• Jonathan Perry Funnell, Linda D'Antona, Claudia Louise Craven, Lewis Thorne, Laurence Dale Watkins, and Ahmed Kassem Toma.
• Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, Box 32, Queen Square, London, WC1N 3BG, UK. jonathan.funnell@nhs.net.
• Acta Neurochir (Wien). 2020 Dec 1; 162 (12): 2967-2974.

BackgroundIdiopathic normal-pressure hydrocephalus (NPH) is a condition of the elderly treated by ventriculoperitoneal shunt (VP) insertion. A subset of NPH patients respond only temporarily to shunt insertion despite low valve opening pressure. This study aims to describe our experience of patients who benefit from further CSF drainage by adding adjustable antigravity valves and draining CSF at ultra-low pressure.MethodsSingle-centre retrospective case series of patients undergoing shunt valve revision from an adjustable differential pressure valve with fixed antigravity unit to a system incorporating an adjustable gravitational valve (Miethke proSA). Patients were screened from a database of NPH patients undergoing CSF diversion over 10 consecutive years (April 2008-April 2018). Clinical records were retrospectively reviewed for interventions and clinical outcomes.ResultsNineteen (10F:9M) patients underwent elective VP shunt revision to a system incorporating an adjustable gravitational valve. Mean age 77.1 ± 7.1 years (mean ± SD). Eleven patients (58%) showed significant improvement in walking speed following shunt revision. Fourteen patients/carers (74%) reported subjective improvements in symptoms following shunt revision.ConclusionsPatients presenting symptoms relapse following VP shunting may represent a group of patients with ultra-low-pressure hydrocephalus, for whom further CSF drainage may lead to an improvement in symptoms. These cases may benefit from shunt revision with an adjustable gravitational valve, adjustment of which can lead to controlled siphoning of CSF and drain CSF despite ultra-low CSF pressure.

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