessary. Accordingly, a precise neuroradiologic evaluation is of the utmost importance, because most lesions, if not symptomatic, only require clinical and radiologic follow-up.

A case of sacral perineurial cyst with ossification of the arachnoid membrane discovered intraoperatively is reported. We are not aware of any similar cases in the literature.

Three unusual meningiomas with extensive microcystic formation were studied by light- and electron-microscopy. The tumor cells in the first and second cases had many morphological characteristics in common with the arachnoid cap cells: prominent and complex interdigitation of the fine cytoplasmic processes, numerous well developed desmosome attachments, and intracytoplasmic microfilaments. The prominent features of these tumors were a marked vascularization and hyaline thickening of the vessel walls, and the microcystic formation was considered to be related to these changes. In contrast, the tumor cells of the last case had characteristic structures in common with trabecular arachnoid cells. They were stellate in shape, and had only a small number of intracytoplasmic filaments. Arborizing relatively thick and long cytoplasmic processes showed simple junctions with occasional desmosomes, and delimitated microcysts. The tumor cells in this case were considered to recapitulate the subarachnoid structure and formed microcysts. Although the histogenesis of microcysts in meningiomas is not considered to be uniform, the biological behavior of these 3 tumors corresponded to those of meningiomas in general.

The best operative intervention for children with arachnoid cysts remains the subject of controversy. Recent reports stress that craniotomy for cyst fenestration is associated with a low incidence of morbidity and mortality and may leave the child shunt-independent. The cases of 40 pediatric patients with arachnoid cysts treated between 1978 and 1989 are reported. Five children with mild symptoms and small cysts that remained stable on follow-up studies have not required surgical intervention. Of 15 patients with cysts initially treated by fenestration, 10 (67%) showed no clinical or radiographic improvement postoperatively and have undergone cyst-peritoneal (eight patients) or ventriculoperitoneal (VP) shunting (one patient), or revision of a VP shunt placed for hydrocephalus before cyst fenestration (one patient). Two other patients with existing VP shunts required no further procedures. Thus, only three (20%) of 15 patients initially treated by fenestration remain shunt-independent after a median follow-up period of 8 years. The 20 other patients were initially treated by cysts shunting and all improved postoperatively; shunt revision has been necessary in six (30%) of these 20 patients because of cysts recurrence. Cyst location influenced the success of shunt treatment; none of the seven middle cranial fossa cysts treated by shunting have required revision, but results with cysts in other locations were less favorable. In all locations, though, shunting was more successful than fenestration. It is concluded that cyst-peritoneal or cyst-VP shunting is the procedure of choice for arachnoid cysts in most locations, including those in the middle cranial fossa.

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.

Two cases of extradural arachnoid cyst in the spinal canal were diagnosed by magnetic resonance imaging (MRI). MRI correctly characterized the extradural location of the cysts as well as the cyst contents as CSF, thus establishing the diagnosis. MRI may be of predictive value in the postoperative prognosis.

A 34-year-old woman developed symptomatic arachnoiditis ossificans and an arachnoid cyst as a consequence of tuberculous meningitis adequately treated 20 years before. Surgical decompression of the cyst stopped the progression of her spastic paraparesis. Pathologic examination confirmed the presence of ossification of the arachnoid.

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.

Arachnoid cysts of the quadrigeminal cistern are rare. Patients with this lesion are usually normal at birth, and signs of increased intracranial pressure (IICP) develop at about 4 to 12 months of age. However, there has been no report about this mechanism. A case of arachnoid cyst of the quadrigeminal cistern is presented. In this case, the process of the cyst growth was observed during the course of follow-up for shunted hydrocephalus. Symptoms coincided with the growth of the cyst. Therefore, the development of the clinical symptoms was thought to be due to IICP caused by cyst expansion. Our case was complicated by inflammation, something that may offer a key to solving the mechanism of cyst fluid accumulation and the relationship between symptoms and development of the cyst.

A rare case of bilateral arachnoid cysts of the middle cranial fossa in a child successfully treated by partial excision of their walls is reported. Patients with bilateral arachnoid cysts are usually severely disabled, presumably due to primary dysgenesis of the operculum; however, in our case no primary dysgenesis was noted and the operative result was excellent.

Two patients with intraventricular arachnoid cysts are reported and a brief review of the relevant literature is presented. Arachnoid cysts are usually extracerebral or extraventricular. Intraventricular arachnoid cysts are rare: including the two cases reported here, only five cases have been described. The following characteristics were noted in these five patients: all were young; headache was the initial symptom in four; the cyst was in the trigone of a lateral ventricle in four; and there was dilatation of the inferior horn in three.

A case of extradural arachnoid cyst in the spinal canal of a 16-year-old male was diagnosed by magnetic resonance imaging. The diagnosis was verified by a metrizamide-enhanced computed tomographic myelogram. An operation with a favorable outcome followed. The noninvasive advantages of magnetic resonance imaging in such a diagnosis are demonstrated by this case.

MR studies in eight patients with extraaxial arachnoid cysts in the middle cranial fossa were reviewed in order to identify any associated structural defect in the ipsilateral temporal lobe. The study was prompted by the original theory that agenesis of the temporal lobe is the primary factor in the development of these cysts. Authors of subsequent studies proposed that the cysts are a consequence of embryological malformation of the meninges only and that the adjacent temporal lobe is compressed. Our findings suggest that middle cranial fossa cysts are associated with temporal lobe hypogenesis, and also that compression of the temporal lobe is an infrequent accompaniment.

A newborn girl was admitted suffering from convulsive seizures in both legs. A computed tomography (CT) scan revealed bilateral symmetrical middle cranial fossa arachnoid cysts and intraventricular hemorrhage. In the course of a year, only the cyst on the right side became gradually larger; the cyst on the left side was reduced in size. At the age of 1 year and 2 months, her intellectual development was normal, but she could not stand by herself. On metrizamide-enhanced CT cisternography, the cyst on the right side was of a noncommunicating type. Membranectomy of the right-sided cyst was performed and the cyst proved to be of the intraarachnoid type. The postoperative course was uneventful and a CT scan, taken 10 months after the operation, revealed no abnormality on either side. The intellectual and motor development was normal, and no abnormality was observed by electroencephalography. This may be the first report of arachnoid cysts found in a neonate. It gives us clues for understanding the etiology of this disease, which has not been fully clarified.

A case of transient global amnesia associated with an arachnoid cyst occupying the middle cranial fossa of the non dominant hemisphere is reported. The relationship between the two conditions is discussed and the value of CT brain scanning in patients with TGA emphasized.

The patients are 15 year old and 13 year old males who complained of a headache, vomiting and general malaise. The plain skull films showed thinning and bulging of the left temporal squama, forwards enlargement of the middle fossa and the elevation of the lesser wing of the sphenoid. The left carotid arteriography indicated significant elevation of the middle cerebral artery and the opercular portion of the middle cerebral artery was absent. Left frontotemporoparietal craniotomy was performed, and the large cyst as the space taking mass lesion of the middle fossa was noted. The cyst contained xanthochromic fluid and its wall probably consisted of arachnoid membrane. In both cases the cyst occupied anterior 6 cm of the left middle fossa and no brain tissue was noted between the cyst and the anterior part of the middle cranial fossa. Histologically, the membrane of the cyst was arachnoid. Their recognition and management are discussed.

An association between arachnoid cysts of the middle fossa (ACMF) and complicating subdural haematoma (SDH) has been previously noted. More recently it has been hypothesized that ACMF may predispose to SDH formation. The Plymouth Neurosurgical Unit has treated twenty patients with ACMF between 1976-1985, seven of these being complicated by SDH. There was an age range of 11-56 years in those with SDH. Six of the seven patients with ACMF and SDH gave no significant trauma history. Four of these were males aged 11 to 20 years. The presenting histories, clinical findings and subsequent management of these patients were compared with the age-matched males with SDH alone (twelve patients). In the SDH alone group 100% suffered major skull trauma and 80% had demonstrable skull fractures. In addition the patients with ACMF were compared with patients presenting with other supratentorial arachnoid cysts in Plymouth. Only ACMF were associated with the development of SDH in our study. Three patients demonstrated total masking of the ACMF by isodense intracystic haematoma on computed tomography. In two of these patients the presence of an ACMF was suspected due to plain radiographic and CT enlargement of the middle fossa. It is advocated that with special reference to young males, in the absence of major skull trauma an ACMF should be suspected as a predisposing factor to SDH. Postoperative CT scans for at least one year are advisable in young patients with SDH as demonstration of the presence of an ACMF and SDH affects future management.

Thirteen pathologically documented intrasellar arachnoid cysts treated by transsphenoidal cyst excision and marsupialization were analyzed. Presenting symptoms included headache (7), visual loss (7), galactorrhea (4), and anterior pituitary dysfunction (2). Postoperatively, the 7 patients with visual loss and 4 with hyperprolactinemia improved. The 2 patients with anterior pituitary dysfunction did not improve and 2 additional patients required hormonal supplements. Based on this operative experience, the pathophysiology of these cysts is discussed. The indications for transsphenoidal exploration include the following: to relieve optic chiasm, pituitary stalk or gland compression, and to exclude the possibility of other sellar neoplasms.

Light and electron microscopic features of four arachnoid cysts in children are presented. The wall of the cyst appeared composed of a dense collagen tissue in which dark and clear cells were intermingled without any specific arrangement. Abutting onto this membrane, at the luminal surface, these cells were arranged in layers. Tight junctions between arachnoid cells were absent. It is suggested that the arachnoid cysts derive from a developmental aberration of the meninges.

A 34-year-old female was admitted to hospital with complaints of headache, left-sided scalp mass, right-sided hemiparesis and seizures and the history of a head injury when she was five years old. X-rays revealed a left temporoparietal lens-shaped defect. CT scans showed a cystic cavity which was connected with the ventricular system. On operation the loss of dura mater was found to be greater in extent than the loss of brain tissue. Recovery after surgical intervention is seen after two weeks.

Accidental death brought to autopsy a 19-year-old girl with asymptomatic arachnoid cyst which had expanded from the region of the interpeduncular cistern so as to replace the third ventricle and extend into both alteral ventricles. Associated with this expansion was a significant degree of hydrocephalus, compression of the walls of the lateral ventricle, and obliteration of the normal structures of the floor of the third ventricle. The histological structure of the cyst wall and its relationship to the normal arachnoid are defined and found to consist of a reduplication of the normal arachnoid membrane resulting in a space within the arachnoid tissue. It is suspected but not proven that the cyst was congenital, resulting from an abnormality in development. Some suggestions are offered regarding the mechanism for its enlargement.

A case of malignant degeneration in a right parapontine epidermoid cyst giving rise to leptomeningeal carcinomatosis in a 57 year old woman is presented. The malignant tissue had infiltrated the right cerebellar hemisphere and produced a symptomatic trigeminal neuralgia, a change in the psychological state of the patient, and an acute conus and cauda syndrome following metastasis implantation. Only eight unequivocal previous reports of malignant transformation of intracranial epidermoid cyst have been reported in the literature with metastases in four.

Arachnoid cysts of the middle cranial fossa are probably not so infrequent as previously thought. Twenty-five cases are reported together with the most relevant clinical and radiological findings. The authors emphasize the importance of computerized tomography (CT) in providing pre- and postoperative anatomical and physiopathological information. The potential morbidity of these lesions is stressed and surgical indications are discussed with preference for a radical craniotomy rather than a shunt procedure.

Flow void due to pulsatile motion of cerebrospinal fluid (CSF) has recently been demonstrated by a variety of magnetic resonance techniques with sensitivity to slow flow. It has been suggested that within fluid collections not communicating with the physiologic CSF space, there is less signal loss than with the physiologic CSF spaces. Utilizing the SSFP MR technique, which is sensitive to flow as slow as 1 mm/sec, we evaluated three patients with isolated arachnoid cysts. Irregular signal loss consistent with fluid motion was noted within all of the cysts, as well as within the physiologic CSF spaces. Definitive anatomic evaluation of these lesions, though, required ventriculography, an invasive technique.

This is a report of a patient who developed sharp intercostal pain and Brown-Séquard syndrome. Displacement of the spinal cord toward an extradural mass was noted at the T4-5 vertebral level on iophendylate myelography and metrizamide computerized tomography myelography. Multiple meningeal diverticular lesions of congenital origin were also found. Surgical correction of the spinal cord, which had herniated into a laterally located extradural arachnoid cyst and become incarcerated, resulted in a complete neurological recovery.

We report a case of post-traumatic lumbar arachnoid cyst, which enlarged the spinal canal and eroded the posterior elements. Computed tomographic myelography and magnetic resonance (MR) were complementary, and both correctly characterized the cystic nature of the lesion. Communication between the cyst and the subarachnoid space was demonstrated on CT myelography, which also clearly showed bone changes in the spinal canal. Continuity of the cyst with the spinal subarachnoid space was seen clearly on sagittal MR, and the MR signal characteristics of the cyst were identical with CSF.

Eight cases of intraspinal arachnoid cysts are described. The clinical, radiological, intraoperative and histological findings are presented and compared with similar reports in the literature. Opinions in the literature concerning the origin of arachnoid cysts are discussed, and compared with our own case reports. A traumatic or inflammatory origin of the arachnoid cysts is denied if accompanying histological changes are lacking. In such cases the arachnoid cysts are to be viewed as congenital malformations.

The clinical features and neuroradiological and computertomographic findings in 125 patients with cystic intracranial processes, which were neither due to tumour nor of vascular origin, have been analysed. The intrathecal injection of iodinated contrast media is absolutely essential for the differential diagnosis of congenital cysts. CT demonstration using 2 mm. slices and coronal and sagittal reconstruction makes it possible to relate the lesions to surrounding brain structures. Additional anomalies of the brain can be diagnosed and considered when planning treatment. Air studies are no longer necessary, but plain films remain the first diagnostic step. In view of modern micro-surgical techniques, angiography remains of value in order to diagnose vascular anomalies at a pre-operative stage.

We have reported a case of epicranial arachnoid cyst, a developmental abnormality that occurs at the obelion, and have reviewed characteristic clinical and radiologic features that facilitate diagnosis.

Two unique findings, advanced calcification and ectopic neuroglia, were encountered in the wall of a giant congenital arachnoid cyst occurring in a 40 year old woman. The cyst almost totally filled the supratentorial subdural space of the left hemicranial cavity, was not connected with the subarachnoid space, and thus developed intra-arachnoidally. Its congenitally derived nature was supported by the unique finding of heterotopic neuroglia in the wall. Congenital arachnoid cyst must be distinguished from various cystic lesions within the central nervous system, including the neuroepithelial cyst which can arise throughout the neuraxis. It is suggested that pathogenesis of the congenital arachnoid cyst is related to aberrant flow of the ventricular cerebrospinal fluid into the developing leptomeninx in the process of differentiation of the subarachnoid space. The tract or pouch may occur within the arachnoid mater, and the cyst is formed intra-arachnoidally when the former filled with fluid is closed off from the subarachnoid space.

Arachnoid intracranial cysts are benign lesions which until recently have been considered to be quite uncommon. They are benign congenital lesions usually discovered at an early age. We have recently treated two patients with advanced age and arachnoid cysts, unusual due to their location and extent. Both of them presented clinically with an organic dementia syndrome with some similarities to that seen in normal pressure hydrocephalus. Both recovered fully after surgery. We review the literature and try to emphasize the clinical differences between arachnoid and the more rare neuroepithelial cysts.

The clinical features of 33 patients with primary intracranial arachnoid cysts are reviewed. Magnetic resonance imaging was performed in 9 patients and was particularly useful in the multiplanar definition of complex cysts and in differentiating arachnoid cysts from other lesions that are hypodense on computed tomographic scans. Hydrocephalus, cranial nerve palsies, or symptomatic brain compression was considered an indication for surgical intervention in 21 patients. Outcome was uniformly good: mild focal weakness and seizure disorders constituted the sequelae.

Choroid plexus-like structures were found in the wall of a congenital frontotemporal arachnoid cyst in a 14-year-old girl who presented with temporal lobe seizures since the age of 6. The temporal cortex beneath the cyst was maldeveloped. The clinical, radiological, and pathological aspects of congenital arachnoid cysts are reviewed.

Two patients were seen. One had chronic monocular choked disc, visual loss, and optociliary veins; the other had optic atrophy and a left-sided frontotemporal porencephalic cyst. Both patients were found on pathologic examination to have arachnoid cysts involving a localized segment of the intraorbital optic nerve.

Spasmus nutans, usually believed to be a benign entity, is a disorder of young children consisting of nystagmus, head nodding and an anomalous head position of unknown etiology. We present a patient with spasmus nutans who proved to have a large arachnoid cyst. When the cyst was shunted the nystagmus lessened. Recent studies suggest that the head nodding and anomalous head position are adaptive mechanisms that compensate for the nystagmus and not pathological in themselves. Therefore, spasmus nutans is not a triad of findings, but an acquired nystagmus with associated adaptive responses. Because spasmus nutans implies a benign entity composed of three requisite components, we feel it is an inaccurate term that should be abandoned. A better designation would be acquired nystagmus of infancy, which would not imply a benign etiology.

The case history is presented of a man with an atypical psychosis and classical clinical features of alexithymia. On his last admission, the patient presented with starvation and hypernatremic coma. A CT scan, which was done because of the coma, revealed a large left fronto-temporal arachnoid cyst. The significance of this finding is reviewed in the light of previously suggested organic bases for alexithymia and related syndromes. Although the symptom of alexithymia is present, the patient's other symptoms do not fit readily into existing diagnostic categories and the resulting diagnostic dilemma is discussed.