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DOI: 10.1055/s-2006-939089
Clinical impact of the intrathecal infusion test to distinguish between Normal Pressure Hydrocephalus (NPH) and Dementia
Introduction: NPH was first described by Hakim in 1964. Although it is still an often unrecognised disease. Especially difficult is to distinguish between dementia and NPH.
Methods: From 2003 to 2005 we examined 16 patients suspected for NPH. Two of three cardinal clinical symptoms had to be present. Charactaristic features on CT/MRI were communicating hydrocephalus, periventricular low densities and rounding of the frontal horns.
All patients were admitted to administer an intrathecal infusion test. Criteria for NPH was an increased resistance to outflow (Rout) and a recovery after CSF tap test. According to Tans Rout >13mmHg*min/ml was defined as pathological increased. Patients whose Rout was within a physiological range and who showed no recovery after the CSF tap test were diagnosed for dementia.
Results: cases: 10 (62.5%) male, 6 (37.5%) female. Mean age: 66.19 y (min. 42, max. 78).
9 (56.3%) patients were diagnosed with dementia, 7 (43.8%) patients with idiopathic NPH. 4 (25.0%) were treated by implanting a VP shunt. 2 patients rejected surgical treatment, one case could not be shunted because of other reasons.
Complication rate due to the examination (spinal headache, infections, hematomas) was 0%.
Discussion: Implantation of a VP shunt is treatment of choice in patients with NPH. The potential complication rate after shunting is high (subdural hematomas due to overshunting (20%), shunt malfunction (17%), infections and obstructions of the implanted shunt system (11%)). The goal of clinical diagnostics is a selection of patients, who benefit from surgical treatment.
The group of patients, who are appropriate for shunting, is small. In only 4 cases the result of the examination leaded to an operation.
On the other hand the infusion test is a possibility to filter out patients who would not benefit from surgical treatment – those with dementia.
We examined only patients with the presumption diagnosis of idiopathic NPH. Cases with another etiology were not included. This fact explains the relative small trial size of only 16 patients.
Conclusion: Together with the clinical examination and the imaging the intrathecal infusion test helps to distinguish between NPH and dementia. It features an additional criteria to determine which patient is likely to respond to a shunt procedure in order to avoid potential complications.