A New Kind of Whiplash-Associated Headache?
Headache is a common symptom after whiplash injury, second only to neck pain in frequency. Because of the complexity of a rear-end collision, headache can have many different origins: it can be caused by direct head trauma, it can originate in injured ligaments in the cervical spine, and it can be caused by muscle injury in the neck. Because of these different etiologies, headache can be difficult to diagnose.
A new study1 from Japan has discovered a new type of headache that may account for symptoms in some patients.
The authors were intrigued by research that shows that some patients experience leakage of the cerebrospinal fluid (CSF) after whiplash trauma. This phenomenon has been reported in 2004 by Moriyama et al.2 and in 2007 by Ishikawa et al.3 Dural leak headaches are experienced by some patients after an epidural injection, and these two studies show that some post-whiplash headaches may have a similar cause.
The authors of this current report studied 20 patients with chronic headache after whiplash. The goal of their research was to determine if leakage of CSF was a common cause of whiplash-induced headache.
The patients had symptoms that indicated orthostatic headache – headaches caused by low CSF or blood pressure: “an upright position worsened the headache, whereas recumbency relieved it in all patients. Low atmospheric pressure (characterized by weather such as rain and typhoons) worsened the headache in 17 cases. Seventeen patients noticed that taking a bath relieved the headache.”
The researchers checked the CSF in the patients, and it appeared normal in all but four patients. However, neuro-imaging tests “showed signs of epidural CSF leakage from the lumbosacral or lower thoracic levels in 10 patients (50%).”
Each of the patients in the study was given an “epidural blood patch,” a procedure where the doctor injects the patient’s blood into the epidural space, which does exactly what the name says – it patches the hole in the dura.
Importantly, the study found that the chronic headaches in the patients were “resolved or diminished in all patients” with the epidural blood patch. The patients did, however, continue to have other symptoms from their injury.
So, how does this kind of injury occur, especially since the leakage of CSF appears in the lower spine and not the head and neck? The authors provide suggest the following:
“When the head hits a seat headrest as a result of a rear-end collision, the cerebellum moves backward with rapid acceleration as a result of inertia and compresses the CSF in the cisterna magna. The arachnoid membrane containing spinal CSF is elastic. Therefore, CSF must be pushed out- and downward into the spinal canal by this motion of the cerebellum.”
The authors speculate that this pressure pulse from the moving brain results in damage to the spinal canal in the lower spine. There is evidence that such a “pressure wave” does occur in the spinal canal; Ortengren et al.4 in 1996 reported findings of increased CSF pressures during impact in pigs during testing.
The authors conclude:
“This study spotlights a new aspect of whiplash injury caused by rear-end collision indicating that the head and/or neck injuries may cause abnormalities of CSF circulation by alterations of fluid dynamics that can result in long lasting neurological symptoms without visible damage of the CNS.”
As this study shows, patients with orthostatic headache should be carefully examined for problems with CSF circulation.