Encephalocele/physiopathology; Gastrectomy/adverse effects; Headache Disorders/physiopathology; Obesity, Morbid/physiopathology; Postoperative Complications/physiopathology; Pseudotumor Cerebri/physiopathology; Adolescent; Causality; Cerebellum/diagnostic imaging; Cerebellum/pathology; Cerebrospinal Fluid Shunts/adverse effects; Cerebrospinal Fluid Shunts/methods; Encephalocele/etiology; Encephalocele/surgery; Female; Headache Disorders/etiology; Humans; Iatrogenic Disease; Obesity, Morbid/complications; Obesity, Morbid/surgery; Postoperative Complications/etiology; Postoperative Complications/pathology; Pseudotumor Cerebri/etiology; Pseudotumor Cerebri/surgery; Subarachnoid Space/diagnostic imaging; Subarachnoid Space/pathology; Subarachnoid Space/physiopathology; Tomography, X-Ray Computed; Treatment Outcome; Ventriculoperitoneal Shunt; Weight Loss/physiology