Document Detail

Alterations of pulsation absorber characteristics in experimental hydrocephalus.
MedLine Citation:
PMID:  20672938     Owner:  NLM     Status:  MEDLINE    
OBJECT: Analysis of waveform data in previous studies suggests that the pulsatile movement of CSF may play a role in attenuating strong arterial pulsations entering the cranium, and its effectiveness in attenuating these pulsations may be altered by changes in intracranial pressure (ICP). These findings were obtained in studies performed in canines with normal anatomy of the CSF spaces. How then would pulsation absorbance respond to changes in CSF movement under obstructive conditions such as the development of hydrocephalus? In the present study, chronic obstructive hydrocephalus was induced by the injection of cyanoacrylate gel into the fourth ventricle of canines, and pulsation absorbance was compared before and after hydrocephalus induction. METHODS: Five animals were evaluated with simultaneous recordings of ICP and arterial blood pressure (ABP) before and at 4 and 12 weeks after fourth ventricle obstruction by cyanoacrylate. To assess how the intracranial system responds to the arterial pulsatile component, ABP and ICP waveforms recorded in a time domain had to be analyzed in a frequency domain. In an earlier study the authors introduced a particular technique that allows characterization of the intracranial system in the frequency domain with sufficient accuracy and efficiency. This same method was used to analyze the relationship between ABP and ICP waveforms recorded during several acute states including hyperventilation as well as CSF withdrawal and infusion under conditions before and after inducing chronic obstructive hydrocephalus. Such a relationship is reflected in terms of a gain, which is a function of frequency. The cardiac pulsation absorbance (CPA) index, which is simply derived from a gain evaluated at the cardiac frequency, was used to quantitatively evaluate the changes in pulsation absorber function associated with the development of hydrocephalus within each of the animals, which did become hydrocephalic. To account for normal and hydrocephalic conditions within the same animal and at multiple time points, statistical analysis was performed by repeated-measures ANOVA. RESULTS: The performance of the pulsation absorber as assessed by CPA significantly deteriorated after the development of chronic hydrocephalus. In these animals the decrement in CPA was far more significant than other anticipated changes including those in ICP, compliance, or ICP pulse amplitude. CONCLUSIONS: To the extent that the free CSF movement acts as a buffer of arterial pulsation input to flow in microvessels, alterations in the pulsation absorber may play a pathophysiological role. One measure of alterations in the way the brain deals with pulsatile input-the CPA measurement-changes dramatically with the imposition of hydrocephalus. Results in the present study suggest that CPA may serve as a complementary metric to the conventional static measure of intracranial compliance in other experimental and clinical studies.
Eun-Hyoung Park; Stephen Dombrowski; Mark Luciano; David Zurakowski; Joseph R Madsen
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of neurosurgery. Pediatrics     Volume:  6     ISSN:  1933-0715     ISO Abbreviation:  J Neurosurg Pediatr     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-08-02     Completed Date:  2010-08-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101463759     Medline TA:  J Neurosurg Pediatr     Country:  United States    
Other Details:
Languages:  eng     Pagination:  159-70     Citation Subset:  IM    
Department of Neurosurgery, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA.
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MeSH Terms
Analysis of Variance
Blood Pressure / physiology*
Disease Models, Animal
Fourth Ventricle / physiopathology
Heart Rate / physiology
Hydrocephalus / physiopathology*,  therapy
Hyperventilation / physiopathology
Intracranial Pressure / physiology*
Pulsatile Flow / physiology*

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