MINIATURIZED METHODS TO MONITOR INTRACRANIAL-PRESSURE - TECHNICAL AND CLINICAL RESULTS

The prognosis of numerous diseases of the central nervous system is essentially determined by the intracranial pressure (ICP) and its therapeutic influencing. Long-term monitoring of the ICP must therefore be the objective in neurological and neurosurgical patients at risk. For this purpose, miniaturized methods were tested and developed. To monitor the intracranial pressure in patients who were not operated on, a miniature pressure transducer the size of a match head was used which was directly implanted 'percutaneously' in the intensive care unit: After a stab wound had been made in the skin, a 5-mm burrhole is made; the specially constructed miniature coaxial burr which disengages as soon as it touches the dura automatically enables coplanar epidural implantation of the transducer by means of an adapter capsule. The skin is closed without tension. For monitoring the pressure after trepanation, a spiralled miniature pressure transducer is implanted. The equally flattened receiver with lateral membranes is placed intracranially as desired, e.g., epidurally or subdurally, during the operation. The zero point can be checked from outside without danger of infection. After the end of the measurements the recorder is easily extracted. Up to the present time, the epidural pressure has been reliably monitored for several weeks by this method in 86 patients. Tén comparative measurements showed corresponding cerebrospinal fluid pressures to within a few mm Hg with very good reproduction of frequency and amplitude. Small zero drift and the external zero control give an accuracy of measurement ± 5 mm Hg independently of the time of measurement. The measurement permits early recognition of progressive intracranial space occupying lesions. In 14 patients (16 %) a measured rise in intracranial pressure was an essential basis for indication for neurosurgical operations. In addition, the pressure measurement provides an objective assessment of the effect of measures to lower the ICP; progressive increases in intracranial pressure which cannot be influenced conservatively can be brought for surgical decompression in good time before the brain has been irreversibly damaged by pressure. In craniocerebral traumata, monitoring the intracranial pressure permits the differentation of primary damage to the brain stem with uniform, normal intracranial pressure from secondary constrictions of the brain stem with considerable rise of intracranial pressure and disturbed autoregulation. Only in chronic subdural haematomata are considerable displacements of intracranial masses to be seen with only slighly increased ICP (< 30 mm Hg). Besides space-occupying lesions, the measurement of pressure also detects generalised epileptic attacks due to a considerable rise in intracranial pressure caused by hyperemia. Also disorders of respiration are recognised by supervision of ICP. The procedures described seem suitable for routine monitoring of ICP in patients at risk, with little operative effort and minimum danger. In contrast to the measurement of the central CSF pressure the method demands neither injury to the brain nor the opening of the meningeal barrier to infection. They are technically reliable, not affected by artefacts and do not hinder the care of the patient. Complications, particularly infections, did not occur. © 1979 Springer-Verlag.