Change in average peak cerebrospinal fluid velocity at the cerebral aqueduct, before and after lumbar CSF tapping by the use of phase contrast MRI, and its effect on gait improvement in patients with normal pressure hydrocephalus.

OBJECTIVES: To compare the change in peak cerebrospinal (CSF) flow velocity at the cerebral aqueduct in patients with normal pressure hydrocephalus (NPH) before and after CSF tapping with clinical outcome of the patients, i.e., gait improvement.

MATERIALS AND METHODS: Forty patients with NPH were evaluated before and after CSF tapping on 3 consecutive days at our institution. Gait improvement was compared with the average peak velocity at the cerebral aqueduct. The average peak velocity was also compared before and after lumbar CSF tapping using phase contrast magnetic resonance imaging (PC-MRI). The different flow parameters were compared using paired t-test.

RESULTS: The average peak velocity before and after lumbar CSF tapping was 5.8196 ± 1.420 cm/s and 4.1411 ± 1.0638 cm/s, respectively. The peak positive, negative, and average velocity decreased in the post-tap group. In our study, 70% of the patients showed gait improvement, and a comparison of the gait improvement with the change in average peak velocity was statistically significant (P = 0.001). Comparison of the change in peak positive and negative velocity with gait improvement was also statistically significant, with a P value of 0.004 and <0.001, respectively. Rest of the CSF flow parameters were statistically insignificant.

CONCLUSION: PC-MRI is a sensitive method to support the diagnosis of NPH. Different flow parameters were comparable before and after CSF tapping. The parameters which might be useful for assessing clinical improvement include a change in the peak average, as well as positive, and negative velocity.