Invasive neuromonitoring of intracranial pressure (ICP) is an important element of neurosurgical critical care that is used primarily as an indicator of adequate cerebral perfusion in patients, when clinical observation is not an option. Due to the constraint in size and the critical structures within the posterior fossa, detection of intracranial pressure particularly in the postoperative phase has been deemed desirable in patients with surgery in this region, particularly in those subjected to prolonged procedures and critical care.

The posterior fossa is an anatomically constricted compartment with narrow spaces and intracranial hypertension quickly leads to brainstem damage and neurological dysfunction. ICP in the supratentorial space not necessarily correlates with ICP in the infratentorial space. Some authors claim that it would be beneficial to measure ICP in infratentorial space after posterior fossa surgery in some cases.

The relationship between the intracranial pressure profiles in the supratentorial and infratentorial compartments remain unclear. After a neurosurgical operation in the posterior fossa there are most likely pressure differences between supra- and infratentorial spaces. It is well known that the pressure within the skull is unevenly distributed, with appreciable ICP gradients.

Thus, the investigators intend to apply the intracranial multimodal monitoring in both infratentorial and supratentorial compartments simultaneously. Such coincident measurements most likely will be the most sensitive way to assess focal swelling, ischemia and tissue perfusion, or other relevant complications in the posterior fossa structures.

The goal of this study is to test whether direct infratentorial monitoring is a more efficacious method for detecting dynamic changes in the operative compartment and whether it is safe, in view of the critical structures within the region.

Invasive neuromonitoring of intracranial pressure (ICP) is an important element of neurosurgical critical care that is used primarily as an indicator of adequate cerebral perfusion in patients, when clinical observation is not an option. Due to the constraint in size and the critical structures within the posterior fossa, continuous detection of postoperative pressures has been deemed desirable in patients with surgery in this region, particularly in those subjected to prolonged procedures and critical care.

The posterior fossa is an anatomically constricted compartment with narrow spaces and intracranial hypertension quickly leads to brainstem damage and neurological dysfunction. ICP in the supratentorial space not necessarily correlates with ICP in the infratentorial space. Some authors claim that it would be beneficial to measure ICP in infratentorial space after posterior fossa surgery in some cases.

In patients whose neurological examination results may be inconclusive or limited, it is valuable to have a reliable alternative method of evaluation. It is generally accepted that continuous ICP monitoring is very important to determine the timing of surgery and to prevent secondary brain damage caused by increased ICP.

There have been few clinical studies in which simultaneous pressures were recorded above and below the tentorium in patients with intracranial pathology. Yet, the relevance of infratentorial neuromonitoring remains largely unclear. So far, the placement of ICP probes in the posterior fossa seems to carry very low morbidity. Furthermore, to rely on autonomic changes, neurological deterioration, or measurements of only the supratentorial compartment as a sign of relevant complications in the posterior fossa highly narrows the temporal margin of safety for the institution of treatment. Comprehensive evaluation of possible risks of posterior fossa lesions and their treatments is crucial. Of note, immediate detection of treatment-related complications is often challenging, still being able to avoid permanent neurological sequelae. The application of the advanced neuromonitoring in the posterior fossa may be supportive in achieving this difficult goal and may provide objective assessments of procedure-related complications.

Therefore, the data generated by our prospective trial can be expected to be beneficial in individualized treatment plans. It is a relatively novel approach to intracranial multimodal neuromonitoring. The application of infratentorial probes offers potential for better understanding of lesion maturation and progression, clinical deterioration, and monitoring the effect of treatments.

The investigators hypothesize that additional multimodal infratentorial neuromonitoring will be of high clinical value detecting any relevant complication and giving detailed insight in pathophysiological interactions in posterior fossa lesions.

Inclusion Criteria:

• Posterior fossa lesions with anticipated prolonged neurointensive critical care
• Patients older than 18 years
• Informed consent if applicable (unconscious patients will be also enrolled)
• No existing exclusion criteria

Exclusion Criteria:

• Coagulation disorders
• Age < 18 years
• Pregnancy

Collection of data and publish results