gms | German Medical Science

Objective: Posterior fossa (PF) pathologies represent a lesion entity which differs from supratentorial lesions. Little is known about pathological ICP values in the infratentorial compartment and outcome-associated factors. Due to brain stem involvement, pressure tolerance may differ from the supratentorial compartment. After approval of the locals ethics committee, we prospectively enrolled patients into our observational study of combined supra- and infratentorial ICP measurement starting before decompressive surgery (DS).

Method: Inclusion criteria were 18 years of age, infratentorial pathology other than tumor (hemorrhage, ischemia), emergency decompression of PF, normal blood count and plasmatic coagulation after substitution. Patients with neoplastic lesion were excluded, if expected survival was unlikely or <48 hours, or in the case of previous PF surgery. DS was indicated in case of neurological deterioration of more than 2 points on the GCS, absence of basal cisterns in imaging and /or supratentorial hydrocephalus and hemorrhage diameter > 3cm regardless of ICP. A single burr hole was drilled after PF exposure and an ICP probe was inserted. ICP measurement was performed followed by bony decompression and dura opening. In addition supratentorial ventriculostomy was performed. Postoperative CT was done on day 1 after DS. ICP measurement was continued until extubation or tracheotomy or in case of GCS <8 until postoperative CT showed absence of space occupying mass. MAP, ICP, CPP, body temperature, arterial blood gases were recorded. Modified ranking scale (MRS) was done 6 months after operation. Data are mean ± standard error of mean.

Results: 11 patients have been included so far (7 ischemia, 4 hemorrhage). Physiological parameters revealed no differences between patients. Infratentorial ICP was significantly elevated in patients before decompression (28.56 ± 3.9 mm Hg), did not decrease after bony decompression alone (28.00 ± 7.5 mm Hg), and significantly dropped after dura opening and hemorrhage evacuation or removal of infarcted tissue (12.00 ± 5.2 mm Hg). Postoperative ICPs were equal in PF (10.00 ± 1.4 mm Hg) compared to supratentorial values (12.83 ± 2.1 mm Hg) without reaching statistical significance. Two patients died due to extracranial causes, MRS in the 9 surviving patients was poor (MRS 3-6).

Conclusions: PF ICP was elevated in almost all patients and was effectively lowered after DS. More patients will have to be included to identify factors associated with outcome.