gms | German Medical Science

Objective: Spontaneous intracranial hypotension (SIH) due to leakage of cerebrospinal fluid (CSF) causes substantial disease burden. In many patients with SIH the course is protracted and refractory to conservative treatment, requiring targeted blood patching or surgery. We propose positron emission tomography (PET) of the CSF space with [⁶⁸Ga]Ga-DOTA as a state-of-the-art approach of radionuclide cisternography (RC) and validate its diagnostic value.

Methods: Forty consecutive patients with suspected intracranial hypotension underwent whole-body hybrid PET/computed tomography (CT) at 1, 3 and 5 hours after intrathecal lumbar injection of [⁶⁸Ga]Ga-DOTA (about 40 MBq). Scans were retrospectively analyzed by two independent raters blinded to clinical data. Direct and indirect signs of tracer egression from the CSF space and summary ratings were filed by the raters separately and in consensus. In addition, a volume of interest analysis was performed to assess the biological half-life of the tracer in CSF space (T1/2,biol) and the ratio of decay-corrected activity in the CSF space at 5 and 3 hours (R5/3) as a simplified marker of tracer clearance.

Results: The working diagnosis was intracranial hypotension due to spontaneous (n = 32, one excluded because of puncture failure) or post-interventional (n = 8) CSF loss. A spinal CSF leak could be verified by comprehensive stepwise neuroradiological workup, surgical findings and follow-up in 18 of 39 patients. As the only direct and indirect diagnostic signs of RC, tracer egression at the cervicothoracic junction and lack of activity over the cerebral convexities (5-h scan) showed a high diagnostic value for CSF leakage(sensitivity/specificity: 67%/90% and 94%/67%, respectively). Their combination provided little improvement (71%/95%), being slightly superior to the summary rating (83%/67%; based on pre-study experience). Additional quantitative analyses added no benefit (T1/2,biol: 94%/53%; R5/3: 94%/58%). Of note, direct signs of tracer egression did not correlate with verified sites of leakage. The estimated radiation exposure due to the entire examination was about 5 mSv.

Conclusion: We propose CSF PET with [⁶⁸Ga]Ga-DOTA as a novel, fast and convenient approach of RC for verification of CSF leaks with high sensitivity and specificity. CSF PET may fulfill an important gatekeeper function to stratify patients towards escalation or de-ecalation of diagnostic and therapeutic measures.

Figure 1 [Fig. 1], Figure 2 [Fig. 2]