Craniocervical Junction Arachnoid Cyst Causing Hydrocephalus: Case Report and Review of the Literature

Military Medicine, Jun 2007 by Kutlay, Murat, �olak, Ahmet, Demircan, Nusret, Akin, Osman

Objective: Arachnoid cysts (ACs) of the craniocervical junction are extremely rare entities. This report describes a craniocervical junction AC with unusual clinical course at an unusual anatomical location. Methods: A 21-year-old man was admitted to our clinic after a craniospinal trauma. Examination was unremarkable. Computed tomography scans demonstrated mild to moderately enlarged third and the lateral ventricles, but the fourth ventricle was typically normal. Neuroimaging studies obtained after the onset of clinical symptoms revealed marked enlargement of the ventricular system and a new cyst formation at the C1-2 level which was absent before. He underwent suboccipital craniectomy and C1-2 laminectomies. The cyst was fenestrated into subarachnoid space. Results: He made a good recovery. The histopathological diagnosis was confirmed as AC. Conclusion: Due to rarity of this clinical entity, we urge readers to keep in mind the possibility of the development of this kind of AC with unusual clinical course.

Introduction

Arachnoid cysts (ACs) of the spinal canal are rare, histologically benign space-occupying lesions. They are predominantly located posterior to the spinal cord; the thoracic spine is the most common site.1'12 Some spinal ACs located anterior to the spinal cord have also been reported.6,8,9,12-16 ACs of the craniocervical junction (CCJ), however, are even rarer, and only six cases have been reported in the literature; all of them had shown extension to the posterior fossa.5,17-21

In the cases of spinal ACs, clinical presentation depends on the location of the lesion. Usually, they become symptomatic by causing myelopathy or radiculopathy.1-4,6-8,11,13,16-22-25 All of these symptoms typically develop over a period of months or years.1,2,6,10-12,14,19,25,26

In this report, a new case of AC with a distinct clinical course is presented and the pertinent literature is reviewed.

CASE Report

This 21-year-old man was admitted to the emergency room with a craniospinal trauma in a traffic accident. He had suffered loss of consciousness for a few minutes. On admission, he was conscious and he was complaining of headache. On physical examination, a frontal scalp laceration was noted. His neurological examination were normal. Routine laboratory examination data were within normal limits. Cervical spine X-ray films were unremarkable for fracture or dislocation. Cranial computed tomography (CT) performed on admission demonstrated that the third and lateral ventricles were mild to moderately dilated but the fourth ventricle was typically normal in size (Fig. 1). The patient was transferred to our clinic for further observation and evaluation. Then, the CT scan was repeated, because he began to experience gradually increasing headache. The scan demonstrated marked dilatation of the lateral ventricle in addition to an enlarged fourth ventricle (Fig. 2). A cystic lesion was also determined at the CCJ, which was absent in the previous CT scans (Fig. 3). Magnetic resonance imaging (MRI) revealed a well-demarcated, extra-axial cystic mass, on both Tl- and T2weighted images consistent with the same signal intensity as cerebrospinal fluid (CSF). It had displaced the spinal cord ventrally at the levels of Cl and C2 (Fig. 4). The MRI also revealed that the enlargement of the fourth ventricle was not related with the mass inside. In the following hours, his headache became worse and he began to vomit. He was transferred to the operating room immediately.

Operation

The patient underwent surgery in the prone position. Initially, an external ventricular drainage to the lateral ventricle was made, but free flow of CSF was not allowed to prevent the risk of upward herniation of vermis. A midline suboccipital craniectomy with C1-2 laminectomies were performed. Following incision of the dura, a translucent thin-walled cyst was found, which had occupied the entire dorsal half of the spinal canal at the C1-2 level. The cyst fluid was aspirated. It was clear and colorless, resembling normal CSF. After aspiration, the cyst did not re-expand and there was no CSF leakage. Using microsurgical techniques, we removed as much of the cyst wall as possible, but no attempt was made to resect the anterior wall because of its adherence to the cord. When the superior wall of the cyst occluding the foramen of Magendie was removed, free flow of CSF was observed.

Postoperative Course

The patient made a good postoperative recovery. The results of CSF examination were normal. The culture was also negative. A light microscopic examination of the biopsy specimen showed histologically the arachnoid membrane. There were no inflammatory reaction and blood pigments in the cyst wall. The CT scan obtained 7 days after surgery revealed remarkable reduction in the size of the fourth ventricle (Fig. 5).

Discussion

Based on a review of the literature, ACs of the spinal canal may be classified as either extradural or intradural.1-4,8-10,12-14,25-27 There is no gender preponderance and the diagnosis is usually established in the third through the fifth decades.1-4,6,7,10,12,22-26 However, the classification of these cysts in the literature is distinct and confusing. For the sake of simplicity, and to avoid further confusion in the nomenclature, Nabors et al.6 have classified these lesions into three major categories (Table I). The patient reported in this study presented with a type III cyst (intradural AC).