Objective: To compare the clinical phenotype between patients with normal and abnormal dopamine transporter scan (DaTscan) in probable and definite idiopathic normal pressure hydrocephalus (iNPH).

Background: While iNPH is more commonly identified as a clinical triad of gait dysfunction, memory impairment, and urinary incontinence, parkinsonian features, such as akinesia and tremor are well described in this population creating an overlap with degenerative parkinsonism. DaTscan is often utilized to evaluate for mimics or co-pathologies. Recent studies have highlighted the presence of striatal degeneration in 60% of cases of iNPH and most often involve the caudate more than putamen. Limited data is available looking at the difference in clinical phenotype in those with abnormal (D+) or normal (D-) DaTscan.

Method: This is a retrospective study comparing the presenting movement disorders in D+ and D- patients who met the Japanese guidelines criteria for probable and definite iNPH and were seen at the University of Connecticut Health Center’s Interdisciplinary NPH clinic between January 2020 and June 2023.

Results: Out of the 54 who patients met the criteria for probable and definite iNPH, 21 patients underwent DaTscan. Two were excluded for non-diagnostic studies. Of the 19 patients included in analysis, 7 were D+ cohort and 12 in D-. In the D+ group: 4 (57%) were male, with a mean age of 82.6 years +/= 3.6 at presentation with a mean age at time of symptom onset of 78.6 years +/= 2.9.  In the D- group: 9 (75%) were male, with a mean age of 76.8 years +/= 5.6 at presentation and mean age at time of symptom onset of 72.5 years +/= 6.4. The mean age at presentation and mean age at time of symptom onset were found to be statistically significant. Tremors, rigidity, and bradykinesia had higher prevalence in D+ and dystonia, myoclonus, and ataxia had higher prevalence in D- group; however, this did not reach statistical significance.

Conclusion: Our study indicates that striatal degeneration is associated with delayed onset of symptoms in iNPH. While difference in clinical profile was noted for the two groups, statistical significance was not achieved, likely due to limited number of subjects. Future investigations with larger sample sizes are needed to confirm these associations and elucidate their clinical significance.

References: [1] Lee SM, Kwon KY. Clinical tips in diagnosing idiopathic normal pressure hydrocephalus: a new concept beyond the cerebrospinal fluid tap test. J Integr Neurosci. 2021 Jun 30;20(2):471–5.

[2] Sakurai A, Tsunemi T, Ishiguro Y, Okuzumi A, Hatano T, Hattori N. Comorbid alpha synucleinopathies in idiopathic normal pressure hydrocephalus. J Neurol. 2022 Apr;269(4):2022–9.

[3] Pozzi NG, Brumberg J, Todisco M, Minafra B, Zangaglia R, Bossert I, et al. Striatal Dopamine Deficit and Motor Impairment in Idiopathic Normal Pressure Hydrocephalus. Mov Disord. 2021 Jan;36(1):124–32.

[4] Lee JY, Park S Bin, Lee M, Ju H, Im K, Kwon KY. Detailed visual assessment of striatal dopaminergic depletion in patients with idiopathic normal pressure hydrocephalus: unremarkable or not? BMC Neurol. 2020 Jul 11;20(1):277.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impact-of-striatal-degeneration-on-clinical-phenotype-in-idiopathic-normal-pressure-hydrocephalus-a-comparative-analysis/