Article
The semi-sitting position in previously shunted patients
Die halbsitzende Position bei Shunt-versorgten Patienten
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Published: | June 4, 2021 |
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Objective: The semi-sitting position is one of the preferred positions for posterior fossa surgery. Although posterior fossa or midline tumors are often associated with hydrocephalus, primary tumor removal with or without perioperative placement of an external ventricular drain is commonly favored since hydrocephalus may resolve after tumor resection. Shunting prior to tumor surgery is reserved for symptomatic cases, whereas there are limited data regarding perioperative management of such cases.
Methods: The medical records of all patients who underwent tumor removal in the semi sitting position over a decade after shunting for hydrocephalus were analysed retrospectively. Patients in whom an external ventricular drain was inserted prior to posterior fossa surgery in the semi sitting position were excluded.
Results: Twelve patients (10 women and 2 men) were previously treated for hydrocephalus and a total of 17 operations in the semi-sitting position were performed. The most common cause of hydrocephalus was acoustic neuroma (6/11). Nine patients had a programmable valve (valve setting range 6-14 cmH20, mean 7,5 cmH20), 2 patients had a medium pressure valve and in one case the valve could not be radiologically identified (not adjustable). In two patients the valve setting was adjusted from 8 to 16 cm H20 and from 14 to 20 cm H20 respectively after resolution of postoperative pneumocephalus revealed bilateral hygromas. In one case with a medium pressure valve bilateral asymptomatic subdural hygromas were found at 3 months follow-up and subsequently resolved spontaneously. In one case postoperative overdrainage with symptomatic slit ventricles was treated with ligation of the shunt catheter and implantation of an adjustable valve in a two stage procedure. In our series there were no cases of obstruction, disconnection, infection or hardware malfunction of the shunt system.
Conclusion: In cases of primary shunting for hydrocephalus associated with posterior fossa tumors a programmable valve set at a medium opening pressure is a valid option in the semi-sitting position. Special caution is necessary to detect overdrainage in cases without programmable valves.