Neurology India, Vol. 58, No. 3, May-June, 2010, pp. 493-495
Letter To Editor
Corticoventriculostomy for the treatment of intracerebral arachnoid cyst
Zonggang Hou, Pengxiang Yan
Department of Neurosurgery, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, China
Date of Acceptance: 08-Jun-2010
Code Number: ni10129
Arachnoid cysts represent approximately 1% of all lesions occupying the intracranial space.  They are most frequently located in the Sylvian fissure, in the cisterna magna, or over the hemisphere convexity. An entirely intracerebral arachnoid cyst is rare.
A 37-year-old male presented with 1 year duration of numbness and 3 months duration of progressive weakness in his left limbs, associated with headache and nausea. Neurologic examination revealed grade 4/5 motor power and impaired superficial and deep sensations of the left limbs. Babinski sign was positive on the left side. The rest of the physical examination was essentially normal. The patient was initially evaluated by contrast-enhanced computed tomography, which showed a large cystic hypodense area in the right frontal and parietal lobes without the enhancement of the cyst wall or perilesional edema [Figure - 1]. Magnetic resonance imaging (MRI) demonstrated a cystic mass lesion with isointense to cerebrospinal fluid (CSF); the wall of the cyst was clear, smooth, and without enhancement [Figure - 2]a and b. Right frontal-parietal craniotomy was done to explore the cystic lesion. After the dura was reflected, swelling of the brain was noted but not of the wall of the cyst [Figure - 3]. An incision was made over the area of maximum fluctuation along the course of a large draining vein [Figure - 3]. After opening a cortical sulcus and continuing downward about 0.5 cm, the wall of the cyst was seen. The cyst was opened, and a discrete amount of clear fluid was evacuated. Further inspection of the cyst found no other solid lesions. Communication of the cyst with the trigone of the lateral ventricle was established by opening along the inferomedial portion of the cyst wall. Thus, the lateral ventricle, the subarachnoid, and the cyst cavity were in free communication. Postoperatively the patient had normal muscle strength on the left side. Repeat MRI showed dramatic decrease in the cyst size and communication between the cyst and the ventricular system [Figure - 4]a and b. Analysis of the fluid aspirated from the cyst had no cells, protein 78 mg/dL, and glucose 4 mg/dL. Histologic examination indicated arachnoid cyst [Figure - 5]. At follow-up, the patient was well and could carry on his daily activities independently.
Arachnoid cysts usually arise within and expand the margin of CSF cisterns rich in arachnoid tissue (eg, Sylvian fissure, suprasellar, quadrigeminal). An entirely intracerebral arachnoid cyst is quite rare. The etiology of arachnoid cysts has been a controversial subject and still remains unclear.  The origin of solely intracerebral arachnoid cysts is not fully clarified. The possible mechanism may be that the congenitally trapped arachnoidal cells in the brain parenchyma multiply and line the cyst wall resulting in progressive enlargement. The differential diagnosis for intracerebral arachnoid cyst includes cystic glioma, low-grade gliomas, hemangioblastoma, and cerebral hydatid disease. ,
Indication for surgery is obvious in patients with signs of raised intracranial pressure, focal neurologic deficits, seizures, or complicated hematoma. Controversy continues regarding the optimal surgical management. There is ongoing debate regarding whether to fenestrate or to perform shunting of the cyst. Endoscopic fenestration of cysts to minimize surgical trauma has also been introduced recently. , As to the present patient, because the possibility of low-grade glioma could not be excluded preoperatively, craniotomy was recommended. After the arachnoid cyst was verified intraoperatively, corticoventriculostomy was performed via the cortical sulci to make the cyst cavity communicate with the cerebral ventricular and subarachnoid regions.
To conclude, an entirely intracerebral arachnoid cyst is rare and the preoperative diagnosis is of great importance. Also the successful outcome of this case suggests that corticoventriculostomy is likely an effective operative method.
Copyright 2010 - Neurology India
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