Suprasellar arachnoid cyst
Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain
They differ from other arachnoid cysts in several ways, making a separate analysis of these cysts worthwhile.
In adults suprasellar cysts represent 9% of all the arachnoid cysts while in pediatric population this percentage reaches 15%. 1).
A suprasellar cyst can be a communicating cyst with a valve at the penetration of the basilar artery (BA) through the prepontine arachnoid membrane or be a noncommunicating cyst 2).
Miyajima et al proposed a classification:
1) a noncommunicating intra-arachnoid cyst of the diencephalic membrane of Liliequist
2) a communicating cyst that is a cystic dilation of the interpeduncular cistern 3).
Their presence in utero and their high prevalence in children who have no history of trauma support the assumption that they are congenital 4) 5) 6) , although there is some question as to how early in development the cysts are formed.
Typically, expand from the prepontine space, displacing the floor of the third ventricle upwards, the pituitary stalk and optic chiasm upwards and forwards, and the mammillary bodies upwards and backwards. As the cyst increases in size it fills and occludes the third ventricle, and distorts and blocks the aqueduct, which finally results in hydrocephalus.
A slit-valve mechanism seems to be at least one factor of the genesis of suprasellar prepontine arachnoid cysts 9).
In postraumatic cases one hypothesis is that the inflammatory process due to subdural hematoma may locally result in arachnoiditis, and thus to the creation of a neomembrane, and eventually to cyst formation 10).
Although their true histological nature is rarely known because their membranes are not often analyzed histologically, it is reasonable to think that the majority are arachnoid cysts.
It can be diagnosed as incidental in asymptomatic patients 11).
There are three reported cases of spontaneous disappearance of a suprasellar arachnoid cyst 12).
Obstructive hydrocephalus is the most common cause of initial symptoms and occurs in almost 90% of the patients with suprasellar arachnoid cyst13) , and can have varied presentations with signs and symptoms of obstructive hydrocephalus by compressing the third ventricle that require urgent decompression. These patients may present with nonfocal symptoms that can quickly lead to a life-threatening condition if not accurately diagnosed and treated.
Urgent endoscopic third ventriculostomy results in normalization of intracranial pressure, return of normal CSF flow, and relief of symptoms 14).
Other clinical features
Distortion of the pituitary infundibulum can also result in endocrine dysfunction
Ramesh et al. present three cases with bobble-head doll syndrome associated with a large suprasellar arachnoid cyst and obstructive hydrocephalus 20).
Precocious puberty is rarely the presenting sign. It is characterized by early onset, patent symptoms and frequent association with growth hormonedeficiency. The latter represents a further risk of short stature. Evolution of precocious puberty varied from one case to another, without any relation with the quality of control of the arachnoid cyst and associated hydrocephalus. Half-yearly follow-up of height and bone age allowed for deciding a suppressive treatment of precocious puberty and a substitutive growth hormone therapy when needed 21).
Various forms of symptomatic and idiopathic epilepsy and other psychoneurological disorders (disorders of behavior and emotions, obsession-compulsion syndromes, stereotypias, aggression, compulsive ideas and movements, anorexia or hypothalamic obesity) coincident with one or more endocrine disorders such as precocious or delayed puberty, multihormonal pituitary deficiency, panhypopituitarism and secondary hypothyroidism were detected 22).
MRI reveal cerebrospinal fluid (CSF) intensity on both T1- and T2-weighted images 24).
As with arachnoid cysts elsewhere, they are very thin walled (often imperceptible except on dedicated hi resolution T2 imaging) cystic lesions which follow CSF on all imaging modalities. There is no solid component and no enhancement.
These cysts invaginate superiorly into the third ventricle, and may even extend into one or both foramina of Monro.
Obstructive hydrocephalus at the level of the aqueduct with expansion of the third ventricle floor of the third ventricle should be depressed no cyst wall should be visible of inferred (by CSF flow)
Cystic suprasellar lesions
Hypothalamic hamartomas have been reported to coexist with lesions like Rathke’s cleft cyst and arachnoid cysts in the suprasellar or temporo-sylvian regions. 25).
Spontaneous Intracystic Hemorrhage 26).
Treatment is required when the cyst evolves or the patient is symptomatic, but endocrine disturbances alone are not an indication for surgery.
When hydrocephalus is present, endoscopic fenestration is the primary treatment of choice. The goal of the procedure should be to open the cyst into both the ventricles and the cisterns.
The use of an endoscope in the treatment of suprasellar arachnoid cysts provides an opening of the upper and lower cyst walls, thereby allowing the surgeon to perform a ventriculocystostomy (VC) or a ventriculocystocisternostomy (VCC). To discover which procedure is appropriate, magnetic resonance (MR)-imaged cerebrospinal fluid (CSF) flow dynamics in two patients were analyzed, one having undergone a VC and the other a VCC using a rigid endoscope. Magnetic resonance imaging studies were performed before and after treatment, with long-term follow-up periods (18 months and 2 years). The two patients were reoperated on during the follow-up period because of slight headache recurrence in one case and MR-imaged CSF flow dynamics modifications in the other. In each case surgery confirmed the CSF flow dynamics modifications appearing on MR imaging. In both cases, long-term MR imaging follow-up studies showed a secondary closing of the upper wall orifice. After VCC, however, the lower communication between the cyst and the cisterns remained functional. The secondary closure of the upper orifice may be explained as follows: when opened, the upper wall becomes unnecessary and tends to return to a normal shape, leading to a secondary closure. The patent sylvian aqueduct aids the phenomenon, as observed after ventriculostomy when the aqueduct is secondarily functional. The simplicity of the VCC performed using endoscopic control, which is the only procedure to allow the opening in the cyst’s lower wall to remain patent, leads the authors to advocate this technique in the treatment of suprasellar arachnoid cysts 30).
Preoperative cisternography may be useful for selecting the optimal endoscopic treatment method.
If the cyst communicates with the basal cisterns, a ventriculocystostomy could be an effective, safe, and simpler treatment option 33).
Suprasellar and third ventricular size does respond to the surgical intervention at long-term follow-up 34).
Intellectual capability after treatment at outcome is not related to age at diagnosis, initial or final cyst size, presence or absence of hydrocephalus, or type of endoscopic treatment 35).
Three cases with bobble-head doll syndrome associated with a large suprasellar arachnoid cyst and obstructive hydrocephalus, which were treated with endoscopic cystoventriculocisternostomy and marsupialization of the cyst 36).
4 cases of suprasellar prepontine arachnoid cysts in which a slit valve was identified. The patients presented with hydrocephalus due to enlargement of the cyst. The valve was located in the arachnoid wall of the cyst directly over the basilar artery. Halani et al believe this slit valve was responsible for the net influx of CSF into the cyst and for its enlargement. They also present 1 case of an arachnoid cyst in the middle cranial fossa that had a small circular opening but lacked a slit valve. This cyst did not enlarge but surgery was required because of rupture and the development of a subdural hygroma. One-way slit valves exist and are a possible mechanism of enlargement of suprasellar prepontine arachnoid cysts. The valve was located directly over the basilar artery in each of these cases. Caudad-to-cephalad CSF flow during the cardiac cycle increased the opening of the valve, whereas cephalad-to-caudad CSF flow during the remainder of the cardiac cycle pushed the slit opening against the basilar artery and decreased the size of the opening. Arachnoid cysts that communicate CSF via circular, nonslit valves are probably more likely to remain stable 37).
73 consecutive patients who were treated between June 2002 and September 2009. Twenty-two patients were treated with VC and 51 with VCC. Outcome was assessed by clinical examination and magnetic resonance imaging.
The patients were divided into five groups based on age at presentation: age less than 1 year (n = 6), 1-5 years (n = 36), 6-10 years (n = 15), 11-20 years (n = 11), and 21-53 years (n = 5). The main clinical presentations were macrocrania (100%), motor deficits (50%), and gaze disturbance (33.3%) in the age less than 1 year group; macrocrania (75%), motor deficits (63.9%), and gaze disturbance (27.8%) in the 1-5 years group; macrocrania (46.7%), symptoms of raised intracranial pressure (ICP) (40.0%), endocrine dysfunction (40%), and seizures (33.3%) in the 6-10 years group; symptoms of raised ICP (54.5%), endocrine dysfunction (54.5%), and reduced visual field or acuity (36.4%) in the 11-20 years group; and symptoms of raised ICP (80.0%) and reduced visual field or acuity (40.0%) in the 21-53 years group. The overall success rate of endoscopic fenestration was 90.4%. A Kaplan-Meier curve for long-term efficacy of the two treatment modalities showed better results for VCC than for VC (p = 0.008).
Different age groups with SSCs have different main clinical presentations. VCC appears to be more efficacious than VC 38).
4 suprasellar arachnoid cysts, diminished for different degrees after operation. There were no surgery-related serious complications or deaths. There were not cyst enlarged and stoma obstructed cases 39).
Crimmins et al reported on 7 patients treated with ventriculocystostomy (VC) and 13 patients with ventriculocystocisternotomy (VCC). They found VCC had a higher success rate but the difference was not statistically significant 40).
Wang et al. retrospectively reviewed six cases, in which endoscopic ventriculocystocisternotomy was performed, to identify specific neuroimaging features that aid both the accurate diagnosis of this entity and the postoperative assessment of fenestration patency.
Six consecutive children underwent treatment for suprasellar arachnoid cysts. Consistent radiographic features in all cases were identified. Through a single entry site, endoscopic fenestration was performed at both the apical and basal cyst membranes. Outcome was assessed using clinical examination, quantitative changes in cyst size, and triplanar magnetic resonance (MR) imaging with flow-sensitive (long TR) sequences. In every case, the suprasellar cysts displayed three diagnostic MR imaging features: 1) vertical displacement of the optic chiasm/tracts; 2) upward deflection of the rostral mesencephalon and mammillary bodies; and 3) effacement of the ventral pons. Two patients initially underwent placement of a ventriculoperitoneal shunt before the cysts were recognized, but MR images obtained after shunt placement revealed the cysts. In a mean follow-up period of 26.2 months, all patients improved clinically. Postoperative imaging revealed a mean cyst volume decrease of 52.7% and a return to more normal suprasellar and prepontine anatomy. Flow-sensitive MR imaging confirmed pulsation artifact at all 12 fenestration sites. There was no surgery-related death and no additional cerebrospinal fluid diversion procedure was required.
To aid in the accurate diagnosis of prepontine arachnoid cysts, the authors identified several pathognomonic features on sagittal MR images: vertical deflection of the optic chiasm and mammillary bodies, as well as pontine effacement. Dual endoscopic fenestration into the intraventricular compartment and basal cistern is safe, and it effectively provides symptomatic relief by decreasing the cyst size. Triplanar flow-sensitive MR imaging sequences can confirm fenestration patency without the need for cine-mode MR imaging 41).
Seven patients who had endoscopic treatment; five were children under 15 years old who presented with delayed development and/or enlarged heads. The two adult patients, both of whom had insertion of shunts as children, presented with headache and vomiting due to shunt blockage. All patients improved following endoscopic cyst fenestration. There was no operative morbidity and there have been no relapses to date 42).
Two cases of partial excision of the cyst wall, through a pterional craniotomy, establishing communication with the basal subarachnoid spaces was carried out. The endocrinological symptoms regressed after surgery 43).
Five children with ventricular dilatation (4 boys, 1 girl) had features seen on computer tomographic scan that were consistent with suprasellar arachnoid cysts. All children were investigated with a CT ventriculogram and/or CT cisternogram, and no communication with the cyst was demonstrated. Three children were seen in the 1st year of life and the remaining 2 children were between 1 and 5 years of age. Hydrocephalus and developmental delay were the most common presenting features, followed by visual disturbance, squint, or ataxia. Direct surgical decompression was performed in all 5 patients to avoid long-term placement of a ventriculoperitoneal shunt. A temporary shunt was placed in 2 children because of high intracranial pressure. Direct partial excision of the cyst wall to allow long-term drainage into the basal cisterns or ventricular system was successful in all children. The presence of subdural collections postoperatively required temporary shunting in 2 children. After follow-up for between 10 and 22 months no clinical endocrinological sequelae have been detected, but 2 children have raised serum prolactin levels. Three children are developmentally delayed; one of these has regained some skills since surgery 44).
A premature neonate who developed a large, acquired arachnoid cyst as a consequence of intraventricular haemorrhage. The child was managed with endoscopic fenestration and made an excellent recovery 45).
Rao et al. report a Giant suprasellar arachnoid cyst presenting with precocious puberty 46).
A 67-year-old man first noticed loss of pubic and axillary hair in 1992 and then a visual field defect in 2001. He experienced loss of consciousness attributed to hyponatremia in April 2002. Magnetic resonance imaging showed a giant intrasellar cystic mass, 40 mm in diameter, that had compressed the optic chiasm. The patient complained of chronic headache, and neurological examination revealed bitemporal hemianopsia. Preoperative endocrinological examination indicated adrenal insufficiency, and hypothyroidism due to hypothalamic dysfunction. The patient underwent endonasal transsphenoidal surgery. The cyst membrane was opened and serous fluid was drained. Histological examination identified the excised cyst membrane as arachnoid membrane. The patient’s headaches resolved postoperatively, but the bitemporal hemianopsia and endocrinological function were unchanged. This arachnoid cyst associated with hypothalamic dysfunction might have been caused by an inflammatory episode in the suprasellar region 47).
Santamarta et al. report one case of a suprasellar arachnoid cyst in which a slit-valve mechanism observed by means of cine-mode MRI preoperatively and confirmed during the endoscopic intervention 48).
Kaisho et al followed a case of suprasellar arachnoid cyst for 12 years. The patient was a sixteen-year-old girl without particular problems in her general condition. She showed optic atrophy in both eyes and optic nerve hypoplasia with an inferotemporal quandranopsia in the left eye. A suprasellar arachnoid cyst communicating with the tubarachnoid space was found to extend into the sella turcica as an empty sella. A cyst wall was resected and a cyst-peritoneal shunt performed. After 12 years from the operation, sensitivity was slightly depressed in the visual field where it had already been disturbed. Although there are few reports in the literature on involvement of the optic nerves and chiasma by suprasellar arachnoid cysts, papilledema and optic atrophy are often found in children, and infero-temporal quandranopsia or homonymous hemianopsia have been reported. Visual field defects were most likely caused by compression of the optic nerve by cyst or prolonged papilledema. They also suspect that some kind of disturbance to the optic nerve occurred during extension of the arachnoid cyst as an empty sella, or during formation of arachnoid cyst in the fetus stage 49).
Rosso et al report a case of periodic sweating with multifocal dystonia is reported in a 60-year-old woman. At the age of 48 years, she presented with involuntary twisting of the lower face on the right. Six months later she noticed similar movements in the head and right arm. Four years later she began having attacks of generalized sweating over the whole face, anterior region of the trunk and both arms. The attacks occurred hourly each and every day. They lasted for about 10 min and were followed by voluntary urinary voiding. The biochemical and laboratory investigations showed no abnormalities except for the luteinizing hormone and follicle-stimulating hormone values that were below normal. The computerized tomography and magnetic resonance imaging scans revealed a suprasellar cyst 50).
A 53-year-old man was admitted because of decreased visual acuity. Magnetic resonance imaging showed a large intrasellar cyst extending into the suprasellar cistern, with compression of optic nerves. The intensity of the cyst was identical to that of the surrounding subarachnoid space on both T1-, T2-, and proton density-weighted images. Transsphenoidal surgery was performed, but subsequent refilling of the cyst required additional transcranial surgery. Analysis of the cerebrospinal fluid-like cystic fluid revealed high levels of protein and pituitary hormones. Histological study revealed that the cyst wall was composed of connective tissue and arachnoid cells, which were ultrastructurally characterized by a number of desmosomes 51).
A 2-year-old infant who presented with paroxysm and short changes characterized by acute drowsiness, cold sweats, ocular reversion, facial cyanosis, and bradycardia. Between these attacks, the condition was normal, suggesting diencephalic seizures. Over 2 months five fits were observed by the parents when some to-and-fro bobbing of the head onto the trunk appeared during drowsiness. One electroencephalogram was normal without a slow background or spikes discharges. As the skull radiographs showed erosion of the jugum and chronic intracranial hypertension features, a CT scan was performed and showed hydrocephalus associated with a congenital suprasellar cyst. The cyst was opened into basal cisterns with cystoperitoneal shunt. The histological examination revealed that it was an arachnoid cyst. Six months later, the infant was free of diencephalic seizures and head bobbing. Thus, we can assert that there was a direct relationship between this cyst and the diencephalic seizures. From this case, the authors make a review of the clinical features of diencephalic epilepsy, and their different causes and show that both diencephalic epilepsy and suprasellar arachnoid cysts are not common 52).
De novo suprasellar arachnoid cyst
A case of a 2-year-old boy who presented with instability and episodes of ocular deviation. A computed tomography scan (CT scan) and magnetic resonance imaging (MRI) of the brain revealed a suprasellar cyst and obstructive hydrocephalus. At birth a transfontanellar ultrasound was normal. The cyst underwent endoscopic fenestration with complete remission of symptoms. In the review of the literature, Gelabert-González et al. found only 6 previous cases of an intracranial arachnoid cyst whose origin was not clearly congenital or traumatic, and Gelabert-González et al. is the second case of a suprasellar arachnoid cyst to arise de novo 53)
A 4-year-old child who was incidentally found to have a suprasellar arachnoid cyst (SAC) after initial CT imaging at 6 weeks of age but who demonstrated no anomalies. This is only the sixth case of intracranial de novo ACs documented in the English literature and only the second case of SAC to arise de novo.
With the use of fast MRI scans instead of CT scans and the continued neuroimaging of premature infants, we can take a better look at the anatomy and better determine the timing of development of the SAC 54)