Objective: To study parkinsonism in iNPH, in order to shed light on its pathogenesis, understand potential overlap with idiopathic parkinsonismsand its impact on the clinical outcome.

Background: Diagnosis of iNPH is based on the presence of Hakim’s triad and ventriculomegaly not due to brain atrophy [1]. Parkinsonism is reported as part of the clinical pictures, sometimes due to the coexistence of a pathologically confirmed idiopathic parkinsonism, sometimes not. To distinguish these two setups is of paramount importance, since they carry different response to ventriculoperitoneal shunt (VPS) [2]. The DaTSCAN can be helpful in this regard, however, its role in predicting the surgical outcome is unclear [3].

Method: Patients with clinical hints of iNPH and extrapyramidal signs, raising suspicion of a concomitant neurodegenerative parkinsonism underwent a chronic trial with levodopa, 3T brain MRI and DaTSCAN.

Results: We found 3 patients (Pt-1, 65-year-old lady; Pt-2, 72-year-old lady; Pt-3, 65-year-old gentleman) with clinical and radiological criteria for iNPH (EI>0.3, DESH criterion, acute callosal angle) and asymmetric akinetic-rigid parkinsonism. 3T MRI with iron-sensitive sequences (SWAN) showed bilateral preservation of the 3-layered organization of the substantia nigra (SN) in Pt-1 and Pt-2, and a loss of the hyperintense intermediate layer of the SN in Pt-3. The DaTSCAN revealed in all of them a bilateral asymmetric striatal degeneration, consistent with clinical asymmetry. Levodopa trial was unsuccessful in all patients. Pt-1 and Pt-3 underwent VPS and 2 years after Pt-1 still shows a significant and sustained clinical improvement (MDS-UPDRS III and 10m walking Test), whereas Pt-3 experienced a transient benefit, which declined after 6 months. A follow up DaTSCAN pointed out an increased striatal tracer uptake in Pt-1, whereas a progressive reduction was seen in Pt-3.

Conclusion: Our results suggest that an abnormal DaTSCAN does not necessarily mean an overlap between iNPH and idiopathic parkinsonisms, since in 2 out of our 3 cases the SN was preserved. The increase in DaT availability post VPS, suggests a secondary and partly reversible damage to the nigrostriatal pathway consistent with a remarkable clinical improvement. Conversely, when there is an underlying neurodegenerative parkinsonism the tracer uptake and the clinical pictures are doomed to deteriorate.

References: [1] Relkin, N., et al., Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery, 2005. 57(3 Suppl): p. S4-16. [2] Espay, A.J., et al., Deconstructing normal pressure hydrocephalus: Ventriculomegaly as early sign of neurodegeneration. Ann Neurol, 2017. 82(4): p. 503-513. [3] Broggi, M., et al., Normal Pressure Hydrocephalus and Parkinsonism: Preliminary Data on Neurosurgical and Neurological Treatment. World Neurosurg, 2016. 90: p. 348-356.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-dat-imaging-abnormality-in-normal-pressure-hydrocephalus-always-suggestive-of-degeneration-evidences-from-three-cases/