Editorial: arachnoid cysts.

Arachnoid cysts possess several features that make them ideal targets for primary endoscopic fenestration. First, the target membrane is typically avascular. Second, there are generous amounts of CSF for optimal image transmission. Third, the technique of membrane fenestration is amply familiar to surgeons regularly practicing neuroendoscopy, principally through the experience of performing endoscopic third ventriculostomy. Lastly, there is no traditional approach that is universally agreed upon as being optimal. While the rationale for primary endoscopic fenestration has been collectively accepted for some arachnoid cyst variants, notably the prepontine arachnoid cyst, there justifiably remains considerable disagreement about its role for cysts of the middle temporal fossa.5–11 In reading the recent publication by Dr. El-Ghandour,4 one would conclude that much of the ongoing debate regarding optimal management of middle cranial fossa arachnoid cysts (MCFACs) has come to closure. Of 32 children with “symptomatic” arachnoid cysts treated with a purely endoscopic fenestration, reported rates of improvement were 87.5% for clinical assessment and 71.9% for radiographic dimensions. Furthermore, 100% of patients with preoperative headache or skull deformity showed improvement. These admirable results include a low complication rate that was composed of a clinically silent subdural hygroma in 2 children and a transient third cranial nerve paresis in 1 patient. While these results could redefine our expectations regarding this form of treatment for children with MCFACs, a degree of caution is called for because these findings are appreciably incongruous with recently published clinical results as well as our own personal experience.3,5,9 With regard to operative indications, we support the consensus that treatment should be reserved for symptomatic patients.2–7,9,10 The operative indications included in the current paper beg some clarification. While there is no argument about offering treatment to children with raised intracranial pressure, the interpretation of this finding is frequently subjective. The definition of “symptomatic” in this current series included cranial deformity (temporal bulging), a frequent finding in infants and young children who are otherwise without symptoms. Further, 72% of children underwent treatment due either to symptoms of headache or signs of macrocrania. These features frequently are not related to elevated intracranial pressure. The rate and trend of head circumference growth (unknown in the current paper) is more meaningful than a single measurement. Similarly, headache alone without supportive evidence can be tenuous as a sole justification for surgery. While papilledema is unambiguous in documenting raised intracranial pressure, the frequency of that finding (37.5%) in this cohort of 32 children is appreciably higher than in most reported series.5,9 While the author notes that prophylactic surgery may be offered to avoid the potential of subdural hematoma, there exists limited clinical data to discount this notion. Recent evidence is convincingly clear that the potential for symptomatic progression in an otherwise asymptomatic child is exceedingly rare.1 In fact, the association of intracranial hemorrhage with arachnoid cysts has been documented after head injury despite long-term postsurgical neuroradiological confirmation of MCFAC size reduction and symptom resolution.9 In short, the indications for surgical treatment of MCFAC are highly variable and open to interpretation. The outcome in this series of 32 patients is even more impressive given the described technique. The author used an embolectomy catheter to create a single fenestration in 75% of patients without intraoperative computer-assisted neuronavigation. This “simple” technique of endoscopic fenestration warrants some elaboration and 228 23