OBJECTIVE: The nomenclature characterizing posterior fossa (PF) extraventricular (EV) CSF collections in radiological reports can be quite variable, leading to uncertainty about the subsequent clinical course that may result in multiple follow-up imaging studies that may not be needed and occasionally to operative intervention that is not warranted. The important factor is the mass effect of the PF EV CSF collection on adjacent structures, the presence of hydrocephalus, and the likelihood of the CSF collection increasing in size over time.
METHODS: The authors respectively reviewed the imaging database at Children\'s Hospital Los Angeles to identify all radiological reports from 2000 to 2015 indicating the presence of an EV CSF collection in the PF that was characterized as containing an arachnoid cyst, being cystic, or being an abnormal CSF collection.
RESULTS: Of the 332 reports in 65 patients, the PF EV CSF collection was described as an arachnoid cyst or cystic in 306 with 20 different terms being used. In those patients who underwent multiple imaging studies, the PF EV CSF collection was often described differently in each report. Of this group, 47 (72%) patients did not undergo PF surgery. Eighteen (28%) patients did undergo PF surgery, of whom 14 had both hydrocephalus and brainstem displacement, 2 had brainstem displacement but no hydrocephalus, and 2 had neither brainstem displacement nor hydrocephalus and in retrospect did not benefit from PF surgery.
CONCLUSIONS: The terminology in radiology reports describing EV PF CSF collections is variable, is inconsistent, and does not correlate well with clinical management or the need for PF surgery. Significant brainstem displacement and hydrocephalus in the presence of EV PF CSF collection is highly correlated with the need for PF surgery. The incidence of a PF EV CSF collection increasing to become symptomatic becomes more remote the older the patient is at the time of diagnosis as compared with those that occur mainly in infancy. There are true EV CSF cysts in the PF, but the ones that are of consequence are those that exert pressure on the brainstem, obstruct CSF flow, or both. Calling any increased amount of CSF in the PF a \"cyst\" or \"cystic\" can cause uncertainty, leading to one or more subsequent imaging studies or, in rare cases, unwarranted operative intervention.

Arachnoid cysts are benign, mostly congenital lesions that are asymptomatic in most patients. In some cases, due to their location or sheer size, they produce a mass effect or hydrocephalic obstruction of the cerebrospinal fluid (CSF) flow and thus might warrant surgical treatment. The goal of the surgery is usually to reduce pressure inside the cysts, to reduce the mass effect, or to restore the CSF pathway. Surgical treatment options are resection, fenestration, or shunting of the cyst. Over the past decades, treatment under sheer endoscopic control either through a tube or via craniotomy of arachnoid cysts has been studied thoroughly and replaced open microsurgical cyst surgery in the opinion of many neurosurgeons. Endoscopic treatment has proven to be a safe and feasible technique for both patients and surgeons. In the following chapter, the authors describe their indications for surgery and pre- and postoperative workup, where precautions should be taken, and discuss the different possibilities and techniques of endoscopic cyst fenestration. The aim is to give detailed instructions and present cases for ventriculocystostomy, cystocisternostomy, ventriculocystocisternostomy, and cystoventriculostomy and point out specifics deemed to be important to avoid complications and to ensure the best possible outcome for each patient.

BACKGROUND: Arachnoid cysts are primarily dysembryogenetic splitting or duplication of the embryonic meningeal mesenchyme, hence the paediatric preponderance. Neuroendoscopic cysto-cisternostomy is now the favoured treatment option. We pooled data on middle fossa arachnoid cysts (MCFAC) demographics, clinical presentations, cyst characteristics, neuro-endoscopic cysto-cisternostomy and its outcomes.
METHODS: Using search words (from the keywords; \'endoscopic treatment\' and \'middle fossa arachnoid cysts\') combined using Boolean operators, a systematic review of the PubMed and Cochrane CENTRAL was started on 1st February 2023, as per protocol (PROSPERO CRD42023394345); 65 records and then 46 reports were screened, 169 cases were pooled from the 19 recruited reports for the qualitative and quantitative syntheses, after methodological assessment (significantly excellent 57.9% quality) using the Joanna Briggs Institute critical appraisal tools.
RESULTS: The male-to-female ratio was 2.4:1, with a weighted average-age of 11.25 years in the modal childhood (32.0%) age-group. Headaches (53/29.3%), seizures (30/16.6%) and macrocephaly (25/13.8%) were the commonest presentations. Right-sided (30/55.6%) and Galassi II (55/48.3%) and III (53/46.5%) lesions were common. Rigid (124/93.9%) endoscopes aided cysto-cisternostomy using mostly bipolar diathermy (31/43.7%) and ventriculostomy forceps (18/25.4%); creating one (22/18.3%), two (14/11.6%) or more (78/65.0%) stomas. Fenestration sites were specifically CNIII&ICA (32/25.8%), CNII&ICA (27/21.8%), CNIII&tentorium cerebelli (23/18.6%), CNIII&PCA (1/0.8%) and through the side of CNVI (1/0.8%) into the pre-pontine cistern. Good clinical and radiological outcomes were reported.
CONCLUSIONS: Largely excellent-to-good quality, low-level evidence reported MCFACs presenting in childhood with headaches, seizures and macrocephaly. At least two fenestrations using bipolar-diathermy/forceps and balloon-catheter expansion were used for cysto-cisternostomy, with good outcomes.

Leptomeningeal cyst (LMC) is a known complication of pediatric head injury but has not been described following a craniotomy other than for craniosynostosis. We present the case of a 20-month-old boy who underwent craniotomy for a traumatic epidural hematoma. There was an inadvertent tear of the dura which was repaired with a pericranial patch and dural sealant. The patient presented with a progressive surgical site swelling 5 months post-surgery and a CT scan revealed an LMC with elevation of the bone flap. He underwent re-exploration with watertight repair of the dural defect and rigid fixation of the bone flap. This iatrogenic LMC provides an opportunity to compare and confirm the pathogenesis vis a vis the more common spontaneous post-traumatic LMC. Our report highlights the importance of proper dural closure and bone fixation after craniotomy in children whose skulls are still growing.

OBJECTIVE: Children diagnosed with suprasellar arachnoid cysts often concurrently have hydrocephalus. This study aims to classify the relationship between suprasellar arachnoid cysts and hydrocephalus, discussing surgical strategies-shunting or neuroendoscopic approaches-and their sequence, based on this classification.
METHODS: A retrospective analysis was conducted on 14 patients diagnosed with suprasellar arachnoid cysts and hydrocephalus, treated surgically by the first author between January 2016 and December 2020. Clinical features, radiological findings, surgical strategies, and outcomes were reviewed. The classification of the relationship between the suprasellar arachnoid cysts and hydrocephalus was developed and illustrated with specific cases. Recommendations for future surgical management based on this classification are provided.
RESULTS: We classified the relationship between suprasellar arachnoid cysts and hydrocephalus into three categories. SACH-R1, the direct type, represents cases where the cysts cause obstructive hydrocephalus. Here, neuroendoscopic ventriculocystocisternostomy (VCC) effectively treats both conditions. SACH-R2, the juxtaposed type, involves concurrent occurrences of cysts and hydrocephalus without a causative link. This is further subdivided into SACH-R2a, where acute progressive communicating hydrocephalus coexists with the cyst, initially managed with a ventriculoperitoneal shunt, followed by VCC upon stabilization of hydrocephalus; and SACH-R2b, where the cyst coexists with chronic stable communicating hydrocephalus, first addressed with VCC, followed by monitoring and potential secondary shunting if needed. Key factors differentiating SACH-R2a from SACH-R2b include the patient\'s age, imaging signs of fourth ventricle and cisterna magna enlargement, and the rapid progression or chronic stability and severity of hydrocephalus symptoms. SACH-R3, the reverse type, describes scenarios where shunting for hydrocephalus leads to the development or enlargement of the cyst, managed via neuroendoscopic VCC with precautions to prevent infections in existing shunt systems.
CONCLUSIONS: The simultaneous presence of suprasellar arachnoid cysts and hydrocephalus requires a nuanced understanding of their complex relationship for optimal surgical intervention. The analysis and classification of their relationship are crucial for determining appropriate surgical approaches, including the choice and sequence of shunting and neuroendoscopic techniques. Treatment should be tailored to the specific type identified, rather than blindly opting for neuroendoscopy. Particularly for SACH-R2a cases, we recommend initial ventriculoperitoneal shunting.

BACKGROUND: Middle fossa arachnoid cysts (MFACs) are rare, congenital lesions that may rupture and cause symptoms of elevated intracranial pressure. We sought to describe the presence of and factors associated with optic nerve edema in MFACs, focusing on the utility of ophthalmologic evaluations for guiding cyst management.
METHODS: We reviewed clinical and radiographic information for all patients with MFACs with ophthalmologic evaluations at our institution. Headache, cranial nerve palsy, emesis, altered mental status, fatigue, and seizures were considered MFAC-related symptoms. Univariate and multivariable analyses evaluated factors associated with optic edema.
RESULTS: Fifty-one patients between 2003 and 2022 were included. Cysts were a median volume of 169.9 cm3 (interquartile range: 70.5, 647.7). Evidence of rupture with subdural hematoma/hygroma occurred in 19 (37.3%) patients. Eighteen (35.3%) patients underwent surgery for their cyst and/or rupture-associated intracranial bleed. Eleven (21.6%) patients had optic edema; all were symptomatic and experienced cyst rupture. Ten of these patients received surgery. Postoperatively, optic edema resolved in 80% of cases. Cyst volume and symptoms were not associated with optic edema; however, patients with ruptured cysts, particularly those with traumatic rupture, were more likely to have optic edema and receive surgery (P < 0.001).
CONCLUSIONS: We found optic edema in 21.6% of evaluated MFACs, and this comprised of 57.9% of ruptured cases. Optic edema was not found in unruptured cysts. Cyst fenestration improved optic edema and patient symptoms. In conjunction with clinical history and neuroimaging, optic edema may help guide MFAC management, particularly in patients with cyst rupture.

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BACKGROUND: Spinal intradural arachnoid cysts (SIACs) are rare spinal entities that are categorized as primary or secondary pathologies. Secondary cysts can arise from various traumatic or inflammatory causes including subarachnoid hemorrhage, intrathecal injection or surgery, and infectious meningitis/arachnoiditis. Only a few cases of SIAC secondary to tuberculous meningitis have been previously reported, without details of the surgical treatment.
METHODS: A 27-year-old woman diagnosed with tuberculous meningitis developed myelopathy caused by thoracic ventral SIAC and intradural abscess. The patient underwent abscess evacuation and cyst fenestration; however, cyst recurrence occurred. The 2nd surgery consisted of cyst resection via a posterolateral approach with expansive duraplasty and spinal arthrodesis. Re-recurrence occurred, and at the 3rd surgery, cyst-subarachnoid bypass was performed. One year after the 3rd surgery, the myelopathic symptoms recovered, and MR images demonstrated a decreased cyst size.
CONCLUSIONS: Here, we report a rare case of recurrent thoracic SIAC secondary to tuberculous meningitis and arachnoiditis. Simple fenestration is associated with a high risk of recurrence in this pathology. Ventrally located thoracic cysts can be approached with posterolateral approach with pedicles resected followed by instrumented arthrodesis. Even in cases involving gross total resection of the cyst wall, there is a risk of recurrence. In such cases, cyst-subarachnoid bypass with a large-diameter tube can be effective.

OBJECTIVE: In recent years there has been a re-evaluation regarding the clinical implications of temporal lobe arachnoid cysts (temporal arachnoid cysts) in children. These cysts have often been considered asymptomatic, or if symptomatic, only causing focal neurological symptoms or signs of increased intracranial pressure. However, several studies have more recently reported on cognitive symptoms improving after surgery. This study aimed to evaluate if reported cognitive improvement after surgery of temporal arachnoid cysts were stable after five years.
METHODS: Ten consecutive children (m = 14.65; range 12.1-19.415 were assessed cognitively five years after micro-neurosurgical fenestration of a temporal arachnoid cyst. Results were compared to results from their pre- and post-surgical evaluations. Evaluations included the Wechsler-scales, Boston Naming Test (BNT), Rey Auditory Verbal Learning Test (RAVLT), verbal fluency test (FAS) and Rey Complex Figure Test (RCFT).
RESULTS: The analysis revealed significant postsurgical improvement compared to baseline on the Wechsler-scales measures of general intelligence (FSIQ), verbal abilities (VCI) and processing speed (PSI). Mean differences after surgery were 8.3 for FSIQ, (p = 0.026), 8.5 for VI (p =  < .01) and 9.9 for PSI (p = 0.03). There were no significant differences in mean test results when comparing postsurgical scores with scores five years after surgery, indicating long-term stability of improvements.
CONCLUSIONS: The results indicate that affected cognitive functions in children with temporal arachnoid cysts improve after surgery and that the improvements remain stable five years later. The improvements and long term stability were also consistent with the experience of both parents and children. The findings provide a strong argument for neurosurgical fenestration of temporal arachnoid cysts in children.

BACKGROUND: Intracranial arachnoid cysts are benign collections of cerebrospinal fluid that are often asymptomatic and discovered incidentally. An interhemispheric location of these lesions is rare, with only a few such cases reported in the literature. Though spontaneous regression of arachnoid cysts has been described in other locations, to date this phenomenon has not been reported in interhemispheric fissure cysts.
METHODS: In this report, we describe a patient with a large, multiloculated interhemispheric arachnoid cyst diagnosed on prenatal ultrasound. She did not exhibit neurologic deficits or signs of increased intracranial pressure and was observed with serial imaging. After several years of observation, imaging revealed spontaneous and progressive decrease in the cyst size.
CONCLUSIONS: We illustrate a case of regression of an interhemispheric arachnoid cyst in a pediatric patient. To our knowledge, this is the first reported case of spontaneous shrinkage of an arachnoid cyst in this location. Although the current presentation is rare, this reporting adds to the current understanding of natural history of arachnoid cysts and provides an example of radiographical improvement without intervention of a cyst located within the interhemispheric fissure.