Dissemination of fat in CSF: a common finding following translabyrinthine acoustic neuroma surgery*

Objectives: Following translabyrinthine craniotomy the temporal bone defect is commonly obliterated using a free autologous fat graft. In this series the dura was put back in place but not closed primarily. As the fat graft remains in direct contact with the cerebro spinal fluid (CSF) there is potential for dispersal of fat within the CSF space. This paper aims to determine the frequency of such CSF fat dissemination and its clinical significance. Design: A retrospective review of translabyrinthine acoustic neuroma removal with free fat autograft obliteration of the temporal bone defect between the years 1997 and 2000. Setting: Tertiary referral oto-neurosurgical centre. Postoperative magnetic resonance (MR) imaging. Participants: All translabyrinthine patients who had postoperative MR imaging were included. Twenty-six cases were identified. Age range was 13–70 years. Fourteen were male patients. Main outcome measures: Evidence of CSF fat dissemination on MR and patients’ clinical findings. Results: Twenty-two of the 26 scans (85%) demonstrated evidence of fat dissemination into the subarachnoid CSF spaces in the form of microemboli. The cerebellopontine angle was the most common site involved. No evidence of ventricular dilation or any other abnormality was noted. There was no relationship between the presence or extent of fat microembolization and the patients’ clinical course. Conclusions: This study suggests that free fat placed in temporal bone defects commonly migrate into the subarachnoid space and subsequently move around in these spaces. This is not associated with any complications such as hydrocephalus, meningitis or prolonged postoperative headache.