Objective: To discuss the possible dopaminergic pathway interference as a mechanism underlying the sustained benefit of the CSF tap test in NPH.

Background: The sustained effect of the CSF tap test in some NPH subjects is emphasized in several recent reports. In this regard, an interesting hypothesis is that the mechanical effect exerted on the striatum by ventriculomegaly ultimately leads to the downregulation of dopaminergic transporters which may improve after surgery.

Method: We present a 68-year-old male with NPH conducting elaborative investigations of the clinical features in the basal state, in response to levodopa therapy and in response to the tap test. We discuss our clinical findings in the context of the DATSAN results.

Results: Our patient presented with a progressive gait disturbance over the last two years. The neurological exam revealed lower-body parkinsonism. Besides, the patient suffered from mild freezing of gait (FOG) episodes during turnings. Extrapyramidal signs also revealed mild bradykinesia and rigidity on the left upper limb. Initially, levodopa was prescribed which provided significant improvement in his gait (the MDS-UPDRS part III score during the basal state was 16 points, and it was evaluated as 12 points during the medication ‘on’ state). However, the cranial MRI showed findings compatible with NPH. Of note, the patient suffered from urge-type urinary incontinence and mild cognitive deterioration. The CSF tap test was performed 12 hours after the levodopa dose which provided a marked improvement in his gait. To investigate a possible dopaminergic deficit and determine the prognosis, a DATSAN was performed one month later that showed normal DAT uptake. Remarkably, the clinical improvement achieved with the tap test persisted at the one-month follow-up. Of note, the levodopa 100 mg attempted this time did not yield further amelioration. Six months later, a tap test was repeated due to the deterioration of gait which provided total recovery. At the last follow-up one year later, no deterioration was detected.

Conclusion: The sustained benefit of the CSF tap test in some NPH subjects might be related to the resolution of the possible abnormal dopamine uptake that is achieved by the resolution of the mechanical effect exerted on the striatum by ventriculomegaly. Future prospective reports may probably provide substantial contributions to these discussions.

References: 1. Del Gamba C, Bruno A, Frosini D, et al. Is DAT imaging abnormality in normal pressure hydrocephalus always suggestive of degeneration? Neurol Sci. Feb 2021;42(2):723-726.
2. Broggi M, Redaelli V, Tringali G, et al. Normal Pressure Hydrocephalus and Parkinsonism: Preliminary Data on Neurosurgical and Neurological Treatment. World Neurosurg. Jun 2016;90:348-356.

« Back to 2023 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/does-the-dopaminergic-pathway-interfere-with-the-sustained-csf-tap-test-effect-in-normal-pressure-hydrocephalus/