Purely Endoscopic Treatment for Arachnoid Cysts.

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.

Post-craniotomy leptomeningeal cyst: a new presentation of an old problem.

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.

Spontaneous regression of an interhemispheric arachnoid cyst: illustrative case.

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. OBSERVATIONS: 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. LESSONS: 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.

Classification of the relationship between suprasellar arachnoid cyst and hydrocephalus based on treatment modalities: shunting versus neuroendoscopic approaches.

PURPOSE: 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. CONCLUSION: 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.

Surgical treatment for recurrent thoracic ventral intradural arachnoid cyst secondary to tuberculous meningitis: a case report.

INTRODUCTION: 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. CASE PRESENTATION: 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. DISCUSSION: 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.

Long term clinical and radiological outcomes following surgical treatment of symptomatic cranial arachnoid cyst: A population based consecutive cohort study.

OBJECTIVE: Symptomatic intracranial arachnoid cysts are treated mainly through surgical resection, endoscopic fenestration, or by implanting cystoperitoneal (CP) shunt. However, the use of a specific technique remains controversial. The purpose of this study is to discuss these surgical modalities in symptomatic patients with intracranial arachnoid cysts (ACs) and investigate which has better outcomes and less complications by comparing variable preoperative and postoperative parameters. METHODS: An analysis of thirty-nine symptomatic patients who underwent intracranial arachnoid cyst surgery in the department of neurosurgery between 2009 and 2023 was performed. Patients were retrospectively compared based on age group, gender, anatomical location, laterality, type of intervention, clinical and volumetric changes, postoperative complications and outcome. RESULTS: Of the 39 patients, 20 patients (51.28 %) received CP shunt. Eleven patients (28.2 %) underwent endoscopic fenestration, and 8 patients (20.5 %) had surgical resection. The age at the time of first operation ranged from 1 month to 59.9 years (mean age: 16.8 years), and the pediatric patients were 25 (64.1 %). The most common initial symptom was headache which was observed in 19 patients (48.7 %), followed by seizure in 12 patients (30.8 %), vomiting in 11 patients (28.2 %), visual dysfunction in 8 patients (20.5 %), drowsiness in 8 patients (20.5 %), visual symptoms in 8 patients (20.5 %), cognitive impairment in 4 patients (10.3 %), focal neurological deficits in 3 patients (7.7 %), and cranial nerve involvement in 1 patient (2.6 %). 24 patients (61.5 %) showed improvement while in 15 patients (38.5 %) the symptoms persisted or worsened. Postoperatively, patients were followed up for an average of one year. The highest improvement rate was noted in endoscopic fenestration with 9 improved patients (81.8 %), followed by surgical resection with 5 symptom-free patients (62.5 %). The worst outcomes were seen in cystoperitoneal shunt with only half of the patients were relieved (50 %). Complications developed in 2 patients (25 %) who underwent surgical resection, 5 patients (45.5 %) who had endoscopic fenestration, and 13 patients (65 %) who had cystoperitoneal shunting. CONCLUSION: Endoscopic fenestration has the highest improvement rate, the lowest serious complications along with being the least invasive technique. These features make it the optimal modality in treatment of ACs. Surgical resection or cystoperitoneal shunt can be considered as secondary techniques when patients report unchanged or worsening symptoms.

Optic Nerve Edema in Pediatric Middle Cranial Fossa Arachnoid Cysts: Report of 51 Patients From a Single Institution.

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.

Staged neurosurgical approach for giant and progressive neonatal arachnoid cysts: a case series and review of the literature.

OBJECTIVES: Prenatally diagnosed complex arachnoid cysts are very rare. While the true prenatal incidence is still unknown, they account for approximately 1% of intracranial masses in newborns. They rarely exhibit rapid growth or cause obstructive hydrocephalus, but if they increase to such a dimension during pregnancy, the ideal management is not well established. We present our detailed perinatal experience, covering prenatal diagnosis, a compassionate delivery process, and neonatal stabilization. Finally, a thorough postnatal neurosurgical intervention was performed. Initially, our focus was on the gradual reduction of cyst size as a primary effort, followed by subsequent definitive surgical treatment. METHODS: This case series shows the treatment course of three fetuses with antenatally diagnosed large arachnoid cysts. We present pre- and postnatal management and imaging, as well as the surgical treatment plan and the available clinical course during follow-up. RESULTS: Two girls and one boy were included in the current review. All three cases presented with prenatally diagnosed complex arachnoid cysts that increased in size during pregnancy. The mean gestational age at delivery was 35 weeks (range 32 to 37 weeks), and all patients were delivered by a caesarian section. Increasing head circumference and compression of brain structures were indications for delivery, as they are associated with a high risk of excess intracranial pressures and CSF diapedesis, as well as traumatic delivery and maternal complications. All cysts were supratentorial in location; one expanded into the posterior fossa, and one was a multicompartment cyst. All children underwent an initial surgical procedure within the first days of life. To relieve cyst pressure and achieve a reduction in head circumference, an ultrasound-guided or endoscopic-assisted internal shunt with drainage of the cyst to the ventricles or subdural/subarachnoid space was inserted. Definite surgical therapy consisted of cyst marsupialization and/or cysto-peritoneal shunt implantation. All children survived without severe neurodevelopmental impairments. CONCLUSION: With the cases presented, we demonstrate that the slow reduction of immense cyst size as an initial procedure until optimal requirements for final surgical treatment were achieved has proven to be optimal for neurological outcome. Special emphasis has to be taken on the delicate nature of premature newborn babies, and surgical steps have to be thoroughly considered within the interdisciplinary team.

Description and clinical relevance of the variable conformation of canine spinal arachnoid diverticula.

The conformation of spinal arachnoid diverticula (SAD) and their clinical implications are poorly characterized in dogs. This retrospective cross-sectional study describes different SAD conformations in dogs and aims to identify if there is an association between SAD conformation and clinical features, localization, syringomyelia (SM) presence, concurrent vertebral condition, treatment option, and short as well as long-term outcome. Sixty-two dogs were included (12 cervical and 50 thoracolumbar SAD). All dogs with a cervical SAD had a cranial tethered conformation and were not included in the statistical analysis. Half of the dogs with a thoracolumbar SAD were cranial tethered, and the other half were caudal tethered. SM associated with SAD had a moderate prevalence in the cervical region (58.3%) and a high prevalence in the thoracolumbar region (82%). All dogs with the presence of SM and caudal tethered SAD had a cranial positioned SM, and all dogs with SM and a cranial tethered SAD had a caudal positioned SM. The SM absolute length and SM length/L2 ratio were significantly higher (P = .018, respectively) in the caudal tethered SAD compared with the cranial tethered SAD. The short-term outcome was statistically different (P = .045) between caudal and cranial tethered thoracolumbar SAD, but not the long-term outcome (P = .062). Multivariable logistic regression identified thoracolumbar caudal tethered SAD conformation had a better short-term outcome (P = 0.017, OR: 0.043, CI: 0.003-0.563), independently of SM length measurements. SAD conformation in dogs can influence SM formation. A possible link between short-term outcome and SAD conformation was found, but further research is warranted.

Coexistence of Trigonocephaly and Sylvian Arachnoid Cysts: A Coincidence?

INTRODUCTION: The association between trigonocephaly and Sylvian fissure arachnoid cysts (ACs) has been occasionally reported in the literature. However, the real incidence of this association and its clinical relevance remain unknown. METHODS: The authors collected and retrospectively reviewed all clinical charts and CT scans of patients surgically treated for trigonocephaly at the Pediatric Neurosurgical Department of Fondazione Policlinico Universitario "Agostino Gemelli" IRCCS from January 2014 to June 2023. RESULTS: During the study period, 136 patients with trigonocephaly underwent surgery. Analysis of the clinical charts revealed that in 39.7% of the cases (54/136), preoperative CT scan depicted the presence of a Sylvian fissure AC. Of these, AC was bilateral in 23 cases and unilateral in the remaining 31. All unilateral ACs were on the left side. The ACs were classified as Galassi grade I in 52 cases (96.3%) and Galassi grade II in 2 cases (3.7%). Interestingly, in 1 case we reported a Galassi grade I AC enlargement during follow-up, thereby necessitating surgical fenestration. CONCLUSION: ACs and trigonocephaly are well-known conditions for pediatric neurosurgeons; however, their association is poorly defined. Despite the lack of reports on the incidence and clinical significance of this association, it is worth knowing that radiological follow-up is essential in monitoring AC evolution.

Intracranial Arachnoid Cyst in Children: Clinical Presentation and Risk Factors for Surgical Intervention.

INTRODUCTION: Intracranial arachnoid cysts (IAC) in children are a common incidental finding on imaging. Most IACs are asymptomatic and can be monitored; however, a small percentage may enlarge and require surgical intervention. This study aimed to identify clinical risk factors in patients with IAC who underwent surgery versus those who did not. METHODS: We conducted a retrospective chart review from 2009 to 2021 at a free-standing children's hospital. A total of 230 patients diagnosed with an IAC aged 0-21 years of age were included in the study. Data on demographics, imaging, and neurological follow-up were analyzed. RESULTS: Out of 230 patients, 45 (19.6%) underwent surgery. At time of IAC diagnosis, the surgical patients were younger (median age 1.1 years), and their median cyst volume was larger (41.7 cm3), compared to nonsurgical patients (median age 5.9 years, volume 11.8 cm3, respectively). Headache was the most common reason for initial imaging in nonsurgical patients (54/185, 29.2%) while prenatal ultrasound (11/45, 24.4%) and macrocephaly (11/45, 24.4%) were the most common reasons for surgical patients. The majority of both surgical and nonsurgical patients had the IAC incidentally found (41/45, 91.1% and 181/185, 97.8%, respectively). Surgery relieved symptoms in 38/45 (84.4%) patients. Cyst volume and age were predictors of increased odds of having surgery. DISCUSSION/CONCLUSION: Patients who underwent surgery were younger and had larger cyst volumes at time of diagnosis. The majority of the IAC were found incidentally and remained stable over prolonged follow-up. The majority of the patients experienced relief of symptoms postsurgical intervention. There is a greater odds of having surgical treatment with decreased age and greater cyst volume at diagnosis, and therefore these patients should be monitored closely for development of symptoms indicating need for surgical intervention.

Evaluation of surgical treatment strategies and outcome for cerebral arachnoid cysts in children and adults.

OBJECTIVE: The best treatment strategies for cerebral arachnoid cysts (CAC) are still up for debate. In this study, we present CAC management, outcome data, and risk factors for recurrence after surgical treatment, focusing on microscopic/endoscopic approaches as compared to minimally invasive stereotactic procedures in children and adults. METHODS: In our single-institution retrospective database, we identified all patients treated surgically for newly diagnosed CAC between 2000 and 2022. Microscopic/endoscopic surgery (ME) aimed for safe cyst wall fenestration. Stereotactic implantation of an internal shunt catheter (STX) to drain CAC into the ventricles and/or cisterns was used as an alternative procedure in patients aged ≥ 3 years. Treatment decisions in favor of ME vs. STX were made by interdisciplinary consensus. The primary study endpoint was time to CAC recurrence (TTR). Secondary endpoints were outcome metrics including clinical symptoms and MR-morphological analyses. Data analysis included subdivision of the total cohort into three distinct age groups (AG1, < 6 years; AG2, 6-18 years; AG3, ≥ 18 years). RESULTS: Sixty-two patients (median age 26.5 years, range 0-82 years) were analyzed. AG1 included 15, AG2 10, and AG3 37 patients, respectively. The main presenting symptoms were headache and vertigo. In AG1 hygromas, an increase in head circumference and thinning of cranial calvaria were most frequent. Thirty-five patients underwent ME and 27 STX, respectively; frequency did not differ between AGs. There were two (22.2%) periprocedural venous complications in infants (4- and 10-month-old) during an attempt at prepontine fenestration of a complex CAC, one with fatal outcome in a 10-month-old boy. Other complications included postoperative bleeding (2, 22.2%), CSF leaks (4, 44.4%), and meningitis (1, 11.1%). Overall, clinical improvement and significant volume reduction (p = 0.008) were seen in all other patients; this did not differ between AGs. Median follow-up for all patients was 25.4 months (range, 3.1-87.1 months). Recurrent cysts were seen in 16.1%, independent of surgical procedure used (p = 0.7). In cases of recurrence, TTR was 7.9 ± 12.7 months. Preoperative ventricular expansion (p = 0.03), paresis (p = 0.008), and age under 6 years (p = 0.03) were significant risk factors for CAC recurrence in multivariate analysis. CONCLUSIONS: In patients suffering from CAC, both ME and STX can improve clinical symptoms at low procedural risk, with equal extent of CAC volume reduction. However, in infants and young children, CAC are more often associated with severe clinical symptoms, stereotactic procedures have limited use, and microsurgery in the posterior fossa may bear the risk of severe venous bleeding.

A 3-Year-Old Girl with Brain Imaging Findings Suggesting Arachnoid Cyst, and Biopsy Diagnosis of Extra-Axial Multicystic Pilocytic Astrocytoma.

BACKGROUND Arachnoid cysts and pilocytic astrocytomas are distinct intracranial entities with differing clinical presentations, origins, and management strategies. Arachnoid cysts are benign fluid-filled sacs associated with congenital or acquired causes, while pilocytic astrocytomas are low-grade brain tumors, primarily affecting pediatric and young adult populations, originating from astrocytes. However, diagnosing pilocytic astrocytomas can be challenging due to their radiological features, sometimes resembling more common intracranial lesions, such as arachnoid cysts. This case underscores the need for vigilance and a multidisciplinary approach when confronted with neuroimaging findings that diverge from typical patterns. CASE REPORT We present a case of a 3-year-old girl who presented with persistent headaches, vomiting, and difficulty walking. Initial radiological assessment suggested an arachnoid cyst, given the patient's symptoms and imaging characteristics. Subsequently, the patient underwent a craniotomy, with intraoperative findings revealing a cystic lesion without a solid mural nodule, which was excised completely. Postoperatively, histopathological examination confirmed a diagnosis of extra-axial pilocytic astrocytoma. The patient's symptoms resolved, and she was discharged without neurological deficits. CONCLUSIONS Diagnosing extra-axial pilocytic astrocytomas presents challenges, due to their radiological similarities with more common intracranial lesions, like arachnoid cysts. This case underscores the importance of histopathological examination to confirm the diagnosis accurately. Surgical resection remains the primary treatment for extra-axial pilocytic astrocytomas, often resulting in a favorable prognosis.

Intracranial arachnoid cyst in pregnancy: case report, literature review and evaluation of neuraxial anaesthesia risk.

Choosing the type of intrapartum anaesthesia for pregnant women with intracranial arachnoid cysts can be challenging due to a lack of research. We report the intrapartum anaesthetic management of a 25-year-old woman with a known 10 cm arachnoid cyst. By means of a literature review and discussion of safety surrounding neuraxial techniques, this report will help to inform obstetric anaesthesia practice. Overall, in the absence of raised intracranial pressure, neuraxial analgesia and anaesthesia during the intrapartum period appears to be a safe option.

Multiple spinal extradural arachnoid cysts presenting as compressive myelopathy in a teenager: case report and literature review with special emphasis on postoperative spine deformity in the current minimally invasive era.

INTRODUCTION: Multiple synchronous spinal extradural arachnoid cysts are extremely rare in children and can lead to cord compression and disability. Multiple spinal extradural arachnoid cysts (SEDACs) in children with immature and growing spine need to be studied separately from multiple SEDACs in adults with mature and fully grown spine because of multiple surgical limitations in children (blood loss, surgery duration, long-term spinal stability after long segment exposure, etc.). MATERIAL AND METHODS: We planned a non-systematic literature review of similar cases described in literature to analyse the pattern of presentation, management, and outcome of this surgically curable disease. RESULTS: A total of 28 cases of paediatric multiple SEDACs in the age range of 5 months to 17 years and mean age of 11.54 years were analysed. Exposure was achieved by laminectomy in 9, laminoplastic laminotomy in 13, laminectomy in first surgery followed by laminoplasty in second surgery (re-exploration) in 1, hemilaminectomy in 2, and technique "not reported" in 3 children. Complete/near-complete recovery was seen in 27 (96.42%) children. Postoperative spine deformity was reported in 7 (25%) children and was progressive in 2 children during serial follow-up. CONCLUSIONS: Symptomatic multiple synchronous SEDACs in children is a rare surgically curable condition. Sincere attempt to find out a dural defect in all cysts is a very important step in multiple SEDAC surgery. Total cyst wall excision with closure of all dural defects is the gold standard treatment for symptomatic cases. Laminoplasty is preferred for excision of multiple SEDACs in children to prevent postoperative spine deformity during long-term follow-up. Long serial follow-up for postoperative spine deformity is necessary.

Microsurgical Fenestration of Middle Fossa Arachnoid Cyst in a Pediatric Patient Through a Keyhole Approach with Endoscopic Inspection. 2-Dimensional Operative Video.

In recent decades, the management of middle fossa arachnoid cysts in pediatric patients has evolved significantly through the integration of novel techniques, such as the utilization of endoscopy systems1 and implementation of minimally invasive approaches like keyhole craniotomy.2,3 These cystic formations, occurring within the arachnoid membrane, may lead to neurologic impairments and raised intracranial pressure if left untreated.4 The utilization of endoscopy to aid microsurgical techniques or as a complement to them provides a level of visualization and manipulation of the cyst walls that is significantly more precise than the isolated use of a microscope.1 The keyhole craniotomy allows for reduced surgical trauma, smaller incisions, and quicker recovery times.5 In Video 1, we present the case of a 2-year-old patient with bilateral middle fossa arachnoid cysts exerting mass effect on the adjacent parenchyma. The patient was referred to our institution due to developmental delay and cognitive issues related to language and social interactions. On the basis of imaging findings and clinical correlation, we opted for a microsurgical fenestration with endoscopic inspection using a keyhole craniotomy to minimize complications and enhance the benefits of both techniques. Throughout the surgical video, tricks and considerations that contribute to the combined procedure's efficiency and ease of execution are highlighted and discussed. Postoperative images showed no complications, and the patient was discharged 3 days after surgery.