This prospective study found that the presence of spontaneous retinal venous pulsation (SVP) as a clinical sign to exclude raised intracranial pressure (ICP) should be used with caution. Although the sensitivity and positive predictive value (PPV) of this clinical sign is high, it is not absolute, and patients with increased ICP could be missed if this clinical sign was solely relied upon.
A well-known clinical dictum states, "The presence of SVP excludes raised intracranial pressure." However, the clinical validity of this dictum has not been tested, and the authors' anecdotal experience of observing SVP immediately before lumbar puncture (LP) in some patients with high ICPs suggests that it is not absolute. Thus, they sought to determine whether the presence of SVP is a valid test to exclude raised ICP.
They recruited 106 patients scheduled to undergo LP as part of a neurological evaluation. Two clinicians blinded to the indications for LP and cerebrospinal fluid opening pressure (OP) evaluated them. All patients were examined before LP with direct ophthalmoscope through undilated pupils in the sitting or upright position. An OP of less than 30 cmH2O was considered normal and greater than or equal to 30 cmH2O was considered elevated.
SVP was present in 88.7 percent of patients. A high OP was seen in 12.3 percent, of which 86 percent had SVP. The sensitivity of the presence of SVP to exclude raised ICP was 0.89 (0.88-0.92), the specificity was 0.15 (0.05-0.37), the PPV was 0.88 (0.87-0.9), and the negative predictive value was 0.17 (0.05-0.4). Interobserver agreement was moderate for SVP (kappa = 0.42).
The authors note that in studies showing a direct relationship between ICP and SVP, SVP is reported to disappear with a CSF pressure above 20 cmH2O. However, in these studies many patients were examined in the recumbent position. ICP is higher in the recumbent than the sitting position, and this factor may affect the presence of SVP.
They write that although the clinical observations were similar between the study's two observers, the results demonstrate that interobserver variability does occur. It is possible that this variability may be reduced with pupillary dilation.
For future studies, they recommend the following to better elucidate the relationship between SVP and IOP:
- Recording IOP and a description of anatomic variations of retinal veins;
- Correlating ICP with SVP grading and examination in both the supine and sitting position;
- Using newer technologies, such as video and time-lapse photography;
- Having a larger number of observers.