Brain comorbidities in normal pressure hydrocephalus

[Observational study on the coincidence of Alzheimer's disease and idiopathic normal pressure hydrocephalus: analysis of coincidence, the influence on response to cerebrospinal fluid drainage and cerebrovascular copathology]

OBJECTIVE

Analysis of the frequency of comorbid Alzheimer's disease in patients with suspected idiopathic normal pressure hydrocephalus (iNPH) and its effects on the response to cerebrospinal fluid (CSF) drainage as well as analysis of the frequency of a vascular copathology in patients with suspected iNPH.

MATERIAL AND METHODS

This was a prospective observational analysis of patients with suspected iNPH who underwent guideline-conform NPH routine diagnostics including CSF drainage during clinical routine diagnostics between 1 July 2022 and 30 June 2023. Patients were recruited via the departments of neurology, neurosurgery and psychiatry of the University Hospital Carl Gustav Carus in Dresden. Typical NPH imaging results were acquired from available magnetic resonance imaging (MRI) and computed tomography (CT) sectional images. Relevant sociodemographic, clinical, cognitive and CSF diagnostic parameters were acquired via patient chart review. The patients were categorized with respect to the CSF results according to the amyloid-tau-neurodegeneration (ATN) classification.

RESULTS

During the observational period 33 patients (14 female, 19 male, mean age 74.6 ± 8.1 years) with suspected iNPH were analyzed. Of the patients 19 (57.6%) had a complete and 14 (42.4%) an incomplete Hakim's triad. The difference between the MoCA scores before and after CSF drainage varied between patients with and without a response to CSF drainage (F(1;22) = 5.725; p = 0.026). There was a trend that patients with a pathological corpus callosum angle and conspicuous Evans index (p = 0.052) as well as patients with a pathological corpus callosum angle, Evans index and complete clinical Hakim's triad (p = 0.055) more frequently show a response. The mean Fazekas score was 1.7. There was no correlation between the Fazekas score and response to CSF drainage. In 25 patients (75.8%) biomarkers for dementia and neurodegeneration were detected. According to the ATN classification 20 patients (80%) were categorized as A+T-, 3 (12.0%) as A+T+ and 2 (8.0%) as A-T-. Patients classified as A+T+ and A+T- did not respond more often to CSF drainage (p = 0.600).

CONCLUSION

The combined determination of the corpus callosum angle and the Evans index as well es their contextualization with clinical characteristics can possibly improve the prognostic evaluation regarding response to CSF draínage. Especially a comorbid amyloid pathology and a cerebral microangiopathy represent frequent copathologies of iNPH but the influence on the response to CSF drainage remains to be elucidated.

[Coincidence of normal pressure hydrocephalus and Alzheimer`s disease: therapeutic implications and open questions]

Normal pressure hydrocephalus (NPH) is prevalent in aging patient populations. Despite its clinical relevance, many patients with NPH may not receive adequate treatment. Because of the frequency of Alzheimer`s disease in these patients, there could be overlapping pathophysiological mechanisms that are as yet incompletely understood. Cerebral comorbidities seem to have negative effects on therapeutic response to ventriculoperitoneal shunting. In order to avoid unnecessary and unsuccessful surgery in highly vulnerable elderly patients, they have to be taken into consideration in the diagnostic process.

The Kuopio idiopathic normal pressure hydrocephalus protocol: initial outcome of 175 patients

BACKGROUND

The Kuopio University Hospital (KUH) idiopathic normal pressure hydrocephalus (iNPH) cerebrospinal fluid (CSF) shunting protocol is described together with the initial outcomes of 175 patients with probable iNPH treated according to this protocol from a defined population. Our secondary aim was to display the variety of differential diagnoses referred to the KUH iNPH outpatient clinic from 2010 until 2017.

METHODS

Patients were divided into four groups according to the prognostic tests: tap test (positive or negative) and infusion test (positive or negative). The short-term outcome was compared between groups. The 3-month outcome following shunt surgery was assessed by measuring gait speed improvement, using a 12-point iNPH grading scale (iNPHGS) and the 15D instrument.

RESULTS

From 341 patients suspected of iNPH, 88 patients were excluded from further research mostly due to deviation from the protocol's gait assessment guidelines. Hence 253 patients with suspected iNPH were included in the study, 177/253 (70%) of whom were treated with a CSF shunt. A favorable clinical outcome following surgery was observed in 79-93% of patients depending on the prognostic group. A moderate association (Cramer's V = 0.32) was found between the gait speed improvement rate and the prognostic group (X², p = 0.003). Patients with a positive tap test had the highest gait speed improvement rate (75%). In addition, an improvement in walking speed was observed in 4/11 patients who had both a negative tap test and a negative infusion test. Other outcome measures did not differ between the prognostic groups. Conditions other than iNPH were found in 25% of the patients referred to iNPH outpatient clinic, with the most prevalent being Alzheimer's disease.

CONCLUSIONS

Our results emphasize the importance of a systematic diagnostic and prognostic workup especially in cases with an atypical presentation of iNPH. Additional diagnostic testing may be required, but should not delay adequate care. Active surgical treatment is recommended in patients with a high clinical probability of iNPH. Other neurological conditions contributed to most of the non iNPH diagnoses.