These cystic lesions are congenital.
Arachnoid cysts account for only 1% of all intracranial space-occupying lesions.
Intracranial arachnoid cysts have a predilection for the temporal fossa.
Intracranial cysts are classified as supratentorial, infratentorial, and supra-infratentorial (tentorial notch).
Supratentorial are divided into:
Quadrigeminal plate cistern
Many theories have been postulated for etiopathogenesis of arachnoid cysts. Various hypotheses are: entrapment of CSF in a diverticulum; CSF flow changes leading to arachnoid cell layer tears during the formation of various cisternae; during embryological separation (at around 15th week of gestation) of arachnoid from the dura mater 1).
Most of them are asymptomatic and are detected as incidental findings on Computed Tomography or Magnetic Resonance Imaging of the head carried out for other reasons.
There are multiple case reports of arachnoid cysts becoming symptomatic with hemorrhagic complications following head trauma. In such cases, the bleeding is often confined to the side ipsilateral to the arachnoid cyst. Occurrence of contralateral subdural hematomas in patients with temporal fossa arachnoid cysts has rarely been observed and is reported less frequently in the medical literature 2).
Usually they remain stable in size and are asymptomatic, however, a few cysts contain remnants of the choroid plexus or arachnoid granulations leading to secretion of CSF resulting in an increase in size with time. These cases may present with features of compression of adjacent structures (Kallmann syndrome, precocious puberty, bitemporal hemianopia in suprasellar lesions, cranial nerve palsies etc.) and/or raised intracranial pressure due to their large size or hemorrhage. Spontaneous hemorrhage is supposed to be due to a minor trauma with rupture of intracystic or bridging vessels 3) 4).
The symptoms related to the presence of arachnoid cysts in the Central Nervous System depend on the size of the cyst and its growth rate, its location and, in some cases, the associated CSF dynamic disorder. Sometimes there is acute clinical presentation due to cyst rupture or acute bleeding.
ACs with mass effect are detected frequently in asymptomatic patients. Conversely, symptomatic patients may present without imaging signs of a focal mass effect that emphasizes the difficulty of relying on imaging as the sole criteria in surgical selection.
Although it is generally accepted that asymptomatic or paucisymptomatic cysts do not require surgical treatment, there is no consensus on the therapeutic approach of choice in symptomatic cases 5).
Acetazolamide known to reduce CSF production, might mimic surgical decompression and therefore could serve as a decision-making tool in patients with ACs.
A total of 103 patients with radiographically proven ACs were initially identified. Twenty (19.4%) were symptomatic and underwent a trial of oral AZM. Data were collected meeting inclusion/exclusion criteria for this cohort study and analyzed retrospectively/prospectively. Results Overall, 17 patients were able to tolerate the AZM and had at least some subjective improvement in their symptoms during the AZM challenge and underwent surgical therapy. Surgery was beneficial in 16 patients (94.1%). Following surgery, symptoms resolved in 13 patients (76.5%) and improved in 3 (17.6%).
The AZM challenge may support the clinical decision to recommend surgery in those patients whose symptoms improve during AZM therapy 6).
Craniotomy and fenestration of membranes is one of the main treatment options for symptomatic arachnoid cysts. Open surgery advantages include, direct inspection of the cyst, biopsy sampling, fenestration in multilocular cysts and, in certain locations, cyst communication to basal cisterns 7).
Surgery for AC can be performed with a fairly low risk of complications and yields significant improvement in quality of life correlated to postoperative improvement in headache and dizziness. These findings may justify a more liberal approach to surgical treatment for AC 8).
Spontaneous intracystic hemorrhage in an arachnoid cyst is a rare complication (although hemorrhagic arachnoid cyst is well known in the clinical setting of trauma), which may present with symptoms of raised intracranial pressure (headache, vomiting, altered sensorium) or focal neurological deficits depending on the location and is an indication for surgery 9) 10).
Although complications such as intracystic, subdural, and extradural hematomas are well known after a trauma, spontaneous hemorrhage in an arachnoid cyst is a rare and serious complication with atypical imaging features on cross-sectional imaging and only less than ten cases are documented in the literature 11).
Surgery can be performed with a fairly low risk of complications and yields significant improvement in quality of life correlated to postoperative improvement in headache and dizziness. These findings may justify a more liberal approach to surgical treatment 12).
There is currently no consensus on the safety of sports participation for patients with an intracranial arachnoid cyst (AC).
A survey was prospectively administered to 185 patients with ACs during a 46-month period at a single institution. Cyst size and location, treatment, sports participation, and any injuries were recorded. Eighty patients completed at least 1 subsequent survey following their initial entry into the registry, and these patients were included in a prospective registry with a mean prospective follow-up interval of 15.9 ± 8.8 months.
A total 112 patients with ACs participated in 261 sports for a cumulative duration of 4410 months or 1470 seasons. Of these, 94 patients participated in 190 contact sports for a cumulative duration of 2818 months or 939 seasons. There were no serious or catastrophic neurological injuries. Two patients presented with symptomatic subdural hygromas following minor sports injuries. In the prospective cohort, there were no neurological injuries
Permanent or catastrophic neurological injuries are very unusual in AC patients who participate in athletic activities. In most cases, sports participation by these patients is safe 13).
A total of 13 patients < 1 year of age with intracranial cysts were operated on between 2005 and 2013. Six presented with hydrocephalus, four presented with seizure, one with abnormal head movement, and two had large asymptomatic cysts. Four children had infratentorial arachnoid cysts; of these, three required a transaqueductal procedure. All the patients underwent endoscopic cystoventriculostomy and/or cystocisternostomy and third ventriculostomy in selected cases with a biopsy from the cyst wall.
Clinically and radiologically all children showed significant improvement with an average follow-up ranging from 8 months to 6 years. There were no intraoperative complications. Three children developed subdural hygroma that subsided with conservative treatment, and one child with pseudomeningocele required a cystoperitoneal shunt at a later date.
A symptomatic intracranial arachnoid cyst or a large asymptomatic cyst are indications for neurosurgical intervention, and endoscopy is a good treatment option with the advantage of minimal invasiveness and fewer complications. Endoscopic surgery has to be tailored according to the location and presentation 14)