Giant Intracranial Arachnoid Cyst Causing Acute Neurologic Symptoms

Intracranial arachnoid cysts (IAC) are benign lesions containing cerebrospinal fluid (CSF). Most of them are clinically silent and remain static in size. However some may present with mild and slow progressive symptoms caused by the cyst. The authors present the case of 54-year-old woman who presented with acute symptoms of severe headache, vomiting, and gait disturbance of 2 day’s duration. She had no history of head trauma. On admission, neurological examination revealed that the patient had a Glasgow Coma Scale score of 15, and a left side hemiplegia. A CT scan revealed a hypodense fluid collection in the right frontoparietal region that mimicked an arachnoid cyst. The symptoms were improved after an emergency marsupialisation via craniotomy.


Introduction
Intracranial arachnoid cysts (IAC) are benign lesions containing cerebrospinal fluid (CSF).Most of them are congenital but acquired cases have been described after trauma, infection or skull base surgery [1] [2] [3] [4].Arachnoid cysts comprise 1% of all intracranial space-occupying lesions [5].The prevalence in adults is approximately 1.4% with a female preponderance, while the prevalence

Case Report
This Malian 54-year-old woman was admitted to our neurosurgical department with acute symptoms of severe headache, vomiting, and gait disturbance of 2 day's duration.She had no history of head trauma.On admission, neurological examination revealed that the patient had a Glasgow Coma Scale score (GCS) of 15, and a left side hemiplegia.Results of routine laboratory studies were normal.
A CT scan (Figure 1) revealed a hypodense fluid collection in the right frontoparietal region that mimicked an arachnoid cyst.An emergency surgery was done.A right frontoparietal craniotomy was performed.When the dura was opened, a typical arachnoid cyst was discovered.The cyst was widely marsupialized (Figure 2), the dura was closed and the craniotomy was repaired.The postoperative course was favorable.The patient's clinical condition improved quickly after surgery.The postoperative CT scan (Figure 3) showed complete resolution of the CSF collection.She was discharged home one week after the operation with GCS of 15 and was able to walk without assistance 3 weeks later.

Discussion
Bright [16] first described IAC in 1831.IAC are congenital lesions of the arachnoid   [19] [20].Although the mechanisms that drive arachnoid cyst enlargement remain unknown, it has been postulated that cysts may expand due to: 1) active secretion of CSF by the cyst wall; 2) water entry into the cyst because of osmotic pressure difference; 3) communication of the cyst with the subarachnoid space and consequent entry of CSF into the cyst either freely or by one-way valve mechanism; and 4) pulsation of intracystic CSF driven by the cardiovascular pump.
Cases of spontaneous regression of AC have been described [17].The signs and symptoms of arachnoid cysts vary according to their size and location.Small cysts are usually asymptomatic, requiring observation and follow up.However, larger cysts can have a mass effect on neurovascular structures, leading to neurological symptoms [13].IAC usually present with mild and slow progressive symptoms [25].Headaches are the most common symptom, accounting for a share of 66% [26].Other symptoms include dizziness, nausea, vomiting, wor-DOI: 10.4236/wjns.2018.83029366 World Journal of Neuroscience sening of mood, mental status changes, ataxia, seizures, and hearing loss [27].
The acute neurologic symptoms in our patient are atypical for a patient with an arachnoid cyst in this localization.The exact mechanism remain unclear but could have been due to the rapidly enlargement of the cyst.Some IAC may cause obstructive hydrocephalus by blocking the outflow of CSF.Obstructive hydrocephalus is frequently seen in patients with cysts in the suprasellar localization [28].IAC appear on both computed tomography (CT) and MRI as homogeneous, non-enhancing, well circumscribed, non-calcified, and extra-parenchymal masses with a signal identical to CSF [29] [30].In this case, the CT scan presentation was in favor of the diagnosis of ICA.This was further confirmed by the peroperative discovery of a typical arachnoid cyst with an arachnoid membrane, which was widely opened during cyst marsupialization.The Galassi [31]

Conclusion
Most of IAC are clinically silent.Symptomatic IAC usually present with mild and slow progressive symptoms caused by the cyst.Acute symptoms are rare and may require prompt surgical treatment.

Figure 3 .
Figure 3. Post-operative CT scan showing the resolution of the cyst.
classification is used to classify middle fossa cysts into three types.Type I cysts are typically asymptomatic and are present in the anterior middle cranial fossa.Type II cysts extend superiorly along the Sylvian fissure, occasionally displacing the temporal lobe.Finally, Type III cysts are very large and occupy the entire middle cranial fossa, displacing not only the temporal lobe but also disrupting the parietal and frontal lobes.There usually is an indication for surgery when there are symptoms of increased intracranial pressure, seizures, focal neurologic deficits or cognitive impairment.Surgical options include craniotomy and cyst excision, cyst-peritoneal and/or ventriculoperitoneal shunt placement, and endoscopic cyst fenestration.Location and size of symptomatic arachnoid cysts are major determinants of treatment strategy.Craniotomy and cyst marsupialization remains the most favored treatment option for Sylvian fissure cysts and other convexity cysts with are ported success rate up to 76% in one series [32] [33].The acute onset of neurological signs and the localization of cyst prompt us to do an emergency marsupialization via craniotomy in our case.