Two obese women, both of whom were 42 years of age, were examined for pseudotumor cerebri. Intracranial venography revealed increased pressure in the dural venous sinuses and the right atrium. The increased right atrial pressure was attributable to the patients' obesity. Both patients underwent bariatric surgery to achieve weight loss. Approximately 1 year later, a clinical evaluation showed that in both women the pseudotumor cerebri had resolved. Repeated measurements of dural venous pressure indicated that the patients' pressures had returned to normal. Obese patients with pseudotumor cerebri and stable visual symptoms are best treated with weight loss to avoid shunt placement or optic nerve sheath fenestration.

Object In this paper the authors define the role of the cortical subarachnoid space (CSAS) in poorly understood forms of hydrocephalus to cerebrospinal fluid (CSF) dynamics to improve understanding of the importance of the CSAS and its role in selecting patients for endoscopic third ventriculostomy (ETV). The secondary purpose of this work was to define testable hypotheses to explain enigmatic disorders of CSF dynamics and to suggest how these concepts could be tested. Methods The magnitude of the contribution of the CSAS is explored using the solid geometry of concentric spheres. With this starting point, clinical conditions in which CSF dynamics are not easily understood are explored regarding the potential role of the CSAS. Overall, problems of CSF dynamics are easily understood. Insights may be gained when the results of a pathological process or its treatment vary from what has been expected. Results Acute changes in ventricular volume at the time that hydrocephalus develops, the failure of shunts, and the changes in ventricular volume with shunt repair may occur very rapidly. Changes in the volume of water in the brain, especially in the brain substance itself, are unlikely to occur at this rapid rate and may be interpreted as a simple redistribution of the CSF between the ventricle and CSAS with no initial change in the actual volume of brain parenchyma. Problems such as pseudotumor cerebri, shunt failure with nonresponsive ventricles, and negative-pressure hydrocephalus can be explained by assessing the ability of ventricular CSF to flow to the CSAS and the ability of this fluid to exit this compartment. Ventricular enlargement at the time of shunt failure implies a failure of flow between the ventricles and CSAS, implying that all patients who show this phenomenon are potential candidates for ETV. Conclusions The important role of the CSAS in the pathophysiology of various forms of hydrocephalus has been largely ignored. Attention to the dynamics of the CSF in this compartment will improve understanding of enigmatic conditions of hydrocephalus and improve selection criteria for treatment paradigms such as ETV. These concepts lead to clearly defined problems that may be solved by the creation of a central database to address these issues.

Objective: To determine the safety and efficacy of lumboperitoneal (LP) shunts in carefully selected children with abnormalities of the absorption of cerebrospinal fluid. Methods: Magnetic resonance imaging studies, indications for treatment and pre- and postoperative symptoms of 25 patients (mean age 9.6 years) who had undergone LP shunting in the past 10 years in a single pediatric neurosurgical practice were analyzed retrospectively. Results: Indications for treatment included postoperative pseudomeningocele, pseudotumor cerebri and a severe form of slit ventricle syndrome. Preoperative symptoms resolved completely in all 25 patients as a result of the shunt, and no patient developed symptomatic or radiographic hindbrain herniation. Twenty-one shunts incorporated valve mechanisms. Conclusion: LP shunts may be used for specific indications without excessive risk of hindbrain herniation.

Object The authors evaluated the efficacy of treating patients with pseudotumor cerebri (PTC) and headaches due to increased intracranial pressure (ICP) by using a lumboperitoneal (LP) shunt with a programmable valve and ventricular access device (VAD). Methods Forty patients in whom PTC was diagnosed were treated using LP shunts with programmable valves and wand-guided placement of a VAD. All patients had papilledema and high opening pressure during spinal tap. The mean follow-up was 18 months (range 3–72 months). When patients complained of headaches that suggested shunt malfunction, the ventricular reservoir was tapped at bedside to assess ICP. The programmable valve was adjusted based on the patient's headache and ICP. Results The VAD was tapped in 21 patients, and the LP valve was redialed in 14. Shunt malfunction was diagnosed accurately. The 10 patients undergoing revision were all found to have shunt obstruction except 1 whose valve was replaced because it could not be reprogrammed. No patient treated with a shunt developed a Chiari malformation. The VAD was exposed in 4 patients with infection or wound breakdown. The LP shunt was revised in 2 patients who developed a pseudomeningocele. In 1 patient, a small bowel obstruction responded to conservative management. Seven patients had headaches despite documented normal ICP. That is, the headaches were unrelated to shunt function, and these patients were referred to a pain management clinic. Conclusions Lumboperitoneal shunts with programmable valves effectively controlled the outflow of lumbar cerebrospinal fluid to ameliorate the symptoms of PTC. The VAD permitted assessment of ICP and thus, indirectly, LP shunt function, and benefits outweighed risks. The programmable valve permitted cerebrospinal fluid flow to be adjusted based on patients' clinical status and ICP to be measured by the VAD.