Cerebrospinal fluid circulation : from the patient to ICM+ and back

Why study hydrocephalus?
Relatively infrequent condition but the only reversible dementia so far!
Modelling CSF dynamics contributes to:

  • Increasing diagnostic accuracy
  • Researching and further understanding the underlying disease mechanisms
  • Predicting the effectiveness of neurosurgical intervention
  • Diagnosing problems with shunts

In both shunted and non-shunted patients:
– Short – term ICP monitoring is achieved with infusion studies
– Long – term (Overnight) ICP monitoring

  • Long-term (Overnight) ICP monitoring of a shunted hydrocephalus patient
    The recording reveals disturbed CSF dynamics, with frequent ICP spikes and high content of B-waves. The detection of Heart rate (HR) aids in identifying whether the patient is sleeping as well as in differentiating between artificial ICP as spikes iduced by movement. The calculated fundamental amplitude of ICP (AMP) also follows genuine changes of ICP.
  • CSF dynamics - CSF test: optimal fit to the theoretical model
    CSF test of a patient without a shunt investigated for NPH. Because of the development and incorporation of ICM+ routinely for diagnostic investigations in hydrocephalic patients, we have managed to build a databse of >5000 patients with possible CSF dynamics disturbance. The use of mathematical modelling combined with traditional data collection allows us to meaningfully quantify CSF dynamics and interpret the plethora of recordings we obtain every year.
  • Infusion study: recording of a patient with possible NPH
    In this patient we are also able to non-invasively measure and record the mean Arterial Blood Pressure (ABP) using photoplethysmography and inputting the data in ICM+. The concomitant recording of CSF dynamics and other cerebral/systemic patient information, especially of vascular nature, allows us to study the interaction between the measured parameters as well as further and more holistically comprehend unknown disease mechanisms, pathophysiology and finally improved prognostication.

Idiopathic Intracranial Hypertension is also a rare disease that remains poorly understood in both the adult but especially the paediatric population.

CSF dynamics of IIH are completely different from hydrocephalic individuals and investigating these patients in conjunction with the clinical and imaging interventions allows us to trace disturbances in many patients with complicated courses requiring interdisciplinary care

Infusion study - non-shunted IIH patient
Baseline ICP is >20 mmHg, with relatively low plteau and sunsequently low Resistance to CSF outflow. Disturbance of CSF dynamics is therefore underlined by different parametres calculated in the ICM+ infusion test

Shunt testing in vivo: the importance & impact of the computerised CSF infusion test

 

CSF infusion tests in shunted individuals are critical in preventing unnecessary, blind revisions of shunts & provide evidence of shunt malfunction.

THe CSF infusion test for shunt testing in vivo was developed after years of experience in the Cambridge shunt testing laboratory;

all the shunt properties and the analysis of the CSF dynamics after shunting for testing of the shunt function are integrated in ICM+

  • Shunt testing in vivo - Plateau ICP and shunt critical ICP in a shunted hydrocephalic patient
  • Shunt critical ICP as one factor in determining shunt function : simplified snapshots from ICM+ ICP recordings