Background: Chronic headache after whiplash injury is common, but the underlying mechanisms have not yet been elucidated. On the basis of human neuroanatomy, we hypothesize that rear-end collision can cause leakage of the cerebrospinal fluid (CSF) into the epidural space most frequently at the lumbosacral level, inducing chronic headache.
Methods: We considered that the following phenomena would be evident in patients with chronic headache after rear-end collision: (1) orthostatic headache with early onset and long duration, (2) low intracranial pressure (ICP =or< 60 mm H2O), (3) CSF leakage mainly in the lumbosacral region on radioisotope-myelocisternography, and (4) diffuse pachymeningeal enhancement (DPE) on gadolinium enhanced magnetic resonant image (Gd-MRI). The clinical signs and symptoms, ICP and neuroimaging findings were analyzed retrospectively in 20 patients who complained of chronic headache after rear-end collisions.
Results: Headaches were orthostatic and started on the day of the accident in 14 patients. The headaches lasted more than 3 months in all patients. Mean ICP was 120 +/- 30 cm H2O. Only one patient showed low ICP. RI-myelocisternography revealed signs of CSF leakage at the lumbosacral level in 10 patients. Gd-MRI showed no abnormalities known to be characteristic of spontaneous intracranial hypotension (SIH). Chronic headache disappeared or was diminished in all patients by epidural blood patching in the lumbosacral region.
Conclusion: This clinical study partly supports the validity of our verifiable hypothetical mechanism. The ICP is not low and DPE is not observed on Gd-MRI. Therefore, CSF leakage into the epidural space may not occur, but spinal CSF absorption may be over-activated. This condition may represent a new clinical entity.