Discussion and conclusions
IACs account for about 1% of all nontraumatic intracranial masses [
1] with a predilection for male gender [
2]. About 50–65% of IACs are located in the middle cranial fossa, more in the left side [
2] (current cases were both in male patients; however, one was in the right and one in the left side). Other less common locations for intracranial arachnoid cysts are suprasellar cistern, quadrigeminal cisterns, cerebral convexities, cerebellopontine angles, and cisterna magna.
Middle cranial fossa IACs are often associated with variable degrees of temporal lobe agenesis and are classified into three types according to Galassi classification. Galassi type 1 cyst is small semicircular cyst confined to the anterior part of temporal fossa; type 2 is medium-sized, quadrangular cyst; and type 3 is large oval cyst with mass effect and midline shift [
3]. The larger cysts are more likely to be symptomatic [
4]. Symptoms can be generalized cranial enlargement, localized cranial bulging, increased intracranial pressure, seizures, psychomotor retardation, focal neurological deficits, hydrocephalus, and even dementia [
5].
Occasionally, IACs may rupture—spontaneously or after trauma—and result in intracystic hemorrhage, subdural hematoma/subdural hygroma, or both [
6], and may cause signs and symptoms of intracranial hypertension, mainly headache and vomiting [
7]. Symptoms of IACs with subdural hygroma usually become increasingly severe for days or weeks after onset, but they eventually resolve [
8].
A case–control study by Cress
et al. on “risk factors for pediatric arachnoid cyst rupture/hemorrhage” demonstrated that children with larger intracranial arachnoid cysts (especially larger than 5 cm) were at increased risk of cyst rupture. A head injury within the previous 30 days, even if considered relatively minor, was also associated with cyst rupture [
9]. These complications may occur at any age and are reported with a wide range of patients, from as young as 12 months to adults 53 years old [
8,
10].
Diagnosis Computed tomography (CT) and magnetic resonance imaging (MRI) can provide the diagnosis of arachnoid cyst and its complications. On CT, IACs appear as well-defined lesions, with the same density of the CSF. MRI can further differentiate between chronic subdural hematoma and hygroma, which CT cannot do.
Treatment and prognosis Treatment of asymptomatic IACs is a matter of controversy. Symptomatic cysts are treated surgically, while disappearance of arachnoid cysts has also been reported, both with and without a history of preceding trauma [
11]. Again, in cases with surgical treatment, the selection of the best neurosurgical approach also remains controversial. The options include cyst shunting, craniotomy for cyst fenestration, endoscopic fenestration, deviation of cyst fluid to another intracranial space, and even cystoperitoneal shunting [
12,
13].
Regarding the management of complicated arachnoid cysts to subdural collections, the best surgical treatment remains controversial due to the lack of reported cases [
2]. Slaviero
et al. reported two cases to suggest that surgical evacuation of the hematoma followed by an endoscopic cyst fenestration was a minimally invasive, safe, and effective approach for the treatment of middle cranial fossa arachnoid cysts complicated with subdural collections [
2]. Maher
et al. reported a series of eight patients with IACs and subdural hygroma, of which seven were managed without surgery and only one underwent surgery. All patients experienced complete resolution of presenting signs and symptoms; however, half of them had objective findings strongly correlated with elevated ICP including cranial nerve (CN) VI, palsy, papilledema, and progressive macrocephaly [
8]. Hence, they disagreed with the idea that surgical treatment of subdural hygroma associated with arachnoid cysts is always, or almost always, necessary; instead, they suggested that the decision to surgically treat symptomatic hygroma associated with arachnoid cysts should be made carefully. They claimed that symptoms of elevated ICP are not an absolute indication for surgical treatment [
8].
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