TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to the treatment of hydrocephalus and, in particular, to an apparatus for the minimally-invasive, including non-invasive, prevention and/or treatment of hydrocephalus in premature infants, term infants, and other individuals and method for use of the same.

BACKGROUND OF THE INVENTION

Cerebrospinal fluid (CSF) is made within the ventricles of the brain and percolates through the ventricular system in response to brain pulsations. In normal circumstances, CSF exits in the fourth ventricle and circulates over the surface of the brain and around the spinal cord to be absorbed into the venous system. Hydrocephalus is a disease that is assumed to occur when the absorption mechanisms are not in equilibrium with the rate of CSF production. The disease is characterized by enlargement of the cerebral ventricles, abnormally high intracranial pressure (ICP), and large heads in children. In addition, the elderly can develop so-called normal pressure hydrocephalus (NPH). In addition, approximately 22% of premature infants have germinal matrix hemorrhages, commonly referred to as intraventricular hemorrhages (IVH), and many of these babies develop post-hemorrhagic hydrocephalus. Approximately 50% of babies with IVH develop ventricular enlargement, and half of these clearly have progressive hydrocephalus, frequently requiring neurosurgical treatment. The other half are said to have so-called arrested hydrocephalus, although slowly-progressive, active hydrocephalus remains a possibility.

The prevailing treatment options for hydrocephalus are limited. Some patients develop obstructive hydrocephalus as a result of an intracranial tumor distorting or blocking CSF pathways. Treating the tumor frequently corrects the hydrocephalus problem. Approximately 90% of children with posterior fossa tumors and hydrocephalus do not require permanent shunts for their hydrocephalus once the tumor has been removed. Some selected patients with obstructive hydrocephalus such as aqueductal stenosis can benefit from endoscopic third ventriculostomy (ETV). However, the majority of patients with hydrocephalus require shunt surgery.

This surgical treatment involves the implantation of a Silastic® device—a cerebrospinal fluid shunt (CSF shunt)—to divert fluid from the brain ventricles to another body compartment, where the CSF can be absorbed into the venous system. Shunt surgery has had a tremendous positive impact on neurosurgery and represents a significant clinical advancement of the 20th century. Shunt surgery has become the mainstay treatment of hydrocephalus. There are numerous valves and shunt systems available in the marketplace. Some utilize relatively simplistic pressure differential valves; some are regulated by flow; and some are programmable. There are reservoirs, antibiotic treated components, and anti-siphon devices. Shunts can malfunction, obstruct, break, or get infected. Thirty percent of shunts fail in the first year after placement. Over-shunting is common, and many patients experience headaches from intracranial hypotension. Some patients can develop subdural hematomas as a result of the ventricular decompression and tearing of bridging veins.

CSF absorption is a sensitive function of ICP; it increases significantly as pressure is increased. Even in communicating hydrocephalus, CSF increases with increasing ICP, although not as much. CSF production is essentially independent of ICP, or may decrease slightly at very high pressures. In other words, there is an absorptive reserve in which absorption exceeds production, and this is maintained even in hydrocephalus.

Ventricular pulsations may be particularly important in the development of hydrocephalus. Augmentation of the ventricular pulse pressure in goats with pulsating balloons synchronized to the cardiac cycle causes hydrocephalus. The pulse pressure in the ventricle with the shunt catheter is smaller than in the other lateral ventricle. Scans show that the shunted ventricle is typically smaller than the other side. Subgaleal shunts divert ventricular CSF into a pocket under the scalp, effectively treating the hydrocephalus, at least temporarily. Subarachnoid hemorrhage patients frequently develop hydrocephalus. Ventricular drainage is frequently used in these patients, and the intracranial pulsations have been noted to gradually increase even though ICP is held constant.

It is possible that shunts work by dampening the ventricular pulse pressure (PP). Diversion of CSF into the peritoneal cavity, pleural cavity, heart, gall bladder, or subgaleal space may be only an epiphenomenon. Further, shunts may be effective in treating hydrocephalus only because a small volume of CSF is displaced out of the ventricle with every heartbeat, therefore reducing the intraventricular pulse pressure. Shunts may work simply because they are shock absorbers. Numerous mathematical models of the CSF system have been suggested and some more recent studies draw parallels with electrical circuitry suggest that increases in ventricular pulsations, indeed, cause hydrocephalus.

In newborns with an open fontanel, the intracranial pulsations can be monitored and modulated through the fontanel without invasive surgical implantation of an intracranial device. Accordingly, hydrocephalus can likely be treated in these infants without surgery, at least until the fontanel begins to close. In premature infants with intraventricular hemorrhage (IVH), who are at risk for developing post-hemorrhagic hydrocephalus, not only can hydrocephalus be treated with PP modulation in infants who already have the disease, but it can also be prevented with PP modulation that offsets the gradual increases in mean intracranial PP during the days, weeks, or months subsequent to the IVH. Advances in medical science are needed to treat hydrocephalus, particularly in premature infants.

SUMMARY OF THE INVENTION

It would be advantageous to achieve an advanced, non-surgical device that can prevent and treat post-hemorrhagic hydrocephalus in premature infants, as well as treating other forms of hydrocephalus in babies with an open fontanel. It would also be desirable to enable a medical-based solution that mitigates the enlargement of the cerebral ventricles and abnormally high intracranial pressure (ICP), particularly in premature infants. To better address one or more of these concerns, an apparatus is disclosed for the minimally-invasive, including non-invasive, prevention and treatment of hydrocephalus, in premature infants and others and a method for use of the same. In one implementation, the apparatus modulates intracranial pulse pressure (PP) though the fontanels of premature and term infants.

The PP is the arithmetic difference between the peak pressure in systole and the lowest pressure in diastole. The terms “pulse pressure modulation” are being used to describe a therapeutic technique that measures the intracranial pulse pressure and adjusts it by either reducing or increasing the intracranial PP according the clinical situation. Moreover, a device that allows non-invasive measurement of ICP and intracranial PP in babies with open fontanels would be a useful clinical tool, not only for patients in neonatal intensive care units but also older infants with open fontanels and ICP issues.

In one embodiment of the apparatus, a housing is sized for superjacent contact on a premature infant skull having a fontanel. Within the housing, a compartment includes a pressure applicator, such as a fluid-filled bladder, under the control of a pressure regulator. The pressure applicator is configured to selectively apply an external pressure to the fontanel. The compartment includes a pressure sensor configured to, in one embodiment, measure displacement, including pulsations, of the fontanel. The apparatus determines intracranial PP. Further, in one embodiment, the apparatus can cause pulse pressure modulation by adjusting the intracranial pulse pressure via the pressure applicator. This enables a non-invasive measurement of the pulse pressure and modulation thereof in infants, for example. More specifically, in one embodiment, to reduce intracranial PP in order to prevent or treat hydrocephalus after IVH, the apparatus monitors pulsations of the fontanel and responds to intracranial pressure increases during systole with relaxation of the pressure applicator, which may be a fluid-filled bladder within a closed component with a ventral opening, positioned on the fontanel thereby reducing the systolic pressure. During diastole, the fluid-filled bladder is gently refilled, thereby increasing the diastolic pressure. The cumulative effect of this cyclical process would work to decrease the intracranial PP. The mean ICP will likely not change, or it may decrease. In this setting, the apparatus may include a solenoid pump and controller software to modulate the intracranial PP.

Clinical conditions may exist in which augmentation of the intracranial PP may be desirable, such as to increase cerebral blood flow (CBF). In such a setting, the apparatus may function to withdraw fluid from the bladder during diastole and reinject this volume back into the bladder during systole. The cumulative result of this process will increase intracranial PP. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

