Cerebral Perfusion, Oxygenation, Electrical Activity
Cerebral Perfusion, Oxygenation, Electrical Activity
The specific aim of the research proposal in preterm infants with IVH and PHH who require
 placement of an Omaya reservoir or a shunt is to determine if decreasing ventricular volume
 improves, middle cerebral artery flow, cerebral oxygenation, and cortical neuronal electrical
 activity. To accomplish this aim, we will simultaneously perform the following evaluations
 prior to shunt placement or prior to and after routine CSF aspiration from reservoir in:

 1. middle cerebral artery velocity time integral and resistive index using Doppler
 ultrasonography

 2. cerebral oxygenation using near infrared spectroscopy (NIRS)

 3. background neuronal electrical activity using an EEG. In addition, we will measure
 serial CSF concentration of neuroproteins, S100B, GFAP, NSE, TGF-ß, and IL-6, as
 evidence of ongoing neuronal damage and correlate the concentration with cerebral
 perfusion and activity as measured above.
Very low birth weight infants are at risk for developing intraventricular hemorrhage (IVH).
 Post hemorrhagic hydrocephalus (PPH) is a major complication of IVH and contributes to
 long-term developmental delays. Progressive PHH often requires management of ventricular
 dilation by adjusting CSF fluid volume. There are 3 methods employed to acutely decrease CSF
 volume: 1) serial lumbar puncture, 2) open drain system (continuous CSF removal), and 3)
 reservoir system. Serial lumbar puncture is only effective if there is communicating
 hydrocephalus. The open drain system is infrequently used as it is cumbersome and there is a
 relatively high risk of infection. The method most commonly used to manage CSF volume is the
 reservoir system where an in-situ drain is connected to a subcutaneous (Omaya) reservoir
 which is periodically aspirated by needle puncture through the scalp. Because the Omaya
 system is closed, intraventricular volume and, thus, pressure must necessarily rise prior to
 and decrease after CSF aspiration. Ventricular dilation is controlled by the frequency and
 volume of CSF aspiration.

 When hydrocephalus continues to be a problem despite removal of CSF, a ventricular-peritoneal
 (VP) shunt is placed. Approximately 50% of infants with hydrocephalus treated with removal of
 CSF resolve their hydrocephalus and do not require VP shunt placement. Placement of a VP
 shunt is difficult in extremely preterm infants due to increased risk of ulceration around
 the shunt site and the high protein concentration in CSF which can occlude the valve in the
 VP shunt requiring revision. Thus, hydrocephalus is usually treated with serial removal of
 CSF to allow for identification of those infant's whose hydrocephalus resolves over time.
 However, timing and method of CSF management is controversial because the effect of
 increasing hydrocephalus on cerebral perfusion, oxygenation, electrical activity, and
 neuronal damage has not been established.

 Serial removal of CSF causes a change in intracranial volume/pressure that can be potentially
 transmitted to intracranial vessels. The caliber of cerebral vessels may be modified by this
 balance between intravascular and intracranial pressure, and if the caliber should change,
 the blood flow characteristics should also change. In cerebral veins and capillaries where
 intraluminal pressure is low, high intraventricular pressure may significantly affect blood
 flow and can cause venous stasis. NIRS measures cerebral oxygenation in capillaries and
 veins. Intracranial arteries and arterioles may be somewhat less affected, except when
 intraventricular pressure greatly increases. The resultant decrease in the arterial supply
 can affect tissue perfusion. Arterial flow can be measured by Doppler ultrasonography. Thus,
 there is concern that during periods of increasing or fluctuating ventricular size cerebral
 arterial perfusion may be compromised and further cerebral injury may result. Intracranial
 pressure is further influenced by the plasticity/deformability of the immature brain and the
 easy expansibility of the cranial vault due to the presence of sutures and open fontanelles.

 There is indirect evidence from experiments in animals that ventricular distention itself may
 cause secondary brain injury. Thus, axonal stretching and disruption secondary to progressive
 ventriculomegaly is be associated with gliosis. Periventricular vascular distortion and
 compression may decrease cerebral blood flow causing ischemic injury to periventricular white
 matter. Inflammation and repair may interfere with CSF flow.

 Little research is available that helps answer the primary question involved in clinical
 management of ventricular dilation in premature infants: Are there relationships between
 ventricular enlargement, cerebral perfusion, brain oxygen delivery, and on-going cerebral
 damage?

 Doppler ultrasonography has been applied in premature infants to characterize post delivery
 changes in arterial and venous cerebral blood flow velocities.[1] Critically low superior
 vena cava flow measured by Doppler ultrasonography in the first 24 hours of life has been
 associated with intraventricular hemorrhage in premature infants born before 30 weeks
 gestation.[2] Using pulsed Doppler ultrasonography, the resistive index can be measured which
 is a inversely related to blood flow. In older infants with established hydrocephalus,
 cerebral blood flow resistive index appeared to be a good indicator of increased intracranial
 pressure.[3] However, in a review article, the value of Doppler indices alone in predicting
 increased intracranial pressure was strongly questioned.[4] In a recent article, the
 resistive index of the anterior cerebral artery decreased significantly after CSF drainage in
 infants with PHH. [5] Although Doppler ultrasonography is easy to perform, its role in
 detecting significant changes in cerebral perfusion associated with increased CSF volume and
 ventricular dilation is not yet established.

 Near infrared spectroscopy (NIRS) is a portable non-invasive technique used to measure
 regional cerebral oxygen saturation in cerebral blood.[6] NIRS has been used to evaluate
 effect of head [7] and body position [8] on cerebral hemodynamics in preterm infants, and the
 effect of certain treatments, such as surfactant administration [9] and suctioning on
 conventional or high-frequency ventilation.[10] NIRS measurement of cerebral oxygenation and
 hemodynamics shows impairment in those neonates at risk for developing severe brain
 ischemia.[11] In premature infants with PHH, CSF fluid aspiration was associated with a
 significant increase in cerebral perfusion, cerebral blood volume, and oxidative
 metabolism.[12,13] In a small animal model of acute hydrocephalus, NIRS measurement of global
 cerebral blood flow using oxygen as a tracer was highly correlated to cerebral blood flow
 measured by radioactive microspheres over a wide range of increased intracranial
 pressure.[14] As intracranial pressure increased, NIRS measurement and absolute measurement
 of cerebral blood flow decreased. NIRS measured cerebral perfusion appears to directly
 reflect absolute cerebral blood flow and is sensitive enough to detect significant changes in
 cerebral perfusion which occur with evacuation of CSF in infants with PHH.

 Amplitude-integrated EEG (aEEG) is a device used for neurologic surveillance. The cortical
 electrical activity is transformed into a single signal that represents overall
 electrocortical background activity of the brain. Specifically the upper and lower voltage
 margins and the amplitude of the tracing and the presence of seizure activity can be
 evaluated. In addition, the presence of sleep-wake cycles, a rhythmic sinusoidal variation in
 amplitude, can be evaluated. Infants > 34 weeks gestation have predictable aEEG patterns. The
 signal depends on gestational age and postnatal age and standards for preterm infants have
 been reported.[15,16] In a case report, 2 preterm infants with PHH demonstrated abnormal
 sleep-wake cycles and markedly decreased cerebral electrical activity with increasing
 ventricular enlargement prior to clinical signs of increased intracranial pressure. In one
 infant, aEEG normalized after VP shunt placement.[17] To date, there are no clinical studies
 on the effect of aspiration of CSF on aEEG in preterm infants with PHH.

 Biomarkers for cerebral injury have been used to predict severity of injury and long-term
 outcome, identify patients early at risk for poor neurologic outcomes, and evaluate
 effectiveness of therapeutic interventions. Neuronal specific enolase (NSE), a marker for
 neuronal damage, and S100B, secreted by astrocytes and a marker of glial/neuronal injury,
 have been shown to be increased in children after traumatic brain injury.[18] In preterm
 infants with PHH, S100B and glial fibrillary acid protein (GFAP), a structural protein in
 astrocytes, were significantly elevated in those infants who had brain parenchymal lesions
 and poor neurological outcomes.[19] These biomarkers are quickly metabolized and thus ongoing
 elevation would indicate ongoing damage. Transforming growth factor beta (TGF-ß), produced by
 fibroblasts and released into the CSF after injury, stimulates production of extracellular
 protein which could result in PHH due to a permanent obstruction to CSF flow.[20] Cytokine
 IL-6 is a marker of inflammation. There are no longitudinal studies on the effect of
 aspiration of CSF on these markers of cerebral damage in preterm infants with PHH.
Inclusion Criteria:

 -  Infants enrolled in this study will be identified at the time of neurosurgical
 evaluation for placement of a shunt or an Omaya reservoir for post-hemorrhagic
 hydrocephalus. Infants who have received vasoactive drugs (e.g. non-steroidal
 anti-inflammatory, dopamine, dobutamine, epinephrine, etc), will not be excluded from
 the study but the measurements will be postponed until 72 hrs after discontinuation of
 the medications.

 Exclusion Criteria: