Pathophysiology of Cerebral Circulatory Disorders in Idiopathic Normal Pressure Hydrocephalus

Increasing brain N-acetylneuraminic acid alleviates hydrocephalus-induced neurological deficits

AIMS

This metabolomic study aimed to evaluate the role of N-acetylneuraminic acid (Neu5Ac) in the neurological deficits of normal pressure hydrocephalus (NPH) and its potential therapeutic effect.

METHODS

We analyzed the metabolic profiles of NPH using cerebrospinal fluid with multivariate and univariate statistical analyses in a set of 42 NPH patients and 38 controls. We further correlated the levels of differential metabolites with severity-related clinical parameters, including the normal pressure hydrocephalus grading scale (NPHGS). We then established kaolin-induced hydrocephalus in mice and treated them using N-acetylmannosamine (ManNAc), a precursor of Neu5Ac. We examined brain Neu5Ac, astrocyte polarization, demyelination, and neurobehavioral outcomes to explore its therapeutic effect.

RESULTS

Three metabolites were significantly altered in NPH patients. Only decreased Neu5Ac levels were correlated with NPHGS scores. Decreased brain Neu5Ac levels have been observed in hydrocephalic mice. Increasing brain Neu5Ac by ManNAc suppressed the activation of astrocytes and promoted their transition from A1 to A2 polarization. ManNAc also attenuated the periventricular white matter demyelination and improved neurobehavioral outcomes in hydrocephalic mice.

CONCLUSION

Increasing brain Neu5Ac improved the neurological outcomes associated with the regulation of astrocyte polarization and the suppression of demyelination in hydrocephalic mice, which may be a potential therapeutic strategy for NPH.

Radiological biomarkers of idiopathic normal pressure hydrocephalus: new approaches for detecting concomitant Alzheimer's disease and predicting prognosis

Idiopathic normal pressure hydrocephalus (iNPH) is a clinical syndrome characterized by cognitive decline, gait disturbance, and urinary incontinence. As iNPH often occurs in elderly individuals prone to many types of comorbidity, a differential diagnosis with other neurodegenerative diseases is crucial, especially Alzheimer's disease (AD). A growing body of published work provides evidence of radiological methods, including multimodal magnetic resonance imaging and positron emission tomography, which may help noninvasively differentiate iNPH from AD or reveal concurrent AD pathology in vivo. Imaging methods detecting morphological changes, white matter microstructural changes, cerebrospinal fluid circulation, and molecular imaging have been widely applied in iNPH patients. Here, we review radiological biomarkers using different methods in evaluating iNPH pathophysiology and differentiating or detecting concomitant AD, to noninvasively predict the possible outcome postshunt and select candidates for shunt surgery.

Association of right precuneus compression with apathy in idiopathic normal pressure hydrocephalus: a pilot study

Apathy is frequently observed in idiopathic normal pressure hydrocephalus (iNPH) and worsens cognitive impairment and gait disturbance. In this study, we evaluated the regions associated with apathy in iNPH using statistical imaging analysis on the whole brain, both in terms of cerebral blood flow and gray matter volume. Twenty-seven patients with iNPH were assigned to two groups based on their scores on the neuropsychiatric inventory items related to apathy; 18 patients were assigned to the group with apathy (iNPH + APA) and 9 to the group without apathy (iNPH - APA). The magnetic resonance images and cerebral blood flow single-photon emission computed tomography data of the two groups were compared using statistical parametric mapping 12. The regional gray matter volume of the right precuneus was significantly larger in the iNPH + APA group than in the iNPH - APA group, but the regional cerebral blood flow in any region of the brain was not significantly different between the two groups. These results suggested that the larger gray matter volume, which is thought to reflect gray matter compression, in the precuneus might be involved in apathy in iNPH.

Thyroid Hormones and Health-Related Quality of Life in Normal Pressure Hydrocephalus Patients before and after the Ventriculoperitoneal Shunt Surgery: A Longitudinal Study

Objective: The aim of this study was to explore the serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3), and to correlate the hormone levels among iNPH patients with their self-reported quality of life before and three months after the surgery. Methods: Twenty-five patients (52% women), mean age 63.5 (SD 9.5) years, were operated on by inserting a VP shunt. Patients with FT3 level ≤3.34 pmol/L were diagnosed as having low T3 syndrome. Results: The changes in thyroid hormones resulted in a U-shaped curve throughout the follow-up period. The significant changes occurred the next day after the surgery, including a decrease in TSH, FT3, and an increase in FT4. Additionally, the decrease occurred in mean FT3 for six patients with preoperative low T3 syndrome. Three months after the surgery, thyroid hormones were restored to their baseline and/or normal values. All six patients with preoperative low T3 syndrome had significant improvement in all SF-36 subscales (except for the role emotional and physical). Patients with preoperative normal high FT3 and low FT4 had increased FT3/FT4 ratio which was associated with deterioration in all SF-36 subscales 3 months after the surgery. Conclusion: Routine assessment of the FT3/FT4 ratio might be a simple and effective tool for the risk stratification of iNPH patients before VP shunt surgery.

Serial Tap Test of patients with idiopathic normal pressure hydrocephalus: impact on cognitive function and its meaning

Background

Idiopathic normal pressure hydrocephalus (INPH) is characterized by gait disturbance, urinary incontinence and cognitive decline. Symptoms are potentially reversible and treatment is based on cerebrospinal fluid shunting. The tap test (TT) is used to identify patients that will benefit from surgery. This procedure consists of the withdrawal of 20 to 50 mL of cerebrospinal fluid (CSF) through a lumbar puncture (LP) after which the symptoms of the triad are tested. Improvement in the quality and speed of gait are already recognized but cognitive improvement depends on several factors such as tests used, the time elapsed after LP for re-testing, and the number of punctures. Serial punctures may trigger similar conditions as external lumbar drainage (ELD) to the organism.

Objective

This study aimed to identify how serial punctures affect cognition to increase the sensitivity of the test and consequently the accuracy of surgical indication.

Methods

Sixty-one patients with INPH underwent baseline memory and executive tests repeatedly following the 2-Step Tap Test protocol (2-STT – two procedures of 30 mL lumbar CSF drainage separated by a 24-h interval). The baseline scores of INPH patients were compared with those of 55 healthy controls, and with intragroup post-puncture scores of the 2-STT.

Results

The group with INPH had lower performance than the control group in all cognitive tests (RAVLT, Stroop, CFT, FAR-COWA, FAB, MMSE, orientation, mental control), except for the forward digit span test (p = 0.707). After conducting LP procedures, the Stroop test (words, colors and errors), RAVLT (stage A1, A6 and B1), and CFT (immediate and delayed R) scores were equal to those of the control group (p > 0.05). The INPH group presented significant improvement after the first puncture in MMSE (p = 0.031) and in the Stroop Test (points) (p < 0.001). After the second puncture, subjects improved in orientation, MMSE, RAVLT (B1), Stroop (points, words, errors) and CFT (IR).

Conclusion

Progressive cognitive improvement occurred over the 2-STT and changes were more significant after the second LP in all cognitive domains except for RAVLT (A7). Encephalic alert system ‘arousal’ seems to participate in early improvements observed during 2-STT. The second LP increased the sensitivity of the drainage test to detect changes in cognitive variables, and consequently improved the quality of the method.

Pathogenesis and pathophysiology of idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH), the most common type of adult-onset hydrocephalus, is a potentially reversible neuropsychiatric entity characterized by dilated ventricles, cognitive deficit, gait apraxia, and urinary incontinence. Despite its relatively typical imaging features and clinical symptoms, the pathogenesis and pathophysiology of iNPH remain unclear. In this review, we summarize current pathogenetic conceptions of iNPH and its pathophysiological features that lead to neurological deficits. The common consensus is that ventriculomegaly resulting from cerebrospinal fluid (CSF) dynamics could initiate a vicious cycle of neurological damages in iNPH. Pathophysiological factors including hypoperfusion, glymphatic impairment, disturbance of metabolism, astrogliosis, neuroinflammation, and blood-brain barrier disruption jointly cause white matter and gray matter lesions, and eventually lead to various iNPH symptoms. Also, we review the current treatment options and discuss the prospective treatment strategies for iNPH. CSF diversion with ventriculoperitoneal or lumboperitonealshunts remains as the standard therapy, while its complications prompt attempts to refine shunt insertion and develop new therapeutic procedures. Recent progress on advanced biomaterials and improved understanding of pathogenesis offers new avenues to treat iNPH.

Usefulness of the convexity apparent hyperperfusion sign in 123I-iodoamphetamine brain perfusion SPECT for the diagnosis of idiopathic normal pressure hydrocephalus

OBJECTIVE

The gold standard for the diagnosis of idiopathic normal pressure hydrocephalus (iNPH) is the CSF removal test. For elderly patients, however, a less invasive diagnostic method is required. On MRI, high-convexity tightness was reported to be an important finding for the diagnosis of iNPH. On SPECT, patients with iNPH often show hyperperfusion of the high-convexity area. The authors tested 2 hypotheses regarding the SPECT finding: 1) it is relative hyperperfusion reflecting the increased gray matter density of the convexity, and 2) it is useful for the diagnosis of iNPH. The authors termed the SPECT finding the convexity apparent hyperperfusion (CAPPAH) sign.

METHODS

Two clinical studies were conducted. In study 1, SPECT was performed for 20 patients suspected of having iNPH, and regional cerebral blood flow (rCBF) of the high-convexity area was examined using quantitative analysis. Clinical differences between patients with the CAPPAH sign (CAP) and those without it (NCAP) were also compared. In study 2, the CAPPAH sign was retrospectively assessed in 30 patients with iNPH and 19 healthy controls using SPECT images and 3D stereotactic surface projection.

RESULTS

In study 1, rCBF of the high-convexity area of the CAP group was calculated as 35.2–43.7 ml/min/100 g, which is not higher than normal values of rCBF determined by SPECT. The NCAP group showed lower cognitive function and weaker responses to the removal of CSF than the CAP group. In study 2, the CAPPAH sign was positive only in patients with iNPH (24/30) and not in controls (sensitivity 80%, specificity 100%). The coincidence rate between tight high convexity on MRI and the CAPPAH sign was very high (28/30).

CONCLUSIONS

Patients with iNPH showed hyperperfusion of the high-convexity area on SPECT; however, the presence of the CAPPAH sign did not indicate real hyperperfusion of rCBF in the high-convexity area. The authors speculated that patients with iNPH without the CAPPAH sign, despite showing tight high convexity on MRI, might have comorbidities such as Alzheimer’s disease.

Neuropsychiatric Manifestations of Cognitively Advanced Idiopathic Normal Pressure Hydrocephalus

Background

Neuropsychiatric manifestations of patients with idiopathic normal pressure hydrocephalus (iNPH) have not been studied in a systematic way.

Aim

To study the spectrum of neuropsychiatric abnormalities in patients with iNPH.

Patient Selection and Evaluation

Patients attending 3 different tertiary care centers during three consecutive time periods spanning from 2010 to 2015 were analyzed for neuropsychiatric manifestations. Patients diagnosed as having probable or possible iNPH as per the consensus criteria were included in the study. Neuropsychiatric manifestations were captured by a comprehensive inventory (Cambridge Behavioral Inventory, CBI).

Results

The CBI score was available for 41 patients. The mean Mini-Mental State Examination score was 15.37 (SD 7.2) and the Addenbrooke's Cognitive Examination score was 34.95 (SD 19.67), thereby indicating cognitively advanced iNPH. All patients had impairment in one or more items on the CBI. The mean score was 55.46 (SD 27) out of 180, thereby indicating a mild degree of impairment. Among the subscores, impairment with motivation was the most observed abnormality followed by memory impairment. When the CBI total score and subscores were compared, all of them (except motivation) were higher for Alzheimer's disease; however, none was statistically significant. Even though the motivation score was higher for iNPH, the difference did not reach statistical significance.

Conclusions

It can be concluded that neurobehavioral abnormalities are common in patients with cognitively advanced normal pressure hydrocephalus. However, the intensity of involvement appeared less when compared to Alzheimer's disease. Apathy appears to be the most common impairment.

Pre-and postoperative cerebral blood flow changes in patients with idiopathic normal pressure hydrocephalus measured by computed tomography (CT)-perfusion

In idiopathic normal pressure hydrocephalus (iNPH), the cerebral blood flow (CBF) is of pathophysiological interest and a potential biomarker. Computed tomography perfusion (CTP), an established technique with high spatial resolution and quantitative measurements, has not yet been used in the iNPH context. If CTP were sensitive to the CBF levels and changes in iNPH, this technique might provide diagnostic and prognostic absolute perfusion thresholds. The aim of this work was to determine the applicability of CTP to iNPH. CBF measurements of 18 patients pre- and 17 three months postoperatively, and six healthy individuals (HI) were evaluated in 12 cortical and subcortical regions of interest. Correlations between CBF and symptomatology were analyzed in shunt-responders. Compared to HI, the preoperative CBF in iNPH was significantly reduced in normal appearing and periventricular white matter (PVWM), the lentiform nucleus and the global parenchyma. No CBF differences were shown between responders and non-responders. In responders, the CBF recovered postoperatively by 2.5-32% to approximately the level of HI, but remained significantly decreased in the PVWM of non-responders. The pre- and postoperative CBF of cortical and subcortical regions correlated with the intensity of symptoms. In spite of limited spatial coverage, CTP can measure CBF changes in iNPH.

Serum IGF-1 is higher in patients with idiopathic normal pressure hydrocephalus than in the population

BACKGROUND

Hypopituitarism has been reported in patients with idiopathic normal pressure hydrocephalus (iNPH), which could enhance characteristic symptoms like impaired wakefulness, gait, body balance, and subcortical cognitive deterioration.

PURPOSE

To compare basal serum levels of pituitary and sex hormones and serum insulin-like growth factor-1 (S-IGF-1) in patients with iNPH and an age-matched control population, and to correlate the preoperative hormone levels with symptoms and signs pre-operatively and three months after surgery.

METHODS

A cross-sectional case control design was used. Patients diagnosed with iNPH, n=108 (65 men and 43 women, mean age 72.3 years), were consecutively included during 2006-2011 at Sahlgrenska University Hospital, Gothenburg, Sweden. S-TSH, S-free T4, S-FSH, S-LH, S-prolactin, plasma ACTH, S-testosterone, S-oestradiol and S-IGF-1 were examined. Symptoms and signs were scored using the iNPH scale score. Population controls, n=146, were recruited from the WHO MONICA project, Gothenburg in 2008.

RESULTS

Men and women with iNPH had higher S-IGF-1 than controls (p<0.001). Women with iNPH had lower S-TSH (p=0.016) than controls, but the frequency of levothyroxine substitution was similar. Among men, a higher level of S-IGF-1 was associated with milder symptoms, while higher levels of S-FSH and S-LH were associated with more severe symptoms.

CONCLUSIONS

Patients with iNPH did not have lower levels of pituitary or sex hormones but presented with higher levels of S-IGF-1, compared with healthy, age-matched controls. Higher S-IGF-1 in men was related to milder mental and physical symptoms and signs.

Association between milder brain deformation before a shunt operation and improvement in cognition and gait in idiopathic normal pressure hydrocephalus

We investigated the association between the degree of deformation of the brain before shunt operation and improvement of gait and cognitive impairment after shunt operation in 16 patients with idiopathic normal pressure hydrocephalus (iNPH). We evaluated gait and cognitive impairment and measured the cerebrospinal fluid volume in the ventricles/sylvian fissure (vVS) and the subarachnoid space at high convexity/midline areas (vHCM) using MR images with voxel-based morphometry before and 3 months after shunt operation. We used the ratio of vVS to vHCM (vVS/vHCM) as an index of the severity of brain deformation. After shunt operation, improvements were observed in gait, as shown by the Timed Up and Go (TUG) test and 10-meter reciprocating walking test (WT), and in cognitive function, as shown by the Mini-Mental State Examination, Alzheimer Disease Assessment Scale, Frontal Assessment battery (FAB), and Trail Making test A (TMT-A). The vVS/vHCM ratio was negatively correlated with improvement of the FAB, TMT-A and TUG. Preoperative vVS/vHCM was not significantly correlated with preoperative clinical assessments. The rate of change of vVS/vHCM was positively correlated with improvement in the WT. The improvements of gait and cognitive function were larger in iNPH patients with milder deformation of the brain before shunt operation.

Lumbosubarachnoid-lumboepidural shunting in patients with idiopathic normal-pressure hydrocephalus: surgical procedures and follow-up study of five cases

The objective of the study is to introduce the surgical procedure of the lumbosubarachnoid–lumboepidural (L–L) shunting performed as treatment for idiopathic normal-pressure hydrocephalus (iNPH) and its follow-up. The subjects were five patients with probable iNPH (aged 78–85 years; mean age 81 years; four males and one female) who were judged to be at high risk from general or lumbar anesthesia due to their systemic complications and age. The L–L shunt operation was performed for all the patients under local anesthesia using Codman–Hakim Programmable Valve^® (Codman & Shurtleff, Inc., Raynham, Massachusetts, USA). The initial pressure for all patients was set at 8 cm H₂O. The evaluation of shunt efficacy and the lumbar epidural space cerebrospinal fluid (CSF) absorption test (injection of contrast media into epidural space) were performed both on the operation day and during follow-up period (9–12 months). The shunt operation was judged to be effective in four out of five patients (regarded as shunt responders), whereas no improvement in symptoms was seen in one patient (regarded as shunt nonresponder) where the shunting had no effect after the initial pressure was changed to 4 cm H₂O. The lumbar epidural space CSF absorption test both on the operation day and during the follow-up period confirmed absorption in all patients. The L–L shunting is useful for patients with probable iNPH who are at high risk from general or lumbar anesthesia due to their systemic complications and age. CSF was continuously absorbed in the lumbar epidural space during postoperative follow-up period. A longer follow-up is required to establish this surgical procedure.

Cerebral perfusion measured by dynamic susceptibility contrast MRI is reduced in patients with idiopathic normal pressure hydrocephalus

PURPOSE

To demonstrate in idiopathic normal pressure hydrocephalus (iNPH) patients by dynamic susceptibility contrast MRI a reduced preoperative cerebral blood flow (CBF) which correlates with the severity of clinical symptoms and predicts shunt outcome.

MATERIALS AND METHODS

In cortical, subcortical, periventricular regions and along peri-and paraventricular profiles absolute perfusion values were estimated by multi-slice DSC MRI in 21 iNPH patients and 16 age-matched healthy individuals (HI). Relative CBF (rCBF), calculated with the occipital cortex as internal reference, was used for comparison between groups and for correlation analysis between regional rCBF and symptoms or outcome.

RESULTS

iNPH patients showed significantly decreased rCBF in the basal medial frontal cortex, hippocampus, lentiform nucleus, periventricular white matter (PVWM), central grey matter and the global parenchyma as compared to HI. iNPH patients with higher preoperative rCBF in the PVWM performed better in clinical tests. A lower overall preoperative function resulted in a more obvious recovery after shunt insertion. Shunt-responders had higher rCBF values in the basal medial frontal cortex than non-responders.

CONCLUSION

DSC MRI perfusion is a potentially useful diagnostic tool in iNPH and perfusion based criteria might be possible predictors of shunt response.

Global cerebral hypoperfusion in preclinical stage of idiopathic normal pressure hydrocephalus

In patients with idiopathic normal pressure hydrocephalus (iNPH), ventriculomegaly and narrowed subarachnoid spaces at the high convexity appear in magnetic resonance (MR) images before the occurrence of objective symptoms. In addition, quantitative regional cerebral blood flow (rCBF) has been reported to be reduced in iNPH patients with objective symptoms. To determine whether reduced rCBF is responsible for the appearance of symptoms, we compared rCBF in patients with suspected iNPH with no objective triad symptoms (NOS), iNPH patients with apparent objective triad symptoms (AOS) and normal control subjects (NC). Regional CBF was quantified in 35 Regions-of-interest (ROIs) by 123I-IMP single photon emission computed tomography (SPECT) using the autoradiography (ARG) method. Multiple comparisons showed that, in all brain regions examined except for in the frontal white matter, rCBF in the NOS group was significantly lower than that in the NC group, but in all brain regions, not significantly different from that of the AOS group. These results suggest that factors other than rCBF in the resting state are responsible for the occurrence of objective symptoms of iNPH.

INPH and Parkinson disease: differentiation by levodopa response

Differentiating between Parkinson disease (PD) and idiopathic normal pressure hydrocephalus (INPH) can be challenging for the practicing clinician. Patients with undiagnosed PD but with incidental ventriculomegaly run the risk of being subjected to unnecessary shunt surgery. Taking a family history of PD and establishing the presence of motor symptoms (tremor, rigidity, bradykinesia) and nonmotor symptoms could help to differentiate between the two disorders. For patients with parkinsonian features, a dopamine challenge test to exclude the possibility of idiopathic PD might be beneficial. In this article, we highlight the difficulty of accurately differentiating INPH from PD as illustrated by three clinical cases of patients referred for shunt surgery.

Ongoing search for diagnostic biomarkers in idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus is a syndrome, which typically has a clinical presentation of gait/balance disturbance, often accompanied by cognitive decline and/or urinary incontinence. Its diagnosis is based on relevant history and clinical examination, appropriate imaging findings and physiological testing. The clinical picture of idiopathic normal pressure hydrocephalus may occasionally be difficult to distinguish from that of Alzheimer’s dementia, subcortical ischemic vascular dementia and Parkinson’s disease. The aim of this article is to systematically review the literature from the last 29 years in order to identify cerebrospinal fluid (CSF) or imaging biomarkers that may aid in the diagnosis of the syndrome. The authors concluded that no CSF or imaging biomarker is currently fulfilling the criteria required to aid in the diagnosis of the condition. However, a few studies have revealed promising CSF and imaging markers that need to be verified by independent groups. The reasons that the progress in this field has been slow so far is also commented on, as well as steps required to apply the current evidence in the design of future studies within the field.

Basilar apex aneurysm manifesting as third ventricular mass and obstructive hydrocephalus--case report--

A 58-year-old male, with a past history of hypertensive thalamic hemorrhage 12 years before, presented with gradually exaggerating gait disturbance, memory disturbance, and urinary incontinence. On admission, he had gait disturbance represented by petit pas and anteropulsion in addition to significant recent memory disturbance. Cranial computed tomography (CT) revealed a hyperdense mass in the third ventricle with triventricular dilation. Cerebral magnetic resonance (MR) imaging and MR angiography identified the third ventricular lesion as saccular basilar apex aneurysm. No other intracranial abnormal intensity contributing to his clinical symptoms was recognized. Cervical MR angiography showed normal findings. Cerebral blood flow (CBF) measurements revealed diffuse CBF reduction in the cerebral hemisphere. The patient underwent coil embolization which accomplished complete aneurysm occlusion. He showed only slight improvement in his gait disturbance after embolization, and CT following embolization revealed persistent ventriculomegaly. Ventriculoperitoneal shunting was carried out. Intraoperative neuroendoscopy demonstrated cerebrospinal fluid (CSF) obstruction caused by the embolized aneurysm at the level of the third ventricle, with normal CSF findings. Postoperatively his gait disturbance and intellectual impairment showed remarkable improvement. Basilar apex aneurysm associated with obstructive hydrocephalus has complex underlying pathology and should be treated by a combination of definitive aneurysm obliteration and CSF diversion.