Arachnoid diverticula associated with anterior cranial base tumors: technical case report

Intrasellar Arachnoid Diverticulae as a Risk Factor for Intraoperative Cerebrospinal Fluid Leakage in Patients Undergoing Endoscopic Transsphenoidal Surgery

BACKGROUND AND OBJECTIVES

Intrasellar arachnoid diverticulae can often be identified on preoperative imaging in patients undergoing endoscopic transsphenoidal surgery. The objective of this study was to characterize arachnoid diverticulae both qualitatively and quantitatively in a large institutional cohort of patients with pituitary tumors and to evaluate its association with intraoperative cerebrospinal fluid (CSF) leak.

METHODS

Preoperative imaging studies of 530 patients who underwent primary endoscopic transsphenoidal resection of pituitary tumors were examined both quantitatively and qualitatively for the presence of an intrasellar arachnoid diverticulum. A matched cohort analysis was performed to compare patients with a "significant" (>50% sellar depth) diverticulum with those with nonsignificant/no diverticulum. Morphologically, diverticulae were separately classified as Type 1 (ventral CSF cleft with no tumor/gland tissue between sellar face and infundibulum) or Type 2 (central CSF cleft with tumor/gland tissue between sellar face and infundibulum).

RESULTS

Arachnoid diverticulae were noted in 40.2% of cases, and diverticulum depth was linearly correlated with tumor size and body mass index. A significant diverticulum was identified in 66 cases (12.5%) and was significantly associated with the functional tumor subtype ( P = .005) and intraoperative CSF leak ( P < .001). Type 1 clefts were associated with nonfunctional pathology ( P = .034) and the presence of suprasellar extension ( P = .035) and tended to be deeper than Type 2 clefts ( P < .001), with a higher incidence of intraoperative CSF leak ( P = .093). On logistic regression analysis, only the presence of a significant diverticulum was independently associated with intraoperative CSF leak (odds ratio 4.545; 95% CI 2.418-8.544; P < .001).

CONCLUSION

The presence of an intrasellar arachnoid diverticulum should alert the surgeon to an elevated risk of intraoperative CSF leak during transsphenoidal surgery for pituitary tumors. A relatively limited surgical exposure tailored to the craniocaudal extent of the sellar pathology should be considered in these patients.

MRI characteristics of fourth ventricle arachnoid diverticula in five dogs

Intracranial arachnoid diverticula (cysts) are rare accumulations of cerebrospinal fluid (CSF) within the arachnoid membrane. The purpose of this retrospective study was to describe magnetic resonance imaging (MRI) characteristics of fourth ventricle arachnoid diverticula in a group of dogs. The hospital's medical records were searched for dogs with MRI studies of the brain and a diagnosis of fourth ventricle arachnoid diverticulum. Clinical characteristics were recorded from medical records and MRI studies were reinterpreted by a board-certified veterinary radiologist. Five pediatric dogs fulfilled inclusion criteria. Clinical signs included cervical hyperaesthesia, obtundation, tetraparesis, and/or central vestibular syndrome. In all five dogs, MRI findings were consistent with obstructive hydrocephalus, based on dilation of all ventricles and compression of the cerebellum and brainstem. All five dogs also had cervical syringohydromyelia, with T2-weighted hyperintensity of the gray matter of the cord adjacent to the syringohydromyelia. A signal void, interpreted as flow disturbance, was observed at the mesencephalic aqueduct in all dogs. Four dogs underwent surgical treatment with occipitalectomy and durotomy. A cystic lesion emerging from the fourth ventricle was detected in all four dogs during surgery and histopathology confirmed the diagnosis of arachnoid diverticula. Three dogs made excellent recovery but deteriorated shortly after surgery and were euthanized. Repeat MRI in two dogs revealed improved hydrocephalus but worsening of the syringohydromyelia. Findings from the current study supported theories that fourth ventricle arachnoid diverticula are secondary to partial obstruction of the central canal or lateral apertures and that arachnoid diverticula are developmental lesions in dogs.