How common is normal cerebrospinal fluid pressure in spontaneous intracranial hypotension?

Objectives To determine the proportion of patients with spontaneous intracranial hypotension (SIH) who had a cerebrospinal fluid (CSF) pressure >6 cm H₂O and to investigate the clinical and imaging variables associated with CSF pressure ( P_CSF) in this condition. Methods We retrospectively reviewed 106 patients with SIH. P_CSF was measured by lumbar puncture prior to treatment. Clinical and imaging variables - including demographic data, brain imaging results, symptom duration, and abdominal circumference - were collected. Univariate and multivariate analyses were performed to determine the correlation of these variables with P_CSF. Results Sixty-one percent of patients had a P_CSF between 6 and 20 cm H₂O; only 34% had a P_CSF ≤6 cm H₂O. The factors associated with increased P_CSF included abdominal circumference ( p < 0.001), symptom duration ( p = 0.015), and the absence of brain magnetic resonance imaging findings of SIH ( p = 0.003). A wide variability in P_CSF was observed among all patients, which was not completely accounted for by the variables included in the model. Conclusions Normal CSF pressure is common in patients with SIH; the absence of a low opening pressure should not exclude this condition. Body habitus, symptom duration, and brain imaging are correlated with P_CSF measurements, but these factors alone do not entirely explain the wide variability in observed pressures in this condition and this suggests the influence of other factors.