Objective: External hydrocephalus, introduced by Dandy and Blackfan in 1914 [Am J Dis Child 1914;8:406–482], is used to describe the clinical condition of cerebrospinal fluid (CSF) accumulation in the subarachnoid space with its space expansion and increased intracranial pressure in pediatric patients. Benign subdural effusion, subdural hygroma and pseudohydrocephalus are some terms used to describe some conditions, not clearly defined at the moment as separate pathological entities. We report 3 pediatric cases which had CSF collections after craniotomy. Neuroimaging investigations revealed CSF collection after surgery. All 3 cases had a poor clinical course with resolution after shunting. This report analyzes the mechanisms and pathophysiology of postoperative extra-axial CSF collections (PECC), indicating that CSF accumulations in the extra-axial spaces (inside or outside the arachnoid) after surgery have a common pathophysiology. Therefore, the treatment protocol can be specific. Patients: Three pediatric cases, aged from 11 months to 6 years, had large tumors located from their suprasellar region to the hypothalamus and third ventricle. The tumors were excised surgically through either an anterior interhemispheric translamina-terminalis or a transsylvian translamina-terminalis approach or both. The surgery conducted created a wide opening of the anterior interhemispheric or the sylvian fissures, dissecting the lamina terminalis and Liliequist’s membrane resulting in a new artificial CSF tract from the basal cisterns to the subdural space. Clinical symptoms such as deterioration of consciousness level developed within a few weeks after surgery, and a follow-up computed tomography image confirmed subdural CSF collection. Symptoms improved after ventriculoperitoneal (V-P) shunting. Discussion: External hydrocephalus, subdural effusion and the other entities mentioned above are frequently observed in children, and little is known about their pathophysiology. To differentiate from the whole entity of CSF accumulation within the subdural and subarachnoid space, we use the term PECC to specify the main pathophysiological condition resulting from a wide dissection and opening of the arachnoid membrane and communication with the basal cisterns. Conclusion: We present the occurrence of CSF collections in the extra-axial space after surgery as the specific condition of PECC. Broadly dissecting the arachnoid membrane, with a communication remaining with the ventricles, is the main factor contributing to PECC, and patients have shown that V-P shunting is an effective procedure preventing progression and effectively treating PECC.

Keywords:
External hydrocephalus, Cerebrospinal fluid tract, Postoperative extra-axial cerebrospinal fluid collection, Ventriculoperitoneal shunt
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2011
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