Changes of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the model of experimental acute hydrocephalus in rabbits

Tract-Specific Relationships Between Cerebrospinal Fluid Biomarkers and Periventricular White Matter in Posthemorrhagic Hydrocephalus of Prematurity

BACKGROUND

Posthemorrhagic hydrocephalus (PHH) is associated with neurological morbidity and complex neurosurgical care. Improved tools are needed to optimize treatments and to investigate the developmental sequelae of PHH.

OBJECTIVE

To examine the relationship between diffusion magnetic resonance imaging (dMRI) and cerebrospinal fluid (CSF) biomarkers of PHH.

METHODS

A total of 14 preterm (PT) infants with PHH and 46 controls were included. PT CSF was collected at temporizing surgery in PHH infants (PHH PT CSF) or lumbar puncture in controls. Term-equivalent age (TEA) CSF was acquired via implanted device or at permanent CSF diversion surgery in PHH (PHH-TEA-CSF) or lumbar puncture in controls. TEA dMRI scans were used to measure fractional anisotropy (FA) and mean diffusivity (MD) in the genu of corpus callosum (gCC), posterior limb of internal capsule (PLIC), and optic radiations (OPRA). Associations between dMRI measures and CSF amyloid precursor protein (APP), neural cell adhesion-1 (NCAM-1), and L1 cell adhesion molecule (L1CAM) were assessed using Pearson correlations.

RESULTS

APP, NCAM-1, and L1CAM were elevated over controls in PHH-PT-CSF and PHH-TEA-CSF. dMRI FA and MD differed between control and PHH infants across all tracts. PHH-PT-CSF APP levels correlated with gCC and OPRA FA and PLIC MD, while L1CAM correlated with gCC and OPRA FA. In PHH-TEA-CSF, only L1CAM correlated with OPRA MD.

CONCLUSION

Tract-specific associations were observed between dMRI and CSF biomarkers at the initiation of PHH treatment. dMRI and CSF biomarker analyses provide innovative complementary methods for examining PHH-related white matter injury and associated developmental sequelae.

The role of perfusion and diffusion MRI in the assessment of patients affected by probable idiopathic normal pressure hydrocephalus. A cohort-prospective preliminary study

Background

Invasive tests measuring resistance to cerebral spinal fluid (CSF) outflow and the effect of temporary drainage of CSF are used to select candidates affected by idiopathic normal pressure hydrocephalus (iNPH) for shunt surgery. Neither test, however, completely excludes patients from treatment. Perfusion and diffusion magnetic resonance imaging (MRI) are non-invasive techniques that might be of value in selecting patients for surgical treatment and understanding brain changes in iNPH patients. The aim of this study was to understand the role of perfusion and diffusion MRI in selecting candidates for shunt surgery and to investigate the relationship between cerebral perfusion and possible microstructural changes in brain tissue before and after invasive tests, and after ventricular-peritoneal (VP) shunt implantation, to better clarify pathophysiological mechanisms underlying iNPH.

Methods

Twenty-three consecutive patients with probable iNPH were included in this study. Patients underwent a clinical and neuroradiological evaluation before and after invasive tests, and after surgery. Only patients who showed a positive result in at least one of the invasive tests were submitted for VP shunt implantation. Perfusion and diffusion magnetic resonance imaging (MRI) was performed before and after invasive tests and after shunt surgery.

Results

Thirteen patients underwent surgery and all showed clinical improvement after VP shunt implantation and a significant increase in perfusion in both periventricular white matter (PVWM) and basal ganglia (BG) regions. The 10 patients that did not have surgery showed after invasive tests, a significant reduction in perfusion in both PVWM and BG regions. Comparing the changes in perfusion with those of diffusion in positive patients we found a significant positive correlation in BG and a significant inverse correlation in PVWM area.

Conclusions

Perfusion MRI is a non-invasive technique that could be useful together with invasive tests in selecting patients for surgical treatment. Furthermore, the relationship between perfusion and diffusion data could better clarify pathophysiological mechanisms underlying iNPH. In PVWM area we suggest that interstitial edema could reduce microvascular blood flow and interfere with the blood supply to these regions. In BG regions we suggest that a chronic hypoxic insult caused by blood hypo-perfusion produces a chronic cytotoxic edema. Both in PVWM and in BG regions, pathophysiological mechanisms could be modified after VP-shunt implantation.