SIH commonly caused by spinal CSF leakage is typically presented as severe orthostatic headaches. Accurate diagnosis of SIH depends largely on brain MRI findings. However, the emergences of brain MRI findings in different disease durations have not been systemically described. 

The aim of the present study was to calculate the time sequence of different brain MRI findings in spontaneous intracranial hypotension (SIH). 

We retrospectively reviewed the medical records and brain MRI findings of consecutive patients with SIH in Taipei Veterans General Hospital. The disease duration was measured as the interval between the onset of the first SIH symptom and the appearance of specified brain MRI findings. We divided our patients into quartiles based on their disease duration. Associations between disease duration and incidences of brain MRI signs were analyzed using chi-square, linear-by-linear association, or exhaustive CHAID algorithms (decision tree analysis).

Between January 2007 and December 2016, 176 SIH patients admitted to our hospital were recruited. Except for the venous distension sign, which has an incidence ≥75% in all quartiles, timings of ≥ 40% incidence rate of MRI signs followed a stepwise fashion: diffuse pachymeningeal enhancement (< 7 days, p=0.009), flattening of pons (≥ 7 days, p=0.021), severe midbrain-pons deformity (≥ 17 days, p=0.007), and subdural hematoma (≥30 days, p<0.001). According to the decision tree analysis, incidence of subdural hematoma markedly increased when duration ≥ 17 days (< 17 vs. ≥17days: 5.8% vs. 36.7%, p<0.001).

Our study showed the brain MRI findings in SIH were associated with the disease duration and occurred sequentially. Our findings can be used to help clinicians make accurate diagnosis of SIH in different durations.