CSF tap test parameters and Short-Term outcomes in operated and non-operated patients with idiopathic normal pressure Hydrocephalus: A cohort study

Sagar Poudel; Deepa Dash; Aparna Wagle Shukla; Ajay Garg; Ashish Dutt Upadhyay; Naveet Wig; Roopa Rajan; Animesh Das; Divya Mr; Manjari Tripathi; Achal K Srivastava; S S Kale; Poodipedi Sarat Chandra; Ashish Suri; Pramod K Pal; Hrishikesh Kumar; Sakoon Saggu; Deepti Vibha; Rajesh Kumar Singh; Jasmine Parihar; Ranveer Singh Jadon; Ved Prakash Meena; Bindu Prakash; Arunmozhimaran Elavarasi

doi:10.1016/j.prdoa.2026.100425

CSF tap test parameters and Short-Term outcomes in operated and non-operated patients with idiopathic normal pressure Hydrocephalus: A cohort study

Clin Park Relat Disord. 2026 Jan 28:14:100425. doi: 10.1016/j.prdoa.2026.100425. eCollection 2026.

Authors

Sagar Poudel¹, Deepa Dash², Aparna Wagle Shukla³, Ajay Garg⁴, Ashish Dutt Upadhyay⁵, Naveet Wig¹, Roopa Rajan⁶, Animesh Das⁶, Divya Mr⁶, Manjari Tripathi⁶, Achal K Srivastava⁶, S S Kale⁷, Poodipedi Sarat Chandra⁷, Ashish Suri⁷, Pramod K Pal⁸, Hrishikesh Kumar⁹, Sakoon Saggu⁶, Deepti Vibha⁶, Rajesh Kumar Singh⁶, Jasmine Parihar⁶, Ranveer Singh Jadon¹, Ved Prakash Meena¹, Bindu Prakash¹, Arunmozhimaran Elavarasi⁶

Affiliations

¹ Department of Medicine, All India Institute of Medical Sciences, New Delhi, India.
² Department of Clinical Neurological Sciences, University of Western Ontario, London, Canada.
³ Department of Neurology, Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, United States of America.
⁴ Department of Neuroimaging and Interventional Neuroradiology, All India Institute of Medical Sciences, New Delhi, India.
⁵ Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India.
⁶ Department of Neurology, All India Institute of Medical Sciences, New Delhi, India.
⁷ Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India.
⁸ Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India.
⁹ Movement Disorders Program, Institute of Neurosciences, Kolkata, India.

Abstract

Background: Normal Pressure hydrocephalus (NPH) is treated by ventriculoperitoneal shunting. The cerebrospinal fluid tap test (CSF-TT) is widely used to identify candidates for shunt surgery in idiopathic NPH (iNPH). This study aimed to compare the CSF tap test responses and 24-week functional outcomes between patients with probable iNPH who underwent surgery and those who did not.

Methods: This Ambispective cohort study included 40 patients with probable iNPH, as defined by the 2019 Japanese guidelines, from 2019 to 2024. All patients underwent a large-volume CSF-TT, and they were offered surgery based on the clinico-radiologic profile.

Results: Twenty-four patients underwent ventriculoperitoneal shunt surgery, and 16 did not for various reasons. No significant differences were found in the baseline or 24-hour post-CSF tap test parameters between the groups. However, at 24 weeks, 62.5% of the operated patients showed at least a 1-point improvement in mRS. In contrast, only 14.3% in the non-operated group did, indicating the beneficial role of VP shunting in NPH. Those who were operated had a 10 times higher odds (95% CI 1.6-105) of achieving at least one point improvement in mRS at 24 weeks. Interestingly, 46.7% of patients whose mRS did not improve after CSF-TT but who underwent surgery still benefited from shunting.

Conclusion: Shunt surgery leads to a favorable short-term functional outcome in patients with probable iNPH. However, the CSF-TT alone lacks sufficient discriminatory power to guide surgical decisions in a cohort of patients with clinico-radiological probable iNPH. A negative tap test should not preclude surgery in patients with supportive clinical and imaging features.